LUVTruck.com

I have read many threads about compression, head gasket, ect. I did a compression test on my truck today and they came back as follows..
Starting at the front of the engine

1.75
2.72
3.70
4.68

I took out all 4 spark plugs, opened my choke all the way, disconnected coil and did each cylinder 3 times to come up with the average. Does anyone know what this could mean? Truck starts up very easy, runs, idles, but has a "pitter patter" miss. I've done a full tune up, oil change, ect.

Any info would be great.

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1974 Mikado 4x4 50,000 orig. miles

If you're sure your compression gauge is working well, I'd say the eng. is just worn out. Does it lack power? Does it use oil?

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OK, I'm over it. Where's the beer?

Yes it lacks power. The guage I was using was a rental from Auto Zone. I was afraid the engine was worn out. Bummer. I might just sell it for what I'm in it for.

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1974 Mikado 4x4 50,000 orig. miles

Either the guage is wrong or you were reading a scale that was not psi, an engine won't even run with less than 5psi compression.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

The "1.75" would mean "number 1 cylinder. 75 psi. Sorry 'bout that.

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1974 Mikado 4x4 50,000 orig. miles

What should it be at? I don't have my book with me to look it up.

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OK, I'm over it. Where's the beer?

compression on rebuilt engine should be around 140 to 150 depending on a number of factors.

if you are reading that low, it may be that you do have a bad engine.

what year and 2wd or 4wd?

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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

It is a '79 4x4. Book says 170 new, 119 "limit" with a variance of 8 or 9 psi

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1974 Mikado 4x4 50,000 orig. miles

You didn't say if the compression went up significantly after oiling the cylinders or if it smokes while running. If either one then I would suspect rings. If not, could be valves, are they adjusted to specs? If valves are adjusted properly then run a leakdown test, it should isolate the problem.
No smoke, no big wet compression change, there is a possibility you just need a valve job.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

It does smoke a bit, but it smells like fuel. I believe I need to adjust the valves, but not sure how to do it yet. I've been reading a lot of posts, but not sure if I'm ready to tackle that yet by myself. Seems real complicated. If my valves are not adjusted right, it could make it read that low? Maby there is still hope for the Luv!!

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1974 Mikado 4x4 50,000 orig. miles

Did you have someone hold the throttle wide open? You should do this while checking compression. If you really want to pinpoint a problem do a leak-down test. We don't do compression test on Sprint Cars or our airplanes, it's all done with leak-down testing.

http://en.wikipedia.org/wiki/Leak-down_tester

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Certified pilots, looking down on people since 1903.

Thanks luvrv8. I will do the leak down test soon, I hope. Work just picked up, so I'm super buisy right now. I put a wedge to hold open the choke. Should I have pushed in the gas peddel also?

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1974 Mikado 4x4 50,000 orig. miles

Throttle must be wide open for a compression test, with the engine at normal running temp, so the choke is automatically open, if you had to wedge the choke open sounds like the engine may have been cold. Looks like the readings weren't taken under the right conditions, if so they aren't reliable. A valve adjusted too tight could let a valve not close completely, more often they are too loose, are noisy & the engine won't produce full power.
Figure out how to adjust the valves, then re-run a compression test under the right test conditions, first dry, then with a squirt of oil in the cylinder & compare readings. A noticable difference dry to wet along with the smoke probably indicates rings. A leakdown test would be better, done right it can indicate the condition of the rings, each valve and the valve stem seals.
EDIT: look in "classifieds", there is a series 10 factory service manual for sale cheap, just what you need for info.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

I already have a series 9 service manual, but I'm still to scared to do something internal like that myself. I bribed my brother in law to come over and adjust valves for me. I told him I'd buy the UFC fights tonight. (I was gonna do it anyway!) I'll see if he can figure anything out. He's a good mechanic. I just hope it is something that doesn't involve a rebuild, cause if it is, I'm gonna have to sell her.

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1974 Mikado 4x4 50,000 orig. miles

Today we adjusted the valves, and timed her. WOW! What a difference. I even smoked the tires! Compression up to 90 psi, all the way around. Is that bad? It was missing real bad, but after I opened it up on the road, things just "cleared up". Now she's running smooth. After sitting for 10 years, I think it just needed to burn some gunk out.

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1974 Mikado 4x4 50,000 orig. miles

90 psi should be MINIMUM for most engines, but it's better than the numbers you had before. i would guess that you still have worn rings, but without being invasive or a leakdown test, it's hard to tell for sure...

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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

The rings could also be crudded up and do better with a little running. I have never used them, but there is a bunch of stuff that claims to help, Auto Rx, Marvel Mystery Oil, Rislone, or even a little ATF.

I did put in a can of Restore. The guy at Auto Zone said the stuff does work. I only have about 30 minutes of idling and maby 5 miles of driving, so it hasn't had a chance to work. But the miss that the Luv had is gone! There is still some old gas that I need to get out, and another oil change. I did an oil change when I first got it, and the oil is already BLACK. Must have been some really dirty oil. Just to give you an idea of how she ran before.. I could barely make it up the hill by my house, which isn't steep at all. Now, I went up it in 3rd, no problem, and then did a doughnut! She's really fun to drive.

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1974 Mikado 4x4 50,000 orig. miles

Wow I am having the same issues with my 79 Mikado 4x4. It was sitting for about 10 years before I got it last year. All I had to do back then to get it to start was replace the battery. It never ran good though and I was blaming all the problems on the Hitachi carb and it's crappy choke, but it seems a compression test is overdue. Oil is also black not even 1000 miles after a change. It does smoke a lot and the smoke does smell like fuel. I also have the same problems with it being extra weak and sluggish. It runs pretty rough and even with no exhaust leaks it is damn loud! I remember parking it in front of AAA when I went to get it registered and an older guy who was standing there says "hey nice truck! what's wrong with it? it sounds like a go-kart!"

I hope it's just piston rings or something like that, I have never done this kind of work (I can change manifolds, pumps, pulleys etc but don't have the confidence to start messing with valves and other internals etc) myself and I have noticed most of the shops in my area don't really want to work on the LUV because "parts are hard to find" -if I tell the guy I can get the parts online they usually say "oh you can't trust online parts", and some guys are just plain honest and tell me they haven't worked on a LUV in a long time, or ever.

So starting from the front of the car the compression is... 110, 110, 110, 75. Not as bad as I expected.