Connecting rod caps, replace caps or whole rods?

[Eclipse45150]

Ok heres the deal, please if you read my profile excuse the motor mods, that motor was blown. I have a stock block that I threw in to get me to and from shows, I just got the head on today and ran into the guy I bought the block from and asked him if it had any problems like it was just to double check. He said there was a knock from the rods, that the caps didnt line up and he doesnt do bottom end so thats why he sold it. He said the crank is in great condition that it is just the caps. I went home and looked and the 2 and 3 piston and cap look fine, maybe a quarter of a mm to the side of the rest of the rod on one. The 1 and 4 have about 1/2 a mm to the side and 4 has a fingernail size gap between the cap and rod. The crank looks good, no scoring or discoloration, and the rods look fine. To me it seems that he didnt put the caps back on the right rods. So Im wondering would it be ok to match up the cap that fits flush if all 4 end up being a perfect fit, buy new caps, or new rods? I am already going to replace the rod bolts and bearings since Im in there.

Please let me know what you think, Im kinda short on cash right now and just need the motor to run for about a year so I can build a race motor.

 

[GVR4592]

Take the rods and the crank to a machine shop and have them check it out. The machinist will be able to mate the caps back up with the correct rods. If the rods are out of round they might be able to be resized. You can't tell if the crank is still round by looking at it, it needs to be measured with a micrometer.

 

[Eclipse45150]

an update and reply:

First, I took all of the caps off and noticed on #4 where the gap was, there is about a mm tall and about 2-3mm long what looked like a chunk out of it, upon taking the #1 cap off it has the exact opposite so I matched them up and it fits perfectly flush with no gaps. Next, I talked to the guy who had the block and he said the crank is perfectly straight he had it checked before his attempt to rebuild, he only had the motor on for a few mintues heard the knock and off it went. I also noticed that there were 6 of the 8 bolts that were not torqued to spec. So do you think that since they all match up flush now it would work? Im thinking that since is wasnt a huge knock maybe that amount of metal being added to the wrong piston and technically taken away from another would offset the balance enough to knock and now should be fine.

I really wont have the money for a few months to get anything done by a machine shop, around here they want to charge over 100 to check them, I was already going to do that before my rebuild but said no when they told me the price.

 

[ArticNemesis]

Mod cheap. Mod Twice.

It sounds like you've already got it made up in your mind that you are going to do what you want.


As stated, take it to a machinist. If it was knocking, even for a second, chances are it warped something. If it were me, I wouldn't take the chance on someone telling me they had a crankshaft checked out before they sold it.

 

[GVR4592]

The machinist probably isn't going to charge you to measure the crank and the rods. I'd really hate to see you back in here a few weeks from now trying to diagnose a rod knock when it could've been prevented.

 

[Eclipse45150]

Ok, problem solved, I am getting new pistons/rod, the wiseco 10.5:1 and eagle H beams, with those do I use the same torque as stock or will the sheet that comes with the rods tell me what to torque them to, and about the last reply I know the machine shop in eastgate ohio will charge me to measure the crank, do you know of/heard of any good shops around the cincinnati ohio area? I would be willing to drive up to 100 miles from here so a pretty good chunk of IN, KY, or OH if you know of any

 

[autonut]

Sorry to chime in late, but Ive had numerous rods resized with GREAT success.

 

[Eclipse45150]

Sorry to chime in late, but Ive had numerous rods resized with GREAT success.

I figured I would just try and start out fresh, I dont know that much about machine work but all four had irregularites from the factory, some had more metal some less, that made me more weary about using them, then I saw the #4 had a pin size chunk taken out from inbetween the rod and cap, almost like it had been dropped. Figured it wouldnt give the same strength as new ones if they were even able to be fixed.