Piston to Crank Counterbalance Clearance...
Piston to Crank Counterbalance Clearance... Today I mocked the bottom end together. I put the crank in with the #3 main cap on then used a piston and rod to check for possible clearance issues. I was primarily concerned with the pistons hitting the reluctor ring, but it actually comes very close to the crank counter balance instead. It looks like there is about .060-.070" clearance between the bottom of the piston and the crank counterbalance on the #8 cylinder. Is this enough? I didnt check any of the other cylinders.
Well I went back and checked again with a feeler gauge and the clearance is about .050 on ALL of the pistons with the crank counterbalances. Is it safe to just machine about .050 off the crank instead of grinding the pistons? I have marked the crank where the problem areas are. Also, the #4 and #5 pistons get REALLY close to the block, so I will grind a little bit off of the pistons for these two cylinders.
Nothing has been balanced yet. And if I machine an equal amount off each counterbalance then theorhetically the crank should still internally balanced, not that they are balanced very well from the factory anyways.
I had a similar problem with my 4 inch stroke eagle crank with mahle pistons. Some of my throws actually touched the pin boss of the piston. What sucked is I already had the rotating assembly balanced. My machinest suggested taking the material off of the counterwts. It was only about 3 inches on the affected throws. He said I should have .060 clearance to be safe. I had to have the crank rebalanced though. It cost me 150.00 to learn to mock up before balancing. I think the cheaper crankes like the eagle probably have larger throws to save on the mallory metal.
My counterweights are close to hitting the piston skirts at BDC instead of the piston bosses. I must have gotten a nice batch of Diamonds because I have plenty of clearance around the reluctor wheel also, which is almost always a trouble spot. That or my reluctor wheel is really off.
Basically my two questions are these: Is it okay to go ahead and machine some material off of the crank? If so, is .050 enough or too much? My second question is, is it safe to go ahead and do a little bit of clearancing on the #4 and #5 piston skirts to clear the block?
Thanks!
Basically my two questions are these: Is it okay to go ahead and machine some material off of the crank? If so, is .050 enough or too much? My second question is, is it safe to go ahead and do a little bit of clearancing on the #4 and #5 piston skirts to clear the block?
Thanks!
Last edited by Ferocity02; Dec 19, 2005 at 07:38 PM.
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Its an Eagle crank, Lunati rods, and Diamond pistons. If you have an Eagle crank you probably know how the counterweights look. I just need to take .050 on the round part of the counterweights on the edges, if that makes sense. I think its would be easy to just throw the crank in a lathe and and dial in .050, then balance everything afterwards. That would give me a safe .080 or so of clearance between the skirts and the crank.
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Verdad Gallardo I think you would only need take .050 off for the couple of inches of travel that occurs when piston is at btdc. I tapered mine from .060 or .050 in your case to nothing as the piston moved away. A grinder with some hand flat filing made it look like it was done professionally. If you take the .050 off on the entire outside of the counterweight it will take more mallory metal to rebalance. I am not sure how critical the balance is though. Maybe someone smarter than us can chime in here?
I don't plan on taking .050 off the entire counterweight. The outside edge of the counterweight doesnt have a constant radius. I can't really describe it, except putting it in a lathe and dialing in .050 will not remove material from the entire outside face of the counterweight, just a few inches of it. As far as I know, the Eagle crank have enough material on them to make removing a litlle bit not an issue.
Ok... I filed down the #4 and #5 pistons to clear the block and they look great. Now I just need to know if I can take about .050 off the crank counterbalances. I found an old thread about someone else doing this and I never saw any negative comments about it.
