compression

[GREASEMONKEY72]

im getting ready to do a compression test and i was wondering what the numbers were originaly on a 72 sb350 4b?? im also getting ready to change the valve guides to stop it from burning oil and fouling plugs, is there any tips or advice anybody has to offer??

thanks in advance

-steven

[Boise69]

ttt

[GREASEMONKEY72]

thanks Boise69

[Boise69]

Originally Posted by GREASEMONKEY72

thanks Boise69

hey i have the same questions and situation, so i'll be watching this one

[skchevota]

dont know on compresion, probeblt around 150psi, if you are changing you valve guides you need to pull the heads, if you are changing the valve seals you can hook up an air hose to your spark plug hole from an air compresor to hold up the valve while you remove the spring. I like to bring the piston to the top as well as a fail safe so you dont drop the valve in the cylinder. I also recomend the umbrella seals, insted of the o rings

[wheels67]

120 to 150 psi is my thinking. Add oil thru spark plug and retest if it jumps 10psi you have bad rings. You prolly know this tho.lol Im not sure Id just do the guides.....proballt time for a more complete check 2cents delivered.

[GREASEMONKEY72]

we are going to change the seals but kepp calling them valve guides i dont why and i have the house to hook up to the plug hole air in the cylinder and thanks for the tip on the umbrella seals and thanks also for the comp numbers and ill let you guys know what happens and ill try to take pictures and post them for reference if anybody should need them

-steven

[jbon64]

i did a rebuild last year and did a compression test , the average was 120psi per cylinder

[GREASEMONKEY72]

thanks jbon64

[chevyc1068]

I have a Haynes manual and it says 150 psi for all V8s. I did a compression test on my old 307 that has 100k miles on it without any rebuild and got a little over 150, about 155-160. But it probably has a lot of carbon build up in it. Although I remember reading somewhere that a good street engine should make about 180, but I think that that was in one of David Vizard's books on how to build max performance sbc, so it might be a little high for a regular old engine.

Just remember to keep the throttle wide open while doing the test or it won't be able to suck as much air. Hope this helps.

[WorkinLonghorn]

My GMC service manual from 1969 says 150 lbs for all v-8s also.

[GREASEMONKEY72]

thanks alot guys i really appreciate it


-steven

[msgross]

so how low is too low? I tested my 327 today and had from 129-149 average for the cylinders... I guess that it's ok then?

[GREASEMONKEY72]

well when i did mine the highest one was 155 and the lowest was 124 so its not perfect but its not horrible either but im gona do seafoam eventually and then do the test again and see how much of a difference there is