With my failed damper, I'm considering an aftermarket part, but most of them are 6-1/4" or 8" in diameter. On my 88 GTA 5.7L engine, the damper appears to be 6-7/8" diameter. What I am looking for is a summary of SBC dampers & timing pointers by part number. If I am forced into a different size damper, I'd like to figure out what interchanges & what timing pointer to use.
Any assistance would be appreciated.
Thanks, FJK

 

Your engine uses what is commonly referred to as a 6 3/4" dampener. It may measure bigger in reality but it's a 6 3/4" replacement you're looking for. I have an 87 short block laying around at it uses the same dampener. Nothing special about it.

Your engine should have the timing marks on the timing cover at about the 1:30 position. That's the usual position and is what most stock and performance replacements are designed to work with. The only other place they put the timing marks is straight up at 12:00 on some emissions-era engines with 6 3/4" balancer but from 87-up I believe they are all at 1:30 at least in 3rd gen F-bodies (trucks may be different- I don't know for sure). All 8" balancers use a timing tab in the 1:30 position.

6 3/4" and 8" are your only choices. No reason to go bigger since you already have the timing cover and tab to go with a 6 3/4". If you are building a stroker motor or other non-stock combo then things can get more complicated. Most aftermarket timing covers come with no timing tab since it is sold separately to match whatever balancer size you are using.

You can use whatever size you like- the 6 3/4" and 8" are totally interchangable, with the exception of the 8" "400 style" balancer that is used ONLY on the 400 and common aftermarket externally balanced 383 stroker kits (350 with a 400 crank).

 

Damon: Thanks for the info very helpful. But, if the 6-3/4" & 8" damper are interchangeable, what do you do with the timing pointer? I am assuming the pointer for the 6-3/4" damper won't clear the 8" damper. Am I wrong or is a different pointer (timing tab) required? I hope you can clarify, because I do have an extra 8" damper on hand.
Thanks, FJK

 

The pointers are designed for either a 6 3/4 or an 8 inch balancer. So of course an 8 inch balancer will interfere with a pointer for a 6 3/4 balancer, like the one you have on your stock timing cover. 8 inch balancers can ONLY be used in externally balanced applications like 400s, 383s, etc... What you need to order is a 6 3/4 balancer and a 6 3/4 timing pointer. When you look in a Jegs or Summmit catalog they will list them as pointers for a 6 3/4 or 8 inch balancer