[DarcyL]

I think I have read about people using lighter weight wrist pins in the old TRW forged pistons- The only .980 pins I can find are 3" long, and the stock pins from the TRW's are 3.25. Will the 3" units work? does anyone have a part number for lighter .980 pins that work with the TRW's?

Darcy

[Tom Vaught]

In the old days lots of people put the Mopar 340 "light weight pins" in the Pontiac cast connecting rods and used higher quality rod bolts.

The pin was positioned on the rod so that it matched a factory Pontiac piston installation with 1/8th less pin on each side. Plenty of support on the piston bosses.

The pins were much lighter vs the factory pins 3.25 length at 250 grams and less than the TRW Ram Air pins 200 grams. The MOPAR .9842 pins weighed 140 grams.

That weight difference helped with the normal HEAVY Pontiac Piston assy.

Tom V.

[elefantrider]

Call Jim Butler. About 25 years ago, I got a set from him that were much lighter than what came with my TRW pistons. I could not believe the weight difference. I ran them for years with stock polished rods and ARP bolts, and the motor spun up faster. Tell him you want his lighter tool pins for TRW pistons.

[Schurkey]

Or get modern, lightweight pistons with lightweight pins.

[Will]

Didn't I read around here awhile back that current TRW pins are lighter than the old 250 gram pins?

I did the Mopar pin deal back when I built my first 400.

[PAUL K]

Originally Posted by Will

Didn't I read around here awhile back that current TRW pins are lighter than the old 250 gram pins?

It's been like that for many years.

[elefantrider]

This is the street section, so I don't think you're racing it.

If you already have TRW pistons and rings, and they are good, I'd run them.
New pistons would cost you $600 + $100 new rings
or
$80 just for new pins.

My TRWs were like new and I already had them. Jim told me to just get new pins and that will make a big difference. He was right.

[Dragncar]

The only pins that were available when my engine was done were heavy Ohio pins. Had them forever. Has not hurt me.

[dataway]

The current TRW pins are much lighter than the original pins sold in the 80's. By about 57 grams if I remember right. Easy to spot, the ID of the pin is way larger on the new pins. Not saying they are "light weight" but the newer "standard" pins are much lighter than 30 years ago.

[Tom Vaught]

57 grams is a nice reduction in weight vs the OLD TRW Pins but the "200 Gram" pins are still heavy vs the 140m gram .984" MOPAR pins or a custom weight pin today.

For a street car, I would just stick with the pins that came with the pistons which should be 200 gram pins.

Tom V.

[t money]

I had a conversation with Butler a couple years ago about this he said back in the day they use mopar pin 984 size and honed the rod and piston to 984. Note the mopar pin are 3’’ long ( trw/speedpro ) Pontiac pins are 3.25’’ long. He said it ok to use a 3’’ pin just press the pin evenly in the piston bore. Now the pins he recommend now was Keith black 0980x300k 149 grams ($4.99 ea) from summit.

[DarcyL]

Great info all- Thanks!

[t money]

A story that I was told when looking into this 3.25 vs 3 inch pins. The late great Pontiac engine builder Jim Taylor would cut lock clip groves in the piston bore of trw/SpeedPro to floated the pin and then cut the pins shorter making them lighter

[racegto65]

Originally Posted by Tom Vaught

In the old days lots of people put the Mopar 340 "light weight pins" in the Pontiac cast connecting rods and used higher quality rod bolts.

The pin was positioned on the rod so that it matched a factory Pontiac piston installation with 1/8th less pin on each side. Plenty of support on the piston bosses.

The pins were much lighter vs the factory pins 3.25 length at 250 grams and less than the TRW Ram Air pins 200 grams. The MOPAR .9842 pins weighed 140 grams.

That weight difference helped with the normal HEAVY Pontiac Piston assy.

Tom V.

I used to do this. Only issue is the Mopar pins are .984 so the rods and pistons need to be honed.

[HWYSTR455]

Originally Posted by Schurkey

Or get modern, lightweight pistons with lightweight pins.

I have to agree with this. I did at one time buy pins from Butler, but the cost difference pushes the piston/pin assembly into the range of new better pistons.

Shorter pins are usually used with spiral locks, so no, you can't interchange to my knowledge.


.

[Will]

Originally Posted by racegto65

I used to do this. Only issue is the Mopar pins are .984 so the rods and pistons need to be honed.

That is what was done to mine. I specifically remember the costs to rebuild my stock rods including beam polishing, weight matching, ARP bolts and honing the small end plus honing the pistons to fit the Mopar pins plus the cost of the pins themselves still worked out to be cheaper than a set of forged rods +prep back in those days.

My we've come a long way. Unless it's a total budget motor that I won't ever rev past 5500 RPM, there's no way I'd bother with stock rods nowadays, and I certainly wouldn't bother having that work done to accommodate those pins.

[Skip Fix]

The "old" light weight pins Butler has he and Barney Moravitz in San Antonio had and they were about .981ish and fit the old forged rods they had heat treated as they would also be a hair larger once resized. That supply ran out. I had a set of pistons honed for them but did not like the forged rods so went to cast rods and had both pistons and rods honed for the Mopar pins. IN the stockish 400 in the 81 TA. Kids drove it to high school and I still drive it some.

To do over I'd just get lighter pistons and pins.

[DarcyL]

Ya, I've got a set of minty used +.030 455 TRW's, and a set of Eagle push pin h beam rods, and yes this is a low budget build, so I think I'll go with those Keith Black .980 x 3" 150 gram pins-