Compression Test Results.. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

LandonL · 06-21-2010, 04:14 PM

Alright, with the engine @ operating temperature all plugs removed, I tested the compression. This is kind of in conjunction with this thread -->http://67-72chevytrucks.com/vboard/s...d.php?t=407911

First of all, does anyone know the correct compression for an inline 6?
My results were:
1st---90PSI
2nd--90PSI
3rd--91PSI
4th--91PSI
5th--91PSI
6th--89-90ishPSI

Hopefully you guys will be able to tell me something.

LandonL · 06-21-2010, 04:58 PM

Does anyone know the correct compression numbers? Im hoping I don't have to do a rebuild

GASoline71 · 06-21-2010, 05:16 PM

That is very low for all cylinders. Was the gauge seated well enough in the plug hole? How many "pulses" did you let the gauge take to get that reading?

Good compression should be around 140 to 150. Decent will be around 120...

Gary

Gary

LandonL · 06-21-2010, 05:19 PM

Screwed all the way in, with about 5 bumps. I had the ingition coil wire grounded as well. Any idea what the problem could be??

fixit-p · 06-21-2010, 05:23 PM

Did you hold the throttle wide open?

LandonL · 06-21-2010, 05:28 PM

Pedal to the floor the whole time.

LandonL · 06-21-2010, 05:36 PM

Okay, my helper just told me not pedal to the floor, she had it about halfway..Could that have caused it?
(Never using my mom as a helper again lol)

Scott Webster · 06-21-2010, 05:49 PM

I've never used the throttle when doing a compression test.

LandonL · 06-21-2010, 06:12 PM

Alright pedal to the floor didn't make a difference, I shot a little oil in the the plug hole to see if the rings were worn, it didn't increase. So it must be leaking somewhere correct?

junkyardjohn · 06-21-2010, 06:21 PM

Quote:

Originally Posted by LandonL

Okay, my helper just told me not pedal to the floor, she had it about halfway..Could that have caused it?
(Never using my mom as a helper again lol)

FOR GODS SAKE.. DON'T LET HER READ THIS... TRUST ME.. YOU'RE GONNA NEED HER HELP PLENTY IN THE FUTURE.

JOHN

LandonL · 06-21-2010, 06:27 PM

Just wish I knew what the problem was.

trusty72 · 06-21-2010, 06:36 PM

that is low but since they all are close its either the gauge or maybe its just a characteristic of those straight 6 engines. what problems are u having?

trusty72 · 06-21-2010, 06:41 PM

i see i read the other thread. atf or marvel down the carb while running, a good tune up, new elctronics in the dist. and drive it is what i would do. and prob clean the carb, recent rebuild doesnt mean a lot.

LandonL · 06-21-2010, 06:59 PM

I was going to try the ATF. By good tune up what all do you think should be done? I was planning on doing the IGNITOR II, and I was gonna do another rebuild on the carb. The gauge was a loaner tools from a brand new Oreilly's, the gauge was never checked out before me.

GASoline71 · 06-21-2010, 09:19 PM

43 years old... unrebuilt engine... is just plain ol' tired. Prolly needs a re-ring at the least. Or a full on rebuild.

How many miles on this engine? 200,000?

Gary

LandonL · 06-21-2010, 09:24 PM

Only 82k, was my g. grandpa's.

trusty72 · 06-21-2010, 09:39 PM

u never really know what was done to it in the past. a good tune up would be plugs, wires, cap, rotor, check out carb, and the ignitor 2 is a great idea. these are things your gonna buy if you rebuild or not, so what do you have to lose?

'72customdeluxe · 06-21-2010, 09:45 PM

Some fresh rotella 10w-30 and beating the tar out of it for an extended length of time might help. 80000 miles isn't extremely high. But it might need a rebuild

LandonL · 06-21-2010, 09:49 PM

Quote:

Originally Posted by trusty72

u never really know what was done to it in the past. a good tune up would be plugs, wires, cap, rotor, check out carb, and the ignitor 2 is a great idea. these are things your gonna buy if you rebuild or not, so what do you have to lose?

