I have a 406 with an unknown cam and I think fuelie heads. I would like to put my supercharger on it, but I'm not sure of the compression. how would I find out what the compression of the engine is, so I would know if it is safe to run the supercharger or not? Thanks for any help

 

Anyone?

 

Get a compression tester. They measure in PSI, but I'm sure there's a formula out there to convert it to the ratio.

 

In short, there is not an easy way. you can take a guess but that would only be a guess.

The only real way is to pull the heads & CC the motor. you can take a guess if you know what piston is in it & you get the head volume from the casting number.

the problem with using the pressure gauge is that there are too many variables. the valve stems seals could be leaking, the gauge could be a bit wrong, the barometric pressure coudl be low that day, a ton of them.



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Bob Wooten
71 Camaro, 91 EFI
r71chevy@earthlink.net
www.r71camaro.homestead.com
<><

 

you can CC the motor with out pulling the heads, Ive seen pics on how they do it on drag cars with a huge syringe and push it in the plug while the piston is at TDC and then at BDC how they get the fluid in the top of the head portion since the plug is at the bottom edge and they are at an angle is a good question.

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'87 Monte Carlo SS,with '89 IROC 350,700 trans, blew up 3.73 posi stuck with crappy 2.73's neeed gears! hooker headers, flowmaster 2 1/2" exhaust true dualls, recently installed a set of alum vette heads 58cc, new cam for a paxton, recently installed paxton, OMG need a posi bad. So if anyone knows where a buick GN 8.5" rear is let me know.

 

If i am not mistaken that is called "pumping" & I thought that this only checked the volume of the engine to ensure that people were not running 700" motors in classes that were size-weight-PA limited.

maybe i am confused, happens quite often.

BW

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Bob Wooten
71 Camaro, 91 EFI
r71chevy@earthlink.net
www.r71camaro.homestead.com
<><

 

ok, maybe I misread it, its been a while, would make more sense to do that cause it was for tech and Im sure those guys know exactly what the compression ratio is before hand.

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'87 Monte Carlo SS,with '89 IROC 350,700 trans, blew up 3.73 posi stuck with crappy 2.73's neeed gears! hooker headers, flowmaster 2 1/2" exhaust true dualls, recently installed a set of alum vette heads 58cc, new cam for a paxton, recently installed paxton, OMG need a posi bad. So if anyone knows where a buick GN 8.5" rear is let me know.

 

Go to KB pistons website they have a formula. but your gonna need the cc of your pistons (check out what theirs are I think the flat tops with 4 valve reliefs are abotu 5.5cc) Also gasket diameter and depth and how much quench/deck height and head cc and probly some other numbers. But you can probly get a rough idea if you know what you got.