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| | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | I've got a winter project. My 216 from 1941 had a problem with the compression on one cylinder - the other five read between 120 and 130. Number 5 was around 40. So I took off the head and found a broken oil ring but no visible damage to the cylinder.
I am pretty green with this kind of work. The engine is in the car and I hope to leave it there. The car has under 80 000 miles on it, this is confirmed. I suspect that the more work I do on the engine the greater the risk that I screw something up.
So first question - with everything opened up I suppose I would be wise to plastigage the mains and rods bearings and of course replace all the rings?
Another question is why is the compression on 5 so low when the two compression rings are good?
Yet another question is what rings to order. The engine has never been bored. There is a little edge at the top of the cylinders, so I will have to do a little honing- deglazing, but I hope to get by with as little work as possible, ha ha. Must I measure the cylinder to order rings? Is this a process with the pistons and feeler gauges?
The engine has been running fine its whole life but leaves a lot of blue smoke. It was purchased new by my great-grandfather.
Karl
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | Oh one other thing. I had the head off two years ago, and sent it to a good expensive shop for rebuilding. New valves, seats, everything else too. So no problems there I hope. Why I didn't take the time to check compression back then I do not know. I suspect that ring has been broken for many years.
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | If your oil rings were the cast iron one piece type then a more modern type with the two thin rails and expander will make a big difference. | | | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | Are these modern rings typically supplied when ordering replacements?
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | | | | Joined: Oct 2006 Posts: 1,847 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 1,847 | how did you see a broken oil ring by taking the head off? You should measure taper as well, 80,000 miles on these is a lot, you are probably close to time for a complete overhaul, I really doubt cylinder taper will be acceptable for new rings, not to mention the smoking.
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | Yes, that is the only type you can buy new. Here is the procedure for measuring the piston fit within the cylinder. 38 Shop Manual If you go back a few pages you will see all the information that you need in a rebuild.
Last edited by truckernix; 01/27/2013 6:42 AM.
| | | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | The oilpan is off, too, so I was able to pull the piston. The cylinder walls are not damaged, but I am sure they have the normal amount of wear. I am really not so excited about a complete overhaul, I am looking forward to a few years of local casual driving before I can find the time for that job.
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | | | | Joined: Oct 2012 Posts: 233 'Bolter | | 'Bolter Joined: Oct 2012 Posts: 233 | to have that large of a compression loss on one cylinder, you have broken compression rings and or a valve not seating. Since you state you ONLY have a broken oil ring fill the intake port with diesel and see if it leaks out. Check the exhaust the same way. You should not have any wetness on the combustion side.If you do, that valve is not seating and is the cause of the low compression
1953 Chevy 3100 261 and SM420 53Chevy 31001953 Mack Firetruck 1972 Porsche 911 1986 Honda Goldwing
| | | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | Do I need to be worried about the small bits of babbitt that are missing from the rod ends?
About the valves, there is a fair amount of carbon already built up on the valves. I wonder if some of that carbon is stuck on the seat.
Last edited by Organbuilder; 01/27/2013 10:03 AM.
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | If you have significant dropouts in the babbitt, they should be reconditioned. If you go that route I would suggest getting them machined for inserts. | | | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | The dropouts are small, I would like to say insignificant. I have only removed one piston so far, I may find more significant dropouts later...
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | | | | Joined: May 2006 Posts: 423 'Bolter | | 'Bolter Joined: May 2006 Posts: 423 | I have an answer to my compression loss. As MountaineerMike guessed, the problem is a valve not seating. With so much oil blowing past the broken oil ring, the exhaust valve had gotten all gummed up in a short time. Hopefully I can remove the one valve and clean it up, otherwise it is brand new.
Rings have been changed, cylinders de-ridged and honed, rod bearings plastigaged. Now I am adjusting the main bearings and scratching my head trying to figure out if I can get to the front main bearing cap with the engine in place. It seems like I have not only the timing cover in the way, but also the motor mounts and a big ol' cross member.
Karl
Last edited by Organbuilder; 03/02/2013 4:53 AM.
It may not be the easy way, but it is the Cowboy Way - Ranger Doug Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri 1953 Chevy 3100 1960 Volvo PV 544 1941 Chevrolet Special Deluxe | | |
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