Bushing six pack rods for 1.094 pins

[Gunner1]

I have the speed pro flat tops in mine on LY rods. I didn’t build it. I have built big block Chevys with a honed to slip fit steel on steel. Drilled a small hole in the rod top for pin oiling. You can buy alloy round bar and easily cut pin buttons on a hobby level lathe.

 

[BSB67]

At last in 2025 a sensible question.
Factory slugs are cast six-pack pistons.

The new replacements are Indian Speed Pro, forged.
How good they are is yet to be discovered?

They are no heavier than the factory High compression cast piston.
I could lighten them but reciprocating weight is only half as bad as Rotational weight.

Taking as much weight as possible out of the BIG END has much more effect on the crank

I asked this question before Christmas. You did not answer.

What pistons are you using, and what is their weight?

 

[polyjohn]

Sorry BSB67,

I am building three six-pack 440 engines at the moment.
Two are factory stock with Speed-pro (Indian forged press fit)

The third one is with Pro Tru (fully floating) and that's why I got mixed up.
I have tracked down a set of six-pack rods that are already bushed in the UK.

I will get some Molnar rods from Tom on here as and when funds allow.
Best wishes to you from John.

 

[BSB67]

Sorry BSB67,

I am building three six-pack 440 engines at the moment.
Two are factory stock with Speed-pro (Indian forged press fit)

The third one is with Pro Tru (fully floating) and that's why I got mixed up.
I have tracked down a set of six-pack rods that are already bushed in the UK.

I will get some Molnar rods from Tom on here as and when funds allow.
Best wishes to you from John.

View attachment 1784698

Thanks.

Not sure if you already stated it, but are you planning to lighten the piston and pin, or live with the 1075 gram weight. How light do you think you can get them? Seems like removing 125 grams would be pretty easy and make a big difference on parts life at rpm.

 

[1968rt]

Ive been running light weight JE/SRP pistons on prepped 6 pack rods for years. Look at the piston weights
182 gr difference! Takes a lot of stress off of the rods.


L2355F 2.061 -7cc 872

213455​

445​

4.350​

3.750​

6.768​

10.705​

2.062​

11.4​

10.5​

10.1​

-6cc​

690​

H​

0.030​

J100F8-4350-5​

 

[Runcharger]

When I used to run those 2355's I had a couple of rod failures. Then we started to machine 100 grams out of the bottom of the tops of them and no more failures. It was either them or the 2295's back then and only stock rods were readily available. We polished the sides of the rods and ran Direct Connection bolts back then.

 

[polyjohn]

Some very valid points here Guys!
I'm happy that the heavy rod, heavy piston works fine for street applications.

I wouldn't put a 2355 onto an LY rod myself.
The best combo I have found is six-pack rod lightened to 840 grams and a Hyper KB piston.

They rev to the moon and back and never broke a rod yet!
It all depends on which crankshaft you start with.

We have an abundance of 72 to 76 H/D truck cranks from Jensen 440's.
They were built as Truck engines (low compression) and some were beefed up to six-pack spec.

The difference being you need external balancing with a true six-pack set-up 70/71.
But you can internal balance if you remove 100grams of all 8 rods (800g)

 

[polyjohn]

1972 to 1976 H/D crankshafts aka truck cranks (Jensen 440 cars UK)

They have wider thrust flanges and also a large mass of metal at the back journal.
The large lump can be massaged down to allow for neutral balance with six-pack rods.

That coupled with a 800gram rod lightening will allow for 2355 pistons and SP rods.
Yep its a heavyweight combo but its correct for my 1971 GTX numbers matching car.