Can the crank still be fine after wearing through babbitt layer?

[ryan7663]

Hello again everybody I have question about the 302 (out of my 95gt) that I have at the machine shop right now. This motor had 250k+miles and had worn through the babbitt on a lot of the bearings. In some places the babbitt looked like it was starting to peel off(delaminate). The wear pattern was a good hourglass type of pattern centered in the middle of the shell. I called them to find out if my crank needed to be turned or anything and was told it was still perfectly fine. I've been told by a machine shop teacher at my college that when there is wear through the babbitt there's a good chance the journal is out of round. The guy working on my stuff said it still mic's out fine and to use a std. bearing when I assemble everything when I get it back. I only have plastigauge to check his work since I don't have the money for a good dial bore guage(the kind with flexible fingers).

My question is does it sound normal that my crank would still be fine with the kind of wear I described? Is this common?

As always I appreciate any help anyone can give me.

 

[ryan7662]

Also would I be able to check for out of round with just a outside mic?

 

[Rick 91GT]

If you mic all the way around you can find taper and defects... If it only went through the outer babbit you may be OK along as no dirt or debris was pulled through, with as many miles on that motor I would expect the babbit wear along with some thrust wear.

Did he polish the crank for you? If not I would give it a good polish....

 

[ryan7662]

If you mic all the way around you can find taper and defects... If it only went through the outer babbit you may be OK along as no dirt or debris was pulled through, with as many miles on that motor I would expect the babbit wear along with some thrust wear.

Did he polish the crank for you? If not I would give it a good polish....

I'm not sure if he polished the crank or not I'm assuming he didn't because he gave me a list showing the costs of the various things he had to do and it wasn't on there. The wear pattern was completely through to the copper backing and was about 1/2"-3/4" wide and only over about 1/2 the width of the shell. There was no scoring or gouging on the journals I would just think after that many miles it wound be out of round but I'm only guessing here I'm not a machinist. A lot of people I've talked to are skeptical that it wouldn't be out of round so that's what has me concerned. Their gonna finish boring/honing the block(w/torque plates) and doing a valve job on the e7's next week and I'll get everything back on friday. Told them I'll wait off on the balancing job till April cause I'm low on cash(true story) and mic the crank myself and see. If it's out of round I'll take my stuff to a different machine shop and get the crank turned and the rotating assembly balanced. I'll also have said shop check the bores cause if their screwed I'm screwed. If the crank mic's out fine I will take my stuff back to the same machine shop though.

I've heard that you can have a max of .003" out of round but I found specs from gonzo motorsports that says only .0006"http://www.gonzomotorsports.com/?page_id=509 . Would .0006" be the max? Thanks for the help Rick

 

[Rick 91GT]

.003" out of round is not correct...that would be a major issue.

 

[whitey68]

do you have your stuff at a reputable shop now?

 

[f8tlfiveo]

You cannot measure runout with a mic.. All your doing is measuring across two points.. Your just measuring the the part one place at a time.

 

[Rick 91GT]

You cannot measure runout with a mic.. All your doing is measuring across two points.. Your just measuring the the part one place at a time.

Correct only taper.....hopefully the machinist put it up in the crank grinder....thats a reason I asked if it was polished....good indicator it was actually looked at.

 

[ryan7662]

do you have your stuff at a reputable shop now?

Not yet they were in the middle of boring the block with torque plates when I called the other day. I'll get everything back this upcoming friday and it'll be a week or two before I can take it to the other shop. The other shop is a little more expensive but screw it they have a much nicer, cleaner, and bigger facility. Talked to them on friday and they said with that many miles it'd definetely need to be reground and be next to impossible to be still in round.

All the current shop is doing is a valve job and boring/honing the block w/torque plates. Hopefully they can't screw that up cause if they do I'm screwed and I'd have to take em to small claims court or something. I'm hoping that doesn't happen and they can just finish boring the block wihout issue but I will have the other shop check the bores out. The pistons were a special order .020 over forged set from speed pro I can't return them so if the block isn't bored correctly the new shop won't be doing anything else on the motor.

