Orr89RocZ

iTrader: (20)

SO i just got these finally after a while of waiting. I wanted the steel version but thunder racing was on back order. i waited 2 weeks and they werent in yet so i just upgraded to the aluminum pulley they had in stock

The crank pulley is aluminum and saved 2 lbs over stock. alternator is steel i do believe and smaller than stock but this is to prevent charging problems and it works.

Couple of things here on install.... At first, i couldnt get the alternator pulley off, so i kept the stock alternator pulley on for a few days.

I deleted my smog pump and DID NOT use a smog delete pulley...i just ran the belt a different way as suggested by the tech article here:
https://www.thirdgen.org/serpentine

I have a 89 L98 with all stock components but a/c delete with a a/c delete pulley the same size as the a/c compressor.

however, that article recommends a 93.5 inch belt or dayco part number 5060935 for underdrive pullies. Another thread recommended 93inch belt or the 5060930. This did NOT work and was short. the 93.5 i didnt try and probly wouldnt have worked or else the tensioner would have to be lifted all the way up. I used the 5060940 or the 94 inch belt and it fits GREAT! just squeezed on there. remember, the stock belt is 94.5 inches. now with other underdrive brands, maybe that belt would have been fine..you'd have to measure on install.

With the stock alternator pulley and march underdrive crank pulley with no smog pump, I was able to keep the stock belt. however at night i did experience voltage drop and didnt charge up till i started moving again. It did have a tad bit of drop in the day on long idle periods but quickly charged up with higher idle revs. After the install of the new smaller pulley, it drives fine so far but i havent drove it at night for long periods of time. i just had the stereo on and lights on and let it idle for a bit. Even hit my manual fan switch which sucks some power out. charge was fine on stock idle.


now for the good part.....before and after results. The lighter smaller pullies makes the motor rev faster. there is a HUGE improvement in throttle response. From any gear/rpm/speed, you mash the throttle and its near instant response and gear downshifts when needed. This really makes the car feel faster. Is there a hp improvement? I think there is and i sure hope so..its hard to feel but the car does seem to pull harder from 4500-5100 where it shifts. I will have track data tommorrow night, so STAY TUNED!! I'll be abit dissapointed if i spent 97 dollars for throttle response....

czbigboy

I was thinking of using the same pulleys on my 85' 305 TPI. Would like to know if the HP was up any on those you used.

LVZ2881

I just installed the same pullies on my '88 TPI car,k although I have the steel pulley. I had to take the alt of the car and down to my brother the chevy dealer tech for him to install alt pulley with impact. I couldnt get stock alt pulley off either.

Orr89RocZ...do you think since I am running the march underdrive alternator pulley that the 93 or 93.5 belt will work for me???

Orr89RocZ

iTrader: (20)

well now that i have driven the car alot, i must say it was worth the cost. charging is fine and i experience little to no voltage drop in the battery.

with both smaller pullies on the car, i used a 94 inch belt. i think you may beable to squeeze a 93.5 on, but the 94 inch was perfect. remember, 94.5 is stock size.

The smaller alternator pulley actually overdrives the alternator. The small pulley on the crank slows everything down, so you need to speed up the alternator with a smaller pulley to keep charging up.

As far as power gains, i expect it was worth a few ponies. how much? its hard to say. I ran 13.49 at 99.1 one night and next week i went 13.46 at 99.6 in abit hotter more humid weather. So i think it helped some. Now i'm running 13.2's in this winter like air at 101mph.