I posted a similar question in the performance forum but didn't get an answer.

Can anyone tell me what the typical bob weight of a "mostly stock" 454 is? My engine has a Lunati forged crank, LS-7 rods and open chamber Wiseco pistions. The bob weight was as follows:

rod rotating - 612 (x2)
rod bearing - 54 (x2)
oil allowance 5.5
piston and pin 156.5 - 879
rings 53
rod reciprocating - 248.5
bobweight total 2518

(sorry, I had posted the bobweight total as 2,533 in the other post. I was going from memory at the time).

This in an internally balanced 454. Is this weight considered normal?

Thanks.

-Kenny

[This message has been edited by kjett (edited 12-06-2002).]

Kenny,
What are you concerned about exactly?
That bobweight number is right for your motor. Don't worry about it, it will be balanced.

Thanks for the reply SS_Dave. I'm just wondering if this bobweight seems high? The real reason I'm asking is I'm already planning on the next iteration of engine for my car to get me into the 10s. Being much more cautious financially this time around I want to try and reuse things I already own where it makes sense.

Some options I've considered include:

- replacing my hydraulic roller with a bigger solid roller and spinning the engine to 7k. I've spoken with the person who built my engine and he says that's not a problem and that I can still expect good service out of the engine. He said LOT of bracket engine's live at that RPM season after season.

- replacing my existing heads/cam with a BSE like combo. Less runner volume, smaller cam and better signal hopefully more torque. A proven good combination, but expensive from where I'm sitting.

- more cubes. I could build a 509+ bottom end and reuse most if not all of the stuff on the top of my engine. I think I can get a good 540 rotating assembly built/balanced turn-key for $4k. Still a lot of money from where I'm sitting.

All this brings me to the question of bobweight. A friend of mine that races in the Super Stock classes recently move from a 468 combo in a 67 Camaro that was running consistent 6.30s to a 427 combo using same heads/cam/intake/headers/etc and has gained ET and nearly 4 mph. Only difference is ~10lbs of rotating mass in the crank. He said that the bobweight of his 468 was ~2,300 grams and the new 427 was around ~1,900. I've already got a good forged 3.76" crank from my 396, so it got me thinking about another possibility. So, in summary I have no immediate plans to change anything, rather I'm trying to look at as many ways as possible to go faster in the future.

If I go with a solid roller as mentioned above what are the reprocussions from spinning a 454 with essentially stock (although very strong) parts? Bad idea altogether? I $500 set of good aftermarket H-Beam rods would lower that weight by ~300 grams? Make a difference when turning it higher?

Always trying to learn more...

[This message has been edited by kjett (edited 12-06-2002).]

There is no question that the lighter recripocating mass will allow better throttle response and will decrease stress on the internals at high rpm. You can get into the 10's with a BSE, but the BSE is not an rpm or HP motor. It is mostly torque. You won't need to be as careful about recrip mass. I don't know what this motor is going in, but you can get 10's pretty easy with a BSE and good suspension and weight reduction.
If you want it in a street car, that is a little different.
I am getting ready to have my motor balanced again. I will let you know what my bobweight comes out to. I have closed chamberd heads, but domed pistons. might be close to yours.

Dave

Don't forget,less rotating weight = less torque.

Kenny,
To answer your question....yes, that is about an average bob wgt for a pretty much stock rat motor.

------------------
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100