Hot Rod Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
1,554 Posts
Discussion Starter · #1 ·
Catchy title, I know.
But this is not your average question. I am about to pull the trigger on a rotating assembly for my 638 Block. This is a 4.030 bore 1 Piece RMS Chevy Block. Our good buddy Skip White has this Kit


This ^ is an External Balance, with an option for Internal Balance for an extra $80.



So my question is, should I plop down the extra $80 for this ^ upgrade?

Motor will be a Flat Top Piston 383 Short Block build yet to be determined. It will be more like a spare short block for me. Maybe go in my Brothers 87 SS Monte Carlo, one day after I finish mine...

Engine will not see any power adders, or over 6500 rpms. Most likely it will have some ProFiler 195, or 210s and a nice custom cam to make lots of torque.

Also what about this Rod Upgrade for another $70


I dont mind spending a little extra, unless you guys think its overkill. I have learned my lesson in the past about pinching pennies, and am still paying for that right now...
 

·
Registered
Joined
·
1,554 Posts
Discussion Starter · #2 ·
Side note, I got basically this crank and rod setup in my 406 and its externally balanced. Only difference is it has 5.7 inch rods. I drive it very aggressively quite often. It has about 10k miles on it so far with no problems. (The Hyper Pistons worry me, but that's a different story...)

My thinking is go for the internal balance upgrade, because I've heard its better. Im pretty sure Bogey said so. Something about how its easier on the crank.
And the 7/16 rod bolts on the standard rods in the kit probably don't need upgraded.
 

·
Registered
Joined
·
15,328 Posts
Internal reduces local imbalances between main bearing stations by reducing to elimination of shaft lengths (lever arm) between balanced points, this helps reduce deflections and vibrations through the shaft that cause the mains to want to run off the shaft centerline. You can see evidence of this where usually the center three main bearings show odd wear patterns on the bearing shells. These vibes and deflections can’t be totally eliminated given that the power strokes are not a counterbalanced force. But if you like or need to use the engine hard every little bit you can improve on helps with crank, bearing, and block bearing web life.

A high quality damper also is important because high power loading put twists into the crank which become traveling waves. The damper is designed to absorb them from the ends of the crank where without sufficient absorption the vibrations and deflections are reflected back into the crank. This can develop a phasing problem where if they synchronize together you can get additive forces that become very destructive. The power out end of the crank absorbs the vibes and twists in that direction with the masses of the flywheel and clutch or torque converter.

Bogie
 
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top