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Username Post: Tuning question        (Topic#361070)
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-22-20 05:41 AM - Post#2794457    

Hey all!

I tuned my car a couple weeks ago out of frustration for it not running "right." the motor has weak compression in a cylinders which doesn't help, and is at the end of its life. but it needs to get me through summer. I more or less said forget the timing light - specs for my motor are irrelevant with everything but the block and heads different than stock. Vacuum guage didnt come out either. Its the best my car has EVER run. If there was anything negative, its that it cranks a hair of a second longer; used to breath on the start button and it was going. Now its a tad bit slower.

Here's what I did:

Car was in drive, all four wheels chuck and a "kill" plan readily available

Started with air fuel, dialed in slowly until it stumbled, backed off slowly till the stumble went away, then back out (rich) an 1/8 turn.

Then to timing: found the highest idle, which was not the smoothest, and "played" with it until the car "backed off" the chucks... like calmed down if that makes sense... smoothest idle, least "lunge forward" feel. Played a lot with this for, again, calmest idle. Went back fine tuned air fuel, and adjusted idle speed for (one more time) the smoothest idle with the car feeling "calm" rather than wanting to go over the chucks. Done. Best its ever run

I have noticed a sound that I never noticed before BUT i've been enjoying my exhaust more than I have before, as well.

So an exhaust pop, or backfire in the exhaust manifolds or pipes likely sounds like a gunshot, this isn't that, but rather, its like a low, rolling thunder when I back off the throttle fast. not the rasp in the video that posted but like a low, rumbling "bop - bop" when I back off the throttle fast. Driving or in park. Doesn't SOUND "wrong" (actually sounds cool) but since i've only just noticed it, I want to understand what it is. Not sure if it has to do with the timing, which if it did, i'd be surprised because the car runs the best it has in every other regard

I'd like to get it on film BUT for some crazy reason, its very hard to film my exhaust... when i rev, it stops the video on my phone... my wife got a video once and even in that one, with her phone, the audio cut out twice

Thanks

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


Edited by drew1987 on 05-22-20 05:41 AM. Reason for edit: No reason given.

 


japete92 
"6th Year" Silver Supporting Member
Posts: 1408
japete92
Loc: No. Virginia
Reg: 01-18-13
05-22-20 07:10 AM - Post#2794466    
    In response to drew1987

The car has a sbc v8 engine?

Recommend reading the below:

https://www.chevelles.com/forums/374-ignition/1 891...

Once you get the timing 'right', then adjust the carb. "Right" may very well NOT be the GM spec. But somewhere between 8 and 16 degrees BTDC (initial) is where you will likely wind up.

Timing the car in neutral with a light is fine.

Just trying to be helpful.

Pete



Edited by japete92 on 05-22-20 07:17 AM. Reason for edit: No reason given.

 
Shepherd 
Frequent Contributor
Posts: 2091

Loc: Lake George, NY
Reg: 11-11-15
05-22-20 08:51 AM - Post#2794474    
    In response to drew1987

Assuming a good timing chain, I am a stickler for using a timing lite.Over many years of tuning these engines, depending on mods and engine condition, 10-15 initial, 35 total at say 3k rpm.



 
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-22-20 11:10 AM - Post#2794485    
    In response to Shepherd

I

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


 
50hotrod 
"8th Year" Silver Supporting Member
Posts: 1066
50hotrod
Loc: Wisconsin
Reg: 07-25-11
05-23-20 05:59 AM - Post#2794534    
    In response to drew1987

Drew, Timing and tuning an engine by performance and not spec's is not uncommon especially for Gen 1 carbureted engines. The following are examples with an engine at operating temperature (hot).

Under timing (retarded) results are sluggish performance and overheating.

Over timing (advanced) results are pinging or light knocking sound under HARD acceleration. Also, hard starter cranking where the engine doesn't crank over smooth and seems like it wants to stop or pause at each compression stroke while cranking.

When you tune an engine manually, the first thing you want dialed in is the timing.

Engine must be to operating temp!!!

Testing for pinging should be done at lower RPM hard acceleration as it will be more prevalent during lugging conditions.

What I do is advance the distributor until I start to experience the hard starting I previously described. Then, retard the distributor slowly until normal starting resumes.

Next, I'll take it for a drive. I'll HARD accelerate and listen for the engine to ping which is pre-detonation of the fuel mixture in the cylinders. If you have ANY pinging you MUST retard the timing to eliminate this. It can and will cause engine damage. Make all your adjustments in small increments. It takes very little movement of the distributor to make a big difference. If you don't have any pinging...... you can slowly advance the distributor until you do...... then back it off until gone. Again, testing can only be done under hard acceleration.

Once you achieve smooth, powerful hard acceleration with no unusual engine noise and normal starter cranking, you'er pretty much in the ball park with what makes your engine happy for timing.

This tuning technique can be used on all carbureted engines.

Your description for carburetor adjusting is spot on. I hope this helps, Good Luck.





1950 CHEVY 2 DOOR 327 TRI POWER FENDERWELL HEADERS HEIDT FRONT SUSPENSION 700R4 TRANS 411 REAR



 
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-23-20 07:21 AM - Post#2794540    
    In response to 50hotrod

Yes! thanks for that. I did it all based on idle in drive, then tested under hard acceleration. Pinging (marbels in a can) doesnt happen just a great sounding motor =) i think its spot on. The "thunder" when backing off of the accelerator pedal sounds cool, doesnt sound "wrong" so I think I am just going to roll with it.

