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Username Post: Single or Dual pattern cam for this otherwise stock 327/300?        (Topic#349682)
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-15-18 08:39 PM - Post#2724539    

I'm at the cam select phase and, although I know the 327 is not a low RPM torque generator, I'm attempting to get the most out of the 1000 to 4500 RPM range. What I'm working with is a stock '65 327/300, carb on down to rams horn exhaust. The only component to be changed is the cam.

Details: 600 AFB, 3844459 iron intake, block (.030, decked), 461's (1.94, 1.6, surfaced), 2" rams horns, 2 1/4" dual exhaust with turbo mufflers, stock TC & Powerglide, 3.55 diff.

At .038 quench she's pressing an SCR of 9.81:1. As best as a calculator can offer I'm targeting 7.5 to 7.9 for DCR. If I decide to tackle the heads and sanitize the combustion chamber I'll shoot for the 7.9 DCR with hopes of still using 91 (or less) octane. It's looking like an IVC of 63 to 69 (dur. 272 to 282, ICL 112) is where it needs to be. I was thinking overlap in the 45 to 55 range with valve lift around .435 to .455 and @.050s of 205 to 215. Original thoughts were to shoot for a 260 to 265 duration range but the numbers (on paper) don't seem to allow it (Please advise if any of my assumptions are off base).

Now the question would be: Given the stock intake and exhaust along with conservative components and operating range would the advantage go to a single or dual pattern grind? Might cleaning up runner flashing and performing a minor pocket port on the exhausts make a difference to this decision?

Any insight much appreciated.

*EDIT* -- Forgot to mention 3,800 lb vehicle.

Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


Edited by chlkorg on 02-15-18 09:24 PM. Reason for edit: No reason given.

 




models916 
Valued Contributor
Posts: 4783

Age: 67
Loc: Addison, IL
Reg: 05-28-10
02-16-18 06:46 AM - Post#2724558    
    In response to chlkorg

Sounds like a boat or RV spec'd cam.



 
rumrumm 
"17th Year" Silver Supporting Member
Posts: 2075
rumrumm
Loc: Macomb, IL
Reg: 10-18-01
02-16-18 07:40 AM - Post#2724563    
    In response to models916

With your combination, you could benefit with a little help on the exhaust side, so I would be looking at a dual pattern cam. Is there are reason why you want to keep the cast iron intake manifold? You really could get a lot of good from an Edelbrock Performer intake. You could always paint it if you wanted it to look stock.

Lynn

"There's no 12-step program for stupid."


383 sbc, Eagle, AFR, SRP, CompCams, Edelbrock, FiTECH. Dyno #'s: 450 hp @ 5700, 468 ft. lbs. torque @ 4300.

http://photo.net/photos/Lynn%20Johanso n


 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-16-18 07:47 AM - Post#2724565    
    In response to chlkorg

Dual pattern, let the exhaust help let the intake work better, stronger.



 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-16-18 08:15 AM - Post#2724569    
    In response to rumrumm

Thanks for the replies!

  • models916 Said:
Sounds like a boat or RV spec'd cam.


Yes, very much so.

  • rumrumm Said:
With your combination, you could benefit with a little help on the exhaust side, so I would be looking at a dual pattern cam. Is there are reason why you want to keep the cast iron intake manifold? You really could get a lot of good from an Edelbrock Performer intake. You could always paint it if you wanted it to look stock.


I too have a hard time believing the 461's ports aren't the weak link in the exhaust system. I guess what sideswiped me is the Isky'ism that single pattern can often be the better choice. In that though I was never convinced it was these earlier iron heads and manifolds being considered.

It's my stubbornness making me retain the original manifold for appearance sake. Funny thing is, I recently sold off a Performer intake and cam/lifters I had laying around since 1986.


Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-16-18 08:18 AM - Post#2724571    
    In response to IgnitionMan

  • IgnitionMan Said:
Dual pattern, let the exhaust help let the intake work better, stronger.


Appreciate the reply and I have a feeling that is going to be consensus.

Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
japete92 
"4th Year" Silver Supporting Member
Posts: 1070
japete92
Loc: No. Virginia
Reg: 01-18-13
02-16-18 09:04 AM - Post#2724579    
    In response to chlkorg

  • chlkorg Said:
I'm at the cam select phase and, although I know the 327 is not a low RPM torque generator, I'm attempting to get the most out of the 1000 to 4500 RPM range. What I'm working with is a stock '65 327/300, carb on down to rams horn exhaust. The only component to be changed is the cam.

