March billet aluminum underdrive pulleys... belt numbers?

[tpaul]

Hey guys,
I've seen a few threads about looking for billet pulleys for the hot airs. As has been stated before, March makes a great set of underdrive pulleys for the hot-airs. They have a much smaller crank pulley, a larger water pump pulley, and I believe a stock sized alternator pulley with a cover.
You may have to dremel out the water pump shaft hole to make them fit. The clear powder coat is too thick. You may have to do the same to the crank pulley. I have not test fit mine. My balancer is powdercoated so that would make a difference as well.
I've got a set of these pulleys sitting in my shed (Florida, no basements) because I can't figure out what belts to use. I contacted March directly and they stated that they don't have belt info for the 84 - 85's. If I had an 86-87 I would be golden!!!
Anyone running these? I need numbers for the belts.

Thanks,
Tim

 

[GN84Turbo]

Well..seeing as the alternator tightens the belt on a swivel, you can probably use the same alternator belt. but you may need a shorter PS belt ( and maybe AC too). Put on the pulleys, and put on your old v-belts, and see if theyre too short or too long. Any auto part store will help you match up bigger and smaller belts. It's a pain in the butt, but its the only way. ( i have the march pulleys too, look great!)

 

[tpaul]

Hey Terry,
Thanks for the reply. What have you seen in gains by running the pulleys? Did you have a problem finding the correct belts? Half the time I'm lucky to find someone to take my money at these chain parts stores. I just went to get an alternator diode the other day, the counter guy looked at me as if this part didn't exist! It's amazing what they find when they go to their computers!

Thanks,
Tim

 

[GN84Turbo]

I know what you mean. The best way to do it is to stretch the belt end to end and get a measurement. Then fit the belt to see if its a little too long or too short. Then take the belt with you to the store and ask them to bring out a variety of lengths; get a shorter or longer one by comparing their lengths end to end.

I havent tested them out yet, but the crank is considerably smaller and the water pump pulley is massive, not to mention theyre very light. I cant imagine that they wouldnt free up some HP.

Cant wait to get my car up and running again, just need to find the time to do it! :biggrin:

 

[tpaul]

I agree, the sizes kind of threw me off for a bit. They are very light and good looking pieces. I'm trying to track down a couple other problems, but when those are resolved I will jump on the pulley situation.

Thanks,
Tim

 

[ct70nut]

How about part numbers for the pulleys? I have seen March pulleys for the 84-85's but I thought they were stock sized. Would love to have a set for my NA v6.

 

[tpaul]

Here's the March link. PONTIAC BIG BLOCK V-GROOVE PULLEYS Set #4220, I purchased my set from Jegs or Summit. Do a search on those sites for that part number. They are a bit on the pricey side!
I just saw that they are stating that the pulleys have a black powdercoat. My set bought a few years ago came in a clear powdercoat. They also list it as a aluminum/steel kit. I thought all my pulleys were aluminum, however, the alternator pulley may have been steel. I'd take a look at my set, but they are sitting in their box in my shed. Too many other things to worry about first.
This kit is much different than the stock size! Crank is much smaller and W.P. is bigger. This kit comes with Allen head bolts for the crank. The stock crank bolt heads are to wide to fit in the new pulley.
Now, with that being said, I don't have a N.A. to compare to. So, I don't know what the size difference would be for that motor.

 

[Boost231]

if you get a chance can you weight them all seperate so i can see how much the weight compared to my stock powder coated pulleys. i might be interested in making the switch and not using the water pump pully and putting a electric water pump on my car.

 

[tpaul]

I'll try... they're in my shed at the in-laws. Next time I get out there I'll see how burried they are. I don't think they'll be too hard to get to. I'll take my postage scale with me next time I go out there.
I've got more stuff to put out there anyhow. I'll try to get out there this weekend!

 

[Boost231]

that would be great. im still thinking about putting the 87 pulleys and stuff and the front of my car. in time i guess.

 

[T- Type Tim]

I got my aluminum stock sized crank and water pump pulley through Wysco. Definatly lighter than stock, but honestly , I got them for the looks. I've heard that underdriving the water pump pulley creates a heating issue as the coolant passes the radiator 2 fast to get sufficient cooling.

 

[tpaul]

Interesting... help me think through this. A smaller crank pulley means the belts at the crank turn more RPM's. A larger water pump pulley should slow down the W.P. RPM's? However, it would seem the P.S. pump would spin faster. Is this correct? Trying to think back to my old go kart days...
I purchased this set assuming they were stock diameter, and as well bought them strictly for looks! Now you bring up an interesting question!
With all that, why would underdriving a V belt motor be any different than underdriving a serpentine belt system?

 

[novaderrik]

a smaller crank pulley slows everything down, since the belt travels a shorter distance in the same amount of time compared to a bigger pulley at the same rpm. a smaller water pump pulley speeds up the pump in relation to the crank, thus negating any power gains you might have found. but i guess the AC and PS pumps are still turning a little slower, thus freeing up a little of the 2 or 3 hp they soak up when the AC is off and the steering isn't being turned.
in the end, you gain a miniscule amount of power due to the lower mass of the pulleys and accessories turning a few less rpm..
i'd rather spend the $250 on something that might actually make the car faster or more reliable.

 

[T- Type Tim]

For sure!

 

[Boost231]

well when i get back it might be time to set up my serpentine belt system since the motor is going to be out of the car. would be kinda cool to run a serpentine belt on our car with the RJC pullyes

 

[GN84Turbo]

did we ever figure out the belt numbers? otherwise i have a new project for today...

 

[tpaul]

Pulleys are still on the back burner for me... let us know if you have any luck with the belt numbers!

Tim

 

[GN84Turbo]

got the part #s

OK finally took the time to figure this out, turns out kragen has a v-belt measuring tool, which is great.

ok part #s:

alternator/water pump: 15456 (or 15450)

Power steering belt: 15371


The 15 is the belt width/thickness and the remaining #s represent the length. These are universal part #s but i picked up Goodyear Gatorbacks brand at Kragen for ~11 bucks a piece.

15456 tightens up at the very top of the alternator bracket. If you want a shorter belt, 15450 will fit perfectly as well.

The power steering belt fit very well (or as well as the original did, i can never get the belt very tight on the PS), but you could go one size smaller (15365 or something) and have no problems.

Hope this helps,

 

[GN84Turbo]

I got my aluminum stock sized crank and water pump pulley through Wysco. Definatly lighter than stock, but honestly , I got them for the looks. I've heard that underdriving the water pump pulley creates a heating issue as the coolant passes the radiator 2 fast to get sufficient cooling.

The water pump isnt underdrived, the water pump pulley in the kit is much larger than stock. wouldnt that make it "overdrived"?

Why Under drive Pulleys Work

 

[GN84Turbo]

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