Anyone have a problem with underdrive pulleys?

GREATWHITE666

Registered User
Ive heard that the underdrive pulley for the alternator can mess with the electrical stuff... is this true? i was thinking about getting some underdrives, i read an instant 12-15 hp.. sounds nice, but are there any draw backs? thanks...
Damon
 
pulleys

If you are running any kind of sound system or live down south like I do, the underdrive alternator won't work. Does not allow it to put out enough to keep up with the electrical system.
 
i have underdrive pulleys and i cant tell you that i haven got any electrical problems and i had a sound system and live in a hot climate , as long as you arent idling much , its ok , of course i have a optima battery and a 5-speed .so i could keep the rpms a little higher when i was using the sound system ,

and i can tell you its worth the $$$ currently i use my sc in n/a mode ( blower belt removed) so i get better mpg when going to school and the car feels a lot better than before i put the UD pulleys. i would also recommend a jackshaft pulley haven tried but there sa good 20hp extra when i remove the belt from the jackshat to the crank :D in n/a mode you feel every hp you get :D
 
Agreed, having an auto makes the UD pulleys a bit of a problem when you are idling in drive. 5spds fare much better. I would still do the underdrives with an auto, just leave the stock alt pulley on. It will put you about 1/2 way on the alternator alone since the crank pulley accounts for 1/2 of the underdrive.
 
cool

yea i have an auto and a sound system and live in a hot climate.. lol. but i guess i could do the other pulleys and leave the stock alternator pulley on.. you think thats even worth it? good for a few hp still..?
Damon
 
Just remember UD pulley's also SLOW down the water pump as well, NOT a good idea on a car with a puny cooling system. I've used UD's before and I saw NO benifits to using them period so none of my cars have them now or ever will in the future. I just never got any benifits from using them that outweighed the disadvantages of using them.
 
uh oh

OK, stop right there! my mind is changed. lol. I much rather give up some xtra hp to keep the cooling system and electrical system at it's best. Thank you guys for your inputs.
-damon
 
good point mike

I have to agree with Mike. Why would you want to slow down the cooling system on a car with a weak system already?

Didn't think about that one also.
 
I have underdrive pulleys on my 95 auto. I do not have a big saound system or any of that but I have not had any problems cooling wise in the hot summer months. I did not put he UD pully on the alternator but did use the crank and water pump one.
 
Mike, your choice to not run an UD pulley is certainly a prudent one, but I do question where you get the idea that the waterpump is in any way a weak point with our cars? Has anyone reported any overheating as a result of UD pulleys? How does it figure that pushing more water through the radiator would help the cooling issues? It would seem that if the waterpump were moving insufficient amounts of water then the rad would be cooler than the motor, no? I've not seen that to be the case. In fact the only time I have cooling issues at all is when I am running for extended periods at higher rpms on the highway (like 3200+ continuously). Just curious.
 
damn!

damn! why did u have to say that lol.. now im getting torn between. if the UD's would mess with my cooling system then id leave it stock but now ure saying it wont.. ok more and more opinions AND experiences!!! thanks guys
-Damon
 
XR7 Dave said:
Mike, your choice to not run an UD pulley is certainly a prudent one, but I do question where you get the idea that the waterpump is in any way a weak point with our cars? Has anyone reported any overheating as a result of UD pulleys? How does it figure that pushing more water through the radiator would help the cooling issues? It would seem that if the waterpump were moving insufficient amounts of water then the rad would be cooler than the motor, no? I've not seen that to be the case. In fact the only time I have cooling issues at all is when I am running for extended periods at higher rpms on the highway (like 3200+ continuously). Just curious.
All I said was that the UD pulley's will slow down the water pump.
I dont think it is a good idea to do something that degrades the performance of this engines cooling system. Thats just how I feel about it, you certainly dont have to agree with me.
The cooling system on these cars is a problem area. Just search the boards, theres all kinds of problems about it on this board.
 
If you are heating up at highway speeds, check the deflector just behind the openings under the front bumper cover. Also, there should be a shield that runs from the radiator support to the anti_sway bar to help create a low pressure zone behind the radiator. These two elements help to direct air through the radiator at higher speeds.

The UD pullies should not be a concern if the rest of the cooling system is in good condition. Don't install them with a old, OEM radiator and expect not to overheat. From the design of the pump I would expect it to cavitate at high RPM, loosing most of its pumping power. I believe the MARCH pullies are the most aggressive and I have no issues with them on an 89 Auto driven hard, but I also had my radiator recored to a 3-row core, flushed the system well and refilled with distilled water.

Check your current radiator, if you have ANY mineral deposits in it you need to get rid of them, both engine and radiator. They will reduce cooling much more than pump volume will. Those deposits insulate twice, first to get the heat into the coolant in the block and again removing it in the radiator.

Aaron

PS: Mike - I agree that the UD set reduce too much, most of the gain is in the weight savings anyway.
 
I agree with you Pastera but the problem is I'd be willing to bet that about 95% of the owners here use tap water in there cooling system. I've seen the mineral deposites in the rads and engines and that stuff is a killer to the rad and you cant clean out the water jacket on the engine until its rebuild time, so once you get it in there youre screwed.

I am completely amazed by the attitude here from most guy's that it is normal for this engine to run hot. I really just do not understand why they beleive that.
The SC is the only forced induction engine I've owned or tinkered with that runs that hot.
I have 2 turbo cars right now that are not exactaly stock and they dont run this hot, infact if they did I would be looking for a leaky HG on them because thats the symptoms they will have when the HG's are leaking.;)
 
I've run ASP's for about 4 years and 40K miles, without issue. I do, however, have a Griffin rad.
 
pastera said:
Also, there should be a shield that runs from the radiator support to the anti_sway bar to help create a low pressure zone behind the radiator.

I believe it attaches to the forward K-Member brace, not the sway bar.
 
Well here's something for you. I have a lot of work on my engine, it's an auto, I have a pretty big stereo system, I drive city streets a lot and have driven in stop and go traffic for years and the worst thing I have ever had happen to me is that radio will shut off every once in a while. So there
 
Sorry about that, I'm not at home and was just trying to picture where it mounts (mine was gone when I bought the car). Things are a little fuzzy on Mondays :confused: .

Aaron
 
I think the best way to look at underdriving the water pump, may best be explianed in terms of high RPM motor. The more RPM's you are reving at, the faster the pump will go, with the stock size pulley on. Then by adding a larger diameter pulley, the pump will slow down. So at higher RPM's the stock pulley will push more coolant faster threw the system. With risking the chance of it not cooling. So by slowing down the W/P, this will cause the coolant too move at slower pace, thus cooling better. Now that was said for a high RPM motor. This is not always the case for SC's.

I have run underives for about a year now, with no real problmes. I am now running a set of "test" stock size aluminum pullies. With a small amount of better cooling over the underive W/P.

A good piont was brough up, use mineral water, not tap water. And be sure the complete coolant system is work propperly.

Hope that helps.
 
Last edited:
I understand the slower water pump theory as has been talked about, but if that theory was correct how do you explain the slightly better cooling you got from running stock sized pulley's?

Randy Baker already proved that pumping more water through the system cooled the engine way down. He install a 55 gal per hour electric pump on his engine and reported that the engine ran way too cool. Randy said he was going to try a 38 gal per hour pump to get aliitle more heat into the engine.;)
 
Back
Top