Gotta be valve guides, right?

Jim Isler · Mar 31, 2009

1943 H giving me fits. Did rings,fuel side, carb rebuild. Head looked very good so I left it alone. Now runs like a watch, pulls well, but smokes. Compression 90 in all cylinders. four hours on engine since assembly.

Question one: Valves and seats looked very good, so I have to guess that now good compression is sucking oil past guides?

Question two: Does anybody sell just the guides? I don"t think i need valves and clipes.

rustyfarmall · Mar 31, 2009

If the guides are worn out, so are the valve stems. Might as well bite the bullet and take the head to a machine shop and have it done right.

ScottyHOMeY · Mar 31, 2009

You could knock me over with a feather if you were losing any compression through the guides. Perhaps losing a little vacuum, yes, but not compression. Compression happens when the valves are closed. The only three places to lose compression with sound pistons and sleeves are at the valves, the rings and the head gasket

So no matter how good they "look" there's a good chance your valves and seats (coked, warped . . .) need attention and, what with the smoke, if it's blue, the guides and stems. How did you size your rings? They're not off the list yet, either did you stagger the gaps on them?

Jim Isler · Mar 31, 2009

Thanks, guys. Since compression is good, I guess I will just have to bite the bullet and redo the valves.

Janicholson · Mar 31, 2009

If the intake valves are not coked up on the back of the head, and all else seems OK, I would suggest putting a set of Umbrela seals on the valve stems. (does not require head removel) this will either reduce or stop the smoke if it is coming from the stems. They are cheap, and can be put on it a few hours total time. Not much to loose. JimN

Bud W · Mar 31, 2009

Jim
Never heard of Umbrella Seals. Where would I get them for a SAV? Thanks Bud

Brownie 450 · Mar 31, 2009

Is it blue or black smoke?? Maybe the carb is running rich. Is the air cleaner & hoses not blocking air into the engine?? How is the timing--on the money?? Valve lash is probably O.K. as the engine runs well. Look at all possibilities before pulling the head. Loosen up a couple of the valves & see if there is side play..

rustyfarmall · Mar 31, 2009

If that engine was worn enough to need new rings, you can bet the valves are not sealing properly either. It takes only a hairline gap between the valve face and the seat to lose bunches of compression and horsepower.

mkirsch · Mar 31, 2009

90PSI is good compression? I was told 125PSI was weak.

Janicholson · Mar 31, 2009

Just a neoprene rubber shield (umbrella) that fits on the valve stem and mostly covers the top of the guide. Sold by stem size mostly. Perfect Circle style are more complex and have a metering system, and a teflon bushing at the top. These clamp on the top ov the guides, and ride on the stem. They are designed to pass correct oil to lube the stem, and not so much as to allow sucking of oil.
Even IH sells them !
But easily found in parts stores. for applications. The PC seals may need the machining of the valve guide outer diameter to allow installation, so the umbrella seals can be used W/O machining or head removal. They just prevent oil from running down the stem in mass quantities. JimN

MN Scott · Mar 31, 2009

90 PSI in on the low side. Did you measure your sleeves for taper and out of round? Willing to bet your new perfectally round rings are not sealing on your worn pistons and sleeves. Most of the time on a gas engine if the rings are worn your pistons and sleeves are to.

diesel dog · Mar 31, 2009

sounds like rings havent seated need to break in at several different rpms.

Gotta be valve guides, right?

Jim Isler

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