I am rebuilding an 88 Duke that had the force balancer explode on it. Fortunately the previous owner is a mechanic and shut it down as soon as it blew. Hence this engine with it's freshly rebuild head is very salvagable. I was checking clearances on the new crank with some plasti gauge tonight when I noticed the connecting rod cap on piston 3 has a dent in the bottom of it where you can tell the very bottom of the cap was ground.
My question is can I just file off the bur that the dent made since it will scrape the side of the reluctor wheel and the oil pump gear, and re-install? Or is it weighted for balance reasons hence filing off a bur would mess that up. Also it seems to be fine since the plasti-gauge was nice and uniform across the journal. So I don't think it is out of round.

Thoughts?

Thanks

Curly

Put a photo of the dent up. If it is not out of round you may be able to get away with using it. Depends on how much you think you'll have to grind off, you dont want to unbalance the crank etc. You may want to just smooth out the edges of the dent with sanding drum. I cant really say without seeing what you call a dent?

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Sorry for the blurred photos my camera seems to not be liking close shots tonight.

Hmm,, I'd just smooth it out the edges with a sanding drum, but you may want to get some more feedback on it. The reason being for smoothing out the edges is: sharp edges/burrs can breed cracks and then catastropic failure. Such is why it's a good idea to smooth out the casting seams on connecting rods etc.

I would be concerned with a crack forming. That looks like it took a pretty good hit. You could have the part checked at the machine shop for concentricity and integrity, might be cheaper to just get a new cap.

Edit: I re-read and saw it was a rod, not main. Same thing though...... get it checked.

[This message has been edited by Joe 1320 (edited 09-05-2011).]

My plan was to replace the crank, bearings and oil pump everything else looks great. So say I order a new connecting rod and pull that piston to replace it. Can I just pop it out put a new rod in, then get a ring compressor and pop it back in? Will everything seal up properly again? I have no idea.

If it were mine, I'd clean it up with a file or dremel tool and reinstall it without any reservations. However, a purist could come up with many objections. I don't think you would have lost enough grams of weight to have a balance problem. Just my opinion and good luck.

quote Originally posted by Ventura: If it were mine, I'd clean it up with a file or dremel tool and reinstall it without any reservations. However, a purist could come up with many objections. I don't think you would have lost enough grams of weight to have a balance problem. Just my opinion and good luck.

Second this. It's not like it's going to see 8000 RPMs, or the 24 hours of Sebring.

Might want to have that rod cap magnaflux for cracks you can't see. Looks like it took a good hit.
Just my 2 cents.

http://en.wikipedia.org/wiki/Magnaflux

Spoon

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quote Originally posted by Raydar: Second this. It's not like it's going to see 8000 RPMs, or the 24 hours of Sebring.

But looks can be deceiving. It could also not even see 24 hours of a running engine, and could cause much worse damage if it fractures. I'd vote to get it checked with proper instruments (not eyes), or just replace the rod. I don't remember how the rods/pistons are married on the duke, so it may or may not be as easy as just pulling it out, and popping the new one in. If the pin is press fit, then it's a bit harder to deal with.

Ok I can actually magnaflux it at work. If it is cracked can I just pop that piston out to replace the connecting rod and put it back in with a ring compressor? It will seal up again? Or will I need to do things like re-ring the piston and/or have the cylinders re-honed?

quote Originally posted by Raydar: or the 24 hours of Sebring.

That's 12 Hours.

quote Originally posted by Curlrup: Ok I can actually magnaflux it at work. If it is cracked can I just pop that piston out to replace the connecting rod and put it back in with a ring compressor? It will seal up again? Or will I need to do things like re-ring the piston and/or have the cylinders re-honed?

You can add a new /rebuilt rod and still use the old rings. When you get it out be sure and make notes on the indexing of the ring positions on the piston. I would just reuse that rod cap. Do not just use a new rod cap. They are a matched set.

-Joe

I would reuse it. It's only holding back 25 hp.

Magna fluxed....no cracks, dyed and checked under a scope. no cracks. Placed in a fixture and checked for roundness. It is round. Gotta love working with a machine shop for a living. So this cap has been precision ground down and will be reinstalled. Thanks folks.