I bought some cast iron 58cc high performance heads from a place called Performance Chevy in AZ. Basically they are copy of the 305 torqurer heads. They are currently on my 305. I intend to build a 350 in the future and wondered if I could get away with using these on the 350. With dished pistons it would run 9:0-9:5 compression and with flat tops it would be 10:5-11:0. One thing I was wondering about is could I have the combustion chambers enlarged to maybe 62-64cc on the heads so I could use flat top pistons? It seems like there is plenty of area to work with. I have TPI so detonation on pump gas is a big concern. If they were aluminum I could get away with the extra compression. Any suggestions would be helpful.

[This message has been edited by IROC315 (edited September 15, 2001).]

 

IROC,

If you can keep the coolant temperature down, and don't get greedy with timing advance, you should be able to use the heads. Stock LT1 engines have 54.4cc chambers, and with flat-top pistons come out at just under 10.6:1 static compression, using 0.039" head gaskets, basically zero deck, and very shallow top ring depths.

I can run them on 89 octane fuel with maybe slightly reduced power and no detonation. At 91 octane, I notice little difference from 93 octane fuel.

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Later,
Vader
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Justice and Freedom will Prevail

 

you could try to get a thick head gasket. I think that felpro makes one that is .051 thick. That may help. Also you could try water wetter or a similar product to help transfer heat from your engine to your coolant faster. If you are going to build the engine yourself then talk to your machnist and see what he says. I would say you could run flat tops as long as your overall compression ratio is 9,9.5 to 1 without any problems.

 

I'm running the 305 heads on my 350 with dished pistons, around 9.5 to 1 compression and it runs great with 92 octane fuel, no detonation. It does run a lot hotter than the stock 305 that was in there so I switched my fan to a Black Magic electric fan and it seems to keep the temp reasonable, it still wants to climb on hot days when I'm stuck in traffic.

 

I might look into using flat-tops. Most of the companies tell you what the compression will be with the pistons they are selling. They list the different combustion chamber volumes to help pick the right piston. Another thing I forgot to mention is I am running Nitrous. I was told to definately try to keep the compression lower with nitrous so it won't detonate. I really hope to use these heads since they are almost new. I will probably be building the engine myself with my mechanic brother's help. He is running my old stock 305 heads on the 350 in his truck with flat tops with no problems. It runs kinda slow since they have tiny valves but he rebuilt the whole motor for less than $200 so you can't beat that.

 

i wouldnt use iron heads with that compression with the flat top pistons. aluminum would be ok, but the cast iron is gonna ping like a s.o.b., maybe if you filled with 93 octane and kept your timing down it would be ok.

 

I wouldnt even think about running a thick head gasket, it will only make matters worse since you will have no more quench area.

Why do you want to use flat top pistons? Theres lots of pistons out there, pick an appropriate one to get the compression you want.

 

I hope to reuse the gaskets I have. I have to look up the part number again but they are .043 thickness I think. They are the reusable steel shim or aluminum type. I don't have to use flat tops. It seems like it doesn't matter how you achieve a compression ratio. It can be with flat tops or the combustion chamber volume. I remember that 305 vs 350 shootout car craft had. They put the vortec heads on the dished piston 350 and got around 379 horses. The heads had been milled to 54 cc I think for the 305 they had them on. That kinda horsepower is all I need.

 

Head gaskets arent reuseable! I havent seen any marketed as reusable even if they did market them its total BS! Once you use them they form to fit and cannot reseal correctly most of them fall apart and have to be scraped off.

As far as the 58cc heads I use them. I have two 350's running them and they kick the bejesues out the the compression ratio.
Expect to run premimum fuel and to use octane booster on top of that if you want more timing advance. The only downfall of these heads is that they have small valves. This isnt really a problem for a street/strip idle to 6k application. So you should be fine.
If you were planning on circle track racing I would choose another type of head.
Good Luck!
SSC

 

Yeah, they were marketed as reusuable. After the heads are taken off the only thing that will probably remain is the steel part. I agree that they form a seal and it would be hard to use any gasket.

 

I thought I would pull this up again..I just got free rebuilt 350 short block 4 bolt main from my brother. It was rebuilt using flat tops. (the motor I mentioned above) The question I have is would this motor survive on 93 octane with octane booster? Its not going to be an everyday driver. I read in a chevy rebuild book about a bigger cam bleeding off too much compression. If that's possible that would be good. I think the higher compression would be great for a steet/strip car as long as I can keep it from detonating. I don't mean to drag this subject on. I just wanted to hear some more opinions.