Details: 600 AFB, 3844459 iron intake, block (.030, decked), 461's (1.94, 1.6, surfaced), 2" rams horns, 2 1/4" dual exhaust with turbo mufflers, stock TC & Powerglide, 3.55 diff.

At .038 quench she's pressing an SCR of 9.81:1. As best as a calculator can offer I'm targeting 7.5 to 7.9 for DCR. If I decide to tackle the heads and sanitize the combustion chamber I'll shoot for the 7.9 DCR with hopes of still using 91 (or less) octane. It's looking like an IVC of 63 to 69 (dur. 272 to 282, ICL 112) is where it needs to be. I was thinking overlap in the 45 to 55 range with valve lift around .435 to .455 and @.050s of 205 to 215. Original thoughts were to shoot for a 260 to 265 duration range but the numbers (on paper) don't seem to allow it (Please advise if any of my assumptions are off base).

Now the question would be: Given the stock intake and exhaust along with conservative components and operating range would the advantage go to a single or dual pattern grind? Might cleaning up runner flashing and performing a minor pocket port on the exhausts make a difference to this decision?

Any insight much appreciated.

*EDIT* -- Forgot to mention 3,800 lb vehicle.




I'm all for the idle to 4500 rpm 'power' range. So was GM (pretty much). I may be wrong for a '65 but I think the standard exhaust for the 300 hp 327 was the 2 1/2" ram horn manifolds, 2 1/2" down pipes (to the muffler), and 2" aft of the muffler. I also thing the intake valves were 2.02 (for the 300 hp). Your engine seems to have been 'modified' at some point in the wrong direction (from which you wish to go).

Regardless of what you do to your 327, the 2 speed power glide is going to stifle the performance. Any thoughts toward a transmission change (more gears)? A 4 speed manual will wake up what you have A LOT.

Finally, more displacement is where I would 'attack' for more torque in the idle to 4500 rpm range. Just for jollys, look at what one person did with a 327 in their '64.

http://www.thecairns.com/Impala/

https://www.youtube.com/watch?v=qe9ke0rQlT8

There's a lot in that link, if you skip to all the engine stuff (it's spread out thru-out the link) you will see what I am referring to. Look at the low end torque numbers. They are almost the same as the 409 BBC numbers.

That owner kept his 327 almost stock. Using newer 350 block (4 bolt mains and one piece rear seal) has some advantages.

You asked for 'Any insight much appreciated.' These are mine. Hope they are helpful.

Pete



Edited by japete92 on 02-16-18 10:05 AM. Reason for edit: No reason given.

 
CNC BLOCKS N/E 
Senior Member
Posts: 976
CNC BLOCKS N/E
Loc: NORTH EAST
Reg: 12-12-03
02-16-18 09:28 AM - Post#2724583    
    In response to japete92

I am doing a restoration 327 for a Vette zero decked left the VIN number on the deck, used a 6.125 rods with a piston C/H 1.250.

Small engine not much compression you need all the Dynamic compression you can get.

Using a 272/272 ADV and 217/217@.050 on 108 .450 valve lift. Installed at .102 Ultradyne om a P55 core using GM Delphi liftes.

I use a lot of single pattern cams in my circle track engines and some builds I use a bigger intake lobe then the exhaust. If you using tight lobe seps single pattern cams work great.



Edited by CNC BLOCKS N/E on 02-16-18 09:30 AM. Reason for edit: No reason given.

 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-16-18 01:14 PM - Post#2724608    
    In response to japete92

  • japete92 Said:
I'm all for the idle to 4500 rpm 'power' range. So was GM (pretty much). I may be wrong for a '65 but I think the standard exhaust for the 300 hp 327 was the 2 1/2" ram horn manifolds, 2 1/2" down pipes (to the muffler), and 2" aft of the muffler. I also thing the intake valves were 2.02 (for the 300 hp). Your engine seems to have been 'modified' at some point in the wrong direction (from which you wish to go).

Regardless of what you do to your 327, the 2 speed power glide is going to stifle the performance. Any thoughts toward a transmission change (more gears)? A 4 speed manual will wake up what you have A LOT.

Finally, more displacement is where I would 'attack' for more torque in the idle to 4500 rpm range. Just for jollys, look at what one person did with a 327 in their '64.

http://www.thecairns.com/Impala/

https://www.youtube.com/watch?v=qe9ke0rQlT8

There's a lot in that link, if you skip to all the engine stuff (it's spread out thru-out the link) you will see what I am referring to. Look at the low end torque numbers. They are almost the same as the 409 BBC numbers.

