recently in a discussion about the scat 9000 series 1 peice seal 383 crank a person on here "smasterson" told me of a problem he encounterd using trw/speedpro pistons...

he explained that the speedpro piston part l2491f30 had a problem with piston clearence.....

he said that the crank throw actually hit the bottom of the pistons in certain bores.. has anyone else had this problem with this piston and crank combo???? the rods are scat 4340 i beam 5.7's

 

i believe i've read of that on here before. you might want to do a search and see what you can dig up.

 

What a PITA. I had everything balanced and then when I tried to assemble my rotating assembly it hit. I ended up having the piston skirts cut and everything rebalanced. I still worry that one day a piston pin is going to pull right out the bottom of the piston, but my machinist said it would be ok.

 

just to make sure that were talking about the same piston here are some pics of it and the rod...

pistons are l2941f30
rods are scat 1cr5700p

 

i just don't see how they could hit... they really don't even have skirts!!!!

 

It may hit the skirts, or it also may hit the bottom of the pin boss. Those scat cranks have very big counterweights on them, to make balancing easier (heavier counterweight = less malory). Just do a good check when installing everything. If you havent put the pistons on yet, you could have any machine shop turn down an old pin for a slipfit in your piston/rod combo, and check your clearance without having to press everything back apart. try to keep a min of .040 or so clearance between counterweight and any part of piston.Use a small piece of wire for a gauge. Also, make sure the rods and bolts have at least .060 clearance where they get close to the pan rail area. IF you only have to remove a few grams from the pistons, you wouldn't have to rebalance it. A small overbalance is not harmful at all, and actually helps at high rpm.

 

I had the same problem with a stroker kit from enginekits.com (Powerhouse). The guy at powerhouse said to grind the counterweights and not the pistons. I didn't have to take off much, and doubt if it will have a noticeable effect on the balance job.

 

i never thought about haveing my old pins turned down!!! i'll do that!!!!

iv'e never heard of this problem before and scoggin dicky had a good price!!!! i just don't see how it can happen!!!!

and i will defanantly check everything....... i was hoping there would be someone on here who had the same setup that didn't have any problems....

i guess i'll have to put my engine skills to the test!!!

who said it was easy to throw a motor together????
oops!! i did!!!