I am getting frustrated with my 408, I am assembling the motor and having problems with the thrust bearing. As soon as I start to torque down the #3 cap with the thrust bearing the crank will no longer spin AT ALL. The sides of the thrust are stopping it from moving, sort of like it is wedging against the crank. I keep taking a little off the sides of the bearing and it is getting better but Im not going to have much left if I keep going at this rate. Anybody ever have a problem like this? Also I am running a iron block with a aftermarket crank and clevite HX bearings.

Any insight would be greatly appreciated.

Thanks

 

Did you set the thrust bearing? Before you torque down the cap, you have to hit the snout of the crank to move it rearward, then hit the rear flange to move it forward. Give it a good smack, preferrably with a brass drift and mallet or something soft so as not to damage the crank.

 

Yes, I have been hitting the crank. I put the crank in then I pull the caps down then I give a good smack forward them back, then I finish torquing them down.

When I pull the caps down against the crank I see if it will spin, then I give it a couple whacks and check it again, after I set the thrust it spins nice and free until I start to torque it down.

 

It's just the #3 cap causing it? What do you have for bearing clearance?

 

Yep, just #3. All the mains are at .0022-.0025.

 

What crank? I've seen Compstars with too little thrust clearance ground into them. You may want to use a caliper and measure.

 

It's an eagle. I'll have to measure the crank in the morning. Its just a little wierd, this was a running motor and I didnt like the way the clearances were set. The bearings were already trash after some track passes and 100 miles. But, the thrust bearing looked fine on the sides. I have tried two different thrust bearings so far with no difference.

 

I am sure this is not the problem but I once had a main cap backwards and it was causing crank to bind when tightened.

 

Got it handled, Thanks for the help.

 

What was the problem? What did you end up doing?

-Geoff

 

I took a grinder to the crank.








J/K LOL
I ended up having to take more off of the sides of the thrust. There was still plenty of bearing left so I think it will work good.

 

Be careful, take too much and you'l trash that thrust surface. It's gotta have those grooves in there to get oil.

 

Groove the thrust bearing for oil supply to the rear of the bearing.

 

Yea, I re-grooved it a little bit to make sure it would get proper oiling.

Thanks for the help guys

 

If you had it line honed they may have jacked up the cap or leaned it. I have not really had that problem so its not that common if you are doing things right but then I don't use Clevites on mains either on LS1s. Maybe they are better nowadays?

 

I used FM bearings the first time around and didnt have problems, probably should have used them again. These are billet mains and that was the only issue I had everything else was perfect.

 

If you sand the front of the cap side of the thrust bearings you should be fine but I wouldn't sand the rear where it actually takes thrust much. Still if straight it should be close but good luck. Is it a manual or auto car?

 

Its an auto. Everything is good now I hope .0025 on the mains and .004 endplay.