wrist pin rod holes loose

looking for input on a ongoing problem of wallering out the wrist pin holes on the rods. BBC 524 CID, big chief ,14/71 std twist-retro-large exit hole. buzzard hat, 11.0-1 comp #1 & 2 cyls. 11.2-1 remaining cyls. Bill Miller rods, std. BBC pin sizes, J&E pistons 28/30 pounds boost @35%, 5 amp mallory @26 degrees. 990 enderle with loop, 37 lb poppet w/85 pill, max pressure 106-112 lbs, total area 36884, average main 120, high speed 72lbs-60 pill, ports open @ 16lbs, average AFR 4.550. 2150lb. car. auto trans/ rossler 210, 4.30 rear gear, leave rpm 4500,shift @6800, rod bearings show no signs of detonation, will damage rods in as little as 6 passes???? any ideas?

 

pin

What is the pin clearance with new rod and pin? What pin diameter do u use? Did u re-use the pins.

 

Pin thickness, taper or staight and what material? Pin to piston clearance? How much meat on the top of the pin bore?

 

Do you have an oil hole in the top of the rod (small end) if so is it clear debris?

 

use new pins, .992

 

straight pin, .220 thick not sure of clearance. 52100 high carbon steel, JE pins

 

I never ran that much boost on a .990 pin. Is this a BME396 style rod are the 426 forgings? If it's the 426 I would try to get the pin end of the rod as wide as the piston allows without anything binding up and set the pin clearance on the low side around .0007. Also try to have.300 min over the top of the pin. Other option is pistons and rods with 1.094 pins.

 

426 forgings

 

Loosen up pin fit in piston, be sure oil ring groove has a feed into the pin, be sure you have plenty of rod side clearance, put a big chamfer on the pin oiling hole on top of rod.

 

Never had any issurs with the 426 forgings. They are pretty tough. Did they come already pin fit are did you have it done? Does it bend the pin? Are they any signs of oil starvation? If they are getting beat up that fast, I would think they started with to much clearance.

 

If you are running BME rods I would call and ask Bill Miller for advice. Have all your information handy because he will ask for it. He loves to solve problems as mich as he loves to talk politics. Tell Annie or Samantha hi for me when you call.

 

NNNNNNAAAAAAAAA Bill's not politicly motivated He Loves our President

 

What is your piston-to-head clearance. Is there any signs of hitting the head? Just thinking out loud. Joe

 

wrist pin rod hole loose

I think it"s detonation, could be a lean spot in your fuel curve, also on hard rodbearings
you can not notice a little detonation.

 

piston to head clearance is good, thinking of getting rid of the buzzard, been running a K valve all along, has a Gerardot spool

 

Well, since it is #1 and 2, one would assume they are getting pounded due to cylinder pressure. Add some fuel. Bigger pins would also help tons.
Wags

 

All the rods get wallered out. this has been happening since assembled. Compression is lower in # 1 & 2, front holes are alot fatter because of the retro blower. Starting to think the pin dia. is the main issue, just looking for ideas because my conventional head BBC did not do this, even with 28-30 lbs boost, but it was 480 CID.

 

I had this problem years ago it was the pins flexing, bigger diameter and better material solved the problem with out changing the tune up.

 

pins

I agree with Bob,loose the .990's,go to the hemi pin somewhere around 300 grams,would also check into oil viscosity,preheating the oil,and timing.hope this helps in some small way.overthehill....