I was wondering if anyone could give me any advice on how to lower the compression CHEAPLY on a 351c/399 stroker engine (built for the strip) that is supposed to be making 600hp thats in a 70 mach 1 that I'm planning to buy. It's got a 12.1 compression ratio and I'd like to be able to run pump gas due to 100plus octane fuel not being available in my area. The price of the car is quite good for the condition of the car itself but I'm worried I might be biting off more than I can chew with the motor if I'm going to have to stick a crapload of $ at it to make it more streetable. I'm not a seasoned mechanic so I don't have much experiance with the "black art" of engine configuration. Any and all feedback would be greatly appreciated!!!!
Pump gas in a 399 stroker?????
- Thread starter wantamach
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jerry S
New Member
you could get thicker cylinder head gaskets but I don't know if this will get you more than 1 point. I run 11:1 compression on 94 octane gas with no problems but I feel like I am pushing the envelope for a street car. 12:1, on the other hand, is just too much for a street car. You can either enlarge the combustion chambers on the cylinder heads or swap out the pistons. Ask a local shop which is cheaper. Or, you might find a used pair of heads with larger combustion chambers than what the car currently has at a swap meet or ebay and just swap heads.
pabear89
Active Member
I have a pair of open chamber heads that will drop it down for street use.
PM me for more info.
jerry s is right. a thicker head gasket would be very cheap and easy but you wont see much benefit. depending on what heads you are running that would be another option. if you are running the 4bbl heads swap for the 2bbl and you should see a good difference. also you could retard timing just a lil bit and that will also help. other than these suggestions you would have to do major surgery and replace pistons. do a combination if needed to get down around 10:1 and you should be plenty good with pump fuel
also for what its worth... im not sure if you are interested in changing rearend ratio but if you go for lower gears that would help too. my car has 10.5:1 with a 289 and it pinged with 3.50 rearend ratios, i picked up 4.30 ratios and it hasnt detonated sinse.
also if you know what the engine parts and specs are you can consult a compression calculator on the internet to kinda feel things out before purchase. you can see basically what difference in compression you will get with say, different gasket thickness and different chamber volume.
also for what its worth... im not sure if you are interested in changing rearend ratio but if you go for lower gears that would help too. my car has 10.5:1 with a 289 and it pinged with 3.50 rearend ratios, i picked up 4.30 ratios and it hasnt detonated sinse.
also if you know what the engine parts and specs are you can consult a compression calculator on the internet to kinda feel things out before purchase. you can see basically what difference in compression you will get with say, different gasket thickness and different chamber volume.
jerry S
New Member
according to the first post, this car is purpose built for the strip and is already pushing 600 hp. It sounds like it is anything but streetable and a bigger cam is only going to make that worse.
mrmustangman357
Member
- Feb 11, 2007
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do you have access to e85?
also a machine shop may be able to enlarge your heads, dependin on what you have
also a machine shop may be able to enlarge your heads, dependin on what you have
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