360, You think it'll run on pump gas?!?!

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318DSTR

318DSTR

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So I'm buildin a 360 and I'm at the point on deciding what thickness headgaskets too go with. I thinking I'm right on the verge of being able to run pump gas (93), but the fact I'm running iron heads makes me think 100 octane might be more realistic. Wanted to give y'all my specs and see what you think.

-0.030 over 360
- speed pro hyper pistons, sitting .005" below the deck
- J heads, ported, gasket matched, bowls blended with 2.02/1.60
stainless valves and 64-65cc chambers (cc'd)
-lunati voodoo solid cam 235/243 @.050 .526/.546 110lsa
-harland sharp 1.5 roller rockers
-edelbrock torker II 340 intake
-holley 750dp

Based on the compression ratio calculators i've found on the web, they're all saying I'm gonna be about 10.8-11.0:1 if I use a .039 thick head gasket. Should I run a thicker gasket, or do you think I'll have more fun/be happier overall with the higher compression? Appreciate any input.

Thanks,
Tom
 
If your at 10.8-11 shes probably gonna ping. Ide run alluminum heads, actually that is what I had to do.
 
That's really going to be iffy. With 93 it might run ok. Might. You really need to know your dynamic CR. That will tell you a lot better if you can run 93 than your static will. Overlap in a cam will help a lot. What is your cranking cylinder pressure? I plan on running pump gas in mine. 11:1 iron heads with a cam that has a decent amount of overlap. Dynamic CR is 8:1. We planned it this way to run the junk 91 around here but I'm going to have to pull the timing back to get there without pinging and lose some power. Put some race fuel in and advance the timing and I get all of the power back. My engine guy was telling me about some head gaskets that they make now where you can add quite a bit of thickness to them to lower the CR if needed. I'll ask him what they were if you need to know.
 
I have the same motor except my cam is a solid at 244 @.050. And my heads were shaved .040 and pistons sit at zero. I'm at 11.25 so I would say your at 10.8. Anyway I run 93 pump and it runs fine if I was going balls out at the strip I would mix race gas with it. My cranking psi is 205. What makes mine live is it is in a lighter car, 4,400 rpm stall, heat crossovers blocked, no heat from a mechanical fuel pump, all sharp edges removed from the heads and piston, 30 total, with very cold plugs, and I sometimes run a sealed scoop to the carb. I really like have the CR high the pop out the exhaust sounds great fires up fast and idles great!! I would run the .039 gaskets but go with a cam that has about 244 at 50 if Hyd or about 250 if it's solid with. 108cl that should bleed psi. Good luck!
 
Agreed with the above but since your cam is 10*'s smaller, there may be an issue. I myself would run a thicker gasket @ .055 for starters. Fel-Pro makes such a gasket.

Your sure the heads cc in at 64-65 cc's?
 
My j's cc at 59. Your going to want a cam with at Least what I have 244 I would go in the 250 range with a 108 mines 110cl. Or as stated the thicker head gasket but even with the gasket I think you need more cam to be safe.
 
I have a buddy who has a old c10 with a 355 running about 10.9 CR ratio, not sure on the other specs. I would run a .54 head gasket.
 
Or you could run a methanol kit on it with some good 93' gas that 360 would be a little screamer. If you ran the methanol kit you could run a .28 head gasket it make it mean.
 
I had a 340 that was 11:1 w alluminum heads. I dont recall exact #s now but my dynamic compression was someplace around 9:1 and it ran fine on 93. Any more and It would have pinged. I think the short stroker was in my favor though. With .054 head gaskets you would be closer to 10.5:1
 
Yea, I had my machinist cc them after he did the valve job and milled them .030, he marked them all, majority is 65 with a few that were 64. I wanna stay with my cam cuz I already bought it and have it sittin in the motor. I just need to decide on my head gaskets so I can put my heads on and measure for my pushrods. Based on what I'm hearing I think I might go with a .055" head gasket and go from there.I definitely learned the hard way on this build, for the time, money, and effort I spent on building the iron heads, I could have just bought a set of aluminum heads and been done with it, o well live and learn I guess.
 
Which pistons are you running? the 116 or 405? Pretty big difference in valve reliefs there...and that extra 5cc could make a noticeable difference in static CR. BTW, when I ran the numbers you supplied, and using 5cc valve relieves, 0.005" under the deck, with the .039x4.15" gasket, I came up with 10.5:1...either way, it is kinda high for static, and the smaller cam...but a modest timing curve, proper setup, correct stall and gearing to take advantage of the cam, and you should be OK, but using a thicker gasket would drop the same combo mentioned to about 10.1:1...hmmm.

Assuming the 405 model pistons with 10cc of valve reliefs would further drop it to 9.6:1...
 
...don't be so hard on yourself...read a few threads. You'd find many folks strongly recommend not running aluminum heads OOTB as the seats are often not very well done, the springs aren't installed to consistent heights, and a few other things. In short, by the time you take the castings, have them looked at, tweaked, and reassembled, you've added a couple hundred to the $1500 already spent.
 
The pistons have the 5cc valve reliefs. So I'm thinking the .055" head gaskets and 100 octane to start and tweak it from there.
 
I bought used eddys for 1000 had them checked over had about 1200 in them and love them but just my 2 cents.
 
I don,t understand why some guys mill the crap out of the heads and then have to use a thick head gasket. A .003"-.005" clean up cut is all that is necessary using a .022" head gasket. Both MP and Cometic make a .022" head gasket. the Cometic has an advantage of having layers. That means it can be used with alloy heads. Our '66 'Cuda runs 11:31 @ 117m.p.h. and is 100% street legal. We use C10 only at the track. To solve your issue using your setup, use the thick gasket. Good luck
 
In this case I'd bet the heads were already cut once. I have never seen a 65cc chamber that didn't have a bunch more than .030 to get them there.
 
The above mention on the aluminum heads. You'll spend a bit more on the check out. Prices vary by area. Add it all up and the iron heads ported are cheaper with better flow but there probably at there max at that point.

Speed costs.
 
rumblefish360 said:
The above mention on the aluminum heads. You'll spend a bit more on the check out. Prices vary by area. Add it all up and the iron heads ported are cheaper with better flow but there probably at there max at that point.

Speed costs.
Click to expand...


No kidding I'm was in the same boat with mine but I have aluminum heads cause the engine builder that I have said that spending the money now for aluminum heads and intake will save a lot of hassle and headaches further down the road

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I was running 2.02 J head stock port. It was a 9.8-1 - 360 engine. The move to the Edelbrock heads was a positive one. The car did pick up well and the aluminum heads still have a higher ceiling over the J heads. Well or near fully ported J heads could have been flowing better than the Edelbrocks but that would have been pretty much it for them.

The edel's can be ported father out. A better bet for myself in the long run.
You can still run 11's with well done iron heads and engine/car combo.
 
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