351cj chainsmoking at startup

[threefittyone]

Hi-
I've been reading this board for a while, first post.

I have a 351 cj that on startup smokes like James Bond's DB-6. I mean, this thing smokes like nothing I've ever seen.

There is no oil accumulating in the air cleaner housing and the filter is dry.

There oil drips from the exhaust during startup, and then leans out, and when the engine reaches operating temp, the smoke subsides.

I ran a dry compression test with a craftsman tester, and all 8 cylinders were within 5 psi of 150psi.

I pulled the valve covers and discovered that back in the 80's the valve stem seals were replaced with what looks like teflon seals (nylon?). I only pulled the springs on one cylinder to have a look at them, and nothing looked apparently wrong- they were tight around the valve stem and around the guide.

Next, I ran a cold leakdown test using a homemade tester. The air hose was regulated to 120 psi, and I used a campbell hausfield regulator/gauge setup for a spray gun (which I regulated to 100 psi) and connected the flexible line.

The results were all cylinders leaking down 3 to 5% using this crude tool. I can hear the air escaping into the crankcase, but no carb, radiator or exhaust sounds.
(the next thing I'm going to do is add a second gauge after the CH gauge with a 1 mm damper in between, hoping that will provide a more refined reading)

Can defective valve seals be the culprit here? Other than a defective head gasket seal could cause this much oil loss?

Thanks. Tom

[okiedragster]

i would say that if you can change those valve seals by putting air on each cylinder with the valve up, that would solve your problem. "time" is what gets those seals and one or two may even be so loose or even cracked from time that is letting oil run down the stems on top of your valves when its setting causing the smoke show. sounds like the rings and valves are in good shape just from your compression check and i think if it was a intake pan leaking it would never stop smokin.. just a thought

[Phillyfanfrombirth]

Definetly sounds like valve seals to me...

[Gearhead999]

Valve guide seals for sure. BUT.....the "C" & "M" engines were known for valve guide wear. If the guides are worn bad the seals won't last.

When you change the seals. After you pressurize the cylinders and pull the springs. Take a close look at the area where the valve meets the guides. You may be able to tell that the guide is worn and egg shaped opening now. If it is the heads have to be pulled and machined for replacable guides.

I'd replace the seals and see how it goes.

[threefittyone]

Thank for the replies. I ordered viton seals. I'll let you know how it goes.
I'm also gonna change the intake manifold for good measure. Any advice on reinstalling a stock manifold? Thanks. Tom