Hi everybody. I have almost completed the process of building my car for the first time. The thing's almost all together now, motor installed, I pretty much just have to plug in the wiring and she'll be ready to go... in theory.

I had used a 0.010" under crank with bearings to match, I measured it a lot, and ended up with some very minor skid marks on some of the journals from the mic (unfortunately no pics) which I very carefully filed down and polished until a bearing slid over the surface of the journal yielded no scratches.
I have since acquired another unground crank that was a good deal, and I'm torn on if it's worth it to get new bearings, clean this crank and tear this thing back apart to throw the other crank and bearings in or if I'm just being paranoid. Help appreciated.

88BB8B said:

I measured it a lot, and ended up with some very minor skid marks on some of the journals from the mic (unfortunately no pics) which I very carefully filed down and polished until a bearing slid over the surface of the journal yielded no scratches.

Click to expand...

That's very normal that you get some marks on bearings by a dial gauge tip and on journals by a micrometer tip.
It's very hard to tell if it would be fine or not, since there is no pic and we don't know how deep the marks are. Too much polishing is no good but generally it would be just fine if the marks are gently cleaned and if you can't feel it by nail.

It was hard to tell if my finger nail was catching or if it was just skipping on the journal, but I spot polished minimally with 3000 grit and WD40, very gently using the file first to get the majority of high spots down.
Your input is very helpful, thank you, I could not find much info on the damage that can be caused by measuring a crank.

Rotate the engine by hand 2 or 3 times and then pull one of the rod caps and check the bottom half of the bearing to see if it got scratched. If not you're good to go. If so, you get the point...

Is this a six bolt crank or a seven bolt crank? if its a six bolt crank I would replace it, the six bolt crank is hard coated, that coating is not very deep and turning the crank down usually removes the hard coating, if you have a fresh one I would personally install it, also anytime that you remove material from a machined part like that you technically weaken it plus you have to depend on the accuracy of some machinist to get it perfectly round and the factory has a much better chance of that that some machinist of questionable talent using tooling of questionable condition.

Depends on goals with the crank. Myself and a buddy built a 6 bolt with .010 cut 5 years ago and it has lived a happy life at all a bolt on hx35 can throw at it with e85. So not huge power but up to around 500whp i don't worry about a .010 cut.

It's a 7 bolt. Cut 0.10 under with an hx35. Just like buddy's ^

Also, I believe that both the 6 and 7 bolt cranks have hardened (nitrided) journals, but to my understanding that process hardens the metal as deep as .080" so cutting 0.010" has been shown to work even though it is not recommended by mitsu. Don't quote me on that tho.

88BB8B said:

my understanding that process hardens the metal as deep as .080"

Click to expand...

I think the case depth when nitriding is more like typical .020", with .016 min. & .024" max. Hardness goes down the more removed & is hardest on the surface. Eighty thou seem exaggerated.

Lmao, don't quote me . I must have my hardening processes mixed up. P.S. I love your cat.

IMO, get a new 100mm eagle crank and some stroker pistons. Might as well go for a 2.3L while you're in there.

I have run cranks that are cut .020" in a 4g motor and more than that on some other applications. No issues as long as the clearances are correct. We used to cut cranks all the time back in the day, some I have seen as much as .030" (in the 400 SBC we are running) but the problem comes in when you try to get performance (harder) bearings for them the more they are cut. Look up rod bearings for a 4g63 crank cut .030", very hard to find in a non-aluminum type bearing. I think I could only find Alumaglide bearings so we changed cranks in that situation.

Disclaimer : These are purely my experiences and may not be typical of yours

Here is an example of a good running build and it's specs, but it isn't a 4g63 motor.
Marty


and HERE and HERE are the passes that car made with that motor (if anyone was interested) before the track closed for the season. This was on Nov 7th, about 70* out.