bowtie44s
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12-14-14 11:14 PM - Post#2506366
I am planning a build on my mark iv block. Here are the specs, I already have the heads so I hope to not change anything on them. My goal is very streetable, nothing radical. Enough vacuum for power brakes is a must, as well as running on 93 octane. THE 93 OCTANE IS THE #1 PRIORITY! I want something that pulls hard from 1500-4000. I'll probably never go much past 5000.
The heads have 300cc intake runners, 2.25 intake and 1.88 exhaust with 118cc combustion chambers.
I plan on going 511 cu in so bored .060 and stroked .375 I am going to go with -18cc dome pistons.
The cam I plan to go with is the Lunati 10110316 Lift is .515/.515 Duration @ .050 is 221º/230º and advertised duration is 276º/286º with a LSA of 112º.
Now I have done some homework. Assuming a stock mark iv has a deck height of .023, the static compression ratio with a .040 head gasket would be 10.09:1. If I took .020 off of the head gasket or deck height it would be 10.48:1 and .020 off the gasket and .020 off the deck height would be 10.91:1. I figured the intake valve on that cam would close at 70º ABDC. So the dynamic compression would be 7.61:1, 7.91:1, and 8.29:1 respectively.
Here are my questions. Would any of those compression ratios be in danger with 93 octane with aluminum heads? Would .3 or .4 on the dynamic CR be noticeable? If so, which is better, thin the head gasket or deck height? Head gaskets choices in the .020 thickness is slim.
Would anyone make any changes to these plans? Could anyone give a rough hp and torque estimate? I plan to feed it with an 850 quick fuel.
I have the cash and I'm getting antsy, I just want to get all my ducks in a row before I order any parts. Thanks for any input.
Jeff
'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap |
Edited by bowtie44s on 12-14-14 11:17 PM. Reason for edit: No reason given.
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0utlaw
Very Senior Member
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12-15-14 04:09 AM - Post#2506378
In response to bowtie44s
What is it going into?
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66cayne
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12-15-14 07:13 AM - Post#2506423
In response to bowtie44s
all of the compression ratios will be fine with 93 octane. I don't really understand your combination choices though. Sounds like this is going into a truck. Are you trying to squeeze the most cubic inches out of that 454 block? Who are you buying the stroker crank from?
I think you would be much better off building a traditional 496 BBC. .060 over, with flat top pistons, 6.385 rods, 0 deck height with a .040 head gasket will put you right about 8.5 compression ratio with your 118cc heads. These combinations have been tried and tested. The cam you have selected is going to produce a lot of low end torque. So it should move really well right off idle, especially with all those cubes. Its too small to produce a lot of horsepower though.
Edited by 66cayne on 12-15-14 07:16 AM. Reason for edit: No reason given.
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bowtie44s
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12-15-14 08:55 AM - Post#2506452
In response to 66cayne
Yes, it's going in a 4x4 truck. 33s, 3.73s and 5speed. I thought of the 496 but just thought, why not go another .125 on the stroke. Is there a reason to go 4.250 stroke instead of 4.375?
I was planning on getting the Eagle assembly from Summit with forged pistons, forged crank, and forged H beams. The one they show is not balanced, I was going to pay the extra and get the balanced assembly.
8.5:1 seems low. Why do you say so low? I built a small block with 9.7:1 and it was fine on 93 with iron heads. I didn't know anything about dynamic compression at the time so I don't know what it was.
The cam you have selected is going to produce a lot of low end torque. So it should move really well right off idle, especially with all those cubes. Its too small to produce a lot of horsepower though.
That's what I'm after. I don't care so much about a high peak HP number, I want a lot of usable power.
Jeff
'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap |
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66cayne
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12-15-14 12:20 PM - Post#2506511
In response to bowtie44s
Three reasons not to bore the block out .125. Reason one; many big blocks will not accept that much overbore. You will have to get it sonic checked before you put that much bore on it. Reason two; after a .125 bore you will not be able to rebuild the engine with a new bore because it is already maxed out. Reason three; if you ever want to sell it potential buyers will shy away from a .125 overbored block (I know I have before). To be honest, you are not going to feel any difference between a 496 and a 502/511.
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bowtie44s
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12-15-14 01:01 PM - Post#2506519
In response to 66cayne
I never said I was going to bore it .125, just .060 and stroked .375. The bore would be 4.310 (.060 over) and stroke of 4.375 (+.375) Which is 510.6". Is there any reason to stroke it .250 instead of .375?
Jeff
'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap |
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mjc1
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12-15-14 03:42 PM - Post#2506570
In response to bowtie44s
Will you not run into some clearance issues with the 4.375" stroke and MarkIV block?
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66cayne
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12-15-14 05:50 PM - Post#2506608
In response to bowtie44s
Okay, my misunderstanding. I am not sure of the cost difference between the 496 and 511 kit from Eagle but as for crank fitment, Mk IV and Gen V/VI blocks all accept a 4.25-inch-stroke crank with no block mods. A 4.375-inch stroker often goes in with minor clearancing of the bottom of the bores and the pan rails. A 4.5-inch stroke always needs block clearancing, but most blocks are thick enough in the relevant areas to do this.
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bowtie44s
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12-15-14 07:44 PM - Post#2506636
In response to mjc1
From the little bit of information I can find, it looks like I'll have to clearance the pan rails a little and the bottom of the cylinders but there is no issue with cam clearance. I don't see any reason not to for no more work than it would be. I had to grind a little bit on my 350 block to get the 400 crank in it.
Jeff
'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap |
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bowtie44s
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12-15-14 07:48 PM - Post#2506637
In response to 66cayne
4.5 stroke sounds like too much work. There are more options in 496, but for the forged crank, forged pistons, and forged H beams, the 4.250 and 4.375 stroke is the same price.
Jeff
'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap |
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66cayne
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12-15-14 09:00 PM - Post#2506662
In response to bowtie44s
are you doing yourself or using an engine builder? If you go with the 511 then find someone with experience building big strokers. They will know the proper clearancing. If you go with the 496 you won't have to worry about that. Best of luck with your build...
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Raven18940
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12-16-14 06:40 AM - Post#2506742
In response to 66cayne
Seems like a lot of work for 15 cubes. That's less than the jump from a 355 to a 383, and an even smaller percentage since the engines are so large to begin with.
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models916
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12-16-14 07:52 AM - Post#2506756
In response to Raven18940
Big stroke may move the piston pin into the ring grooves and have to be custom ordered and be assembled very carefully.
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bowtie44s
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12-16-14 09:24 AM - Post#2506771
In response to models916
I don't think that is a problem. Here is the unbalanced kit.
http://www.summitracing.com/parts/esp-11014060
Here is the balanced that says unavailable. Summit is supposedly working on making it available and getting a price.
http://www.summitracing.com/parts/esp-b11014060
They said it would be $100-$150 more which would definitely be worth it.
Yes, its only 15", but with just a little grinding, I keep thinking why not. Every thing I read says very minor clearancing.
Back to the compression, would .5 make a noticeable difference?
Jeff
'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap |
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