[many birds]

I’d never heard of King bearings when I was assembling my ‘68 400 stock crank engine. I was initially considering clevite. For whatever reason that I don’t remember, my machinist recommended king, and now 8k miles later, no problems.

[wbnapier]

I spoke to the machinist today. He's done with the diagnostic.

He is 100% sure the problem is with the #5 bearing. The bearing sits too far rearward, due to the locater tangs. This combined with an aftermarket forged crankshaft with the large fillet radius resulted in catastrophe.

"Too far rearward" as compared with an older Clevite bearing and modern FM bearing. The older Clevite bearing is defined as when they still ground the tear-drop relief in the #4 thrust face. That older series Clevite bearings and FM bearings would be no problem with a new aftermarket forged crankshaft. Of note, Clevite's new 10 under #5 bearing is equally problematic too, not just standard size.

The Clevite sales representative has visited the shop to view the problem and the machinist has emailed them some photos. The representative is scheduled to return to his shop in 1-2 weeks.

The machinist has set up my block, a series of crankshafts, and a series of bearings to run through the issue with them as a proper experiment. He is re-align honing the block later this week, but will pause after that so as to keep the set up pure for the testing.

Of note, he has some stock Pontiac cranks, Scat 400/455 cranks, and an Eagle crank he measured and the after market cranks (including mine) are 0.005-0.006 thousandth longer and therefore my endplay is fine, but rubbing up against the #5 bearing, not the thrust bearing. If I had tested end play with a stock crank, it would have been too tight. I don't know if I am communicating that correctly, but something along those lines.

He has reground my crankshaft 10 under, and there is no issue now, as the fillet radius is reduced from that.

The shrapnel in the oil pan is from the bearing, he doesn't see any issue with my block, but I told him I thought I saw a piece missing in a photo which is another photo illusion.

The collapsed spark plugs remain a mystery. He says there is no sign of mechanical interference and those cylinders show no sign of combustion having every occured. His best guess is a dropped them before install and they bent in. I told him no, that didn't happen, but there is no other explaination.

I'm going to contact Butler to see what relied I can get from their side and make them aware. I'll also start ordering parts.

[johnta1]

Glad your getting it figured out!



Also glad you took it apart instead of just trying to work on the plug situation.

[Scott Stoneburg]

Glad you didnt give up, and are getting it back together.

[tekuhn]

You drove the car a fair distance before the seize, and surely you would have known if the engine was running on 5 cylinders. I tend to agree the spark plugs are a real mystery, but can't believe you wouldn't have detected that severe of a misfire if the gaps were closed from the first fire-up. Especially with a manual transmission and clutch where everything is transmitted to the driveline.

[wbnapier]

Originally Posted by tekuhn

You drove the car a fair distance before the seize, and surely you would have known if the engine was running on 5 cylinders. I tend to agree the spark plugs are a real mystery, but can't believe you wouldn't have detected that severe of a misfire if the gaps were closed from the first fire-up. Especially with a manual transmission and clutch where everything is transmitted to the driveline.

I did detect the misfire. I thought it was A/F or timing. I didn't think it was a no fire in the plugs. My plan was to cruise for a few minutes then return home and figure out the misfire.

And, I used the temp gun on each exhaust port and all were + or - 10 degrees. So, I assumed all cylinders were firing.

Remember, this is my first rodeo... Not an expert.

[tekuhn]

Originally Posted by wbnapier

Remember, this is my first rodeo... Not an expert.

Ah, OK. I didn't realize it was missing from the beginning. Not being critical at all. Has me rethinking whether I need to pull an engine I've had sitting installed in the chassis and never fired yet. I'm pretty sure I used Clevite 77's. This bearing thing could have been easily missed. I think I do understand what the machinist is saying. When you measured your thrust end-play, the crank was stopping short of reaching the rear-facing thrust face on #4 and instead stopping because the crank journal radius was hitting the rear edge of the #5 bearing shell. That would explain the weird noise that you heard when you pushed in the clutch in the final moments before seizure. The number 5 bearing edge and crank journal radius was under extreme contact from the pressure plate pushing the crank forward until it failed.

[wbnapier]

Originally Posted by tekuhn

Ah, OK. I didn't realize it was missing from the beginning. Not being critical at all. Has me rethinking whether I need to pull an engine I've had sitting installed in the chassis and never fired yet. I'm pretty sure I used Clevite 77's. This bearing thing could have been easily missed. I think I do understand what the machinist is saying. When you measured your thrust end-play, the crank was stopping short of reaching the rear-facing thrust face on #4 and instead stopping because the crank journal radius was hitting the rear edge of the #5 bearing shell. That would explain the weird noise that you heard when you pushed in the clutch in the final moments before seizure. The number 5 bearing edge and crank journal radius was under extreme contact from the pressure plate pushing the crank forward until it failed.

