Thread: pistons in for the test fit

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now i am lost i had a nuther guy on a diffrint thred tell me this!

Hi heads up!!

Those are TRW slugs and are designed around the stock width pin bosses from G.M. The width on the factory rods runs between 1.050" and 1.060".

With all G.M. components That leaves enough room between the pin bosses and the rod pin cheeks.

However, the rods in your photo appear to be either Eagle "SIR's" or Scat's "ICR's", either way I would recommend looking closer at the gaps between the pin bosses.

The Eagles' average 1.125"/1.130" across, I have no numbers handy for the Scat's, but they are probably similar. If this is the case by you, remember you need at least .060" clearance on both sides to be "safe"!

Very important! The pin bosses (on the pistons) are usually "tapered" at the tops, it would be wise to check the "room" at the top of the rod-eye, not at the bottoms!!! Most of those rod-eye cheeks themselves (on the rods) are
"straight" from top to bottom and this will have a 'wedge" effect from the bottom of the pin to the top.

(Add) It does appear to be L2328F's, if that's correct, it means they are
"pressed"!

Thanks, Gary in N.Y.

P.S. It's sometimes very hard to make judgement calls from photo's, they can be very deceiving at times, but your clearances look very close as I stated! I also can't make out the full piston number, but if they're pressed pins, you MAY need to disassemble them for a correction. The amount removed, if any will have little to no effect on the balancing. In other words, you will not have to rebalance!!

Double P.S. Just caught my eye, almost missed it!!! Factory 2 B.M. with "flow notches", you probably could have made a "heads-up" trade for a spankin' brand new G.M. Bow-Tie iron piece. At least around here it would have been possible. Just guessin' but it's probably a "3902406" block? Error, wrong oil filter base, has to be '68 or later, still valuable to the resto guys!



in reply to what he said:
the pistons are P/N:TRW-L2328F30 "pressed" the rods are Eagle "SIR"
i tried to measure the pin slide and it look like it is coming out at .055
the i can slide a .003 feeler gage in between the piston skirt and cylinder walls