The Stovebolt Site Forums The Shop Area Engine Shop Chevrolet 235 Piston Rod End-Caps question

Today I am removing the oil pan on my 1948 Chevrolet Truck (motor is a 1962 235ci). Removing the oil pan to replace the gasket on it and also the timing gear cover. Things look really good on the inside, very clean. This motor was re-built sometime after 1962, as it has a new stamp in place of the serial number, that is "DR 6 digit # CAL"

So Question is; I noticed after removing the oil pan, that the End-Caps on each of the Piston Rods seem to have a little bit of play in them, I wasn't expecting that (sorta like they are not tightened down all the way, maybe 1/16" of play) Is that normal? Or should I tighten the 2 nuts on all 6 of the End-Caps to some specific # ft lbs. torque?

Yes, the rod caps may feel excessively loose until the bolts are torqued. They will then have some amount of front to back movement, this is called side clearance. They also have some movement on the journals in an up and down direction, this is called bearing clearance. How much they have of each will need to be checked to see if they are in spec.

Are you talking the end cap is loose on the rod, or the rod slides side to side on the crank? As 12 port said, some side to side play is normal. I am assuming this has been running fine and not knocking a bunch? If the rod bearings were loose enough for you to move them up and down, you should have been able to hear them knocking.

It's been running very smooth, no noise at all. I just noticed after I removed the oil pan, that the end cap (bottom of the piston rod) seems like it has some play, over where the flat bearings cover the crankshaft.I can move the bearing up and down maybe 1/16" inch.

If the rod or crank can be moved up and down 1/16 of an inch it should have beat the bottom end out the pan. Side to side is an entirely different deal. You can slide the rods slightly in a side to side motion but a 1/16 inch seems a bit much. A ‘62 is a full pressure and insert bearing engine and has torque requirements for rod and main caps.🛠

You need to either send us pics or a video of the movement of which you speak, or find a qualified mechanic locally who can take a look and let you know what is going on.

Please be a little more specific about the direction of movement. If the big ends of the rods can be moved a little forward and aft, like toward the radiator and the flywheel, no problem. 1/16" is WAY too much, however. I'd be more comfortable with less than 1/32" forward/aft movement. Have you measured the actual movement, or are you making a SWAG? Try stacking up feeler gauge blades until you can take up the movement, add them up, and get back to us.

An engine would not run for over 5 minutes with 1/16" up and down clearance on even one connecting rod.
Jerry

Hey Jerry, I'm sorry it's not so much that the end cap is moving it's the bearing inside that seems like it has play, up and down between the end cap and the crank. I'm guessing 1/16 but it could be less. The engine ran very smoothly (no strange noises or such) before I took the oil pan off. I'm wondering if there is supposed to be a slight gap for oil or? I'll try and get some close up pics soon.

I wouldn't take the chance and with the pan already off I'd certainly Plastigauge it. The Plasti gauge can be found at most parts stores and is cheap. Get some in the 0.001-0.003 range. The sleeve the plastic wire is in has the scale to read what the clearance is. Wipe journal and bearing clean, put a strip of Plasti gauge across the bearing, install and torque to spec, remove and hold the scale up to the flattened plastic. Do NOT turn crank and re-lube bearing before final install. Jerry was a teacher so he can give more lucid instructions I'm sure.

I can't see the engine lasting long if there is any perceptible play up and down. Certainly should be noisy.

There will be some forward and backward movement on the journal, but not sure one could "feel" .002 " movement especially is any oil is on the crank between the bearing and the crank.

Gentleman, I'm back under the engine today. It must have been I was disoriented (laying on dolly), tired from the struggle in getting the oil pan off, or the oil vapors and the oil laden cork bits getting into my eye sockets with each motion of my scraper. There is ZERO up and down movement with the piston rod end-caps. The movement is strictly forward and backward on all 6, like from the radiator back to the flywheel direction. It's not very much play either, like less then 1/16, probably 1/32 in either direction. I surmise from previous messages above, that this is perfectly normal?

Yes, that's normal. Your description previously didn't make good nonsense- - - -vertical clearance for oil is approximately the thickness of a strand of hair- - - -1 to 2 thousandths of an inch, ideally, and it can only be measured with something called "Plastigauge" that's available at good parts stores, or by making precision measurements of the rod bearing and crankshaft journal with micrometers. There must be a slight end play of the rod to allow for heat expansion of the big end as the engine reaches normal operating temperature.
Jerry