Exactly. He said that with aftermarket crankshafts, specifically my Scat and an Eagle he measured, they are longer compared to the stock Pontiacs he measured. Either overall or in a specific area, I don't know.

So, when one measures end play, you get a good mesurement. This is a false measurement though. Had I used a stock crank, I would have had too little endplay with these bearings and known there was a problem.

I don't know what to suggest to you. Of course, based on my experience, I would tear it down. Remember, my machinist bought a 10 under set of Clevites, and same problem as mine. So, this wasn't a one off error.

I emailed Butler tonight. I want them to test the Clevites vs. FM.

[wbnapier]

Does anyone know why Clevite no longer grinds the teardrop-shaped relief in the thrust bearing? Does FM or King do this?

[johnta1]

Probably saving money?
(extra maching step)

[charlie66]

When setting up a new set of bearing one should check the endplay with out the caps . If its good then go forward with the caps starting with the thrust. If good go to the next one and so on.. As you go the problem will reveal itself if there is one..

[Gary H]

Originally Posted by wbnapier

Does anyone know why Clevite no longer grinds the teardrop-shaped relief in the thrust bearing? Does FM or King do this?

I don't use many Clevite bearings, mostly FM, but I don't ever remember Clevite having the reliefs on the thrust surface of the thrust bearing.

[darbikrash]

King does put the oil relief on Pontiac thrust bearings.

The thrust bearing on top came out of my 400, not sure of the brand, the bearings below still in the package are King.

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[chiphead]

The FM4040 (3" main) do have the reliefs in the thrust shoulders. They also have an oiling slot and not just a round hole to line up with the block oil passage.

Ditto to what Charlie66 says about checking each half of the thrust bearing. Sometimes the upper and lower halves of a thrust bearing are slightly different thicknesses at the thrust shoulders.

If you have .007" endplay with the upper insert only and .005" with the cap installed, there is a .002" misalignment somewhere. Usually requires feeler gauges between the thrust faces and the crank to find it. Then glass plate sand the thrust face of the tightest insert to get back to .007" with the cap installed. This prevents all the thrust load of the crank shoulder from being loaded on only the upper or lower half of the thrust bearing.

[ponjohn]

Originally Posted by chiphead

The FM4040 (3" main) do have the reliefs in the thrust shoulders. They also have an oiling slot and not just a round hole to line up with the block oil passage.

Ditto to what Charlie66 says about checking each half of the thrust bearing. Sometimes the upper and lower halves of a thrust bearing are slightly different thicknesses at the thrust shoulders.

If you have .007" endplay with the upper insert only and .005" with the cap installed, there is a .002" misalignment somewhere. Usually requires feeler gauges between the thrust faces and the crank to find it. Then glass plate sand the thrust face of the tightest insert to get back to .007" with the cap installed. This prevents all the thrust load of the crank shoulder from being loaded on only the upper or lower half of the thrust bearing.

Interesting.

[charlie66]

Also,as you tighten each cap down rotate the crankshaft to see if it locks up or gets tighter. After all checks out try rotating it while holding pressure to the thrust just like you would for checking end play.. If theres a radius problem it will show signs of wanting to get tight .

[wbnapier]

From Butler:

"We have seen this with every brand of bearing and it seems to be more a difference in the blocks to us (most likely core shift over time possibly?)

We just recently had the same issue with a 389 but this is something we always check and sometimes have to slightly narrow and/or re-chamfer the bearing.

This is just part of the blueprinting process and a step we always check."

I wonder what else is always checked that I don't know about.

[MarkS57]

Originally Posted by wbnapier

From Butler:

"We have seen this with every brand of bearing and it seems to be more a difference in the blocks to us (most likely core shift over time possibly?)

Core shift? I can believe that of the rear main seal area but the main bearing saddles, thrust location and the bearing tangs- aren't they machined operations? As well, why no warning in the kit instructions? Hmmm..

[61-63]

As someone above said we the end users must perform the quality control on products. It behooves all of us to buy some quality measuring instruments and learn how to use them. This thread has been an eye opener for me beyond what I already knew to be true.

[mgarblik]

You do get an appreciation for how well the original engines and all the internal components fit together and worked flawlessly for millions and millions of miles when weird stacked-up tolerance problems like this happen. I have built probably just under 100 Pontiac V-8 engines and I have never seen this problem crop up. But there it is and apparently Butler has seen it. Another little thing I will certainly check moving forward. I am glad the OP won't have a huge expense getting this fixed. A tough lesson for sure. My personal thank you for sticking with the Pontiac engine and getting it repaired so you can enjoy the car. It will be worth it.