The Stovebolt Site Forums The Parking Lot Big Bolts Piston out through oil pan w/o dropping crank

Hello again, from a new member.'57 chev 6400, 281 engine. The truck sat for 8 or 9 years according to the guy I bought it from. Got it running, but made it less than 100 miles before it broke a ring or burned the piston. 5 cyl's read 115 to 120 psi. #5 reads 5. I put compressed air on the cylinder and the air came out the dipstick tube so I believe I need to drop the piston and would like to know if that will work on this engine without dropping the crank. Thanks for any help.

261 or 283?

From your cylinder count I'm thinking its a 261 inline six, not a V-8 283.

You might get a broken piston out without removing the crank, but its very unlikely you'd get a good piston back in. I think the head needs to come off.

I have a broken motor out in my shop with a hole in the pan where a rod tried to exit, and most of the piston was laying in the bottom of the pan.

It is a 261 straight six. Some engines it seems you can just remove the oil pan, unbolt the rod, turn the crank and slip out the piston. Wanting to spend the least amount of time fixing this I was hoping not to remove the manifolds, heads, etc.

It was a pretty common practice to change a set of rods from the bottom, back when the 216's had babbited rods and they would wear too far to just take shims out and re-establish the proper oil clearance. The piston will drop down far enough to unclamp the wrist pin and slide it out of the rod, but it's very unlikely the piston will come all the way out the bottom with the crankshaft in the way. Getting the rings compressed so the piston could be re-installed would be practically impossible. Pull the head and do it the right way!
Jerry

Hotrod Lincoln is right!

While you have the head off, cut the ridge, hone or break the glaze on the cylinder walls and be sure to use cast iron rings. Chrome or other hard rings will not seat without a rebore. If you have 5# compression, your piston is still in one piece, but make sure you inspect the ring lands and clean the ring groves. You probably had stuck rings. I would fill the other 5 holes with something like Marvel mystery oil or better yet, you might consider pulling all 6 and putting on a set of cast iron rings. I have a grove cleaner, but you can use a broken ring ground square to scrape the carbon off.

Your best bet is to pop the top and have a close look at the cylenders anyway. My old beast sat alot and aquired some really swee pitting in a couple of the cyclender walls that was too deep to be machined out and was eating the rings. Add on a coupledeteriorated valve seats,... Really, just a good idea to have a look inside unless you plan on letting it sit another 8-9 years.

Thanks for your suggestions. It looks like its off with the beasts head! Plus the oil pan. I appreciate the comment about the cast iron rings. Never would have thought of that. I hope that the cylinder walls are not pitted. I know a lot of you are doing complete restorations but at this time I am not planning that step. This cool old truck (I like old vehicles) is still going to work (fairly hard) on my land. It has a 15 foot grain/cattle bed in great shape with dual hydralic lifts. The outside could remain a little rough but I wish the truck to run good. Thanks again.

Nothin wrong with workin these old buggers, I work mine pretty hard too. But ya definately want the engine in good order to be able to handle the strain. Dont have to do the full resotration rebuild, but makin sure you have solid guts is just good sense.
These engines are tough and dont require a lot of care, but they will eat themselves if ya let them.

The fellas are right about pulling the head and doing a little block prep before dropping the piston back in. If you find too many problems with your motor consider picking up a good used 261 to drop in. I've seen several available on stovebolt and the guys here are great about pointing you in the right direction.
I've got a '57 similar to yours and I've used it alot without any problems. Its great to pull a heavy load and feel the truck muscle its way down the road.

Would love to see some pics of your truck!!!

JAMES

I had a friend that removed a piston without removing the head. He also didn't have to remove the oil pan. Sent it out the side of a 396 around 8500 rpm!