[25stevem]

Did the shop that last built you that motor supply the crank?

If they did that would confirm that they likely got a good discount on that crank and chose to modify the main bearings and then not tell you!

That my take on it if they supplied the crank, but even if they did not and chose to do the bearings mod without notifications to you as such is just flat out wrong!

["QUICK-SILVER"]

Is this a stick shift car with an extra strong pressure plate?

How often do you get the oil hot enough to have an oil film failure? Sounds like you're planning on it, so why not use better oil?

Flat tappet cam and lifters is hard metal against hard metal. Overhead cam followers is hard metal against hard metal.

What kind of shape is the original milled down thrust bearings in? Does it need replaced, just because, or is it used up?

Oil grooves don't have to be deep.. .002"~.003" is plenty. Few licks with a chainsaw file.

Not seeing the problem with the original build
Clay

[25stevem]

I am changing my thinking on this.
Steel on steel is ok as long as the softer steel is the bearing so that any hard dirt or grit in the oil wares out the bearing.

Floating wrist pins can run steel on steel and the are loaded far greater then the thrust faces of number 4 .

[zippy]

No. This shop did not supply the previous crank, only this one. Previous crank was perfect fit. It is a auto car, but may go stick in future. And yes cam and lifters are hardened metal on metal. But with the bearings ground to steel, it has already ground approx .010" into the thrust face of the crank. But there is no oil grooves put back in the thrust face of the bearing. I don't know if that would have made a difference, not really wanting to test the theory with a $1800cdn crank.

[Sirrotica]

The reason there is Babbitt on one soft surface is so it will be a replaceable wear surface. If you have 2 surfaces that are steel, of approximately the same hardness they will both wear. Then you replace both parts when the wear exceeds the specified tolerance. A thrust bearing is a lot cheaper to replace than a forged crank.

It isn't rocket science here, they didn't do the correct fix for the problem. The crank should have been refused when the problem was found, not butchering the bearing to make an incorrect part fit. No matter how you spin it, they didn't perform a professional assembly method.

Just wondering if anyone would build their own engine like the questionable fix that the shop did to make it work. I surely wouldn't put my own engine together like that. If I was paying a professional to do it, and later came across this half assed fix, I'd be pissed off.

If I was cobbling a 50 year old tractor engine together, that was obsolete, and couldn't find parts for, that would never see 2500 RPM , and I was trying to save a buck, maybe, but not a street rod/musclecar engine, nope, no way.

[mgarblik]

I think what's important to realize here is this is an EASY fix to make 100% correct. For less than $100.00, this entire problem disappears and the crankshaft and bearings are working once again exactly as the Pontiac engineers designed them in 1954. No crazy re-engineering required.

[jhein]

Originally Posted by Sirrotica

The reason there is Babbitt on one soft surface is so it will be a replaceable wear surface. If you have 2 surfaces that are steel, of approximately the same hardness they will both wear. Then you replace both parts when the wear exceeds the specified tolerance. A thrust bearing is a lot cheaper to replace than a forged crank.

It isn't rocket science here, they didn't do the correct fix for the problem. The crank should have been refused when the problem was found, not butchering the bearing to make an incorrect part fit. No matter how you spin it, they didn't perform a professional assembly method.

Just wondering if anyone would build their own engine like the questionable fix that the shop did to make it work. I surely wouldn't put my own engine together like that. If I was paying a professional to do it, and later came across this half assed fix, I'd be pissed off.

If I was cobbling a 50 year old tractor engine together, that was obsolete, and couldn't find parts for, that would never see 2500 RPM , and I was trying to save a buck, maybe, but not a street rod/musclecar engine, nope, no way.

Yep

[Formulabruce]

Originally Posted by mgarblik

I think what's important to realize here is this is an EASY fix to make 100% correct. For less than $100.00, this entire problem disappears and the crankshaft and bearings are working once again exactly as the Pontiac engineers designed them in 1954. No crazy re-engineering required.

While it is fairly easy, Once done, shops charge more than 100 to balance a crank.
IF they kept records of the Bob weights, that could help lower the costs.

[hurryinhoosier62]

Originally Posted by 25stevem

I am changing my thinking on this.
Steel on steel is ok as long as the softer steel is the bearing so that any hard dirt or grit in the oil wares out the bearing.

