[zippy]

So I am freshening up my 455 from having a cam lobe go flat. All new bearings. Crank is a Scat forged 4.25" stroke. Well upon fitting the new bearings, I see the thrust opening in the crank is about .060" thinner than the bearings. My machine shop ground down the thrust surfaces on the bearings he installed in my engine. BUT, he ground them to the steel backer!!! I don't see any crank damage, Engine only had maybe 3000 street miles on it. But is there thinner thrust bearings a guy can get? Or am I looking at machining the crank? New bearings won't even fit in the lobes.

The crank PN is Scat 4-455P-4250-6700-2200

[25stevem]

So you have a 4.250” stroke crank, what size are the mains, 3.00” or 3.250”?
Cranks with a 3.00” main use a thrust bearing that is 1.135” in width, cranks with a 3.250” main use a thrust bearing that is 1.195” wide, so there’s your .060”!

[zippy]

It is 3.25" mains. 455. But the thrust is 1.135" wide on the Scat Crank

[25stevem]

Do you still have your old main bearings?

[zippy]

Yes I do. But the thrust surfaces were ground down to fit the crank by the builder, whom I'm never using again. He had to grind .030 off each side of the bearings. So much that it's to the steel backer of the thrust surface Now I dunno if this a messed up scat crank or what.

[67Fbird]

an average shop SHOULD be able to FIX your crank without too much issue....yeah it sux but that's what it is.

[mgarblik]

Sounds like a 3.00" crank got mixed into the 3.25" main line when they were grinding thrust surfaces. At least your crank is too narrow instead of too wide. Just need to find a highly recommended shop with a crank grinder and someone who actually knows how to use it. They should be able to grind that just right for you and you won't have to use jacked-up bearings in it anymore. I have tweaked the thrust faces on the bearings with a surface plate and wet/dry paper to get the exact thrust clearance I want. But typically no more than .003-.005" off the faces.

[zippy]

Ya. That's what I'm thinking too. And I guess it'll have to get rebalanced too as they have to open up the counterweight spacing there too.

[turbo69bird]

Wow that sucks did you guys we the thread about the crank w a hole in it brand new eBay / China part 4.50 stroke. Seems China isn’t doing such a great job these days. At least yours is fixable. Kinda rethinking my purchase of a stroker set up right now though.

[tom s]

Who did you buy the crank from?Did you try going back to them to handle the deal?I would not touch the crank until you talk to them or SCAT!They were just sold and im told things are a little messed up right now.In the past I have had good luck with their products.Tom

[zippy]

Originally Posted by tom s

Who did you buy the crank from?Did you try going back to them to handle the deal?I would not touch the crank until you talk to them or SCAT!They were just sold and im told things are a little messed up right now.In the past I have had good luck with their products.Tom

Crank was purchased by the machine shop about 6 or 7 years ago. So I got no recourse there. Really not impressed with the shop just grinding the thrust surfaces to steel backer. So I don't really even what to contact them about it, I'm so mad. It took me a year to get car driving. The. 2 years later cam lobe went flat. Life forced me to put the engine on back burner for a few years till now. I have emailed scat. But as well, with the time frame of 6+ years. Prob going to have to have it machined myself.

[mgarblik]

Originally Posted by tom s

Who did you buy the crank from?Did you try going back to them to handle the deal?I would not touch the crank until you talk to them or SCAT!They were just sold and im told things are a little messed up right now.In the past I have had good luck with their products.Tom

SCAT was recently purchased by Taglich Private Equity Group along with AFR, (Air Flow Research). Look for the "Brain Drain" to begin in the next month or two. Like rats fleeing a sinking ship, everyone making a decent living or having any real knowledge will be shown the door. Look for both companies to be ruined shells of themselves in a couple years. Two more good names gone to the bean counters.

[tom s]

Good crank shops can do wonder with forged cranks.Just had the thrust welded up,turned and reheat treated at a local shop here.Tom

[hurryinhoosier62]

Originally Posted by mgarblik

Sounds like a 3.00" crank got mixed into the 3.25" main line when they were grinding thrust surfaces. At least your crank is too narrow instead of too wide. Just need to find a highly recommended shop with a crank grinder and someone who actually knows how to use it. They should be able to grind that just right for you and you won't have to use jacked-up bearings in it anymore. I have tweaked the thrust faces on the bearings with a surface plate and wet/dry paper to get the exact thrust clearance I want. But typically no more than .003-.005" off the faces.

X2, Mike. A COMPETENT crank grinder should be able to correct this manufacturing defect. WHY would anyone grind .060 off of a thrust bearing?

[zippy]

So, I've been in contact with the shop who assembled the bottom end like this and ground the bearings down. He says not a problem. Just needs crank, bearings and main cap. My dilemma tho is, he, or someone at his shop, ground the thrusts to steel, then assembled and shipped off to me. Now do I trust this shop to make it right? Or do I bite the bullet and pay another shop to do it? Also, everything has been balanced before. Looks like probably going to have to take .010" off each inside of counterweights at the thrust bearing at least. It's about .015" narrower than the bearing thrust surfaces right now. 1.1795" between counterweights. Is this going to throw my balance off enough to warrant a rebalance?

[Joe's Garage]

Originally Posted by zippy

My dilemma tho is, he, or someone at his shop, ground the thrusts to steel, then assembled and shipped off to me. Now do I trust this shop to make it right? Or do I bite the bullet and pay another shop to do it? Also, everything has been balanced before.

Spend the extra cash now or you will be wondering about it FOREVER.....

[zippy]

Originally Posted by Joe's Garage

Spend the extra cash now or you will be wondering about it FOREVER.....

For the record, I will be doing my own assembly and measuring everything. This has been the first time I ever had someone assemble a bottom end for me. Prob 8-10 engines in my life with no problems with me checking everything

[Formulabruce]

I have seen the thrust bearing ground when using Scat cranks before and they last and last. I doubt it was incompetence, the "thrust" surface doesn't get much wear at all if everything is right.
Scat, like Eagle, had a machine shop in the US and fixed the forgings made in Asia on old American made equipment.

[zippy]

Originally Posted by Formulabruce

I have seen the thrust bearing ground when using Scat cranks before and they last and last. I doubt it was incompetence, the "thrust" surface doesn't get much wear at all if everything is right.
Scat, like Eagle, had a machine shop in the US and fixed the forgings made in Asia on old American made equipment.

You have seen the shells thrust surface ground to the base steel and they lasted???? Just wanting confirmation. I don't think it's right, no oil grooves left when grinding that far

[turbo69bird]

Sounds like a hack job to me. Why wouldn’t you (the shop) just fix it right rather than band aid it And even IF they were going to band aid it, why wouldn’t they ask you if that’s what you want them to do. I know I wouldn’t let them do it again Id have a better shop do it, if you know of anyone better. Sometimes it’s hard to find good machine shops especially these days .

When your buzzing that thing high up in the revs you’ll be happy you did .