[Gach]

Ok just saw you said bearings looked good. I’m guessing crank is bent. Wish I could be there to check it all out for you.

[jhein]

I don't know squat, but I've followed this thread with great interest. The way you went about your repair was quite meticulous so that makes me think something else is wrong that's not related to workmanship or small parts. As mentioned maybe something with the crank?

Whatever it is, I hope (I know) you'll get it figured out because with all the blood, sweat and tears you've put into that thing you deserve it.

[Verdoro 68]

By using a SpeedPro bearing on #5 I was able to get the clearance to .0025. I used King bearings on 1-4 with .0024-.0025 clearance. Two things I didn’t check - the line bore and the crank straightness.

The crank is a cast Eagle unit from Butler. I’m not sure if they check them for straightness before they ship them out. I would imagine they do, but things happen.

I’m thinking I’ll pull it l, get it torn down again and have our local Pontiac builder take a look at the block and the crank.

[Gach]

Originally Posted by Verdoro 68

By using a SpeedPro bearing on #5 I was able to get the clearance to .0025. I used King bearings on 1-4 with .0024-.0025 clearance. Two things I didn’t check - the line bore and the crank straightness.

The crank is a cast Eagle unit from Butler. I’m not sure if they check them for straightness before they ship them out. I would imagine they do, but things happen.

I’m thinking I’ll pull it l, get it torn down again and have our local Pontiac builder take a look at the block and the crank.

Thats only way to go..smart move. Although Butler is good..I hate to say this but you can’t trust any you get. I’ve also learn not to trust anything done by machine shops or I should don’t take it for granted. I know it sucks !

[Gach]

I’m dealing with a bent crank right now for a friend. Yeah he’s going to make good, but what a hassle sending it back.

[Verdoro 68]

Just the name of the game. Stuff happens. You fix it, learn some stuff in the process, move on and hope it helps someone else in the future.

The fact that this happened twice - and not immediately after start up - makes me think it’s a deeper problem than incorrect installation.

[Dragncar]

Originally Posted by Verdoro 68

By using a SpeedPro bearing on #5 I was able to get the clearance to .0025. I used King bearings on 1-4 with .0024-.0025 clearance. Two things I didn’t check - the line bore and the crank straightness.

The crank is a cast Eagle unit from Butler. I’m not sure if they check them for straightness before they ship them out. I would imagine they do, but things happen.

I’m thinking I’ll pull it l, get it torn down again and have our local Pontiac builder take a look at the block and the crank.

I had a Eagle cast crank once. Sent it to Dan Whitmore and he checked it from one end to the other.
It was bent .004 and has .001 tapper on journals along with a very rough thrust surface. Had to have it straightened, cut .010-,010 and polished.
Bet its the crank,

[Gach]

Originally Posted by Verdoro 68

Just the name of the game. Stuff happens. You fix it, learn some stuff in the process, move on and hope it helps someone else in the future.

The fact that this happened twice - and not immediately after start up - makes me think it’s a deeper problem than incorrect installation.

Yep !

[lust4speed]

Refer back to my #90 post. Having been there, done that, and got the melted strands, I can tell you that whether you thought you didn't pack it too tight or not -- you packed the seal in the groove too tight. To prevent this you need to lay the seal in the grove and roll it out to the ends with absolutely no compacting of the seal. After this first failure I started to just set them in place, and the oldest one is about six years old now. Here's a photo of my melted shards. I probably have about eight engines with the graphite/Teflon rear main seal out on the road and they are doing fine.

[Verdoro 68]

Maybe so. I did pack this one tighter than the first one I did. How long did that seal last?

[HWYSTR455]

Just to say out loud, should wipe the surface with assembly lube, and not go dry.

I honestly have never seen a rear main seal do that. Was the drag on the crank excessive? After you dropped the crank in etc, did you check how much drag there was?


.

[Tandyman]

Mick ,
Did you use RTV on the back of the seal or pin them or did you just drop them in place right out of the package ?
Thanks,
Glenn

[Gach]

I could be wrong, but either way the Crank has to come back out. To all of a sudden to end up with .010 clearance when first installed was 2.5 thousand tells me something else is going on. I don’t think it was packed to tight. So either crank is bent or line bore isn’t correct. Getting crank checked will answer allot of questions. Or main question.

Anyway thoughts on why all of a sudden he’d end up with .010 clearance ?

[Verdoro 68]

Originally Posted by Gach

I could be wrong, but either way the Crank has to come back out. To all of a sudden to end up with .010 clearance when first installed was 2.5 thousand tells me something else is going on. I don’t think it was packed to tight. So either crank is bent or line bore isn’t correct. Getting crank checked will answer allot of questions. Or main question.

Anyway thoughts on why all of a sudden he’d end up with .010 clearance ?

I think some signals got crossed here. Nothing is .010 clearance.

When I assembled the engine the #5 crank journal clearance measured .0035 while #1-#4 bearing clearances were .0024-.0025. I used a different bearing shell to get #5 to .0025. As far as I know, none of the clearances have changed.

I was pointing this out because it could indicate a problem with the line bore that I band aided with a different bearing.

Originally Posted by HWYSTR455

Just to say out loud, should wipe the surface with assembly lube, and not go dry.
I honestly have never seen a rear main seal do that. Was the drag on the crank excessive? After you dropped the crank in etc, did you check how much drag there was?
.

I used red assembly lube on the seal when I installed it, as the instructions say. Nothing seemed out of the ordinary with crank drag.

I may send a few pics to Best Gasket and see if they have anything to say. I'm sure they've seen it before. I'll still get the crank checked just in case.

[Gach]

Ok, must of got that confused thanks

[Gach]

Be interesting to see what Best Gasket says, or their thoughts.

[grandam1979]

I hate to say it but I’m going with packed to tight also I just didn’t want be mister negative when you were spending a lot of time getting it where you wanted it. Will be interesting to see what actually happen when you get it apart.

[400 Lemans]

https://forums.maxperformanceinc.com...torquing+mains You may have already seen this older thread.

[Verdoro 68]

Originally Posted by grandam1979

I hate to say it but I’m going with packed to tight also I just didn’t want be mister negative when you were spending a lot of time getting it where you wanted it. Will be interesting to see what actually happen when you get it apart.

When you are saying "packed too tight" are you speaking about how I pressed it in place in the cap, the pressure on the seal once the cap was torqued down or both?

I'm having a hard time wrapping my head around how packing the seal into place in the cap and block would cause more pre-load, but I can see how the cap torque (140 ft/lbs w/ studs) could bungle things. The only thing I can think of is maybe I didn't cut the seal down far enough with the spacer and/or press the ends down flush enough. Maybe when the cap was torqued it put a little too much load on the seal which caused it to eventually eat itself. Still odd that it failed after a few hundred miles and not immediately. The dissection will tell the tale.

[b-man]

Have you considered going to the one piece BOP seal?

Here’s how Mick (lust4speed) did the seal and crankshaft install on my 421 HO.

After checking the main seal fit in the block with the rear main cap tightened it was determined that it fit the machined receiver groove in the block perfectly with just the right amount of compression.

Main bearings in place ready for the crankshaft install. All main bearing clearances were checked with the proper measuring tools. After shuffling around some of the bearing halves all the clearances ended up between .0023" and .0024" so we're looking good there.

No helpers were present to help install the heavy 80+ pound crankshaft and BOP one-piece main seal at the same time, so an engine hoist was employed to help accomplish this important and somewhat delicate task.