Floating wrist pins can run steel on steel and the are loaded far greater then the thrust faces of number 4 .

In all my years as an aircraft engine mechanic and an ASE master engine machinist I have NEVER seen a full floating piston pin in anything other than a bronze bushing. This includes thousands of mid-range diesel engines.

[TedRamAirII]

Originally Posted by hurryinhoosier62

In all my years as an aircraft engine mechanic and an ASE master engine machinist I have NEVER seen a full floating piston pin in anything other than a bronze bushing. This includes thousands of mid-range diesel engines.

I think some MO and DZ 302 Chevy engines had floating pins, but no bushings?

[Jay S]

Originally Posted by TedRamAirII

I think some MO and DZ 302 Chevy engines had floating pins, but no bushings?

Chevy free floating rods in that era had the small end of the rod dipped in Babbitt.

[zippy]

FWIW, my Eagle rods have bushed floating pins. Also, As a aspiring Machinist, I know Cast and polished hardened steel wear really well together for slow moving, high load bushings. Like what would be in a wrist pin. BUT, they still don't do it!!!

Taking my new, proper 455 thrust bearing, the main cap and crank back to original shop tomorrow. It's a 2hr drive one way and with gas being about $7.50/Gal here in BC Canada, that sucks. Hopefully he will do it free, like I feel he should. Not my fault I ran his engine for 3 years, then life made me park for another 3 before I could open it up and see his mistake.

[grivera]

Originally Posted by Formulabruce

While it is fairly easy, Once done, shops charge more than 100 to balance a crank.
IF they kept records of the Bob weights, that could help lower the costs.

Will that small amount of metal added in that area of the crank require a rebalance?

[zippy]

Originally Posted by grivera

Will that small amount of metal added in that area of the crank require a rebalance?

What I am wondering too. I mean technically I would say Yes, But taking .015" off each counterweight, I estimate 12 sq in, so .18ci Just looked up density of 4340 and it/s .28Lb/CI So that makes .8 oz removed from 1 counterweight at a .015" cut. Definitely a question for the balancer.

[johnta1]

Are the counterweights full?
If not, could just cut the necessary amount on crank using just the height (diameter) of the bearing shell (plus a small amount). Then have the counterweight up when installing the crank in block. It should rotate since the counterweight is outside of the milled area (and thus the bearing is in the milled area).
The amount milled would be very small and close to the center of crank.

[zippy]

Originally Posted by johnta1

Are the counterweights full?
If not, could just cut the necessary amount on crank using just the height (diameter) of the bearing shell (plus a small amount). Then have the counterweight up when installing the crank in block. It should rotate since the counterweight is outside of the milled area (and thus the bearing is in the milled area).
The amount milled would be very small and close to the center of crank.

Oh yeah, never thought of that. I'll make sure to ask

[RAIV55]

I don't think countersinking the thrust surface will work. The grinding wheel will still have to clear the counterweights when grinding the thrusts.

Concerning the balance, I'd check and correct as needed. Although you are talking a small amount of weight, due to the diameter of the counterweights the balancer will see it as more since its about 3.5" from the center.

[TedRamAirII]

Originally Posted by Jay S

Chevy free floating rods in that era had the small end of the rod dipped in Babbitt.

How did that work out? Probably not a good long term solution?

[hurryinhoosier62]

Originally Posted by Jay S

Chevy free floating rods in that era had the small end of the rod dipped in Babbitt.

Which acted as a bushing. I will reiterate: in all my years as an aircraft engine mechanic and an ASE master engine machinist I have NEVER seen a full floating pin that ran steel on steel WITHOUT a bearing or bushing of some kind.

[hurryinhoosier62]

Originally Posted by RAIV55

I don't think countersinking the thrust surface will work. The grinding wheel will still have to clear the counterweights when grinding the thrusts.

Concerning the balance, I'd check and correct as needed. Although you are talking a small amount of weight, due to the diameter of the counterweights the balancer will see it as more since its about 3.5" from the center.

HUH? The grinding wheel ALWAYS clears the counterweights on a crank journal. There are two methods of grinding the thrust surface on a crankshaft: plunge cut, which is the most problematic, and a gradual feeding of the grinding wheel into the thrust surfaces. Either method clears the counterweights.