compression - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GREASEMONKEY72 · 01-16-2007, 12:15 AM

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 · 01-16-2007, 12:27 AM

ttt

GREASEMONKEY72 · 01-16-2007, 12:52 AM

thanks Boise69

Boise69 · 01-16-2007, 01:06 AM

Quote:

Originally Posted by GREASEMONKEY72

thanks Boise69

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

skchevota · 01-16-2007, 01:11 AM

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 · 01-16-2007, 01:13 AM

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 · 01-16-2007, 01:59 AM

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 · 01-16-2007, 08:02 AM

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

GREASEMONKEY72 · 01-16-2007, 08:49 PM

thanks jbon64

chevyc1068 · 01-16-2007, 11:07 PM

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** · 01-17-2007, 12:11 AM

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

GREASEMONKEY72 · 01-17-2007, 04:08 AM

thanks alot guys i really appreciate it

-steven

msgross · 01-27-2007, 10:06 PM

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 · 01-28-2007, 01:17 AM

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

01-16-2007, 12:15 AM	#1
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	compression 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 __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME Last edited by GREASEMONKEY72; 01-16-2007 at 12:16 AM.

01-16-2007, 12:27 AM	#2
Boise69 The Hammer Man Join Date: Oct 2006 Location: Wilmington, NC Posts: 864	Re: compression ttt __________________ Boise69. Bought in Boise ID and its a '69 ___________________________________________ 1969 Chevy C-10 SWB 350/400 - drivable project www.americanhammer.com 2013 MBZ Sprinter customized 2005 MBZ Sprinter Van 2004 Land Rover Discovery 2001 Yamaha Road Star 1997 MBZ E420 1989 Ferrari Mondial T

01-16-2007, 12:52 AM	#3
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: compression thanks Boise69 __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

01-16-2007, 01:11 AM	#5
skchevota Registered User Join Date: Oct 2006 Location: Evans, Colorado Posts: 530	Re: compression 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

01-16-2007, 01:13 AM	#6
wheels67 Registered User Join Date: Dec 2006 Location: southern Utah Posts: 103	Re: compression 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.

01-16-2007, 01:59 AM	#7
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: compression 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 __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

01-16-2007, 08:02 AM	#8
jbon64 Registered User Join Date: Jan 2006 Location: sidney , illinois Posts: 312	Re: compression i did a rebuild last year and did a compression test , the average was 120psi per cylinder __________________ hey.....smell my finger 64 nova wagon , 63 nova convertible

01-16-2007, 08:49 PM	#9
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: compression thanks jbon64 __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

01-16-2007, 11:07 PM	#10
chevyc1068 Registered User Join Date: Oct 2006 Location: Murdock, Kansas Posts: 147	Re: compression 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. __________________ 1968 C-10 longbed, 307 V8, 4spd- currently under construction Last edited by chevyc1068; 01-16-2007 at 11:07 PM.

01-17-2007, 12:11 AM	#11
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: compression My GMC service manual from 1969 says 150 lbs for all v-8s also. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

01-17-2007, 04:08 AM	#12
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: compression thanks alot guys i really appreciate it -steven __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

01-27-2007, 10:06 PM	#13
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Re: compression 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? __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer"

01-28-2007, 01:17 AM	#14
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: compression 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 __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.