ccdguy

For what it's worth... I have an 87 GT vert, and have been running the March Performance under drive pulleys for over a year. Initially I did have some problems with charging, but since then, I've dialed my car in by adding supporting mods. I now have a PA 95 amp 3G alternator, a 3 row aluminum radiator and Proform electric cooling. What I have done, is I've used only the crank, and water pump pulley. I've swapped out the alternator pulley for an ASP 1 7/8" diameter pulley to "overdrive" the alternator a bit. In doing so, I have retained "normal" charging with the 95 amp alternator. I can run headlights, heater/fan and six speaker stereo when idling with no issues at all. On your applications, the radio/sub/speakers might be an issue if you are going to run UD pulleys with a stock 65/75 amp alternator, unless you get a smaller alternator pulley like I did.

Also, it is a proven fact that you will free up some power on your 5.0 after the install of pulleys... See this article...

http://www.marchperf.com/superford1.html

Hope this helps?

projectresto83

Sounds like your thermostat sticks sometimes. Replace it and flush your coolant system out

wydopnthrtl

I too have run underdrives on many fords. Two of them have been 5.0L mustangs w/stock long blocks.

IMO for a stock engine I'd at least wait to do this until steeper than stock rearend gears have been installed. With gears your constantly running at higher rpms except when idling. So PS, charging, AC performance are generally ok. With 2.73gears though.. I'd not do it.

If you can raise the idle by 50-100rpms.. that will help if you see stop and go traffic often.

w/my 95 the power steering would get a little hard when I was in heavily decelerating situations. (engine idling because clutch was in and I was on the brakes w/ car sliding into a corner)

Even if your driving in the country there may be times when you get stuck in traffic on a hot day. So having steeper gears will allow you to creep along at a higher rpm where charging and coolant flow can be regained.

My 89 has a stock alt, 4.10s, e-fan, aluminum radiator, march underdrives, Edelbrock curved vane W.P., and a 180T-stat. I have the e-fan set to come on at 200F w/a probe near the outlet (top passenger side of rad). No issues cooling or staying charged.

Here is a pic:

Mandrew

How much is an e fan?