N8Miller

i was looking into some cheap ways to add some HP and thought of underdrives. They are very very common on the mustangs, but how do they work on the Gm products? i used a set on my trans am, they were ok, but i think i was sold the wrong set. what do you guys think of underdrive pullies on the motor that i have listed below.
should i call March and talk to them about the proper set up for my car???

ThirdGenZ28 92

I have them but never ran ET before and after since back then I just threw stuff on because it was SUPPOSE to work out of ignornace. The motor doesnt seem to labor like it does with the stock pullies, that part is noticeable but if you can score them cheap I cant see them hurting you but depending on whats done to your car the $ might be better spent elsewhere. Also I had to replace the stock alt. pulley as my car wasnt charging properly so I only have the March crank pulley in place of stock, hope this helps some....

Rob P

iTrader: (1)

I had them on a basically stock L98 I had dropped in my 89RSconvt. I dropped 2 tenths and gained 2mph. However I did not like how my charging system reacted. Sitting at a traffic light with headlights on and intermittent wipers on would cause volts to drop below 8. I think I had the three piece (crank/water pump/alt) MAC set.

PonyKiller87

I put the March ones on my 87 which has a beefed up L98 in it. I put a post up on them a while ago, pretty much a long smoking letter about how terrible March is.

Part of my problem may have been that I converted from the multiple belt to the serp style but none the less it was still a big hassle and March didnt seem to willing to help me get things squared away.

I do notice the headlights dim at idle, not sure that I really like that but not much I can do about it.

89BlueTA

My results are in my sig. If you get the march pulley's, the 2 piece gives you more underdrive compared to the 3 piece.

nick

92BLKL98

Ditto here, they will kill your battery. Mine died in the drive up line at the bank one day and that was it, off the crank pulley came. Till I get a hotter alternator at idle I will not reinstall it. I did leave the water pump and alt pulley on, they are pretty and don't affect accessory operation. You can do the ratio math: crank pulley/ alternator pulley. The alt currently on my Z supposedly puts out 50 amps at 1500 alt rpm or with my set up 500 engine rpm. It idles at ~550 in drive. Considering accessories running at idle with lights brake lights engine and ancillary equipment this is probably OK but with the March crank pulley the alt is running at ~1250 rpm.... NOT GOOD. TPIS recommends a 2% underdrive, I can't believe this is worth the effort. But to my understanding Myron Cotrell is one of the TPI gods.

Beast5spdGTA

I have the 2 pc MAC(alt./crank), I believe they were like $60+~$20 for a new belt. Noticed weak charging at idle(less than 1000rpm), but never caused a problem. Couldn't tell you about a power difference(cam at the same time), but it's pretty much a given 5 to 10+hp, every test I've seen dyno or 1/4 mile, there's always a small gain.

N8Miller

ok guys how about this: we get the 2 peice set. but not the alternator ones...just the water pump and crank. the way i figure it, this should allow me to keep my charge and still under drive the accesories.
what do you think about that idea? if you think about it running too hot, i could just install a 180* thermostat.
let me know

89BlueTA

Just get the crank pulley, the water pump pulley from march will provide less underdrive. I think you just want to get the crank pulley only.


nick

92BLKL98

Guys' as I said the march kit does about a 2.17:1 ratio. The factory is about 3.32:1 which is about a 33% change The March crank pulley does most of the overdrive with a 2" smaller diameter. The March alt. pulley is .338" or 3/8" larger. So my point is the crank pulley is the biggest problem. For the cost of the overpriced march pulleys, ~ $150.00+, you could get more hp out of a set of headers. 5 - 10 hp ain't gonna show on the SOTP dyno and not as much at the track as headers. These TPI engines need all the current they can get to run right so if you want looks polish and clearcoat your pullies and drive on. I did keep the alt. and water pump pulleys on but just 'cause they look nice. JMO.

Dwayne88IROC

The crank pulley is the only under drive in the March pulley's. The water pump is the same size as stock, it's just shinny that's all. Last I checked there were 2 types of March system you could get. One has a smaller alt pulley that spins the alt at the same speed as stock. No voltage drop.

March Pulley's technical service does s u c k though.

92BLKL98

The kit I bought had a visibly larger .338" alt. pulley and 2.10" smaller crank pulley. The 3/8" difference gives ~ 3% underdrive, add the 2.10" crank pulley and it comes up to ~33%. I didn't measure the water pump pulley but I'm pretty sure it's larger than stock. I'll measure and tell you, I can tell you the March kit is a waste in the power dept. it looks good but that's it the extent of it.

Mark A Shields

I had a small crank pulley, caused charging problems so I took it off, I couldn't really tell a performance difference.

PonyKiller87

Something to think about with the charging problems. I have the underdrive pulleys on still and while at idle the voltage drops down to about 9 or 10 the battery still has enough juice to start the car every time. I am running an Optima Red Top battery though this may be the difference. And the guy at batteries plus told me that its guarantied for 2 years no matter what so if the underdrive pulley does mess it up Ill just take it back and get a new one.

92BLKL98

Yes battery quality means a lot but still a low performing charging system can rear its ugly head at the most inopportune time like in the staging lanes or even in the bank drive thru. I agree with Mark, when I removed my crank pully, no change, even at the dragstrip.

BretD 88GTA

I had the HyperTech pullies on my car for a little while and had charging problems as well. Even with the stock alt. pulley back on and just using the under-drive crank pulley.

If I had to idle for a period of time the volts would drop pretty bad. The car almost died on me one night in severe stop and go traffic on the fwy.

I agree that your money would be better spent on other mods.

CC

iTrader: (1)

Get the March Pulleys w/high Amp Power (2 set) instead of the regular March 2 set and you wont have any battery/alternator issue. I obtained it from Summit part number #04400 for Camaro/Firebird 1988-1992