project engine bonneville
- Thread starter jlop3s91
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Depends. I built an honest 9.5 to 1 400 and it pinged and sufferred valve recession. Others run 10 to 1 and get away with it. You can science it out and get away with high compression by tailoring the cam, timing, carb etc, but I just take the easy way out and shoot for no more than 8 to 1 on a street motor. That way I can use a decent cam, stock timing and still burn cheap gas.
Before we decides on compression, get the engine code, casting number and julian code (date).
I will bet your engine is a 350.
Pontiac cast the blocks as early of June (IIRC) of the previous year, so a "67" date coded block could be in 68 car.
I will bet your engine is a 350.
Pontiac cast the blocks as early of June (IIRC) of the previous year, so a "67" date coded block could be in 68 car.
No, I would leave it alone if it runs well. If the previous owner went through the trouble of swapping the Edelbrock intake and Holley carb and roller rockers I'd bet they did a cam too. The 2 barrel valves aren't THAT small, certainly not a big difference on a street motor. Later 70's 400's had the small valves also. My only concern would be the compression, but if premium gas works with no pinging you would be in good shape. If you can't get rid of pinging then you could always swap later low compression heads with bigger valves to boot. You will love the classic Pontiac power.
I agree with Bonnewagon, just run it and gun it.
Compression has been proven to be 'listed" higher then "actual' compression.
Camshaft could also lower dynamic compression.
I had a 2v 350 motor in my 70 LeMans that snapped the oil pump drive tang on the dist drive. I shut the car off right away and saved the heads.
Had a low mile 400 block. Short story, put the bone stock "small vlave 350" heads on the 400, mild cam, edelbrock performer manifold (same as stock),qjet, headers, Pypes 2 1/2" X system with dynomax mufflers, a B&M 2000stall, th350 and 3.23 posi.
Drove the car for years on pump gas (87) as my daily driver and the 3800# car ran 13.80z.
Compression has been proven to be 'listed" higher then "actual' compression.
Camshaft could also lower dynamic compression.
I had a 2v 350 motor in my 70 LeMans that snapped the oil pump drive tang on the dist drive. I shut the car off right away and saved the heads.
Had a low mile 400 block. Short story, put the bone stock "small vlave 350" heads on the 400, mild cam, edelbrock performer manifold (same as stock),qjet, headers, Pypes 2 1/2" X system with dynomax mufflers, a B&M 2000stall, th350 and 3.23 posi.
Drove the car for years on pump gas (87) as my daily driver and the 3800# car ran 13.80z.
alright this is alot better than i expected ....everyones input has been extremely helpful ...i just got one final question hahah ...now this engine has been sitting for at least 4 years that i know of and what should i do to bring it back healthy again (turns over fairly easy)
i plan on getting all new gaskets but anything else
i plan on getting all new gaskets but anything else
Before you take anything apart, try getting it running and then evaluate. Do a tune-up, oil change, fine adjustments, fill with fresh gas. Do a compression test, oil pressure test, road test, and then decide what if anything it needs.
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