Connecting Rod Question About Play????

[PHANTASM]

109 engine stock crank, recond. rods.,TRW FORGED PISTONS(30 OVER)

engine ran fine before it was gone thru, good oil pressure and no noises(block was frozen and cracked) and the crank looked perfect. i bought new rod and main bearings and had the rods recondtioned with arp bolts.

side clearence is good. but you can take the cap and try to twist the rod on the journal and there is a little bit of rotation as you can see the piston move a little bit in a cicular way.

is this normal with these engines?

It has good side clearence and no play when you try to push and pull the cap with your fingers.
you can twist the cap a little.

 

[Squid4life]

First off, are you SURE the piston moves in a circular motion? When I was checking my bottom end, it looked like the rod would "rotate" when all it really did was move side to side a bit. Did you mic the crank, and make sure you have the correct bearings? When in doubt and can"t get a mic in there, use plasti-gauge as a cheap check. (but not everyone agrees with the plasti-gauge stuff...)

Squid

 

[PHANTASM]

With the engine still on the stand looking down at the piston skirt with a light, you can see the piston skirt rotate just a tiny bit.

it's been a while since i have rebuilt an engine but i don't think you are supposed to have the rods do this, side to side fine but twist no.

 

[Squid4life]

Grab some plasti-gage and check the clearance real quick. Make sure the bearings are right, etc.

Let me know what you find! I am getting ready to put mine together.

Squid

 

[Steve V]

Check the rod side clearence while your at it,use feeler guages. I bet its about .020 or more. Spec is .006-.015. It's darn near impossible to get it to .006 but .015 maybe with a new crank,not a .010 etc. I seen as much as .028 and let it go with no problems.

 

[Squid4life]

Even with a bit too much side clearance, you still shouldn't be able to rotate the piston, though, should you?

Squid

 

[Steve V]

Sure it can,with excess side play the rod will twist on the rod jounrnal and the will in turn rotate the piston. That's the joy of a on center rod motor,if it was on center than it wouldn't be an issue.