ChainHartMachin

I've got quite a project going since my 88 was wrecked. I'm more or less transfering everything from my 88 to my new 92. I decided to make a cam swap part of the process.

While I was removing the crank pulley bolts, I was able to pull the whole pulley, damper basically everything forward a little bit (I saw the flexplate move as well). I didn't think that was good so I measured it w/ a dial indicator. It measured out to .024", definitely way out from the .003 - .008 called for in alldata and other references.

The engine has roughly 20,000 on it. Oil pressure is between 30 - 45 psi at a hot 600 rpm idle, 60+ down the highway. The gauge pegs upon cold startup and stays there till operating temp is reached. All cylinders have compression w/ in 10% or less of each other as of last summer. Never tried for peak pressure (I.E. all plugs out and throttle wide open) but they all produced 180-190 psi with a decently charged battery and the cylinders able to suck air through fuel injector holes (had them out for flow testing at the time).

Since the cam was stock before the 88 got hit, the motor ran real smooth.
I've never seen any metal in the oil.

My questions are:

1) Assuming the rest of the engine is okay for the sake of argument, what killed my thrust bearing w/o hurting the rest of the motor? The engine has been in front of a stock 700R4 its whole life. I did not mis-install the torque converter (it seated all the way).

2) Would it be a reasonable course of action to simply pull the crank and leave the rods / pistons still in the block with the heads on? (I've found multiple cases of people pulling just a crank, some with the engine still in the car, I'm not that brave however)

3) Is .024" of crank end play enough to cause other issues such as scuffed wrist pins / bores or bent connecting rods?

4) Is there a thrust bearing design that will handle more load than the P - series Clevites? I know the speed-pro competition bearings claim to have an improved thrust design.

5) If I must pull the rods / pistons, is it neccessary to remove all the rings and clean out the grooves? Or do I just leave them alone and dip the ring belt in oil upon reinstallation ensuring that each piston goes back into the bore it came from?

6) Is fixing a crank thrust surface a typical machining operation? I'd rather not buy a new crank since that would mean a re-balance.

7) I've read there is such a thing as mains with oversize thrust bearings. Where do I get these?

Thanks very much!

jv9999

iTrader: (1)

This might help answer your questions: http://www.4secondsflat.com/Thrust_b..._failures.html

It's possible to pull the crank with the engine in the car, buy I'd never even try. You need to keep everything perfectly clean and check the clearances as you go. That's pretty much impossible laying on your back with limited access.

You either need a new crank or need to have that one ground by a machine shop. It's about $200 around here.

Or you can just keep driving it. It may never cause a problem if you're not driving it hard.

Apeiron

Machining the crank can't fix an excess of clearance. What brand of crank was this?

jv9999

iTrader: (1)

They weld and regrind the thrust surface. I had it done to a 327 crank a couple months ago.

Apeiron

They can weld it up, but unless you have some kind of emotional investment in the crank it's almost always cheaper to buy a new crank.

ChainHartMachin

Thanks for the replys so far,

I was not intending to try and drop the crank with the engine still installed, I was only wondering if it was possible with the motor on a stand.

I'll definitely check for the items in the write-up, thanks for pointing me to it.

I will replace my torque converter and get new tranny cooler lines.

Apeiron: The crank is a Scat cast steel stock replacement one piece seal 350 crank. http://www.cnc-motorsports.com/produ...646&CtgID=7645

I used clevite p-series bearings.

It was custom balanced so I'd have to factor that in once I get the engine out and I am able to inspect the crank.

Apeiron

I thought it would be a Scat. If you check the thrust face on the crank, you'll probably find it was machined with a rough finish and it's worn the bearing away.

ChainHartMachin

I'll check for that then, would the surface be rougher to the touch compared to the main journal itself? Or will it be impossible to tell?

Also, do you think removing the crank w/o removing pistons and heads is a reasonable approach in this case? (I'll have helpers available)

Apeiron

You'll be able to feel it if that's what it is.

You could pull the crank while you leave the pistons in. It'll help to have lots of extra hands to get things lined up when you put the crank back in.

ljnowell

Thats a good possibility. Perhaps a polishing of the crank and a bearing replacement.

ChainHartMachin

Got the engine out and onto a stand today. I took the rear main cap off and found that the thrust bearing was burned and worn mostly on the side that faces the rear main seal. It had worn enough that I couldn't see where the grooved spots were. The side facing towards the front of the engine was not so bad though, it still had the grooves and the copper new penny appearance that a new rear main bearing shell has. The rest of the bearing looked fine to my eyes, no copper appearance anywhere and the original tin flash plating was still present in some spots.

The crank thrust surfaces felt smooth, but I didn't have a chance to examine all of it. I did see a pattern on the thrust surfaces that vaguely reminded me of the cross-hatch pattern on a freshly honed cylinder. It was faint, but I could see it. The main journal itself had no such appearance.

I will post pics of the rear main cap and bearing shell later tonight.

I suppose I'll learn more about the cause of this failure when I can examine the upper half of the shell. If the thrust surface is worn on the same side and same degree as the lower half, then perhaps the transmission (or the thrust surface) is to blame. If the opposite side of the upper shell's thrust surface is the one that is really chewed up, then I suppose thrust alignment would be to blame in which case this would be my fault (though I'm positve I aligned it by levering the crank back and forth with the cap bolts tightened to 10 ft-lbs).

ChainHartMachin

Well, the whole motor is apart now, I abandoned the idea of removing just the crank, it makes sense that I should look a the rest of the bottom end while I have it open.

Here are pics of the thrust bearing, the black and burned looking side is the one that is facing the transmission, the side that still has a copper appearance is facing the front of the engine. The upper shell had the same wear patterns on the same side. So the whole burnt side of the thrust bearing was facing the transmission.

gluntly

So what is that telling you about the thrust washer?? I've wiped out 2 in the last 4 months, so I'd really love to know ... Thanks.
I have a 4 speed big block, so ballooning of the converter isn't the issue with this one..