Poor compression on rt. bank?

[lcjjbeav]

1970 2.2e

After rebuild, my right bank cyls. 4-6 all read 120lbs on a conventional compression test. Cyls 1-3 all read 165lbs.-170lbs. Don’t have the equipment to do a leak down but have put 120lbs of air in # 1 and #4 and have about the same amount of blowby, as heard from the breather hose.

Have just a few miles on it since rebuild. Can’t drive it far as the plugs quickly foul with oily soot.

Here’s the background.

After the initial rebuild I had constant bad smoke, compression was 165lbs on all cylinders. Took it back apart and found about all of the Teflon stem seals torn. Took the heads back into the shop, that did the initial work, and they replaced all the seals with the vivaton (sp?) type and furnished a new gasket set. The initial assembly was done with Goetz rings. In reading and talking to others I decided to go ahead and replace these with the Dietz type. This was done just to make sure all of the oil was indeed from the stem seals. I rehoned my metal sleeved cylinders myself and reassembled. After just a quick run in I had fouling. Re ran a compression check and this is where I found the the low compression on 4-6. Figuring I messed up I took that side of the engine back apart. Did not find any gaps lined up. Took all parts into the machine shop. They checked all cylinders, pistons and rings, rehoned the cylinders and I thought I was good to go. Re assembled, being careful not to line up any gaps, immediately drove it with the technique of low gear accell to about 4,000 rpm and letting it back down against itself. Did this for about 10 miles. Obviously mis-firing after a short time. Re ran compression check, same results. Re-checked the cam timing, was .01” over the spec. Today I replaced the tensioner with a manual type I had just to see if that made a difference. It pulled the spec back in range but still low compression. I’m stumped! Any suggestions what to do next. Don’t mind tearing into it again but don’t know what to look for.

Just to double check my method for valve timing measurement (on rt. bank): TDC #4, mount guage #4 intake, preload guage, zero guage. rotate 360 degrees, read guage, at specs. (.11-.14"), rotate another 360 degrees to confirm zero. Repeat to verify.

Thanks in advance.
Beav.

[Wayne 962]

Originally posted by lcjjbeav
Have just a few miles on it since rebuild. Can’t drive it far as the plugs quickly foul with oily soot.

It does take almost a thousand miles to completely wear in an engine to the point where it's not going to blow oil or exhaust gaskets. If you only have a few miles on it, you're going to find that the rings have not seated. Did you follow the break-in procedures in my book? What type of oil did you use for the initial run?

Your compression numbers are not all that bad - I would think a broken ring would give you much worse numbers. It looks to me like your rings are not broken in quite yet. Perhaps the engine is running rich on that side too? Your '70 2.2 should have MFI on it, but if you have carbs, it's possible they are placing too much fuel on the right side, and not allowing the rings to seat?

How's the smoke situation? If your plugs are fouling tremendously, then you should be getting large amounts of smoke? You didn't mention this? If there's not much smoke, it may just be a fuel injection issue and not completely an engine issue. Did the MFI system sit for a long while during the rebuild?

-Wayne

[lcjjbeav]

Break in done with 30w non-det. Original break in done by 20min. at 2000rpm, oil change. then drove with varing rpm letting it back down against itself. Never got many miles on it due to heavy smoke first time and misfiring this time. Just light smoke now, worse at higher rpm.

Maybe I'm focusing too much on the compression. All injectors were cleaned and calibrated by an injector shop. I do suspect MFI issues. Was too lean, might have it too rich now. The few brief times I took it above 4500 rpm had very bad misfiring, so I also suspect ign components may have issues.

Think I'll take your advice and try to get some more miles on it. I have another module I might try. I'll post a photo of the plugs next time they feel fouled to get an opinion if they look like oil or fuel fouled to the collective experts.

Thanks for the help.

[Wayne 962]

I think you're on the right track. The compression values really aren't valuable just yet - untill the rings are broken in.

If you have recently overhauled your MFI and ignition systems, then I would look there first. Take the car out to a shop and have them check the CO and hydrocarbon emissions - that should give you some answers. You are describing a situation where the car is running rich, I think that perhaps the MFI was tuned too rich, which may be causing the rings to not seat properly...

-Wayne

[cstreit]

Since it's only on one side, could it be slightly off cam timing?

[john walker's workshop]

funny that it's all on one side. with all the teardown work, you never checked the valves to see if they're slightly bent, maybe from a momentary tensioner failure, or improper cam timing. you can't always tell from looking at them assembled in the head. they have to be removed and spun in a lathe, or valve facing machine, to detect an out of true situation.
the plug fouling may be an entirely seperate thing. MFI is a bigtime plug fouler until you get it dialed in. also, the plugs need to be fairly hot to stay alive in a MFI engine. factory heat range charts for old engines don't relate to today's fuel. they need to be considerably hotter, like a bosch platinum WR8DP, or the supposedly unfoulable NGK Iridium equivelent.

[BK911]

I didn't have time to read everything, but if compression is low on an entire bank of cylinders, I would agree that it might be the cam timing.