I have these on my '84 carbed 305 road race car, did not think much about ordering them for my '91 TPI five speed Formula project. Good or bad idea? PN is March 4010. Or should I have gotten the GM amplifier series March pulleys? This is a street car with a small stereo, nothing fancy.

 

Is everyone running another kind of ud pulley or is everyone out Christmas shopping? Any input appreciated.

 

Heres a copy/paste of a reply I gave to someone earlier about my UD pulleys.

My underdrive set came with two pulleys, a smaller than stock crank pulley and a bigger than stock alt pulley. When I installed them both, the car would not stay charged to my content. So I put the stock smaller alt pulley back on (spins it faster) the charging system operates flawlessly, AC, PS and Waterpump are all still underdriven. It doesnt overheat either, constant 180-190 temps (180 Thermo & low temp fan switch installed) and PS & AC work great.

Never took it to the track after the upgrade though.

 

Matt, thank you for your input. I have gathered that UD pulleys that work on race cars are not good for the street. Yours sounds like a good adaptation of that. I will be going with the GM amp series of March pulleys as that sounds more like what I am looking for. I'll be sure and post how I like them.

 

I bought the March 2 piece set for my car a few years ago, around '95 I think. Never once had any problem related to them. I actually felt a difference with them on. I did K&N, screens in MAF, crappy Hypertech chip, 160 stat, & fan switch, and TPIS airfoil. I noticed NO difference. Swapped just pulleys, noticed a difference. I believe the claims of 10-15 hp. Maybe it was a combo of all the parts working togeather, (I also had exhaust) I don't know.

 

UD pulleys would be good on a road race car that sees higher RPM's for long periods of time, it will help your alternator live longer and free up some HP. Everyone I know who runs them on the street has been unsatisfied with there alternator operation.

 

Thanks again guys. I sent back the March 4010 today!

 

i purchased march underdrive pulleys just lately and installed them

mch-6090 50% under drive crank pulley
mch-6112 water pump pulley

you are suppose to see gains of 10-15HP from that, that is quite a bit

 

I did a dyno test with a '91 LB9 and march pullies.

Saw 14 rwhp.

I am a big fan of u-drives on LB9s and L98s. They always show a diff unlike many other nonsense upgrades (air-foils ).

I did SLP runners barely noticed it what a rip-off. Did the pullies noticed it right now at 3500rpms no ifs ands or butts.

Never had a charging problem.

But you sent yours back eh?

 

85Rocker, do you have your air pump assembly still hooked up? I have been considering getting UD pulley for my set up, but was always hesitant because I already have smaller belt on it because I have no air pump hooked to it. If i were to get the UD pulley's would I have to figure out a different routing, or different size belt? Or do you think my current (smaller than stock) belt would work? Thanks

 

from my experiences with UD's
i personally love them many pro's and a few cons
again from my personal experience on various motors, like my pontiac 400 and her 3.1v6 90 FB and some friends cars

Pros:
improved MPG's, especially when taking a trip
felt like motor could rev quicker
less chance of belt throwing
less squealing
polished aluminum looks real nice

Cons:
slighter tendendy to overheat or get hotter
alternator may not charge sufficiently
have to get a new belt

as a quick reference, the difference of using UD's from not is about the same when you turn your AC on and off and you feel the difference.

on a lower HP motor you will definately feel the improvement
on a higher HP motor, i doubt you will

I have compensated the alt issue by getting a higher output alt

the heating issue tackled a few ways:
larger rad
higher flowing water pump
blanced sleeved thermoustat with two air bleeds drilled in it

her 90 FB was great with them, except i used the stock alt pulley so charging was less of an issue. with the UD pulley you definately felt it.

MY TA, i felt it when i floored it, as opposed to feeling the difference with her v6

again v6 gainging 5-10hp is alot more noticeable then a v8 gaining 5-10
but when it comes to the looks, the march polished ones look awesome

i've had mine for over 10 years and still look brand new
not to mention the smaller pulleys make it easier to work/clean around the engine.

just some thoughts i'd share

if you got the $$ and want the looks, i think it's worth it without a doubt

 

Schweet guys, thanks for all the great input! 85Rocker I sent back the 4010s and got the March GM Amp series UD pulleys instead. They are also polished - sounds like this set of pulleys is more what I am after with this car being a street driver with a modest set of tunes. March says about 11hp with these, not bad!

I'll let you know when I do my next dyno how it works out.

 

I have A/C and air pump all the gizmos hanging off the front. I think the a/c delete pulley is enough to keep belt geometry even if you lose the air pump.

My factory belt was k6960 (6 rib, 96.0 onches long) my current with u-drive is k6925 or 92.5 inches long. So you only lose a few inches.

if you have a/c or a/c delete and no air pump you should lose another inch not much more. People do it I've seen it at the track.

 

I mounted my alt in the a/c bracket reposition the tensioner and deleted the air pump. completely different belt routing

 

you'll be happy with the power amp series
plus they look great

if anyone deletes the air pump if you route the belt the same way a 89 full size balzer is, you'd be all set.

if the alt doesn't charge to your liking, you can always look at the CS140 alt or a high output cs130, but i doubt a CS130 will be as good as a Cs140 in the lower charging rpm range

 

Cool Don, much appreciate the info.

 

i'm also interested to see how you liked them, and to see what difference you feel afterwards.

 

Ive had the 3 piece set on my car for about 3-4 years now. The only time I had a problem was when my alt wore out and stopped charging. If you dont have a big amp and alot of subs I dont think you will have a problem.

At night with the headlights, ac, and radio on the lights might get alittle dim at idle.