Connecting rod weight change...

[Krooser]

I just bought a nice, low mileage set of used Crower billet connecting rods for my SBM project engine. They came out after 6 years of weekend cruising and a few runs down the track.

I had resized, rebushed and balanced a set of OEM 340 rods to use in this engine but there was always a question of durability in the back of my mind. For a non race engine this would never been a factor but this deal this will run 30-40 laps each night on a big half mile and I always had a question of durability in my old noggin. So when I saw these advertised for sale I made the move.

Now my question... the Crower rods are 15 grams heavier than the Mopar rods... 745 vs. 730. How much will this affect my balance? The new RaceTec pistons are spot on and within a couple grams of the old Ross slugs. The billet crank I have was repaired after some rod damage in the #1-2 journal... I was thinking the crank may not have to be re-spun... your opinions?

Seems odd that I'm using these heavy rods after i was trying to get my rotating weight down as much as possible. But when you have a 63# crank I guess it's a moot point!

[PackardV8]

One option is just smile and tell anyone who asks, "I had it overbalanced; better for extended high RPM, ya' know."

[Dave Koehler]

Have the big end and small end weighed and get back to us.

[PackardV8]

Bill K rightly points out it will now be underbalanced, so say, "I had it underbalanced; better for durability, ya' know."

[Krooser]

Have the big end and small end weighed and get back to us.

I had my GF do that....

[piston guy]

Run it!

[Dave Koehler]

No reason to balance anything I assume.

[Krooser]

Ok.... so now I have another question.

I put my calipers to these Crower rods last night... seems the stock .984 rod bushings have shrunk down to .927! I bought these with the understanding they were for the stock .984 Mopar pins.

Now this would not be an issue but I have a shiny new set of slugs with .984 holes!

Can those .927 bushings be honed to .984? Or can I find .984 bushings to fit in the stock machined pin bore? The bore is larger than one inch.

[Dan Timberlake]

Honing to size would take a while, and at best duplicate whatever geometry rod "straightness" and center-to-center length exist now.

It would be better to have the bushings bored to the desired size in a rig that controls C-C length and makes the pin bore very parallel to the BE bore.

Tobin-Arp made a machine to do just that. It was pretty slick.

[Krooser]

Thanks Dan... this was a surprise to me. I'm not a pro builder but have put enough engines together over the last 61 years that I like to check things out as much as I can and have an expert do the same if there are any questions.

I have three shops that I deal with and i would imagine at least one would be able to handle that job.

The guy I bought these from said they were stock Mopar sized... could be his engine builder used the Chevy size pin and it was never dsicussed with him.

[PackardV8]

Can those .927 bushings be honed to .984? Or can I find .984 bushings to fit in the stock machined pin bore? The bore is larger than one inch.

Yes, to both.

It would be better to have the bushings bored to the desired size in a rig that controls C-C length and makes the pin bore very parallel to the BE bore.

Tobin-Arp made a machine to do just that. It was pretty slick.

For true, Dan. We've got one and it is incredibly well-designed and well-made. Since it only gets used at most once every six months, my machinist hates me for making him think that hard remembering how to set it up.

[Mark O'Neal]

Nothing costs more than a super duper deal on parts.

[Krooser]

Nothing costs more than a super duper deal on parts.

Not the first time for me. But I can dispute this because I paid via PayPal and used " goods and services" rather than F&F...

These are older rods with six seasons of street use with some passes down the track.

When a guy is putting a whole car together on $12K per year plus a PT job it's tough to spend the $$$ for new. I didn't NEED these I guess... I trust the stock rods for my application but these were just an insurance policy.

We will see...

[Krooser]

These are the rods in question.

[piston guy]

Plenty of room in the bushing to go to .985 (.001 clearance) Bore it like Dan suggested , honing that much is tough to do "right". Those are some nice rods.