We're going to do a 408 stroker using a 360 block and will need a new balancer for an internal balance. Hope to see the machinist tomorrow, but I have a question or two.

Are all small block balancers the same diameter? I think the one on the 318 is 7.25. I've seen a few at 7.10 diameter

Some of the Summit ones that are priced below $100 have extra weights that are included. Is this for an external balance?

What does the SFI rating represent?

Thanks

Edit: I don't ever expect to make more than 450 hp with this motor.

Extra weights are for external balance of cast crank 340 and the 360. I wonder if there is a different weight for the 5.9 Mag engine?

Horsepower doesn't kill dampers, rpm does. The SFI have been tested to an obscene rpm, non SFI have not. No factory balancer that I know about was SFI approved. As you go faster in racing that SFI sticker becomes a necessity.

The OD varies by manufacturer. They're pretty close, so they all work. Other engine families have, for example, two different diameters, say 6 3/4 for low perf and 8" for high perf. This due to the higher twisting loads put on the crank by those larger power strokes of the HP engine. Drag racers sometimes would cheat by running the smaller damper for less rotational inertia, at least my friend John did.......

For your intended level of performance I see no reason why a Pioneer street damper wouldn't meet your needs.

R.

Don't cheep out on a damper. There are too many good one out there to use an elastomer damper.

Innovaters West comes to mind, if you don't want to use a Fluidamper.

The SEMA damper standard (S.F.I. 18-1) does not rate a damper’s effectiveness, or certify that it works at all (let alone on a specific motor) - only that it fit the designated engine, and didn’t explode during the test. Their interest is limited to safety and qualify control, not specific engineering results.
The exact design of a damper varies somewhat with journal sizes, stroke length, and crank length. A 408 and a 360 aren't an exact match, but the difference is probably harmless in a street engine.

Most stock SB balancers are 7.25... I am running
a Fluidamper on my 416(340 base) but if you are
running a internal balance then any SB zero balance
is what you need.. dont cheap out because a lot of
the cheaper ones will spin on the rubber joint.. a
cheaper SFI inst that pricey and will be better in
the long run.. on my 416 I only turn 7200 rpm which
to me is low rpm.. that Fluidamper is heavy.. on my
race engine I went ATI.. much lighter weight and I
have turned that one up to 9600 rpm
EDIT
If I recall... the tape that MP sells was for all
7.25 diameter balancers(that gave you a full 360*
on balancers that only had 10* indication on them

I've been looking at Summit. It looks like most of those are elastometric. A bunch have the SFI rating of 18 or above. I've seen nodular iron, steel and aluminum. I could use the 7.25" damper from the 318 but it would probably be best to change it out since it is 46 years old.

I'll stick with a steel SFI rated damper.


Does the diameter matter? My current one, that we used, is 7.25".


Thanks

18 is not a quality rating, it's a paragraph marker.