Woody620 Posted March 20, 2014 Report Share Posted March 20, 2014 I'm replacing the bearings on my ka24de and I ran into an issue. I got my crank and bearings back from the machine shop and checked my clearances with plastigage, my mains are perfect but my rods have .038-.051mm when spec is .010-.035mm. My brand new fowler digital micrometer isn't working so I bought a cheap harbor freight one to measure my inner rod diameter (torqued to spec, no bearings). The spec is 53.000-53.013mm and I'm getting 53.03-53.06mm. So my question is, Is it more likely that with how old the engine is the rods have expanded from heat or something along those lines or could my micrometer be wrong and/or the machinist have made a mistake? And what can I do to fix it? Can I get away with that amount of clearance And just always run a thicker oil like 20w50, or should I get my rods double checked more accurately and get new ones if they are out of spec? Sorry for the long question but I'm kind of stuck at the moment and I'm paranoid because I know these engines don't like rod bearings, unfortunately from a lot of experience. Quote Link to comment
ggzilla Posted March 20, 2014 Report Share Posted March 20, 2014 Rods cannot expand due to engine heat. And you have double-checked it. Once via plastigauge and secondly with micrometer Why did the crank go to the machinist? Quote Link to comment
ggzilla Posted March 20, 2014 Report Share Posted March 20, 2014 Do not run with larger than spec oil clearances. Quote Link to comment
ggzilla Posted March 20, 2014 Report Share Posted March 20, 2014 Could you have gotten the wrong bearings? KA uses select fit bearings for close-tolerance fit. For example STD (non-undersize) rod bearings come in Grade 0, Grade 1 and Grade 2 variants. The grades are stamped on the crank #1 counterweight. Quote Link to comment
ggzilla Posted March 20, 2014 Report Share Posted March 20, 2014 my inner rod diameter (torqued to spec, no bearings). The spec is 53.000-53.013mm and I'm getting 53.03-53.06mm. So the rod big ends are machined too big. Did your machinist do that? It normally will be adjusted after fitting new rod bolts. Or if they are new aftermarket rods sounds like they are defective. Quote Link to comment
Woody620 Posted March 20, 2014 Author Report Share Posted March 20, 2014 I was told he went 20 under on the rods and he sourced the bearings as well, rods are still in the block because I didn't want to pull the head off, so they haven't been touched. One of the bearings was spun, which I understand that being out of tolerance but the other three matched it as well as a spare set of sohc rods I had that I measured out of curiosity. Quote Link to comment
ggzilla Posted March 20, 2014 Report Share Posted March 20, 2014 He must have meant .020 inch under on the crank journals. Still doesn't explain why the rods are bored out too large. Do you still have the old rod bearings? Maybe they were custom from a previous rebuild. Quote Link to comment
Woody620 Posted March 20, 2014 Author Report Share Posted March 20, 2014 The rods don't look like they were ever previously machined also that would have to be extremely coincidental that my others are the same size out of another engine. Which is why I think my mic might just be inaccurate, but then it doesn't explain my extra clearance. My first time actually getting into bearing sizes and it has to be super confusing. Quote Link to comment
Woody620 Posted March 20, 2014 Author Report Share Posted March 20, 2014 The old bearings got trashed. Quote Link to comment
zed Posted March 20, 2014 Report Share Posted March 20, 2014 don't take the chance and try to run it with bad oil clearances. I did that with a Mazda motor and lived to regret it... Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.