The Stovebolt Site Forums The Shop Area Engine Shop no compression after piston ring replacement

ok folks back for your help yet once again,a few weeks ago we decided we were going to replace the piston rings on our 1954 235 engine.We decided to install them without removing the engine from the truck.We removed rocker shafts ,then the head,removed pistons rotating engine to remove each piston.We used a ridge reamer to remove upper ridge then honed each cylinder wall.We reassembled with all new rings and connecting rod bearings and new head gasket.Upon completion,when we tried to start the motor,it would not start.We are getting spark and fuel and firing order is correct.There is no compression!
Distributer was never removed.
Any help will be greatly appreciated.
PS truck was running before we started the job,but was burning oil (smoking out tailpipe)and low compression but ran well.

Check your valve adjustment. I usually back the adjusters off at least 1/4 turn to create noticeable valve lash at the rocker arm with both valves closed if I suspect that valve lash is affecting a compression reading. Also try squirting a little oil into the cylinder before checking the compression.

You did remember to install the new rings, right? LOL! I did a post-mortem on a failed engine rebuild once, and discovered somebody had forgotten to install one oil ring. The guy who assembled that engine came down with a case of Budweiser Fever on a regular basis!
Jerry

I have never changed piston rings like you did. But curious to know! Is it possible to replace the head with the crankshaft off 1 turn? The fix would be to take the head off again, turn the engine 360 degrees and replace the head.

I was assuming if the camshaft and crankshaft were not removed ,that it should have no affect on installing the head.

That would only affect the spark timing, not the compression. Somebody has dropped the ball on the valve adjustment.

If you have a source of compressed air available do a cylinder leakdown test to see where the compression is going.
Jerry

hotrod,we put some oil on the cylinder walls before installing the pistons,Do you feel that may affect the compression?

hotrod,we do have a leak down tester,we will check that and get back to you.Not sure if we will get to it today because we are a little discouraged and aggravated(alot of cursing taking place LOL)the temperature here in NY isnt helping either LOL thanks again.

You need to stop guessing and start doing some logical diagnosis. Drop me a PM message and I'll give you my phone number. I can do more to help you in 10 minutes on the phone than in two weeks on the open forum.
Jerry

Yes, thank you.

I suspect this engine is just worn slap out. The cylinders are probably egg-shaped and the old rings were seated to them, albeit worn out to the point they were passing oil. Now that you have reamed it and honed it and put new - perfectly round rings - in it, it probably just can't seal up. I have run into this before. That engine probably needs to be bored and have oversized pistons installed. Just my $.02.

Actually, he got the engine running pretty well after we spent a few minutes on the telephone. It still needs a ring-seating procedure done that will need a break in the weather before the necessary road miles can be logged.
Jerry

Chock another one up for Jerry, way to go Bud!

I love when that happens...

Looking forward to hearing about the ring break in procedure.

It's a simple procedure that's been recommended by Perfect Circle for over 60 years- - - - -Make 10 full-throttle accelerations in top gear from 30 to 50 MPH (without going into kickdown if you're running an automatic transmission). This loads the rings against the cylinder walls with combustion pressure and establishes a good running fit. It's necessary to have a good honed crosshatch pattern in the cylinders before the procedure is very effective.
Jerry

Hi, just saw your post. I have the same issue. New rings also. Put oil in cylinders to check for blow by and got no change. 45-50 psi is all I can get. So it was suggested I have the head rebuilt. And replace the cam and solid lifters.
Id rather not do either if there were an easier way to get it to fire. The push rods are all tru but my rockers don't all have the same range of motion. That's why a cam was suggested. I'm not sold on the idea. I really don't want to pull the engine out again. Is there a way to replace the cam with the block in place? Help!

Lazarus.

JMO, pull the valve cover and pull the rocker Assy. Take the pushrods and measure to see if they are all the same. If not then correct the issue. If they are the same manually manipulate each valve using a pry bar to make sure each valve moves/closes smoothly. If they don't then soak with penetrating oil and work until they do. If that doesn't work then the head will have to come off. If they all work smoothly then reinstall everything and properly adjust the valves. Hope it works out.

Be aware that intake and exhaust lobes have a different lift.

On seating rings, I'm not a mechanic but I've built and rebuilt over a dozen engines of various types over the past 40 years for myself and friends. A trick I've used on my personal engines several times is to wipe all the oil possible from the cylinder walls After the rotating assembly is together just before bolting the heads on.

Obviously the cylinder walls and pistons/rings are oiled to aid in assembly and to prevent the cylinder walls from flash rusting. When the cylinder walls are wiped down just prior to installing the heads, the rings have (everytime) seated immediately on start up.

Obviously there's still oil in the crosshatch of the cylinder walls and behind the piston rings so it's not a true dry, high friction situation on startup. Also I would not do this on a engine that might set several weeks before first start.

Flame away

Added in edit; I do believe in and still do something similar to what HRL suggested, my procedure is to accelerate in high gear from 40 to 50, let it coast down to 40, then 40 to 60, coast down to 40, a few times as part of the break-in procedure. Can't say where/when I picked this tidbit up. It was a long time ago and made sense when I read it wayback them, always seemed to be worth the little bit of time it takes.

Flaming is not allowed here!

The ring break-in procedure I described was reccomended by Perfect Circle piston ring company as early as the mid-1950's that I can remember, and probably for some time before that. The majority of a piston ring's sealing happens due to combustion pressure getting above and behind the ring and forcing the ring against the cylinder wall and the ring lands of the piston. Only a small fraction of the ring seal against the cylinder wall is from the spring tension of the ring itself. The second ring on a piston usually serves a dual purpose- - - -sealing whatever compression gets past the top ring on the upstroke of the piston, and flexing to become a secondary oil control ring on the downstroke. To function properly, a ring needs a smooth, straight cylinder wall to bear against. Taper-worn cylinder walls result in very short ring life, and more than normal leakage during both compression and combustion.
Jerry