New build, Rear Main bearing melt down -Frag - toast... WHY?????

[cptcrusty1]

HI all;

My friend and I have been basking in the afterglow of having successfully built our 1776 engine. runs like a champ, 32/36 carb was acting like it wanted more than "just" a 200 jet in the Secondary Main, life was good. We pulled the engine to retorque the heads and do a general look through and I just happened to feel the crank move a bit... the wrong way. When I measured, the crang was moving about 1.5mm's, which is much further than it should.

I pull the flywheel, no oil leaking, but... the shims were worn razor thin and two were welded together in one spot. The attached picture shows the condition of the rear bearing as we found it over the weekend.

74mm crank, 110 cam, 87mm p/c, 40mm valve heads, EMPI 32/36 carb, Pertronix ignition, external filter.

We were super careful. We paid very close attention to all the details, going through "the book", etc.

The rods slide back and forth a little, but not forward and backwards, if that makes sense. Haven't split the case yet.

Everything spud freely when the engine was together, no binding so we are certain we didn't pinch a bearing.

The case is one of the "newer" cases from VW with dual relief; however, I did have to put a helicoil into one of the cam bearing studs... that wasn't fun, but it isn't where the problem is.

Any friendly input is very welcome. I've built engines before and my confidence has been kicked in the teeth.

Signed... dejected, frustrated, and really confused.

[vwinnovator]

That stamping on case indicates .020" align bore..

By change is the trust cut made as well and you used std brgs?

[MuzzcoVW]

Are you sure the end play was set right? You didn't just throw three shims in without measuring I hope. It sounds like it was tight, or maybe the shims were put in dry?

[cptcrusty1]

I had a local engine builder measure the case and the crank (it -was- new) even though it said it was line-bored.

The shims were definitely not put in dry. At least, that was a few weeks ago, so I don't remember 100% and... just because you're asking I'm going to start doubting myself. Since you're asking, let's say I didn't forget, how do they stay lubed? The rear seal didn't have large amounts of oil around it so I've been wondering if the rear oil channel feeding the rear bearing wasn't pushing enough oil... not sure and won't be until I crack the case.

We measured the shims with calipers even though the bag said what they were supposed to be. Also, we measured the end-play with a dial indicator. However again... this is something I've never done before. I always just "used what it had before" when I was younger and dumber and poorer.... so now that I'm doing it right, I screw it up?? UGH.... I'll need to think about this.

[Busstom]

This might seem like a dumb question, but did you crank and prime until you had oil pressure?

Generally, all the parts should be mocked up on the bench and measured, examined, remeasured, numbers tallied up, pre-assembled, disassembled, measured and reexamined, checking for compatibility and smoothness of operation and clearances before it's all sandwiched into a semi-permanent cluster of an engine.

[jpaull]

Mine looked like that when i set the end play at .0035-.004. Soon as it gets hot and expand there is no where to go, so it grabs the shims and also trys to spin the rear main.
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[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[mark tucker]

rear main gally pluge, blocked off, rear thrust bearing put in backwards. set up to tight, crank got hot fast,many things can go rong.even sliding the flywheel 4' across the floor befor installing it and scraping the thrust serface... possiably forgoted the dowel pin...tear it apart and lettuce know.

[cptcrusty1]

[MuzzcoVW]

[Ohio Tom]

Looks like the main is melted.
I have seen that before.
Main oil feed is likely blocked for some reason.
I see alot of silicone on the case split line. That is a big No-No.
Silicone takes up too much space and will hold the case open and the bearings will fit loose. (among other issues).

Or, the silicone got squeezed into an oil passage and is blocking flow.

Or, the main bearing oil groove doesn't line up with the oil feed hole in the case.

All things to check once you get it apart.

Story on using Silicone on case halves:

There once was a guy in PA that folks respected and went to for HiPo builds.

I got to service 3 motors that he had put together. All of them used silicone on the case halves. All of the cases were warped and had to be scrapped. You could lay a straight edge across the case and see it was warped badly.

I was amazed at the crappy workmanship of such a respected builder: JB weld to fix a break-thru; holes plugged with 3/8" bolt JB welded in place (not a pipe plug). Good quality parts, just thrown together.

High HP motors with serious issues that lead to their short lives.

[fl59bug]

[cptcrusty1]

[cptcrusty1]

Ohio Tom;

Been putting lots of thought into this while I recovered from a beeyatch of a cold, and that work thing that keeps happening.

The crank still moves freely. Just wanted to put that out there. Also, I spun the crank and the bearing doesn't move so likely the pin didn't sheer.

I need to determine if my rotating parts are toast. When I took apart the top end, I had a bear of a time getting the wrist pins out of the pistons. The still wobbled up and down like nothing was wrong, but the pins didn't want to come out. I will check if that is because of the rod, or because of the piston.

The rods shift back and forth some, I just don't know what is acceptable, but I'm going to do a full tear down and inspect. I do not feel any forward/back movement in the rods though.

Does any of that mean anything to you? Or anyone...

Here's what kills me. The last 3 times I did this, we had the book, but we just threw things together and it was great. Drove the crap out of it. Beefed it up a couple times more. But this time, I'm being very careful, and something really bad goes wrong... just a confidence killer... wow.

[67rustavenger]

Gently warm the piston wristpin bosses with a propane torch or a heat gun.
The wrist pins will slide right out of the pistons.
They don't need to be too hot to touch. Just warmed a little.
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