compression ?
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Re: compression ? (kingdavidrules)
http://www.vettenet.org has a enginesize and compression calculator under assorted automotive info then click on engine size
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Racer
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From: bklyn ny
Re: compression ? (Guru_4_hire)
that is fabulous. although i dont really know how to answer most of the questions :confused: :lol: how do i find out my stroke length? chamber in cc`s , piston dome in cc`s and gasket thickness ? i know its alot to ask but this info will be very helpfull . p.s thanks for the great website tip.
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From: Hoosier
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Re: compression ? (kingdavidrules)
A compression tester will get you there and/or if you don't know the history of the engine you'll have to pull the heads and take the measurements.
[Modified by AlwaysWave, 7:36 AM 8/29/2002]
[Modified by AlwaysWave, 7:36 AM 8/29/2002]
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Re: compression ? (kingdavidrules)
Well, you're pretty much in a tough spot.
We know the displacement of your engine (350 bored 0.060 over) but that's about it. To get the rest of the stuff you need to know:
Pistons. Most pistons have a compression rating for a given head cc. For example, they might say that they're 9.8:1 with a 64cc head. I'm not sure what gasket thickness they assume there.
Heads: What casting # do you have? Are they aftermarket? Either way, there should be enough identifying characteristics in the way of casting marks & stampings to ID them. But then you don't know if they've been milled, so you'll just have to assume they're the base cc value.
Gasket thickeness. Hmmm....I'd check a Summit Catalog and see what 'normal' thicknesses are. I'm thinking in the 0.030 range is pretty common.
Doing a compression check won't get you there because of valve overlap. It's quite possible that an engine with a higher compression ratio will have a lower test compression if it has a bigger cam with longer duration.
Hope that helps somewhat.
Dave
We know the displacement of your engine (350 bored 0.060 over) but that's about it. To get the rest of the stuff you need to know:
Pistons. Most pistons have a compression rating for a given head cc. For example, they might say that they're 9.8:1 with a 64cc head. I'm not sure what gasket thickness they assume there.
Heads: What casting # do you have? Are they aftermarket? Either way, there should be enough identifying characteristics in the way of casting marks & stampings to ID them. But then you don't know if they've been milled, so you'll just have to assume they're the base cc value.
Gasket thickeness. Hmmm....I'd check a Summit Catalog and see what 'normal' thicknesses are. I'm thinking in the 0.030 range is pretty common.
Doing a compression check won't get you there because of valve overlap. It's quite possible that an engine with a higher compression ratio will have a lower test compression if it has a bigger cam with longer duration.
Hope that helps somewhat.
Dave
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From: Des Moines Iowa
Re: compression ? (ddecart)
Dave is absolutely correct! If you need to be dead on in your numbers, then really only way is to pull a head and have the head cc'd for chamber size, and measure block for deck height, and know what compressed thickness of head gasket you are using. Head gaskets can run from .017" steel shim to .040", or even more if you want/need thicker gasket to reduce compression ratio. Generally the thinner the head gasket, the better to reduce the 'quench' area between piston and head, as smaller quench area = better movement of air and gases which = more complete combustion which = more power and better economy.
Having said all of that............suggest you get your hands on issue of chevy high performance magazine, maybe August, Sept, or Oct. issue, can't remember for sure, but they had a great article regarding performance and compression ratios and how to pick a camshaft to maximise your current compression ratio.
Having said all of that............suggest you get your hands on issue of chevy high performance magazine, maybe August, Sept, or Oct. issue, can't remember for sure, but they had a great article regarding performance and compression ratios and how to pick a camshaft to maximise your current compression ratio.
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From: bklyn ny
Re: compression ? (ddecart)
this is all the info i could find out about the engine . its a 350 bored .60 over ( i was told to a 383), dart 2 heads , crane "hot " cam , weiland intake , holley 750 custom built carb. its a gm engine ( GM stamped ) but i was also told it was a crate engine . the guy who had all the work done didnt do the work , just paid for it and couldnt find the reciept which showed what was done or in the engine. thanks for the help.
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Re: compression ? (kingdavidrules)
Hmmm...your heads are easy if they're Dart. There should be some numbers cast into the head under the valve cover. You can call Dart and they can help you out with ID-ing them.
The pistons are a big mystery though. You're pretty well screwed unless you can find out what they are.
The pistons are a big mystery though. You're pretty well screwed unless you can find out what they are.
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From: bklyn ny
Re: compression ? (Matt Gruber)
im having some difficulty diagnosing a problem . at 1000-3500 rpm the car drives fine . when i go over 4000 rpm the gauge buggs out ( going past redline to 4k like a sesaw). at the same time i feel the car bogg , i have loss of continuous power , and at times it feels like the car will shut off. it got really bad yesterday when the car was in park , the rpm gauge went up to 3000 and back down to 1000 back and forth . my carb is fresh . im thinking my worst case scenario is timing chain or balancer .at some point someone is going to ask me about the engine in "detail" and thats the way i want to tell them. i might need to know for upgrade purposes. i might be totally out of my mind and it could be a minor adjustment on the distributor. to tell you the truth , the only thing i know is that my shark doesnt run the way she did last week .