Bushing six pack rods for 1.094 pins

[Bird 426]

I took over 4 lbs out of my Hemi's lower end, after rebalancing, with Molnar H-beams. This was the rod that I took out.

 

[lewtot184]

OEM rods are made from 5140 material. Sure you can go in and lighten them, but the material is not nears as strong as 4340, so you are actually weakening them by doing so.

Plus the aftermarket rods have a 7/16" bolt over the OEM, but they are also a cap screw design which is superior, and doweled.

For what it cost to build an engine today using old OEM rods is like riding around with the pin pulled out of a grenade. The $720 investment in new rods is cheap insurance.

Tom

I thought oem was 1040 and aftermarket i- beam was 5140?

 

[Cranky]

I thought oem was 1040 and aftermarket i- beam was 5140?

IIRC, Direct Connection had some stock appearing rods that were high strength but don't remember what the number was. Thinking it was even higher than what you quoted for the aftermarket I beam

 

[lewtot184]

IIRC, Direct Connection had some stock appearing rods that were high strength but don't remember what the number was. Thinking it was even higher than what you quoted for the aftermarket I beam

Either 4140 or 4340 Chrome steel. 5140 is chrome steel with no moly. It's my understanding that moly is added for machine ability. I don't think moly adds strength. Pretty sure there were no chrome steels used for production pieces. Wish I had more detailed info on these steels.

 

[PROSTOCKTOM]

I thought oem was 1040 and aftermarket i- beam was 5140?

Thank, I've corrected it in the previous post. I so rarely deal with the OEM stuff I had forgot what it was. I used to sell some 5140 rods that PEP carried, but those are long gone.

Tom

 

[33 IMP]

I haven't read this whole thread, but.....
If lightness is a concern (and it should be) I would never build another bbm without using a .990 bbc pin
From what I have read, the Sixpack rods are 60-70 grams heavier than an LY rod, and considered heavy. The chevy pins are 75 grams less than a 440 pin. Light pistons/pins automatically make ANY rod in the engine effectively stronger.
The piston/pin for my stroker 440 is 400 grams lighter than my maxwedge pistons that I took out.

 

[lewtot184]

Thank, I've corrected it in the previous post. I so rarely deal with the OEM stuff I had forgot what it was. I used to sell some 5140 rods that PEP carried, but those are long gone.

Tom

Seems like most, if not all, aftermarket rods are Chinese. All i-beam aftermarket rods I've seen are 5140 Chinese. Why 5140 i don't know. Apparently cheaper than 4340. I've read were 5140 is used a lot in ship building. For what I do 5140 is good enough or maybe better than factory steel. Keep in mind that back in that era cast rods were still being used by some manufacturers. I think i- beam versus h- beam might be a good discussion.

 

[Cranky]

Seems like most, if not all, aftermarket rods are Chinese. All i-beam aftermarket rods I've seen are 5140 Chinese. Why 5140 i don't know. Apparently cheaper than 4340. I've read were 5140 is used a lot in ship building. For what I do 5140 is good enough or maybe better than factory steel. Keep in mind that back in that era cast rods were still being used by some manufacturers. I think i- beam versus h- beam might be a good discussion.

Cast rods as in cast iron?

 

[70bigblockdodge]

If your going to lighten stock rods first to go is those giant balancing pads. No way to fix the thin spot for the factory bolt.
I would say even the 440 source stock replacement rod is a way better piece than a stock LY rod with a gazillion cycles on it.
Stock rods are for re-ring and gasket rebuild only.

 

[lewtot184]

Cast rods as in cast iron?

Yes

 

[lewtot184]

I've done the bushing LY rod thing before. It's really not straightforward. Some of the forgings look like the top and bottom dies aren't perfectly aligned. Notice how the pin hole will look offset on one side and ok on the other side. To do it right you'll probably need a couple sets of rods to pick out 8 good ones.

 

[1KoolBee]

To do it right you need aftermarket rods. Pouring money into over-stressed low quality oem rods is a fools errand. Save the $350 at the machine shop to try to make them “right “, and sell the 6 pack rods to someone building a museum car for $350. Pull $20 out of your wallet and buy the Molnars for $720. 4340 steel, 7/16 arp’s, lighter, probably 50%+ stronger, probably 10x fatigue life, better machining. Get .990 pins and good pistons. Seriously, the 80’s called and they want their rods back! It’s a no brainer.

 

[Diodedog]

I haven't read this whole thread, but.....
If lightness is a concern (and it should be) I would never build another bbm without using a .990 bbc pin
From what I have read, the Sixpack rods are 60-70 grams heavier than an LY rod, and considered heavy. The chevy pins are 75 grams less than a 440 pin. Light pistons/pins automatically make ANY rod in the engine effectively stronger.
The piston/pin for my stroker 440 is 400 grams lighter than my maxwedge pistons that I took out.

You can get light weight pins in a 1.094 and cutting the stock ones down to 3" will bring them from 225 to 190ish.

 

[Geoff 2]

Not cast iron, cast steel. Pontiac V8 rods were all cast steel except for a few higher output engines.

 

[PROSTOCKTOM]

You can get light weight pins in a 1.094 and cutting the stock ones down to 3" will bring them from 225 to 190ish.

If not a shelf item you can get Trend Performance to make them. However if you're switching to aftermarket rods going to the .990" BBC pin is really where it's at since it allows

basically an unlimited amount of options. However, unless it's a race engine that someone else is paying for playing with really lite pins is a place to stay away in my opinion.

Tom

 

[lewtot184]

I've done pin juggleing . Not complicated. Variety of pins out there.

 

[Moparfever65]

In my old 67 Charger I used to hit 7000rpms regularly with the stock forged crank and six-pack rods. No issues. Why spend money that you don't have to?

 

[1KoolBee]

In my old 67 Charger I used to hit 7000rpms regularly with the stock forged crank and six-pack rods. No issues. Why spend money that you don't have to?

Boom! please pass the dust pan!

 

[RemCharger]

Boom! please pass the dust pan!

But the boom never happened and the dust pan wasn't needed.
After 30 yrs of living at the track I've shifted my focus from rod delamination to blocks and cranks falling apart.

 

[Geoff 2]

Many do not realise that with a high rpm performance engine, the destructive force on the rod are not from combustion in the chamber. The greatest load is at the end of the exh stroke where the rod has to arrest/stop the piston at TDC.....& then reverse direction This load can be several tons. If you measure the brg shells, they are thinner at the parting line. That is because the rod goes egg shaped with the above load & this helps to stop the brgs pinching the rod journal. If you are using factory 440 piston & pin, close to 1100 grams, & piddling 3/8" bolts, I would be on one knee every night thanking Allah that the engine is still together.........