Compression: How bad?
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
I think I'll pull a head off, hopefully Tuesday. With that bad of a compression loss, something is messed up in there. Oh well, this might work out, if it needs new pistons maybe I have some flat tops in and run propane. Gas is suppose to get to $5 a gallon this summer.
RW: that's exactly what I was thinking, the #90 jets should be so rich the motor should hardly run at all.
Sam
RW: that's exactly what I was thinking, the #90 jets should be so rich the motor should hardly run at all.
Sam
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
I think I'll pull a head off, hopefully Tuesday. With that bad of a compression loss, something is messed up in there. Oh well, this might work out, if it needs new pistons maybe I have some flat tops in and run propane. Gas is suppose to get to $5 a gallon this summer.
RW: that's exactly what I was thinking, the #90 jets should be so rich the motor should hardly run at all.
Sam
RW: that's exactly what I was thinking, the #90 jets should be so rich the motor should hardly run at all.
Sam
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
As far as i know, i've been running just regular 10% ethanol gas. Is is possible the passages for the main jets got plugged up?
Either way, we'll see what the damage is tomorrow.
Sam
Either way, we'll see what the damage is tomorrow.
Sam
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
I pulled a head off this mourning, and so far the pistons look ok. The problem looks like a massive intake leak, affecting the #2, 3 and 4 cylinders. We checked out the intake and it's warped badly.
Sam
Sam
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Look at the bores and see if there's scratches from broken rings. Broken ring lands can't be seen unless you pull the pistons. If the bores look OK, then the rings and lands probly are too. Might just be the warped intake and the heads casuing the lowered compression on those cylinders.
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
I sure hope so, i didn't look real close today. I'll check tomorrow, but either way, I think I'll pull it out and haul it back to the shop for an autopsy. The lifters were getting noisy too, so something else it is out of sorts with that engine. I'm not sure I'd trust it with those pistons in it either, they've been through a lot.
Sam
Sam
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Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
Today worked out pretty well, I looked at the bores, no scratches at all, just nice clean hone lines. So I dropped the head off at the machinists and he said it didn't look very bad, but he is going to take a closer look at it tomorrow. He said most likely the cylinder with low compression was just getting washed down with gas and oil.
I also picked up a different intake for the motor, it's an old offenhauser 4bbl aluminum, and it will check it for warping tomorrow. It even came with a carb, all for $80!
Sam
I also picked up a different intake for the motor, it's an old offenhauser 4bbl aluminum, and it will check it for warping tomorrow. It even came with a carb, all for $80!
Sam
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
I finally got the engine back together and running today! It was still misfiring bad though, I wasn't very happy with it, until by chance I pulled off a plug wire and looked inside the boot. To my surprise, I couldn't see any metal in there! Turns out 6 or the 8 plug wires had pulled back into the boots and weren't touching the contacts inside the cap! I pulled them back down and plugged them back in, and it was amazing the difference it makes! It's still not perfect, but it is much better than it was.
Sam
Sam
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
What are you setting your timing at? Now what size of carb jets are you now running? And have you reset the carb air/fuel idel jets? Also have you checked your spark plug color for a lean or rich conditions?
Orich
Orich
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
Right now I've decided to send the truck to a mechanic, I found a guy with an AFR meter who can tune it in for me. But I'm running 15* of timing and I haven't touched the carb, it's just the way it came out of the box.
Sam
Sam
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
Well, I took the truck to a mechanic and I think he found another issue, the intake is sitting on the engine crooked, he showed it to me and you can see the difference side to side. It looks like one head got shaved more than the other, or one head was shaved on the intake side at some point. He hooked it up to a smoke machine and ran some other tests and said it is sealing, but the question is, for how long?
Sam
Sam
If it aint broke, don't fix it.