I have to lose money

Plugs & Wires have been recently done, but I think I might upgrade a MSD kit. Im thinking on one of the offenhauser intakes, what carb would be best 4bbl or 2bbl and how many CFM?

06-21-2010, 04:14 PM	#1
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Compression Test Results.. Alright, with the engine @ operating temperature all plugs removed, I tested the compression. This is kind of in conjunction with this thread -->http://67-72chevytrucks.com/vboard/s...d.php?t=407911 First of all, does anyone know the correct compression for an inline 6? My results were: 1st---90PSI 2nd--90PSI 3rd--91PSI 4th--91PSI 5th--91PSI 6th--89-90ishPSI Hopefully you guys will be able to tell me something. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 04:58 PM	#2
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Does anyone know the correct compression numbers? Im hoping I don't have to do a rebuild __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 05:19 PM	#4
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Screwed all the way in, with about 5 bumps. I had the ingition coil wire grounded as well. Any idea what the problem could be?? __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640 Last edited by LandonL; 06-21-2010 at 05:21 PM.

06-21-2010, 05:28 PM	#6
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Pedal to the floor the whole time. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 05:36 PM	#7
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Okay, my helper just told me not pedal to the floor, she had it about halfway..Could that have caused it? (Never using my mom as a helper again lol) __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640 Last edited by LandonL; 06-21-2010 at 05:36 PM.

06-21-2010, 05:49 PM	#8
Scott Webster Sheetmetal Psycho Join Date: May 2005 Location: athens PA Posts: 515	Re: Compression Test Results.. I've never used the throttle when doing a compression test. __________________ I didn't say you were stupid, but I was thinking it... I need a check up from the neck up! Project "Rigginstine's Monster" 1971 C-10 longbed 355/4spd Future mods: 67 front clip Webby's Rigginations - where everything has potential!

06-21-2010, 06:12 PM	#9
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Alright pedal to the floor didn't make a difference, I shot a little oil in the the plug hole to see if the rings were worn, it didn't increase. So it must be leaking somewhere correct? __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 06:27 PM	#11
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Just wish I knew what the problem was. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 06:36 PM	#12
trusty72 Registered User Join Date: May 2010 Location: ft smith arkansas Posts: 131	Re: Compression Test Results.. that is low but since they all are close its either the gauge or maybe its just a characteristic of those straight 6 engines. what problems are u having? __________________ 1972 super cheyenne 1970 Suburb

06-21-2010, 06:41 PM	#13
trusty72 Registered User Join Date: May 2010 Location: ft smith arkansas Posts: 131	Re: Compression Test Results.. i see i read the other thread. atf or marvel down the carb while running, a good tune up, new elctronics in the dist. and drive it is what i would do. and prob clean the carb, recent rebuild doesnt mean a lot. __________________ 1972 super cheyenne 1970 Suburb

06-21-2010, 06:59 PM	#14
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. I was going to try the ATF. By good tune up what all do you think should be done? I was planning on doing the IGNITOR II, and I was gonna do another rebuild on the carb. The gauge was a loaner tools from a brand new Oreilly's, the gauge was never checked out before me. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 09:24 PM	#16
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Compression Test Results.. Only 82k, was my g. grandpa's. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

06-21-2010, 09:39 PM	#17
trusty72 Registered User Join Date: May 2010 Location: ft smith arkansas Posts: 131	Re: Compression Test Results.. u never really know what was done to it in the past. a good tune up would be plugs, wires, cap, rotor, check out carb, and the ignitor 2 is a great idea. these are things your gonna buy if you rebuild or not, so what do you have to lose? __________________ 1972 super cheyenne 1970 Suburb

06-21-2010, 09:45 PM	#18
'72customdeluxe Registered User Join Date: Jan 2008 Location: Tejas Posts: 691	Re: Compression Test Results.. Some fresh rotella 10w-30 and beating the tar out of it for an extended length of time might help. 80000 miles isn't extremely high. But it might need a rebuild __________________ '72 cheyenne super step, '05 long bed gmc



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.