How can I keep this motor together?

[turbowrenchhead]

I have already mildly rebuilt my motor twice. The first time I had the heads worked on. Ground the vavles and seats and had them surfaced. I had the block cleaned and checked for cracks and honed the clyinders. The crank was checked and polished. I put new mains and rod bearings and rings in it. The second time around the thrust bearing was wearing bad on the side of the trust bearing. All of the rod bearings on the rod side were copper. So I had the crank cut, checked the rods and replace the bearings and rings again. I know that the rod bearings have too much tolerance again becuase I am getting a rattling noise when the motor has no load on it around 2 or 3 thousand rpm's. It is the same noise it made the last time it needed a rebuild. So my question is how can I keep this thing from chewing up bearings besides no knock. I have a knock gauge. I have always let off by the first glance of the light on the gauge. There was one time the gauge pegged becuase I was going down the track and the pressue line for the alcohol line came off. So I was no getting any spray. That didn't help any. Will some billet caps help any. Or forged pistons? I don't see how these things will help the rod bearings.
Comments?

 

[cool 84]

If the motor was built right, the only thing that will cause the rods to wear like that is a lot of knock but you would think you would've blown a headgasket if that were the case.

What exactly is it doing? Just a rattle? Mine's done that for the last 20,000 miles. I learned after my third engine failure before 5,000 miles that the only way to get it done right is to do it yourself or have someone like Ken Duttweiler do it. It's sad when this is the first motor I built by myself and it's gone 4 times as long as when the "pros" did it and I've beat the hell out of it. The main thing is to set it up tight. I had around 1.9 thousanths on the mains and 1.5 on the rods. It seems the normal life expectancy when set up loose like a Chevy is about 5,000 miles and when you tear it apart the bearings look like they came out of a 200,000 mile motor. I double checked everything that came back from the machine shop and had to send my crank back twice because they didn't take enough off of it. I believe the thrust was 5 thousanths.

I paid for them to blueprint everything. When none of the clearances were right I asked how they went about blueprinting. It blew my mind when they measured the bearing thickness, mesured the rod diameter and the crank diameter and figured it up. They didn't install the bearing and torque the rod down to measure and they only did it with one rod, one bearing, and one crank journal. The moral is don't trust anyone. Do it yourself.

 

[turbowrenchhead]

I plastic gauged a coupld of the rods and mains and they seemed to within specs. Do you have to get the tolerances alot tighter? If I can get some specs there is a very good machine shop close and I trust them if I told them what to do.