Single Row Crank Pulley 1.6

Posted this to the big board but thought I would check here as well

The motor in the 90 that I built for STS2 had a two piece crank pulley. (1-alt/WP + 1 AC) I replaced it with an OEM double pulley but have been wondering about using the single alt/WP as a low cost way to reduce rotating mass. Shop manual does not show a single row crank pulley so I assume that it came from another car (323?). Diameter and mounting holes including keyway are identical to the double row. Can't find any reference to this in the archives and I know that Andy in his build cut the 2nd pulley off an aftermarket underdrive pulley. Is there any hazard in running just the alt/WP pulley?

Thanks
Steve

Is it really worth all that trouble just to shave off a few ounces? I'd just leave it alone personally. If you want to take some weight out of the car ditch the passenger seat, rip the carpet up and any other cosmetic stuff that isnt important. oh and like in all the crappy street racing games remove the spare tire, that way when you get a flat out in BFE your screwed :)

He is talking about reducing rotating mass, not reducing the weight of the car.

I got that and its not really going to make that much of a difference. I better option would be to get an aluminum flywheel as opposed to the old heavy steel one. That way you are taking off pounds of rotating mass instead of only a few ounces. The engine will thank you for it and will rev so much quicker.

Quote:

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Originally Posted by Black_devil_miata

better option would be to get an aluminum flywheel as opposed to the old heavy steel one.

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not legal for SCCA STS2

don't know why -- stated objective of the class is to accommodate common bolt on mods

Reducing the dampning on a high revving "engine" is not smart.
Especially on an engine with a known weakness at the nose shaft.
Just my .02 of course.

I'd go lighter flywheel, but you can go to light too.
I've seen flywheels loose in the bell housing, from a sheared crank.
(This was on a high reved Super 6 and a Diesel with the governor removed)

no reduction in dampening running the single row pulley. It has the dampener incorporated, it just rids itself of the unneeded AC pulley. Now if I can just stop butchering the crank seal trying to get it in. (even with the FM tool) I'm sure Mazda's part system has FTW marked as a high demand area for crank seals now. So far none of my old school motor tricks have worked. That is one tight SOB. Hopefully I'll make it to MW for the double.

Agree with you on the flywheel rule Neal, its dumb. Wish the service manual reface/trim spec was as nice as what the 2nd gen MR2s get for stock.

Steve E