Kev70ss

iTrader: (4)

I just bought a set of sportsman II heads, since the stud was pulling out of my camel humps. The engine is a 350 either bored .030 or .060 i cant remember which one. I want to achieve around 11:1 compression. My question is do you use the gasket bore exactly the same as the engine bore? and also do stock size pushrods work or do i need longer ones with these heads?

fast01

iTrader: (16)

Gonna need some more info to get you on the right track to 11:1 compression. Most notably, what piston are you running, flat top, dome, dish? Also, do you know the volume (cc) of the valve reliefs, dome or dish? As far as gasket bore, no, it won't be the same as the block. It'll be a bit larger. I think the Fel Pro's are 4.166". Stock push rods may work, but there are other factors besides the heads that come into play there. You really need to measure for proper length. You can get pushrod length checking tools from any of your favorite speed shops. They're not a big ticket item, $20 or so.

Kev70ss

iTrader: (4)

oh sorry i forgot to include that, my heads are 64cc and the pistons are flat tops with 4 valve reliefs. Would a 4.100 bore head gasket work

ZONES89RS

iTrader: (25)

The gasket will work, but you are looking at about 10 to 1 or so compression, maybe 10.3. Which is fine if you are going to use 93 octane. Any more than 10.5 to 1 and you will have detonation usually with iron heads.

fast01

iTrader: (16)

With that combo, I'm thinking you're under 10:1. Probably more in the 9.6:1 range. To get 11:1 you'll need chambers in the 55cc range with a thin gasket. Not going to happen and as stated before, unless you're running race gas you're going to run into detonation problems with cast iron heads.

Kev70ss

iTrader: (4)

I'm using a virtual engine calculator, but I keep getting I different number form you guys can you tell me if i made a mistake somewhere? I entered 4.060 for the bore size 3.48 for the stroke and for the head volume i took the 64cc and added 6cc for the valve reliefs on the pistons and 4cc for the gasket. Then for the gasket bore I used a 4.1 inch and the last criteria was gasket+deck in inches. I wasnt sure about that one so i entered the gasket thickness of 0.018 and I keep coming up with 10.47comp, can you tell me if I messed up somewhere?

fast01

iTrader: (16)

Everything looks good with 2 exceptions. The valve reliefs are most likely a little bit bigger, maybe 7-8cc's. The big number you left out is how far down the pistons are in the bore. Unless the block has been decked, they are probably .020"-.025" down in the hole and most standard head gaskets are around .040". That'll give you .060"-.065" for the entry you were not sure about. Punch those numbers in and you should come up with somewhere around 9.6 or 9.7:1.

Kev70ss

iTrader: (4)

thanks for the help I punched those numbers in using the -8cc for the valve clearance and 0.025 for the deck height. Im gonna get 4.1bore x 0.015 thickness gaskets and that gave me a 10.1:1-10.2:1 comp which should be good for pump gas

7.0 camaro

ive used those 1094 gaskets for years. never had a problem. they say you gain more power through more quench than the compression ration increase

fast01

iTrader: (16)

That sounds about right with a .015" gasket. That's a little on the high side with iron heads, so watch your tune up and you'll be fine.

The optimized quench is a big plus, especially in the area of detonation resistance, which will only help in this case.

Please double check the deck height while the engine's all broken down just to be safe. Without knowing the compression height of the pistons or weather or not the deck has been cut you can't be sure of the deck height. The .020"-.025" I used before is a general number and to assume here could cause severe engine damage. You really don't want to go any tighter than about .035" with the quench (deck height+gasket thickness=quench).

Kev70ss

iTrader: (4)

Thats a good idea, the engine builder just gave me an invoice so I dont have any specs on it. Ill call them up tomorrow and ask what their normal deck height is and how many cc's the pistons are, so i dont blow up my engine