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Author Topic:   How Much Compression???
Speed Racer X
Member
posted December 08, 2002 08:01 PM
the more compression, the bigger cam you can run without killing the low end power. as long as you have the correct fuel, more is better. you'll also need a cooling system that is up to the task, a good balance job and a stout bottom end to keep all those extra ponies from trotting out the side of the block.

on another note, hypereutectics aren't the best choice for a 13:1 engine. lightweight forged pistons are the best alternative. my opinion.......

dirtracer14
Member
posted December 09, 2002 06:37 PM
Hey x thats sounds just like the motor we ran last year but on allky. It was a good motor and really likes the top end...i ran the thing around 8600 one night at a small track that i didnt have time to change gears so i ran the trans in 3rd instead of 4th. The motor just ran like a raped ...well you know, untill i tore 3rd out of the trans and was done. I think the comp was around 13.5 to 1


awkwardjeff
Member
posted December 10, 2002 01:40 AM
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[This message has been edited by awkwardjeff (edited December 11, 2002).]

RentOcrew
Member
posted December 10, 2002 04:39 AM
Hey AwkwardJeff what about a 6in rod in a 2350lb car? Now there is a limitation on fuel and compression. Pump gas only (93 octane) and also no more than 10.5 with flat tops.

I like the way you explain things, it helps me understand this alot better. Thanks

outlawstock17
Member
posted December 10, 2002 07:20 AM
awkwardjeff, i'm going to disagree....you can't physically fit a long enough rod in a 3.75 stroke small block chevy to achieve the ideal rod/stroke ratio(2.2:1) of an UNRESTRICTED engine. longer is always going to be better.

december's speedway illustrated has a dyno comparison on rod lengths conducted by david vizard that details what i'm saying. vizard says a RESTRICTED engine should have a rod/stroke ratio of around 1.9:1. a 5.7 rod, 302 chevy works out to 1.9:1. now you know why those suckers scream.

a longer rodded engine outperforms a shorter one of the same design every time from 2400 rpms and up. you're not going to be doing any competitive racing below 2400, so the longer the better. size does matter!

[This message has been edited by outlawstock17 (edited December 10, 2002).]

awkwardjeff
Member
posted December 10, 2002 10:03 AM
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[This message has been edited by awkwardjeff (edited December 11, 2002).]

outlawstock17
Member
posted December 10, 2002 03:16 PM
i don't have the patience to delve into this with a keyboard. i suggest you read the article and until then, i'll agree to disagree and move on. i'll stick to my guns, say longer is better and quote smokey yunick, "put the longest rod in it that will fit and go racing".


Earl Parker II
Member
posted December 10, 2002 04:09 PM
If anyone would like to compare the effect of long vs. short rods upon piston position at X crank angle, the go to www.parkercarburetion.com/calculators.html and download the Engine Analysis v. 2.0 calculator. If nothing else it will save a lot of calculator time.

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Earl Parker II
www.parkercarburetion.com
704.482.7588


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