Aquired a great 355 block with perfect 4.030 bores for a song withh a steel 350 crank good rods and high compression pistons all disassembled..
Something minor ran thu this right after it was built years ago by some one else and pooched the mains and slightly scored the crank very minor ( I used to be a crankshaft grinder myself for a decade)
The seller knew little about it to my benefit.

My problem is apparently todays 2020 auto parts guys and the internet can't provide me with a byte of information I need to check out.

The thrust bearing that was in the block was badly worn on one side. The crank mains are .020 and look very good. Thrust is clean and was touched up with the stone but I can't figure out by how much. Great radii and near max grind BTW.
The measurement across the crankshaft thrust itself is 1.749"
A machinist at Cetus Automotive in Calgary said the stock dimension should be 1.724"
I've doubled checked twice! I have mics and snap gauges and I can read them.

What should the stock thrust width on the crankshaft itself be?

I also know for sure these mild steel chey cranks can be weld repaired on the thrust relatively easily, if need be.

BTW the block main saddles are straight as are the untouched decks.

 

A force from the rear (super heavy-duty clutch, ballooned torque converter) would push the crankshaft forward and wear the rear flange of the thrust bearing.
I can't imagine how there could be a force from the front. Which surfaces on the bearing and crank are worn?

 

Thanks for the reply

I do not know the history of the short block other than it sure wasn't run for long. Zero ring ridge zero piston skirt wear. To be sure its the back, clutch side of the thrust bearing worn out badly at least .020 itself. There is NO corresponding wear on the crankshaft thrust. At all. So I don't know the actual engineering factory dimension across the rear main thrust and it would be helpful.

See pics the bearing is wiped out yet the crank thrust looks fine..definitely kissed with a staone when the mains were ground....but is it acceptable? Is it ground to far? That's my question and I do have a set of main bearings coming so will find out sooner or later.

 

Found it myself.
Took forever to trace the numbers off the old thrust shell and find an ACL bearing catalog site with just enough info to help.

1.724 is the stock dimension. The shells are 1.718 stock and it appears +.020 and +.030 oversized thrusts are/were available and perhaps this was one. The crank thrust would be .011 (max) IF a .020 over main set with a +.020 thrust was used and that appears possible.

I'll look at welding it back carefully and having the thrust reground back to stock. Its actually obviously a lot easier to repair the steel than if it was a cast crank. Of course I could also crack open my wallet and pick up a Scat crank for about $300.00. Cdn.

 

Good to see you found your thrust dimension answer.
As for a $300 crank, I take you'd go with a SCAT 9000 series? That was suggested for me by AMS Engines in Edmonton for what they assumed was my application. Thing is they didn't know what my application was at the time.
Internet wise men suggest that it may not be the best choice for where my build direction is going to go and that's (hopefully) sustained WOT on some open road event. Or at least that's the intention. That would require a 4340 spec in a Gen 1 SBC. (A factory LS3 on the other hand should capable of that).
That said, the 9000 series appear to be up to the task of the modest drag racer or certain circle track classes.

 

I've seen them advertised in Red Deer for as little as $284.

Thanks I sure tried a lot of twists and turns to find it. I used to have a handbook with all those dimensions but I haven't seen it in years.

I have great faith in cast cranks to a certain level, especially the Scat 9000. Think about it, how often do you see a broken? crank in a naturally aspirated under 7000 rpm 500 hp street engine? If the radii are properly done there should be no stress risers. A lot of late 60s super V-8s especially Fords were cast even in NASCAR. There's a old school of thought that suggests the cast materials damped shock a little better in NASCAR racing but I have no backing for it, just heard it back in day once or twice.

Recall I drag raced a solid 515 HP thru a Scat 9000 in my 406 in a 3400 lb 74 Camaro for 7 years myself. I abused it plenty. That car is in Cranbrook now and was still running in the Rocky Mountain Pro Tour series with the engine untouched after I sold it last I heard.

I think if your not throwing power adders like Nitrous or turboes or such or launching at 5000 rpm LOL a well prepped cast crank can hold up pretty well. That said you have to like the safety net of steel.
I hope to use the one I have if just for the fact its an actual 1182 casting which could have been found in a 70 Z-28! Just for the fun of it on the build sheet!

 

I hear what you're saying about cast vs forged. Back home, one of the local circle track/wrecking yard owners had said they found the same was true as to what you heard about the damping. X-rays at the end of the season put the cast crank in a pretty good light. Keep in mind these weren't world beater race cars but still put a lot stress on them just from the on/off throttle alone.
Following up on that though, I found it's very true about the applications you describe and the usefulness of the 9000. If my intended purpose was to be in line with those, I'd jump on the relatively inexpensive "kit" that JB's has on sale right now. Full SCAT rotating assembly with the cast steel crank, forged rods and pistons. Plus a fully machined block all for under $3400.
But I fully intend to step outside of those boundaries so it's a step up in durability that I'm after. Something like Howard's non-twist 4340 appeals to me. Or a Lunati Sledgehammer. Bigger bucks for sure.

What material is the crankshaft you have? Seems to me they were 5140 back in the day. Which should be what I have in the wounded lump at this moment. But's it's been so long since I've had it in my hands, that I'm no longer certain.
EDIT: It may be a 1053 forging too. Something that I'll have to investigate further.
I started a conversation a few years back over at Speed Talk. Some interesting insights there.


https://www.speed-talk.com/forum/vie...hp?f=1&t=31756

 

1053 wins the cigar

According to my handy dandy "Chevrolet Small Block Parts Interchange Manual" by Ed Staffel the #1182 steel casting is "1053 forged steel 3.48" stroke ...not nitrided, two piece seal." The same manual states "these days a large number of aftermarket cranks that use a very strong 4340 steel are available".

I seems the Howards is a pretty good crank then.

 

Handy dandy manual indeed.
1053 was in my discussion topic title at Speed Talk (had to go back in time to look that up). So that part is figured out. Thanks.
Seems the 1053 and the cast steel cranks have about the same tensile strength at around 110 000 PSI although it's said the forging is less brittle. Interesting comparison.
Yes, the Howard's is a pretty good unit. Then again it's $1250 CAD whereas the SCAT 4340 "equivalent" is only $1050.

 

This looks almost identical to my friend Doug's 400 SBC that I mentioned earlier, except that the journal surface of the bearing was fine - only the rear thrust part of the bearing was wiped out. New crank, new bearings, proper clearances, .006 thrust clearance and it happened again. Only took 1/2 hour on the test stand. Never did figure that one out.
http://garage.grumpysperformance.com...41/#post-71921

Here is a tip on how to provide a little more oil to the thrust surface: http://garage.grumpysperformance.com...19/#post-37676


I found this on the King Proflange bearings:

 

Thanks for the help. I read a string by Ruskbucket from a decade ago that mentioned bearings that were available. I'll be checking that out. From my measurements with a .020 main with a .020 over size thrust I should be good to go.I should get away with about .009 end play.

Strange that happening twice on the same engine. No one likes a mystery and one would hope there's an explanation. The rear seal main bearing surface is supposed to be 1/2 thou lower than the other mains on an SBC. Maybe it wasn't enough clearance to start with??? Just spit ballin as I've never encountered that problem.

I'm pretty sure from the rest of the bearings and a few tiny marks on a piston that something minor and very fine ran thru my engine explaining the failure. He may have "dusted it" as they say in the diesel engine world when air filtration screws up.