 

[ryan7662]

You cannot measure runout with a mic.. All your doing is measuring across two points.. Your just measuring the the part one place at a time.

That's what I was afraid of I saw a youtube video of a guy demonstrating that. He had a triangular shaped oblong-looking shaft and it measured the same no matter where he put the mic. Leaves me to wonder how you would even measure for out of round? Seen rebuild manuals that say to measure on multiple places to determine out of round but that doesn't seem to produce reliable results. Guess the only way to be sure would be to grind the crank .010" over after I put 250,000 miles on it? Would tearing it down at say 100,000 miles and replacing the bearings make a difference in keeping the crank from wearing or becoming out of round?

 

[ryan7662]

.003" out of round is not correct...that would be a major issue.

Thought .003" sounded like a lot I think up to .0006" is probably the right maximum OOR allowed. .0006" would be less than the thickness of the oil film any higher and it might penetrate through. That website says I want a oil clearance of .0004"-.0015" on the rods and mains which sounds a little tight to me? I thought I was wanting to shoot for .002"-.003" on the mains and .0012"-.002" on the rods. Should I shoot for that kind of clearance or go with the tighter clearance indicated on that gonzo motorsports site? Mind you I do have a hot side single turbo kit from forced inductions and once I get a turbo, quarterhorse, fuel injecters and the cold side made up it'll be a turbo motor. That's why I'm going back with SCAT forged I beams and speed pro powerforged pistons right now.

 

[ryan7662]

Correct only taper.....hopefully the machinist put it up in the crank grinder....thats a reason I asked if it was polished....good indicator it was actually looked at.

Nah I think he only put a mic on it......at least I think he did who knows. Maybe he just eyeballed the sucker.

 

[Rick 91GT]

Yeah with a standard volume oil pump Id shoot for. 0025"-.003" on the Mains, .005" thrust if man trans, .007" if automatic. Rods .0018"-.0023"....Make sure you gap the rings for the added boost. Did you go with a plasmamoly top ring?

 

[f8tlfiveo]

You would have to put the crank in some sort of a fixture that would allow you to spin it and use a drop indicator or dial indicator to measure the surface as you are spinning in. That would get your runout... Total runout you would have to do the same but move the indicator left to right over the bearing surface to check the whole surface while spinning the crank not just one spot like runout would check... I just took a geometric tolerancing and dimensioning class at work for a refresher..

 

[ryan7662]

Yeah with a standard volume oil pump Id shoot for. 0025"-.003" on the Mains, .005" thrust if man trans, .007" if automatic. Rods .0018"-.0023"....Make sure you gap the rings for the added boost. Did you go with a plasmamoly top ring?

Yeah I got the E458k plasma rings to go with my L2488 forged pistons. I have a 400 grit flex-a-hone the kind with the little balls all over it that I used on a previous 351w build. I've been told by a lot of people that I should have a 400 grit finish but the guy at the machine shop insists a 280 grit is sufficent. He said he'd charge more to do a 400 grit finish and got defensive when I told him I thought plasma-moly rings needed it. Rather than argue with him about it I'll just pass my 400 grit hone through it when I get it back.

I have a ring filer so I can gap the rings more like you say but how much do you think I should open them up? Thanks again Rick

 

[ryan7662]

You would have to put the crank in some sort of a fixture that would allow you to spin it and use a drop indicator or dial indicator to measure the surface as you are spinning in. That would get your runout... Total runout you would have to do the same but move the indicator left to right over the bearing surface to check the whole surface while spinning the crank not just one spot like runout would check... I just took a geometric tolerancing and dimensioning class at work for a refresher..

Not sure if these guys did that or not but I'll have the second shop verify it. I've called around to a bunch of different machine shops in the houston area and they were all unanimous in the opinion that it'd be HIGHLY unlikely for the crank to be fine still after 250k+ miles. Even the machine shop teacher at my college who's been in the buisness for decades said that with wear through to the copper backing that it'd probably be out of round. With that many miles he said it'd be wise to go ahead and turn it .010" and that's what he'd do in my situation.