compression ratio for a 350 sbc??? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-24-2003, 01:29 PM
classic_chevy_guy's Avatar
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Question compression ratio for a 350 sbc???

would anybody know if 10.73:1 would be too much for a 350 sbc??? im not all that sure that the engine in my truck is stock cause from the look of it its got all new intake, and new heads and valve covers. for christmas all the money i get is going to my truck, for the truck im not sure if i wanna buy a rebuild kit and change the compression that way, or go out and individually buy everything. if im going to upgrade my compression, would i have to upgrade my heads to??? summit offers some really good engine rebuild kits, but im not sure if i want to upgrade the compression or the cam. if anybody can help just chime in at anytime.

thanks,
classic

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Old 10-24-2003, 01:40 PM
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Depends. If you are running a mild cam, that much compression will likely ping even with premium gas. However, if you have a fairly aggressive cam with a lot of overlap, you may get away with it. Just too many variables to say yes or no without more info on your plans. How did you decide on 10.73:1 compression? Why not 10.5 or 11? What is the purpose of the engine? Cruiser (high compression will cause more headaches than it is worth)? Street/Strip (requires more compression)? All out drag engine (crank in all the compression and other engine mods you can)?

It sounds to me that you want to rebuild your engine and upgrade performance at the same time. If so, spend a little time in research so you will achieve the best COMBINATION of components that will achieve your goal. Don't become enamored with a "hot" cam or pistons or intake manifold, etc., without considering the entire package.
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Old 10-24-2003, 02:48 PM
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Classic,

I drove my '66 Chevelle as a dailey driver for 2yrs. with a 355sbc 10.5-1 comp., 280H Cam, Camel Hump Heads, Edelbrock Performer RPM manifold running on 87 octane gasoline with no problems. But I certainly wouldn't want to run higher compression than that on a daily driver.
This was also good for 7.90's in the eight with 3.73 gears. Gas mileage wasn't the greatest, but who cares!
I'm like Willys36, if you are just looking for a street cruiser stick with lower compression.

James

Last edited by Chevymetal; 10-25-2003 at 10:04 PM.
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Old 10-25-2003, 07:32 PM
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i have an 11 to 1 350 in my daily driver with a mild roller cam runs great on the street with 93
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Old 10-25-2003, 09:28 PM
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I'm at 11:1 on my 400. I had to pollish my pistons, remove all of the sharp egdes and polish the combustion chambers in the heads. I run a 160o thermostat. I have a quick timing timing curve, in by 2,500. I have a 2,400 stall that gets it there right away. My cam has a 234o duration. All of this together helps keep it from pinging. I can only get 91 octane where I am.

Whatever you do don't raise your compression with a dome piston. Do it at the heads.
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Old 10-27-2003, 12:27 AM
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I agree, 11:1 is fine probably with a big cam (upwards of 280 adv dur.) and some nice intake and exhaust equipment. This will be a high-revving motor, so think also about the rods and pistons you're going to use. Depending on the combo you use, you could end up with something on the top side of 500 horse. 400-450 horse is really the practical cut-off point for reasonably priced parts and few mods... and pretty much the street in general. If you're not used to driving something like that, it could get away from you too. Make sure you're going to build something enjoyable!

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Old 10-27-2003, 11:44 AM
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i got 10.73:1 compression from the summit engine rebuild kit that they offer. i dont wanna run nitrous or a supercharger, so its just going to be a straight engine. i dont want any more than 550hp/550lb-ft, and so i think that 9.5:1 would be a better choice, but like i said earlier i dont know if my heads are stock or not. i guess when i get my chevelle going then i'll work on my 350, i guess you could say i was just wounderin what all upgrades and mods yall have made to yalls engines have worked.

thanks,
classic
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