That owner kept his 327 almost stock. Using newer 350 block (4 bolt mains and one piece rear seal) has some advantages.

You asked for 'Any insight much appreciated.' These are mine. Hope they are helpful.

Pete


Much appreciate your feedback.

I think it would be a safe bet to say the '65 SS Impala 327/300 had 1.95" intake valves and 2" ram horn manifolds. My one deviation (obviously, beside the cam) is, as you noted, the exhaust. The original did have 2 1/2" downpipes and 2" tail. This vehicle has been in the family since '68 with absolutely no mods by us.

My intention is to use the powerglide for now hence my looking for a low RPM broad powerband cam. I'm trying to be realistic as I know this combo (short stroke 327 & 2-speed PG) is not ideal. I have already started keeping an eye out for TH350's and TH2004R's. Almost snagged a GN TH2004R a few weeks ago but upon inspection could see it had unquantifiable mods and the governor was missing. Although I'm a 4-spd manual fan a 3 or 4 speed auto is in the future for this stand-off resto. With that upgrade will be a suitable cam replacement.

Beyond the cam (and future trans upgrade) I'm a stick in the mud regarding any other changes to this vehicle. She'll not be much more than a cruiser that has been optimized.

Thanks for the links! Always enjoy a cataloged rebuild.


Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-16-18 01:40 PM - Post#2724610    
    In response to CNC BLOCKS N/E

  • CNC BLOCKS N/E Said:
I am doing a restoration 327 for a Vette zero decked left the VIN number on the deck, used a 6.125 rods with a piston C/H 1.250.

Small engine not much compression you need all the Dynamic compression you can get.

Using a 272/272 ADV and 217/217@.050 on 108 .450 valve lift. Installed at .102 Ultradyne om a P55 core using GM Delphi liftes.

I use a lot of single pattern cams in my circle track engines and some builds I use a bigger intake lobe then the exhaust. If you using tight lobe seps single pattern cams work great.


Thanks for the post.

Dialing in on a DCR has been difficult for me. I know I'd like ideally to be in the low 8.2-8.4 region but don't want to be a fuel hostage or have to dial back the timing when driving out of town into the unknown's. Hoping to find a happy medium.

I looked at the UD lobe catalog a few weeks back and found a couple patterns that I've since ticked as prospects. Just have to determine where I'm going.

Your mention of single pattern in conjunction with circle track has me seeming to remember that as one of the Isky scenarios. My thinking was tuned free flowing exhaust easily allowing for a single pattern (or, as you stated, reverse pattern). Unfortunately my exhaustive search has not found any hard numbers showing the difference between the two in a 60's stock motor scenario.


Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
CNC BLOCKS N/E 
Senior Member
Posts: 976
CNC BLOCKS N/E
Loc: NORTH EAST
Reg: 12-12-03
02-16-18 01:43 PM - Post#2724612    
    In response to chlkorg

  • chlkorg Said:
  • CNC BLOCKS N/E Said:
I am doing a restoration 327 for a Vette zero decked left the VIN number on the deck, used a 6.125 rods with a piston C/H 1.250.

Small engine not much compression you need all the Dynamic compression you can get.

Using a 272/272 ADV and 217/217@.050 on 108 .450 valve lift. Installed at .102 Ultradyne om a P55 core using GM Delphi liftes.

I use a lot of single pattern cams in my circle track engines and some builds I use a bigger intake lobe then the exhaust. If you using tight lobe seps single pattern cams work great.


Thanks for the post.

Dialing in on a DCR has been difficult for me. I know I'd like ideally to be in the low 8.2-8.4 region but don't want to be a fuel hostage or have to dial back the timing when driving out of town into the unknown's. Hoping to find a happy medium.

I looked at the UD lobe catalog a few weeks back and found a couple patterns that I've since ticked as prospects. Just have to determine where I'm going.

Your mention of single pattern in conjunction with circle track has me seeming to remember that as one of the Isky scenarios. My thinking was tuned free flowing exhaust easily allowing for a single pattern (or, as you stated, reverse pattern). Unfortunately my exhaustive search has not found any hard numbers showing the difference between the two in a 60's stock motor scenario.




Your 327 will like the single pattern cam with that short stroke. You will create more torque over a dual pattern cam. Lobe sep is a big factor as well no one ever thinks about.

A lot of people go by what they read in books and have no real world experience.




