Smallblock, marking of internal parts

Posted By: Moparbil

Smallblock, marking of internal parts - 01/28/10 07:16 PM

During disassembly I noticed that the numbers stamped on the side of con. rods did not match ther actual position, acording to the corresponding piston. I have seen it before in another Mopar engine, and thought it has been assembled wrong. But this engine has never been opened before I belief.

Did chrysler not take much care about these internal markings ?
Also the rods do not exact look like each other, however they all have the casting no 3418645

Anyway, if con rods are reconditioned with new bearings and V groove is positioned correct it does not matter so much with the numbers, or what?
The bearing bore is camfered the same amount on both sides as far as I can see.

Any comments

Posted By: buildanother

Re: Smallblock, marking of internal parts - 01/28/10 07:32 PM

The rods are all the same, but have to be installed to pistons in a certain order. Most shops know which way to position rods on crank, so they then can install pistons on them to match them all up. Even most flattops have an offset pin in them and have a forward facing mark. If your rod number stampings have a number on rod and another on rod cap, I think the engine has been apart before.

Posted By: Moparbil

Re: Smallblock, marking of internal parts - 01/28/10 07:45 PM

rod and rod cap have the same number, but number do not match actual position.
Engine is 360

Posted By: buildanother

Re: Smallblock, marking of internal parts - 01/28/10 07:54 PM

If they are numbered 1 through 8, they must have been out of there at some point if not in correct cylinders.

Posted By: Moparbil

Re: Smallblock, marking of internal parts - 01/29/10 08:35 AM

Quote:

If they are numbered 1 through 8, they must have been out of there at some point if not in correct cylinders.

Four of them are stamped with figure 4 ??

It is always difficult to judge, but I am pretty sure it has never been opened.

360 rods do not have offset and are camfered the on both sides. So if matched cap and rod is installed with respect to oil V groove pointing at opposite cylinder , it does not matter where on crankshaft it is positioned. Right ?

Posted By: buildanother

Re: Smallblock, marking of internal parts - 01/29/10 01:19 PM

As long as the caps match the rods, and have not been switched, thrown in a bucket etc, than it really is not an issue. I just had a 360 apart and I think there is an offset on the rods, as the one I had apart had some rods flipped around, and a couple of the rods were not even close to center at piston-wrist pin area. Those were actually making slight contact with piston. Somebody butched that one up. IIRC the big and small mopars have bearing lock tabs facing outside of engine at each bank, when installed right.

Posted By: RapidRobert

Re: Smallblock, marking of internal parts - 01/29/10 03:57 PM

If you keep the stamped #'s on both halves together you're fine. the chamfer on each side is the same so they can go on the throw either way. OE bearings allowed oil to flow to the squirt hole that was aimed at the opposite cyl to lube them. This was subsequently discovered to be too much lube and new bearing do not have this feature so actually the rod can go either way/in any cyl if the side clearances are not excessively more than normal specs (& rarely are). To your orig Q that is strange (never seen it) but I'd say it is OE since you dont have #'s 1 thru #8 rods and the assembly line guy on that particular day grabbed rods out of the wrong pile or used what he had left to get the eng on down the line or if they stamp them later the guy who did the stamping got careless but I say you can turn them over/put them in any cyl but putting them back the way you took them out will give you peace of mind that you are being meticulous with your build. If it had been opened up & several rods were bad (not likely) and were replaced they'd have different #'s & iirc you said some have the same #'s so I'd say oe/slight assembly line transgression

Posted By: MoparforLife

Re: Smallblock, marking of internal parts - 01/29/10 06:01 PM

OEM pistons had a very slight off center offset for the purpose of a quieter engine by eliminating cold piston clatter. Most if not all after market pistons do not have this.
Many old time racers actually reversed the OEM pistons to achieve a slight horsepower gain.