The Stovebolt Site Forums The Shop Area Engine Shop Rod caps on new rebuild?

I am in the process of rebuilding a 283. I have a friend helping who I pretty well trust his judgement but..

On #7 & #8. The rod caps were backward from all the others. Ther is a side with 90 degrees and an angled side. If that makes sense. He said that the machine shop who pressed the pistons on the rods must have put the last two on backwards. Since there is only one way the bearings and caps go on.

He didn't think it was a big deal.

Your thoughts.

The pistons should have a "front" mark, either an "F" cast into the pin boss area, and/or a notch in the piston crown. These MUST face toward the front of the engine,or you'll get a piston slap. The piston pin is offset, and if it's installed with the offset the wrong way, the piston "floats" in the cylinder at the top of the stroke, and slams into the cylinder wall when the plug fires. Even if it's necessary to install the rods with the numbers out of sequence, be sure the front of the piston is facing the right way. Has the engine been run with the pistons you're using, or are they new? If they're new, go back to the machine shop and have them correct their mistake.
Jerry

Hotrod,

Thanks,

The pistons are new. Crank turned .010 cylinders bored .040. It is just #7 & #8. The dimple on the pistons all are facing to the fron of the block. I think they put the rods on backwards on these two pistons. Therefore the rod caps look completely opposite of all the others.

I haven't run the motor just turned it over by hand. I still have to get the heads done and only have the crank, pistons, cam, timing chain on now.

I'm calling the machine shop. It stinks because the motor is 1/2 hour away at a friends shop and he's going to be laid up for a while from surgery so another delay is innevitable.

Thanks,

Tim

raza frazin &*&%$!!!!

OK the machine shop said bring them back in. Thanks HRLincoln.

Better safe than sorry. He said they would be ok but why risk it?

Hi Bessie

Let me see if I can explain this without drawing pictures. The crank throw on a V8 engine does not have a perfect square machine end at each end of the throw and if you look at the inside of the rod with the insert installed, you will note that the insert doesn't come to the edge of the rod on one side. This side has to go to the outside of the crank throw so the gap can leave room for the machined rounded edge. When the two rods come together on a throw, the two sides that are next to each other can be flush with the insert since they have no rounded edge to make room for. When you install the rod cap, place the locks - the indentions that the insert fits into - over each other or other words, on the same side of the rod.
The notch on the piston has to go to the front and this should put the space on the insert to the outside of the crank throw. You can't use the rod with the cap on backwords or your insert will spin in a short time. But you can turn the rod around on the piston, listen to this closely. If you turn the rod around, you would have to use that piston, with the notch pointing to the front on "the other side of the engine". I hope that this doesn't confuse you but I really suggest that you get the rod(s) turned around. Maybe you can use what I have described to determine if your rods are on backwords or just the caps turned around. I have taught automotive mechanics for 29 years but I am used to having a chalkboard to explain. Hope this helps.

Truck Tinker from Talking Rock