I've got the LT1 down to the short block and was about to take it to the machine shop to have the deck surface looked at. I have some pitting which caused a small head gasket coolant leak into the #7 cylinder.

I am measuring .035 crank shaft end play and the book says it should be .002 - .008. The engine has 80K miles since the complete rebuild. It is a daily driver and not beaten.

I haven't pulled the oil pan yet to measure clearances on the journals but my question is, how do you correct excessive end play? Do you just replace the bearings (especialy the thrust bearing) or could the entire crank need to be replaced? Just trying to understand the possible corrective measures that might need to be taken so I can discuss intelligently with the machine shop.

Can anyone elaborate?

 

Probably need a new thrust bearing if the crank is in good shape, but they should be able to measure the main journal for you and tell you what kind of shape it is in.

 

I had my original crank and torque converter reconditioned. When I orginally installed them, the gap between them was about 1/8" - 3/16". My trans builder said to use washers to fill the gap so the torque converter can not move too far forward. They went in easy so I don't believe there is any preload on the thrust bearing. What is the spec for that gap and should I not use the washers? for the gap mentioned?

 

I've got the block on the stand and the oil pan off. Before I untorque the bearing caps, what measurements should I take? I don't have a bore guage but I have a digital vernier caliper, a dial guage and feeler guages.

 

This is confusing. What exactly was done to the crank and torque converter? How were they "reconditioned?" Where was this "gap" meassured, between what and what?
I'm assuming that you put these washers between the Flex Plate and the Torque Converter??? If this is the case, it's wrong!! There is supposed to be "a gap", i.e. movement between the torque converter and the flex plate. When you installed the trans. and have tightened the bell housing bolts you then pull the torque converter forward and tighten the converter-to-flex plate bolts. The flex plate allows the converter to move fore and aft (slightly) on the trans. splines. If you removed this gap with washers it would put excessive load on the crank i.e. thrust bearing. Which is probably why it's worn out.

 

I believe the crank was polished. Maybe they ground the journals. I don't know exactly what was done as I paid the machine shop to check it and do what they needed to do to make it right. They also assembled the short block for me. I did have them balance the rotating assembly.

The torque converter was rebuilt. The trans shop had it sent out and they told me it sometimes is a little shorter after reassembly and that the gap between the flex plate and the converter can increase a little. They recommended using some washers, if the gap is too large, rather than pulling the converter forward. In hind sight, I should have measured the gap before dissassembly to see if it in fact increased.

So my question is, what is the normal gap between the flex plate and converter? Mine is about 3/16".

 

Don't know if this helps or not but when I got my Yank converter they said it should pull away at least 3/32" but not more than 3/16". If its more than that you need to use spacers.

 

Thanks. I appreciate the perspective. I am at the outside of the range you mentioned. It looks like I got bad advice from the "professionals" to put the spacers in. I am not going to use them this time.

 

Ok, this helps.
I would think that the crank shaft should be fine and that all you will need to replace would be the main bearings. Don't see why there would be any damage to the rods or rod bearings, unless you have gotten alot of metal in the oil. You'll know more after you've removed the crank and inspected the bearings. If the crank shaft was ground, say 10 under, it should be stamped to indicate this and the main bearing shells should be marked as ".10" over etc. Also the shop that did the work should have records of what they did(maybe) so you can check with them.
If the converter was rebuilt that means the shop had to cut the case open and weld it back together after the rebuild. This could effect the total "thickness" of the torque converter. However the SHOP is supposed to make sure this messurement is within manufactures specs. and if it is not THEY should weld "washers/spacers" onto the converter, not tell the customer to add washers. How are you supposed to know how thick the washers should be??
Anyway sounds like there has been more time wasted then damage done. So good luck with the rebuild!

 

Thanks. I just dropped the block at the machine shop. Different one than last time. The rear surface of the thrust bearing is worn and so is the rear thrust surface of the crank (badly). The shop is going to see if they can machine for an oversize thrust bearing and save the crank. If not, I am considering stroking it. Also, the deck needs to be surfaced as there is pitting which cause the original head gasket leak that started all of this.

It looks like I preloaded the thrust bearing based on bad advice to use washers by the transmission shop. Wo't make that mistake again.

Now I need to research the pros and cons of stroking. I need to make sure I comply with NJ emissions. Anybody know if stroking the LT1 will put me out of compliance?