I bought a set of Trw L2256L forged flat tops already on a set of reconditioned x rods. My crank is a factory cast crank thats been turned on rods and mains. when i was putting my first piston in and got it in the block bolted down and tried to spin it over the counter weight hits the bottom of the piston and the piston ends up about a 1/8 inch in the hole. i tried one of my old pistons and it went in fine and spun fine. not sure what my problem is please help.

 

Sounds like maybe you got 383 pistons for a 355 engine. Check the distance from the wrist pin to the top of the piston and they should be the same as the old ones. The distance from the pin to bottom of the skirts should be the same or less on the new ones compaired to the old ones.

 

They are 350 pistons. i checked the part number and compared them to the other piston and there almost exactly the same height.

 

There is a picture of them. tell me what you think guys. this is so dissapointing. i was so physched about gettin my motor done and now i ran into this problem. thanks guys.

 

in your pics. it appears the old rod is longer than the new one . this would cause your problem . good luck .

 

I kinda thought so also but wasnt sure. the rods with the new pistons were resized with new rod bolts. Would a shop be able to put the new pistons onto new rods? Or will i not be able to put them on new rods?

 

You might have 400 rods installed on the new pistons, I cannot tell from the picture but the 400 rod is 5.565 long the 350 rod is 5.70 long. Check it out.

 

Yeah, you got the wrong length connecting rods (too short).

Any machine shop can press off the pins and reinstall everything on a different set of rods for modest money.

The only time I've run into the kind of problem you are having is when I used a 383 stroker crank designed to be used with 6" rods. We were only using stock length 5.7" rods (with matching pistons for the 5.7s). Our deck height was just fine at TDC, as you would expect it to be, but the counterweights hit the bottoms of quite a few of the pistons, just like yours.

 

Well after some time sitting down reading calculations on how to measure rod size and everything i i couldnt get those right so i came up with a other way to measure and it seems that they are 400 rods. so i should be fine with using a 383 stroker crank correct? may have to clearence the block?

 

If it hits with the smaller crank throw, it'll probably hit worse with more stroke. Might be worth a try thought if you could borrow or find a real cheapy just to double check first.

 

yeah i am going to take one of the rods up to the machine shop tommorow and see what they say, my friend that i work with has a 383 crank in a block right now with out pistons so im going to take one over and try it out first and see what it does.

 

the piston setup on the right looks like it has a longer skirt than the new one, but it also connects closer to the top of the piston than the one on the left.
be sure to let us know what happens - so we dont make the same mistake.

 

yeah i hope to get this straightend out. if they are 400 rods and i end up using a stroker crank. what would i use as a flywheel for my t5 since my 350 flywheel wont work cause of the balance. i know there are internal balance stroker cranks but there quite a bit more.

 

Went to the machine shop today to confirm that there 400 rods. Im considering using them and finding a Internal balance 383 stroker crank so i can use my 350 flywheel and balancer. Is there a specific crank i need to look for since il be using the 400 rods. because most of the info on the cranks say must use 5.7 or 6.0 rods. thanks for your help so far guys.