I tore down my engine today and found the rear thrust surface badly worn. The bearing was worn away and the crank's thrust surface was worn about .080" deep. This is the thrust that keeps the crank from going forward. How difficult is repairing this. I think it can be welded and assume the regrinding of the surface is critical. Is this something any machine shop that grinds cranks can handle or should it go to a crank specialty shop.

It is a Scat 9000 cast crank. It is in a car that only see the strip and is shifted at 7000 rpm. The engine had 71 passes, both 1/4 and 1/8 mile. Probably 200 hours and 20 or so miles. When built the thrust was .0065".

I understand from BillK's previous post that the cause is most likely the converter pushing forward on the crank, for various reasons. I plan on visiting the trans builder tomorrow and showing him the crank. Obviously, this needs to be resolved before the engine can go back in. Thanks!

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Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street (12.08, 113mph, 7.500@92.14 1/8 mile) 355 powered
Pat's Page (Dynamic Compression Ratio Calculator, car specs, Spark plug reading info) (http://cochise.uia.net/pkelley2/)

Not every shop that repairs cranks can fix that crank. Welding up the thrust main is not that easy and I'm betting you will have a tough time finding someone who can do the job correctly. It might be easier to buy a new crank.

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www.muncie4speed.com (http://www.muncie4speed.com)
Gold 67
1967 Malibu, 2nd owner.
1971 Malibu, new rat motor going in.
There is nothing like rowing through the gears at 7500. Stick cars are so much fun they should be a controlled substance!

Pat,
.080" wear is a lot for an engine with 71 passes on it. You might contact Scat and see if they are having similar problems reported by other customers. I have dealt with these guys a lot and they are very helpful in diagnosing problems, even when their part might have been at fault. As you may already know, Clevite (and others) offer main bearings with oversize thrust flanges, however the largest available at this time is .040" over.

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Bill
64 Chevelle Malibu Sport Coupe (original owner) car now has 427" BB, Chrysler HEMI 4-spd. trans., 12 bolt 5.57 w/spool & axles.
"HOT RODDER is NOT a dirty word"
"Too much horsepower is just enough"

Pat,
On a cast crank, I am not sure it is worth trying to fix it. The welding is not a problem....regrinding it afterwards is the hard part.
Something else that you need to look at if your block was align honed......I had one done a few years back for my own Blazer. It kept wearing the thrust bearing. I caught it almost immediately because of metal in the oil. The problem was that when they ground the cap to align hone the block, they somehow got it crooked, so that the thrust bearing was not aligned properly. The cap has to be exactly 90 deg to the thrust surface.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

Thanks for the replies. I'll call Scat today and see what they say. Also, I'll check the squareness of the cap (it was align honed), I hadn't thought of that. I would like to save the crank, I have many hours of detailing time in it. Plus a new one would have to be balanced. Anyway, I'll be checking all this out over the next couple days. Thanks again,

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Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street (12.08, 113mph, 7.500@92.14 1/8 mile) 355 powered
Pat's Page (Dynamic Compression Ratio Calculator, car specs, Spark plug reading info) (http://cochise.uia.net/pkelley2/)

I didn't think to mention that the previous engine in front of this trans showed some fairly severe thrust damage. At the time I didn't think much about it, figuring it was part of the damage done by a broken rod. I now realize this was unlikely and that the trans was probably the culprit. The engine is solid mounted so electrical grounding shouldn't be a problem.

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Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street (12.08, 113mph, 7.500@92.14 1/8 mile) 355 powered
Pat's Page (Dynamic Compression Ratio Calculator, car specs, Spark plug reading info) (http://cochise.uia.net/pkelley2/)

also check driveshaft length. convertor and or whole transmission.