The best way I can describe the feeling I went by is this: The car wants to go over the chucks... you can feel that its pushing into them. When the timing is in its sweet spot, it sort of "backs off" of the chucks, and that happens to be right where the "in drive" idle is the smoothest/calmest. With clockwise retarding the timing, I can tell you this: its far more retarded that it was going by vacuum. It runs mint. Cold starts better than my lexus. Warm starts arent perfect with out a light bit of throttle but whatever, its not EFI.

Thanks for the reply =)

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


 
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-23-20 07:26 AM - Post#2794542    
    In response to drew1987

My bride egged me on at a light the other day on the way to a covid19 birthday parade. Shes probly got more horsepower, which is sad.

https://youtu.be/DtphhiKVpew

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


 
Ray P W 
Contributor
Posts: 514

Reg: 09-30-15
05-23-20 07:41 AM - Post#2794544    
    In response to drew1987

I'm hoping Grumpy will chime in on this.

Ray W



 
Shepherd 
Frequent Contributor
Posts: 2091

Loc: Lake George, NY
Reg: 11-11-15
05-23-20 12:26 PM - Post#2794560    
    In response to drew1987

Called old school power timing, problem is as temperature, barometric press., and humidity changes, so do engine demands. I'll stick with the basic set ups for the sbc, then " tickle" it from there. Again, timing light, I guess I am stuck with 20 years of drag racing backround. Lol



 
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-23-20 04:13 PM - Post#2794572    
    In response to Shepherd

Still curious about that sound. Doesn

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


 
50hotrod 
"8th Year" Silver Supporting Member
Posts: 1066
50hotrod
Loc: Wisconsin
Reg: 07-25-11
05-24-20 07:58 AM - Post#2794630    
    In response to drew1987

Drew,
Grumpy is an engine performance guru. The best of the best. Works mostly with GM stuff. He's on this site, in the performance sections. His knowledge is unsurpassed by anyone I've found.

1950 CHEVY 2 DOOR 327 TRI POWER FENDERWELL HEADERS HEIDT FRONT SUSPENSION 700R4 TRANS 411 REAR



 
bobb 
Super Senior Member
Posts: 5636

Loc: paradise
Reg: 09-05-03
05-24-20 10:45 AM - Post#2794645    
    In response to drew1987

your exhaust noise sounds like it may be retarded timing. the timing mark on your dampener may not be correct. if there is a rubber ring in your dampner you need to verify tdc and mark it. timing is a complicated thing if you get into timing curves. there is initial , or idle timing, total timing and the rate of timing increase controlled by the springs in your timing advance. you may also have vacuum timing. most stock springs are too stiff so the timing advance is too slow. i would set total timing first, best power no pinging then maybe 2 degrees less for safety and deaf ears. you would probly need to modify and or fabricate the parts needed to get the rest where you need it to be unless there are kits out there in the aftermarket.the most important thing is that it dosent ping.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
Keith_Knox 
Member #189 Moderator and "18th Year" Gold Supporting Member
Posts: 6429
Keith_Knox
Age: 78
Loc: Napa, Ca USA
Reg: 04-02-00
05-24-20 11:24 AM - Post#2794647    
    In response to drew1987

Here is grumpyvette.
https://www.chevytalk.org/fusionbb/showtopic.php?t...

29-41, 42-48, 49-54 Moderator
1948 Chevy Fleetmaster Coupe Purchased 6/2010. Stock with rebuilt 52 216 installed May 1966.
1946 Chevy 1/2 ton pickup, stock. Purchased 11/18/17.
2019 Ford Ranger Lariat Super Crew


 
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-25-20 04:40 AM - Post#2794726    
    In response to Keith_Knox

So retarded timing makes that

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


Edited by drew1987 on 05-25-20 04:41 AM. Reason for edit: No reason given.

 
Shepherd 
Frequent Contributor
Posts: 2091

Loc: Lake George, NY
Reg: 11-11-15
05-25-20 06:52 AM - Post#2794735    
    In response to drew1987

To be sure you can get a piston stop that goes in #1 plug hole, turn the engine over til piston hits the stop, Mark the damper, turn it back the other way, mark the damper. Now measure the distance between the two, use a soft tape, split the difference as accurately as you can. See how that center line now lines up with the timing tab. Engine front accessories stripped off this is much easier as you could a caliper for measuring. Now you are at absolute tdc if the timing tab lines up, if not fix it.



Edited by Shepherd on 05-25-20 06:53 AM. Reason for edit: No reason given.

 
drew1987 
"7th Year" Silver Supporting Member
Posts: 3648
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
05-25-20 10:07 AM - Post#2794755    
    In response to drew1987

Thanks for that. Checked where I was at with a timing light, with my

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


 
Shepherd 
Frequent Contributor
Posts: 2091

Loc: Lake George, NY
Reg: 11-11-15
05-25-20 01:30 PM - Post#2794788    
    In response to drew1987

Good target all around setting, and better seat of the pants.Lol



 


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