Edited by CNC BLOCKS N/E on 02-16-18 01:44 PM. Reason for edit: No reason given.

 
chlkorg 
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Posts: 59

Loc: Maryland
Reg: 01-24-17
02-16-18 04:14 PM - Post#2724624    
    In response to CNC BLOCKS N/E

  • CNC BLOCKS N/E Said:
Your 327 will like the single pattern cam with that short stroke. You will create more torque over a dual pattern cam. Lobe sep is a big factor as well no one ever thinks about.

A lot of people go by what they read in books and have no real world experience.



About that last sentence of yours -- Exactly! That is what I don't have regarding cam choice for an otherwise very stock SBC. I'm leaning on you guys at the moment for practical experience.

Hadn't thought about the fact stroke length could be a considerable factor.

Flipping through my notes I find that from the UD master list I was considering the H267/290 - 267/212 .435. Could single pattern it with 112/108 which would give an IVC of 61.5° and overlap of 43° resulting in a DCR in the vacinity of 7.8.

Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-16-18 06:39 PM - Post#2724635    
    In response to chlkorg

My recommendation came from hands on engine work to 327's I have owned, built, and raced for two decades, over 50 of them. I like the 327's much better than any 350 I have ever seen.

The street engines that were low perf just ran better with a dual pattern cam profile, the race engines just the opposite, single pattern worked better.






 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-16-18 07:23 PM - Post#2724638    
    In response to IgnitionMan

  • IgnitionMan Said:
My recommendation came from hands on engine work to 327's I have owned, built, and raced for two decades, over 50 of them. I like the 327's much better than any 350 I have ever seen.

The street engines that were low perf just ran better with a dual pattern cam profile, the race engines just the opposite, single pattern worked better.


I here ya. Have to admit my last post was to spur additional comment. My friend who performed the machine work (gratis) also use to grind cams from the 60's to early 90's, back when it was profitable. He's been pushing for the GM-151 grind (Melling C400P) but I've not felt comfortable with that for, amongst other reasons, it being single pattern. With basically a 160/65 bias it only seems natural these 461's could, in all conditions, benefit from a little exhaust aid.

It would be great to hear you spec a cam based on your past experience in conjunction with the parameters I've provided. Might help add to my enjoyed paralisis.


Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17206
grumpyvette
Age: 70
Loc: FLORIDA USA
Reg: 03-16-01
02-17-18 12:12 PM - Post#2724687    
    In response to chlkorg

http://garage.grumpysperformance.com/index.php?thr...


http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-17-18 12:53 PM - Post#2724694    
    In response to chlkorg

In one instance, flatbed truck, car 427 oval port engine, used to go from Reno to Los Angeles to pick up new motorcycles in their crates for a dealership. Ran well stock with its single pattern cam. Mileage was dismal, reno os 4,800 feet elevation, lits of hills and two mountain passes in between.

One day, it needed a revamp, so, dual pattern cam went in. Engine pulled harder, more torque, gained almost two MPG< and pulled the hills much easier even when loaded with 20 new bikes in their crates.

That is the way I have hands on found it works with just about any engine I have seen, built, done. Now, race engines, single pattern works in just about all of them.

Just my 45 years of doing it.



 
CNC BLOCKS N/E 
Senior Member
Posts: 976
CNC BLOCKS N/E
Loc: NORTH EAST
Reg: 12-12-03
02-17-18 02:55 PM - Post#2724700    
    In response to IgnitionMan

Single pattern cams with the correct lobe sep will always build more torque over a dual,pattern cam as thats a no brainer.

Do a search with dual pattern cams VS single pattern cams. The exhaust opens to early.

Isky has an article on that as well some where.

My circle track engines make the best torque with single pattern cams and horse power is right there.

On 327 low RPM engine with low compression a single pattern cam is the way to go believe I have seen enough of them on the dyno. And have some happy customers.

The old 327/350 horse cam was a single pattern HMMMMMMM



Edited by CNC BLOCKS N/E on 02-17-18 03:01 PM. Reason for edit: No reason given.

 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-17-18 06:03 PM - Post#2724713    
    In response to chlkorg

Again, much appreciate the replies!

@grumpyvette
Ha! You are one of the reasons I have yet to finalize cam selection. You've been so prolific in very kindly compiling and offering up so much cam related info over the years that, what I use to easily decide on, now has me double-thinking.

@IgnitionMan & CNC BLOCKS N/E
Therein lies my dilema. Two people, both quite experienced on the subject, but with opposing opinions. I know every build and operational usage is unique (even if just slightly) therefore there very well could be justification for each choice. At the risk of hijacking my own thread -- I'd find it incredibly useful if I could solicit from each of you (and anyone else) an opinion as to what cam stats you'd use for this application. I find it very worthwhile to study other peoples cam suggestions in an attempt to help understand their view of performance expectations.



Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
1983G20Van 
Super Senior Member
Posts: 3718

Loc: Bedford, Texas, USA
Reg: 11-13-02
02-17-18 06:40 PM - Post#2724717    
    In response to chlkorg

As for torque the dual patterncam will tend to trade low-end torque for power gains over 4,500 rpm intake duration/LSA being even. Provided I am running headers and a decent flowing exhaust system, I prefer a properly spec'd single pattern cam. The cammed 305 in my Tahoe pulls just fine at 70 mph @ 1,650 rpm and gets 22 mpg at that speed. Cam is a 268/268 @ .006, 218/218 @ .050, .457/.457 on a 110 LSA, installed on a 104° ICL. I am running 1.6:1 rockers for about 0.030" more lift and 2-3° more duration at 0.050". It pulls smoothly from 1,200 rpm under load and pulls its strongest from 3,500-5,800.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-18-18 09:11 AM - Post#2724749    
    In response to IgnitionMan

I was under the impression the OP wanted to build low rpm torque, not build a Top Fueler. Just posting what I have done over the years that worked.

Knowing that, I agree, the 327/350 horse "151" cam works best on the upper end of the rpm range.

I grew up in Southern California, have been a hot rodder and racer all my life, son of one of the first hot rodders. The people I grew up around were they likes of the Iskenderian brothers, T. Willy, Sig and Babe Erson, the Crower brothers, piston, rod, crank,you head, other parts people, Edelbrock, Weiand, Ed Pink, Keith Black, and every other parts maker and engine builder that started all this stuff, and every drag and road racer you could find there, and other places. This led to working at Chevrolet Development, Shelby, Holley, more, and as a consultant to many other performance entities.

I'll hold my hand of cards for the dual pattern in this instance.



 
japete92 
"4th Year" Silver Supporting Member
Posts: 1070
japete92
Loc: No. Virginia
Reg: 01-18-13
02-18-18 09:59 AM - Post#2724755    
    In response to chlkorg

  • chlkorg Said:
  • japete92 Said:
I'm all for the idle to 4500 rpm 'power' range. So was GM (pretty much). I may be wrong for a '65 but I think the standard exhaust for the 300 hp 327 was the 2 1/2" ram horn manifolds, 2 1/2" down pipes (to the muffler), and 2" aft of the muffler. I also thing the intake valves were 2.02 (for the 300 hp). Your engine seems to have been 'modified' at some point in the wrong direction (from which you wish to go).

Regardless of what you do to your 327, the 2 speed power glide is going to stifle the performance. Any thoughts toward a transmission change (more gears)? A 4 speed manual will wake up what you have A LOT.

Finally, more displacement is where I would 'attack' for more torque in the idle to 4500 rpm range. Just for jollys, look at what one person did with a 327 in their '64.

http://www.thecairns.com/Impala/

https://www.youtube.com/watch?v=qe9ke0rQlT8

There's a lot in that link, if you skip to all the engine stuff (it's spread out thru-out the link) you will see what I am referring to. Look at the low end torque numbers. They are almost the same as the 409 BBC numbers.

That owner kept his 327 almost stock. Using newer 350 block (4 bolt mains and one piece rear seal) has some advantages.

You asked for 'Any insight much appreciated.' These are mine. Hope they are helpful.

Pete


Much appreciate your feedback.

I think it would be a safe bet to say the '65 SS Impala 327/300 had 1.95" intake valves and 2" ram horn manifolds. My one deviation (obviously, beside the cam) is, as you noted, the exhaust. The original did have 2 1/2" downpipes and 2" tail. This vehicle has been in the family since '68 with absolutely no mods by us.

My intention is to use the powerglide for now hence my looking for a low RPM broad powerband cam. I'm trying to be realistic as I know this combo (short stroke 327 & 2-speed PG) is not ideal. I have already started keeping an eye out for TH350's and TH2004R's. Almost snagged a GN TH2004R a few weeks ago but upon inspection could see it had unquantifiable mods and the governor was missing. Although I'm a 4-spd manual fan a 3 or 4 speed auto is in the future for this stand-off resto. With that upgrade will be a suitable cam replacement.

Beyond the cam (and future trans upgrade) I'm a stick in the mud regarding any other changes to this vehicle. She'll not be much more than a cruiser that has been optimized.

