I had a 6 inch harmonic balancer on my 305 which got screwed up and someone gave me an 8 inch. The machine shop said it was fine, and a friend who worked on these cars new for GM said the same. So now I ask all of you? Besides water pump clearance is there anything I should consider/need to know?? A fast response would be much appreciated as in its going back on soon. Thanks.

James

 

It won't fit with your timing comb.

 

timing tab gets in the way... the 8" is for 400 blocks and is also needed for 383. 305-350's require 6 3/4" dia balancer... in theory they are the same, but why put it on if it requires something else... besides being heavier theres no real diff. make sure its a internal balance balancer.

same thing could be said for putting a 350head on a 305... it will work but the 350 head is overkill and the combustion chambers are too larger for the small bore 305. spend the extra 30-50$ on a new and correct balancer

 

Thanks for the info, I knew the timing tab was in the way we were going to take care of that, but I would like for the 6 3/4 to be on there.

 

You are correct on the timing tab getting in the way, but you are wrong on the 8" balancer being for the 400 only.... ALOT of 350s and 305s came with the 8" balancer and timing cover. Just depends on the application. The stock 305 in my G20 Van had a 8" balancer and the stock L31 Vortec 350 in my truck had an 8" balancer.

 

most 8" balancers are external balanced tho. most if not all 6 3/4" balancers are internal balance. u need the right one for the right applicaiton. 400's and 383s are usually externally balanced so the blancer has a bolt on weight. if the 8" balancer is internal balance then i would assume it would work. but less weight can only help with the 6 3/4". my .02 would be always to stick a 6 3/4" on a 305/350 and a 8" on 383/400 etc. balancers are so cheap now unless ur lookin at a fluid dampner...

 

Everyone tells me the one I have is internally balanced, is there any way to tell them apart cause I'm pretty sure its internally balanced also.

 

If the edge of the rim is the same width over the entire circumference, it's neutrally balanced.
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The weight is cast-in, not bolted on.

 

go to autozone they are very cheap to replace i just did it to my 91 gta the only non stock set up part on my car is the new 24lb LT-1 injectors lol.... if its on there and works keep it that trust me

 

Apeiron "If the edge of the rim is the same width over the entire circumference, it's neutrally balanced"

Its that way on both of them, so should I be fine?

 

Yes, should be fine.

 

Ok, thanks for all the info.

 

i have a 8" profession products balancer right in front of me and it has a bolt on weight... hmmm i kno bc i bought it.

 

Well I finally got my car all back together today and started it up, sure enough it ran perfectly smooth. No problems with the bigger 8" balancer. Thanks for helping the decision easier.