Re: 440 compression check
[Re: 73bbroadrunner]
#2250624
02/09/17 08:56 PM
02/09/17 08:56 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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agreed, that is very high. It'd be nice if you had a borescope to see whats in there. My HF unit was not cheap but it has came in very handy/saved my bacon several times.
live every 24 hour block of time like it's your last day on earth
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Re: 440 compression check
[Re: 73bbroadrunner]
#2250703
02/09/17 11:06 PM
02/09/17 11:06 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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If it has been sitting for a while, it's very possible the lifters are no longer pumped up, which makes the duration at the valve much shorter....... And the compression test will read high. If the 250psi had been observed just after the motor was run and warmed up, and you knew the gauge was accurate....... Then I'd say the cam was like a tooth off(advanced), or the motor is way over 10:1cr(as in waaaaaaaaaaay over).
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: 440 compression check
[Re: BSB67]
#2250720
02/09/17 11:30 PM
02/09/17 11:30 PM
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Joined: Apr 2012
Posts: 1,235 Phoenix, AZ
Jjs72D
Deep in the closet
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Deep in the closet
Joined: Apr 2012
Posts: 1,235
Phoenix, AZ
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check the gauge, or try another gauge. Yeah, I agree. I've seen them be in error before. Has anyone ever seen an engine with these cylinder numbers run on even 93 octane unleaded? It seems to me an engine with 250psi would need over 100 octane to avoid knocking like 20 bill collectors at the door.
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Re: 440 compression check
[Re: Jjs72D]
#2250822
02/10/17 01:54 AM
02/10/17 01:54 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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agreed, sumpin ain't right (& if it is, it is race gas city). Keep after it & keep us posted.
live every 24 hour block of time like it's your last day on earth
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Re: 440 compression check
[Re: 73bbroadrunner]
#2250998
02/10/17 01:29 PM
02/10/17 01:29 PM
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Joined: Jun 2006
Posts: 5,163 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,163
CT
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That sounds like almost 100 PSI too much for that CR and cam, if you told me 150-175 I'd say it sounds right. That sounds like a 13.5:1 engine
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: 440 compression check
[Re: 73bbroadrunner]
#2251025
02/10/17 02:08 PM
02/10/17 02:08 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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I don't know what kinds of parts the op has laying around, but if the motor has an adjustable valvetrain, or the op has some rockers kicking around, and some solid lifters..... You could pull two hyd lifters out, swap in two solids, adjust lash to about .003 lash, retest.
If it still tests stupid high(and you're absolutely sure the gauge is accurate.....then IMO, something needs to come apart to see what's what.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: 440 compression check
[Re: fast68plymouth]
#2251098
02/10/17 04:29 PM
02/10/17 04:29 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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I agree with Fast68.
You are doing the compression check right, with all the plugs out.
You say average. What is the spread? Have you gotten the same result on more than one cylinder?
R.
Last edited by dogdays; 02/10/17 04:33 PM.
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