Thanks for the links! Always enjoy a cataloged rebuild.





Some food for thought:

Let's assume you are seeking better acceleration than you have now(my words, not yours but that's how I interpret your post).

If your current engine runs just fine AND you defiantly intend to change the drive train (nix the power glide), I would do the drive train work first. You may find that's sufficient. Acceleration WILL improve. That's just how I would approach the acceleration upgrade. I'm NOT being critical.

Just a little begging from me; if you like the manual trans, switch to manual. You won't regret it; from a performance standpoint and a looks/originality standpoint. Nothing's more fun to drive, and 'cooler' (to me), than a full size '60s vintage car w/4 speed manual. With a 4 speed manual transmission you can put the car into it's 'power band', and keep it there, whenever you wish.

An aside (no bearing on your question); the link below is my reference (it also matches my VERY unreliable memory):

http://outintheshop.com/faq/casting/heads.html

I am unaware (which does not make me accurate) of a early/mid 60s GM sbc cylinder head with the 1.94" intake valves AND 1.60" exhaust. All those heads w/1.60" exhaust valves came w/2.02" intake valves. Again I am NOT being critical. If there is a GM sbc head w/the 1.94"x1.60" valve combo, I'm curious to learn of it to correct my memory.

Another aside; here's a link (if you already haven'e found it) to A LOT of info (first page is blank, scroll down):

https://www.gmheritagecenter.com/docs/gm-heritage-...

If you study the torque curve of the stock 300/327 you may notice how it already produces it's torque rather 'low' in the rpm range. I'm not saying it can't be improved, but w/just a cam change, I don't know how much more one can get out of it.

Just though I'd share some view points from a different perspective. Give them whatever weight you deem appropriate. Hope they are helpful.

Pete




 
Shepherd 
Frequent Contributor
Posts: 1424

Loc: Lake George, NY
Reg: 11-11-15
02-19-18 11:37 AM - Post#2724876    
    In response to IgnitionMan

Mid range torque, all things being equal, will provide the best acceleration experience, I'd say the intake ports and valve size are the biggest deciding factor in the cam choice, of course the weight and glide are in the formula. My 64 Max Wedge race car, hauled censored in mid range, with stock regrind, mild by today's standards cam. 11.0s at 122, on 9" tires, back in the 80's.



 
1983G20Van 
Super Senior Member
Posts: 3718

Loc: Bedford, Texas, USA
Reg: 11-13-02
02-19-18 12:59 PM - Post#2724885    
    In response to Shepherd

I agree on the mid-range torque providing the best increase in accelertion and it is what you will actually feel.

If you go by the modern specs of the cam that GM used in the 300 HP 327 engine it came with a cam that had very lazy lobes. The duration was 260/271 @ .006, 194/203 @ .050 with .390/.410" lift, cut on a 112* LSA with a 108* ICL. It is very easy to pick a modern cam to produce more cylinder pressure and torque than that cam.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17206
grumpyvette
Age: 70
Loc: FLORIDA USA
Reg: 03-16-01
02-19-18 02:25 PM - Post#2724888    
    In response to 1983G20Van

  • Quote:
Again, much appreciate the replies!

grumpyvette
Ha! You are one of the reasons I have yet to finalize cam selection. You've been so prolific in very kindly compiling and offering up so much cam related info over the years that, what I use to easily decide on, now has me double-thinking.




I'm always rather amazed at the number of people that don,t logically mentally step back and ask themselves, a couple simple question, especially if they are not personally familiar with the tech aspects of the subject at hand.
but , Id point out that if your wondering why some cams have a longer exhaust duration, the basic fact here is, that longer exhaust duration, in some cam designs is a design factor whose main purpose is to allow a slightly longer time frame for the cars with a restrictive stock exhaust port to have exhaust flowing that longer time frame is being designed in to the engine too allow a constrictive exhaust time to let the pressure bleed down.
an engine with a non-restricted exhaust (open properly tuned headers, or properly tuned headers feeding a very low restriction exhaust) (and yes the size and length can be both calculated and the restriction easily measured) has no need for a longer exhaust duration, as cylinder scavenging with a properly matched intake manifold, displacement port flow cam timing and compression can be properly matched and would function correctly with a cam timing on both the intake and exhaust matched to a certain rpm and power range.

