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Author Topic:   comp. to lbs conversion
juni
Dirt Maniac

Total posts: 184
posted September 28, 2005 04:46 PM  
Is there a formula to figure how many lbs of cranking comp. is to ratio say 190 lbs cranking is 10.5to 1?

b4racing
Dirt Forum Champ
Total posts: 626
posted September 28, 2005 05:56 PM  
cranking compression has relitively low reflection of what your compression ratio is. It depends on cam lift ,duration ring seal, etc etc.

hoosierdaddy48
Dirt Maniac

Total posts: 107
posted September 28, 2005 10:45 PM  
so is it stupid when your track has a 170lb max compression rule?

ford5
Dirt Forum Champ
Total posts: 711
posted September 29, 2005 04:37 AM  
yep

mike9
Dirt Full Roller

Total posts: 72
posted September 29, 2005 07:00 AM  
totally stupid and unenforceable we used to have a 140 lb rule the intent being to keep em at 9 to 1
people figured out big cams lowered the cranking compression we had 11 to 1 motors cranking 140 while a mild cammed 9 to 1 that was sealed up good was cranking 170 so yes a very stupid rule

b4racing
Dirt Forum Champ
Total posts: 626
posted September 29, 2005 07:00 AM  
no it isn't stupid then you can get a big cam. Also your starter speed will have some to do with it

juni
Dirt Maniac

Total posts: 184
posted September 29, 2005 10:44 AM  
I'm building a 4 cylinder motor our rules read 190lbs . I was gonna overhaul the motor its bone stock. So i thought i would mill the head some . I guess i will pump and see what it is now and try and figure out how much i dare mill it.They have dqd car at this track for over 190 lbs that pumped okay the week before so i guess it don't matter it's a gamble.

b4racing
Dirt Forum Champ
Total posts: 626
posted September 29, 2005 01:31 PM  
do they have a cam rule?

hoosierdaddy48
Dirt Maniac

Total posts: 107
posted September 29, 2005 03:33 PM  
there is a cam rule at our track,.500 max, must be hydraulic

b4racing
Dirt Forum Champ
Total posts: 626
posted September 29, 2005 04:05 PM  
I would give schnieder cams a call talk to Jerry and have your exact rules car weight track size and he will set you up.;.

James Ott
Dirt Maniac

Total posts: 131
posted September 29, 2005 05:42 PM  
Heck I wish our rules were that simple!

Sidebite252
Dirt Forum Racer

Total posts: 98
posted October 07, 2005 12:01 PM  
We've check a lot of motors for psi from the cylinder on motors ranging from 10 to 1 through almost 14 to 1. Duration, lift, temperature (hot vs. cold) and I believe mostly overlap of the cam affect this a lot. Hard to make sense of a hard psi per cylinder rule.

juliaferrell
Dirt Freak

Total posts: 370
posted October 07, 2005 01:33 PM  
bsr racing has a calculator based on dynamic compression ect...A cranking compression rule is a joke...

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