Rod bolts for the 4.0l OHV...

[gwn95747]

We had a crate engine (97 block, 98 Ranger 4x4) blow the bottom end because they used the wrong timing sprockets, and in the process of rebuilding over torqued the rod bolts and broke one. We could not find replcements ANYWHERE! So we bought an old block (a 90 block) and are pulling the bolts out of the rods to replace the ones on the 97 block rods. They (the 90's) look identical to the 97's except for the head size, which is a bit smaller than the 97's. As such, we will replace all the rod bolts so as to not have weight/balance issues. Has anyone had a similar issue and resolved it in this way or in any other way? Should these bolts work? This is all new territory for me.

 

[enginepaul]

I'm surprised that a machine shop can't answer the bolt question, but as long as the rods have the same part numbers the bolts should be the same. I've seen mid-year changes with Ford but the parts should be the same if the numbers are the same. I seriously doubt there would be any out of balance problem.

I've never had to mix and match on any Ranger engine, but have on Ford V8's with no problems.

Where did you get that crate engine? A little warning to future customers on here would be nice.

 

[gwn95747]

The machine shops looked for bolts but couldn't find any. They suggested reconditioned rods, but also suggested replacing all rods due to the over torque issue having been done to all the bolts. This was gonna cost $400-600 depending on the shop. That's why we went to the old block scavinging route.

I don't know where the crate engine came from. We bought it off of craigslist with head problems, replaced the heads, ran it from northern CA to utah and back, then the bottom blew (timing sprocket slipped, and one bent rod as a result).

The 97 rods are 7AE's and the 90 rods are 6AA's. They look exsctly the same except for the weight bumps on the top and bottom (minor differences). The 97 rod bolts have the number KX-920 on the head, and the 90 rod bolts have the number KX-110 on the head, and the head is a little smaller then the bolts from the 97. I'm only using the rod bolts from the 90 on my 97. Just a little added info in case that means anything to you or anyone else.

Thanks for your reply.

 

[enginepaul]

Been thinking a bit: make sure those replacement rods weigh the same as the old ones or everything will be out of balance. Otherwise replace the crank, flywheel and balancer too. Unless they have the same part number, they may not weigh the same.
Rods can be 565 0r 585 grams. Sorry that I don't have a real answer.