I've written several related threads, with plenty of related and detailed sub-links
it could easily take a couple very well spent hours to read the links and sub-links but youll gain a good deal more insight into how an engine functions,

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
Shepherd 
Frequent Contributor
Posts: 1424

Loc: Lake George, NY
Reg: 11-11-15
02-19-18 02:26 PM - Post#2724889    
    In response to 1983G20Van

Agreed, modern grinds wifh almost the same specs, out perform the old school cams by a bunch, especially the roller versions. To add, as usual, Grump's ahead of the curve.




Edited by Shepherd on 02-19-18 02:29 PM. Reason for edit: No reason given.

 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-20-18 03:24 AM - Post#2724951    
    In response to Shepherd

Of course, it is all in getting the rest of the parameters and components right, but, in the scheme of things, every cam we ever did along the way, WAS state of the art, for it's time, that is evolution.

So, the "older, out of date cams" of those days weren't "out if date"......all the way back then, along the way to now.

I agree, roller profiles are so much better than flat tappet offerings, but not everyone can afford them. Nice if every push rod engine had some sort of roller cam, but it just ain't gonna happen.




 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-26-18 03:25 PM - Post#2725715    
    In response to chlkorg

Great posts gentlemen! I'd be remiss not to respond.

  • 1982G20Van Said:
As for torque the dual patterncam will tend to trade low-end torque for power gains over 4,500 rpm intake duration/LSA being even. Provided I am running headers and a decent flowing exhaust system, I prefer a properly spec'd single pattern cam. [snip]


The "running headers and decent flowing exhaust" quote is something I'm not sure I can claim. While the pipes on back may not be a major concern I tend to suspect the 461's exhaust ports and ram horns could be. Whether a deciding factor or not, this thread seems to offer differing opinions.

Interestingly the following is on my short list which closely matches your cam.

Howards 111021-11 (or 110931 .450/.450)
Advertised Duration (Int/Exh): 267/267
Duration @ .050 = 213/213
Gross Valve Lift (Int/Exh): .430/.430
intensity = 49.5
LSA/ICL: 111/107
IVC is 60.5 ° ABDC
Overlap is 45 °
DCR 8.05

  • IgnitionMan Said:
I was under the impression the OP wanted to build low rpm torque [snip]
Knowing that, I agree, the 327/350 horse "151" cam works best on the upper end of the rpm range. [snip]


Correct about intended use.

A good reason for the "151" being optioned only with M/T and short gear offerings.

  • japete92 Said:
[snip] Just a little begging from me; if you like the manual trans, switch to manual. You won't regret it; from a performance standpoint and a looks/originality standpoint. Nothing's more fun to drive, and 'cooler' (to me), than a full size '60s vintage car w/4 speed manual.
[snip]
I am unaware (which does not make me accurate) of a early/mid 60s GM sbc cylinder head with the 1.94" intake valves AND 1.60" exhaust. All those heads w/1.60" exhaust valves came w/2.02" intake valves. Again I am NOT being critical. If there is a GM sbc head w/the 1.94"x1.60" valve combo, I'm curious to learn of it to correct my memory.
[snip]
If you study the torque curve of the stock 300/327 you may notice how it already produces it's torque rather 'low' in the rpm range. I'm not saying it can't be improved, but w/just a cam change, I don't know how much more one can get out of it.


I feel ya and my heart is there too. I just vowed to myself that this particular vehicle would remain in "basically" original-as-purchased condition. Have to admit though I would like to experience a full size vehicle with am M21 although I think it would be an even more enjoyable streeter with a much bigger cubed torque motor.

Your memory is accurate in regards to valve sizing. I had a sad experience of "losing" the original heads during a move. The 461 heads my machinist friend sourced (for free) had already been resized for 1.60 exhausts.

From what I understand the 327/300 with a fresh "929" was a pretty stout full RPM range motor. I'm attempting to be realistic and just looking to optimize (if possible) with an updated grind.

  • Shepherd Said:
Mid range torque, all things being equal, will provide the best acceleration experience [snip]


I'm beginning more and more to target a bit further off idle as I'm not looking to smoke the tires. I'm expecting the PG and 3.55 gears to necessitate as broad a torque range as possible.

  • grumpyvette Said:
Id point out that if your wondering why some cams have a longer exhaust duration, the basic fact here is, that longer exhaust duration, in some cam designs is a design factor whose main purpose is to allow a slightly longer time frame for the cars with a restrictive stock exhaust port to have exhaust flowing that longer time frame is being designed in to the engine too allow a constrictive exhaust time to let the pressure bleed down.
an engine with a non-restricted exhaust [snip] has no need for a longer exhaust duration [snip]


Thanks again for all the links. Some were new to me and, those that weren't, continue to remain worthy of rereading.

