Crank hits piston?

[boozersdart]

Hello
I have installed my 4" stroke Eagle crankshaft in my 340 replacement block with the pistons and rods (no rings installed). The crankshaft, rods and pistons was bought as a rotating assembly kit. Found that the crankshaft would hit the pistons (counterweight against piston pin area).
It would still rotate so it would just barely touch.
My best guess is to grind on the crankshaft counterweight to get at least .040 clearance at all locations of interference possibilities. Then I will have to have the assembly balanced.
I would like some feedback on this to make sure I'm on the right track so will sleep better.

Thanks again

 

[Mrmopartech]

Possible causes:
Rods are wrong and too short
Pistons need to be re machined to clearance the counter weights
Crank needs to be turned down on weights by at least a 1/8 of a inch
Pistons wrong,with wrong pin height
Call supplier and complain,and ask why?
Mrmopartech

 

[69B-Cuda]

I agree with Mrmopartech also, if you bought the whole thing as a kit, the supplier should make it right, with NO EXTRA COST TO YOU... Please let us know the outcome, if the supplier won't make it right, we should all stay away from them!

 

[dusterdoug]

If the supplier won't do anything, it's most likley easier (read: Cheaper) to touch the pistons on a bridgeport than turing down the crank counterweights. On the other hand, you'll take more weight out of the rotataing assembly (quicker to accelerate) by cutting the counterweights. Either way, a rebalance is in order...

Curious: What rods (brand and length) and pistons??

 

[needsaresto]

Where did you get the parts?

 

[boozersdart]

I have sent an E-mail to eagle crankshaft about the problem. If I do not hear from them I will call them within a week.
I bought the parts through Jegs.
Rotating assembly 20106
Eagle 4" 4340 steel crankshaft
Eagle 6.123" standard H-beam rods
Mahle forged 4032 -5.0cc flat top pistons
Thanks and I will update the response after I deal with Eagle

 

[Petzschler]

mabey the piston is "just" touching becouse you have NO RINGS on the piston and it rocking in the bore.

 

[dusterdoug]

mabey the piston is "just" touching becouse you have NO RINGS on the piston and it rocking in the bore.

Hmmmmm...

 

[64physhy]

I noticed that my forged eagle crank clears by about .060. The cast one I mocked up in it had a lot more, close to 1/4". Are your pistons correct for the application? I'm running KB 745 stroker step-dished pistons with .030 milled off the step..

 

[1wild&crazyguy]

I would look at the pistons.

I sure hope your pistons don't rock so much that they touch , for you'll have more to worry about down the road...

 

[len340]

the pistons have wrong pin location

 

[Petzschler]

i very much doubt that eagle had the wrong pistons in their rotating assemblies.

 

[len340]

i have built 4 416 strokers and one did have the wrong pistons with it and eagle don't make the pistons just the crank and rods in my case ross sent them the wrong pistons

 

[1wild&crazyguy]

yep, in reality anything can happen.

 

[boozersdart]

I called eagle crankshafts today and they said to grind off of the crankshaft counterweights to obtain a .050" clearance and do not grind on the pistons. Also they said that it would not be enough to need rebalanced but I am not sure about that so my assembly will be balanced before final assembly.

 

[moper]

I wouldn't be really happy about that, and I'd definately have the crank re-balanced. Assuming you have to take off .051" from the whole circumference of the counterweight that is a lot of metal from the most effective spot. You definately dont want the crank to be lighter than it should be if you can avoid it. Remeber we're talking grams here. That metal probably represents about 10g of weight and my assemblies are within .1g of perfect. Factory stuff can be off as much as 20-30g but the goal is to have better than factory, right?