The Stovebolt Site Forums The Shop Area Engine Shop Clouds of Blue Smoke - Help!

We recently pulled the head on our 235 for the 61 Apache and took it to a local machine shop with a good reputation. They checked it out, cleaned and brought everything to spec saying that it all looked good. We re-installed the head with a new gasket and new manifold gasket, and torqued the head bolts to spec. She started right up, and runs very well, but after warmup, smokes like crazy. I put a little marvel mystery oil on top of the pistons while the head was off since this truck has been sitting 8+ years in a field. I thought maybe it would take a bit to burn this off but I took it out and drove around 8-10 miles the other day, keeping the engine running for about an hour - still clouds of bluish smoke. Compression from front to back is 134, 136, 35, 150, 135, 155. Funny thin is, compression was low on numbers 4 and 6 before removing the head and is now low on number 3 and high on numbers 4 and 6. Two other notes: We've not yet adjusted the valves, and I noticed a bit of oil running down the manifold side of the engine opposite the number 3 plug (which has compression of 35). The truck seems to run and idle great except for the smoke. My son and I have never gone this deep into a vehicle before and really need some of your expert advice on how to proceed. Thanks in advance for any advice you can provide. A couple of final notes---we did'nt use gasket sealer with the new head gasket and we have not re-torqued the head bolts. Hope this thread is not overly confusing. Thanks!

Go ahead and adjust the valves, this could well be your problem. You might want to re-torque the head bolts as well before adjusting.

The number 3 is the big problem, perhaps the rocker is too tight and never closes completely.

Machining the head and a new gasket changed all the valve clearances. When valves are adjusted correctly, look for pretty even compression numbers for all cylinders - if one or two are off, recheck.

One thing I noticed when I rebuilt my 235 years ago is that once I warmed the motor up I had to re torque the head. I think this is your main problem. Let us know how things work out,
Bo

Sure sounds like you have a ring/piston problem. 35 psi says there is no sealing with this piston. Pull the plugs and see which one is fouled/oil soaked.

On the cylinder with the low compression. Pull the spark plug and squirt in about 3 to 5 squirts of 30W oil. Spin the engine over a short time with out starting it. Then recheck the compression on that cylinder. If the compression increases a bunch, you either have a stuck oil ring on the piston or a broken ring.

I agree. Nothing you have done should have hurt the piston or rings for #3, so adjusting your valves will almost certainly resolve the situation. And I would personally also re-torque the head bolts. That shouldn't hurt, and it might help.

Btw, did you replace the head bolts? I've done that, in the past, on some old engines (not Chevy). I don't know if it's recommended to replace them on the 235 but, after all, they're over 40 years old if they are the original bolts. Just a thought....

That's a long time for an engine to sit. Give it time to come back.

My son's 235 used to smoke a lot. His engine was abused by someone who apparently ran it without an air filter. We've done numerous oil changes, which has helped about 99%.

We also changed the carb. It runs great now. I hate to see him sell it....

Btw, why did you pull the head?

We pulled the head because we were getting low compression (30-40) in the number 4 and 6 cylinders and it was running very raggedly even though we've done a complete carb rebuild and replaced plugs, plug wires, distributer, rotor, etc...We know gas is good since we pulled and relined the tank and replaced all the lines. We will retorque the head bolts and adjust the valves and see what happens. Thanks all for the responses.

BE SURE TO RE- TORQUE ONCE WARMED.

My son's 235 was running so badly that he was going to sell it. Then he decided, against my "better" wisdom, to adjust the valves.

What a lesson I learned. It ran at least 50% better! It's actually fun to drive now.



I hope you get the same results.

P.S. How does your oil look?

If adjusting the valves doesn't fix it (I hope it does) you might have to reseat the rings. In high gear speed up to about 40, drop back to 25 or so, and back up to 40. Do this several times, as fast as you can. Usually creates enough vacuum and compression to seat the rings.

We did a valve adjustment, drove the truck for about 45 minutes to get it good and warmed up, retorqued the head bolts and did a final valve adjustment. Smoke is almost completely gone and the engine seems to run very strong and smooth. Thanks for all the info---it helped a lot. We set clearance for intake at .006 and exhaust at .018 as specified in the shop manual. I have seen several places on this site where it was recommended to set exhaust clearance at .013 for the 235. Anyone have any thoughts on this?