SBC Harmonic Balancer Question

Started by Mac, February 10, 2016, 10:58:01 PM

Previous topic - Next topic

0 Members and 2 Guests are viewing this topic.

Mac

I've been living with an annoying slight engine vibration in a roller cam 305 that comes on at 1K rpms and goes away by 2K, most pronounced at 1200.

I thought I'd spring for a new balancer so I measured the one that's on now and came with the engine when I bought it used. It measures 7.25 inches and I find that size referenced to the 400 SB while the 305's are listed at 6.75 size. 400's are external balance and 305's are internal.

If this were a 400 spec balancer that somehow found it's way onto this 305 wouldn't I see more than slight vibration?
Who\'s yer Data?

wayne petty

small block 400 balancers have a NOTCH cut in the outer surface to offset the weight..    ----------------__________---------------____________  as the outer surface goes around..

all other balancers have a smooth outer surface.

=======================================  an even surface on the outside of the damper ring..

Mac

Well, mine's smooth. Rules that out. Thanks Wayne.
Who\'s yer Data?

chimp koose

Isn't 1200 rpm about when the torque converter 'stall' speed is ? Could it be related ?

Mac

Good suggestion Chimp but this is a manual 5 speed. I had the trans and clutch out and ran the engine to see if it still had the vib and it did. I also took accessory drive belts off and tested and made sure to separate 5 & 7 plug wires.
Some remaining sources are: old mounts under the iron bellhousing, budget FWheel from summit, balancer still, etc..
Who\'s yer Data?