What I'd be interested in haring is how much exhaust restriction comes into play in my scenario (stock 461's, ran horns, and 2 1/4" duals to the bumper) at typical street RPM's therefore making dual pattern beneficial. That said, I do find it telling that the "929" is a dual pattern cam, albeit on a small scale.

Again, I'm not to the point of assuming either dual or single is "generally" the better choice as there are always very many variables. This is one of the reasons I enjoy reading others opinions (such as in this thread) which provide much food-for-thought.

--------------------

Also on my short list -- To prove I'm not yet wed to single pattern:

Howards 112571-12
Advertised Duration (Int/Exh): 269/279
Duration @ .050 = 215/225
Gross Valve Lift (Int/Exh): .455/.465
intensity = 47.2
LSA/ICL: 112/108
IVC is 62.5 ° ABDC
Overlap is 50 °
DCR 7.94

At just one step up from the "929" I actually prefer the Howards 112561-12 (259/269, 205/215, .420/.455, 112/108). It has a fairly reduced overlap (40°) but comes at the cost of a theoretical .28 higher DCR. Not sure I want to come that close to the limit. If I really wanted to play it safe (7.72 DCR) with another dual pattern cam I could settle on the Summit-1102 (Performer Plus) although overlap is looking on the high side for me at 59°.

Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 
1983G20Van 
Super Senior Member
Posts: 3718

Loc: Bedford, Texas, USA
Reg: 11-13-02
02-27-18 07:13 AM - Post#2725810    
    In response to chlkorg

One other thing you might have overlooked. Have you considered Comp Cams Nostalgia Plus cams. They are intended to sound like the stock cam but have better performance. If I had a 300 HP 327 in a period correct car, I would want it to sound like a 300 HP 327.

https://www.summitracing.com/parts/cca-12-670-4

This cam is still a dual pattern cam but the duration split is much less than many other offerings.

At typical street RPM and load your exhaust will be perfectly adequate. It will not provide a good scavenging effect like headers will but none the less will not have much back pressure.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


Edited by 1983G20Van on 02-27-18 07:18 AM. Reason for edit: No reason given.

 
rumrumm 
"17th Year" Silver Supporting Member
Posts: 2075
rumrumm
Loc: Macomb, IL
Reg: 10-18-01
02-27-18 09:37 AM - Post#2725830    
    In response to 1983G20Van

Grumpyvette had a great suggestion years ago, and I think it makes a lot of sense. Call four or five of the major cam companies, give them your specs, and see what cam each of them recommend for your engine. Compare all of the cams. The one that is closest to the average of them will probably be the most optimal choice. Report back after you do this. We will all be curious to see what they recommend.

Lynn

"There's no 12-step program for stupid."


383 sbc, Eagle, AFR, SRP, CompCams, Edelbrock, FiTECH. Dyno #'s: 450 hp @ 5700, 468 ft. lbs. torque @ 4300.

http://photo.net/photos/Lynn%20Johanso n


 
chlkorg 
Poster
Posts: 59

Loc: Maryland
Reg: 01-24-17
02-27-18 11:07 AM - Post#2725844    
    In response to 1983G20Van

  • 1983G20Van Said:
One other thing you might have overlooked. Have you considered Comp Cams Nostalgia Plus cams. They are intended to sound like the stock cam but have better performance. If I had a 300 HP 327 in a period correct car, I would want it to sound like a 300 HP 327.

https://www.summitracing.com/parts/cca-12-670-4

This cam is still a dual pattern cam but the duration split is much less than many other offerings.

At typical street RPM and load your exhaust will be perfectly adequate. It will not provide a good scavenging effect like headers will but none the less will not have much back pressure.


Appreciate the reply.

I had previously looked at those but an @50 duration of 258° has my theoretical DCR on the ragged edge using max octane. It seems many of these street cams are designed with low compression motors being the target users. Interesting note about that cam is, while it does have a slightly larger exhaust duration, the exhaust lift is actually smaller. Granted, nothing offers insight as to actual lobe profile so the exhaust could still "run" larger.

I'm with you on the exhaust. I had little concern when choosing the 2 1/4" pipes. Seeing as that I'm using the stock cast iron intake, which isn't likely to overwhelm the heads ports or exhaust manifold, I'll be doing little more than port matching, flashing/casting seam removal in the runners and chamber polishing (for ping reduction).

Ej

'65 Impala SS, 327/300/PG, Madeira Maroon/Black (just getting started on stand-off resto)


 




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