Engine Underdrive pulleys

Mindseye007 · Feb 1, 2026

Are you running underdrive pulleys ?
I'm running March underdrive pulleys with a 200amp alternator so sweet I could feel the hp power increase after they were installed. That was one of the first mods i did years ago. Wonder how the cobra pulleys are? But after watching this I think I might upgrade to the SVE pulleys.going to check the size specs for the March pulleys first.

View: https://youtu.be/Nkwg3lyZB_A?si=8A0-Kvz61jwboeAu

AeroCoupe · Feb 1, 2026

I have run a set of BBK under drive pulleys on my Coupe for about 24 years and have had zero issues with them. Alternator charges at about 14.3V at idle and I don't have any cooling issues either. Have had March pulleys on the Thunderbird for about 28 years and same thing.

Mindseye007 · Feb 1, 2026

AeroCoupe said:
I have run a set of BBK under drive pulleys on my Coupe for about 24 years and have had zero issues with them. Alternator charges at about 14.3V at idle and I don't have any cooling issues either. Have had March pulleys on the Thunderbird for about 28 years and same thing.

What cooling guage are you using in your coupe? can you take a picture of your setup?

Mustang5L5 · Feb 1, 2026

I ran them for 20 years with an overdrive pulley. Never really had any issues with them .

Latest rebuild I was more concerned with cooling so I put a set of the SVE 93 Cobra pullies on

nickyb · Feb 1, 2026

Mustang5L5 said:
I ran them for 20 years with an overdrive pulley. Never really had any issues with them .

Latest rebuild I was more concerned with cooling so I put a set of the SVE 93 Cobra pullies on

Why you running overdrive pulleys?asking for a friend.

AeroCoupe · Feb 1, 2026

Mindseye007 said:
What cooling guage are you using in your coupe? can you take a picture of your setup?

Autometer 2-1/16” full sweep electric water temperature, fuel pressure, and oil pressure gauges on the A pillar. The factory water temperature gauge still works but I never hooked the factory oil pressure gauge up. I’ve been contemplating taping the factory extension and holing it back up.

Mindseye007 · Feb 1, 2026

AeroCoupe said:
Autometer 2-1/16” full sweep electric water temperature, fuel pressure, and oil pressure gauges on the A pillar. The factory water temperature gauge still works but I never hooked the factory oil pressure gauge up. I’ve been contemplating taping the factory extension and holing it back up.

Can you have those autometer gauges working and still have the stock gauges working to compare readings?

Mustang5L5 · Feb 1, 2026

nickyb said:
Why you running overdrive pulleys?asking for a i

Overdrive alternator pulley. 3G alt still has a min RPM that is needed to make full charge. I wasn’t getting it with the underdrive crank and alt pulley, so stuck the overdrive alt pulley in and that solved my charging issues at idle. I could run pretty much everything at idle and still made 14v with it.

gkomo · Feb 1, 2026

I ran the LMR cobra pulleys for a while but they didn’t work well with my Paxton supercharger for some reason. Too much belt squeal with relocating the smog and alternator.

Prior to that I had zero issues though.

AeroCoupe · Feb 2, 2026

Mindseye007 said:
Can you have those autometer gauges working and still have the stock gauges working to compare readings?

Yes. You will need to either drill and tap the oil pressure extension that screws into the block on the driver side just behind the timing chain cover or buy one already done. Will look something like this:

https://www.cjponyparts.com/oil-pressure-sending-unit-extension-dual-port-zinc-plated-mustang-v8-1965-1973/p/OSUF6/?srsltid=AfmBOooZXYEs2sf43ujB1LEkKfIOe0j0k3K7sjfnIs0vmu2_V3AnBzfn

For the stock temperature gauge you can utilize the port in the rear of the lower intake.

Install the aftermarket gauge sendor in the front hole the stock sender came out of. This is just from several years of people installing the aftermarket one in one of the rear holes only to find out it reads lower than the front holes and is slower to react than the stock gauge. Swapping them around keeps the stock unit working (albeit not super accurate but it wasn't before so no harm no foul) and puts the aftermarket one where it is more accurate so it is of more use to you.

JD1964 · Feb 8, 2026

My area is congested with traffic on a regular basis. I ran underdrive that was built into my vortech crank pulley. Sometimes in summer congested traffic it was sketchy giving concerns with cooling and charging. I went back to stock accessory drive speed. Its best for my driving conditions in my location. Underdrive is not worth the minimal gain in useable power for my situation. The crank pulley change also slowed the supercharger down but I have partially compensated for that with a smaller supercharger pulley.

Mindseye007 · Feb 8, 2026

JD1964 said:
My area is congested with traffic on a regular basis. I ran underdrive that was built into my vortech crank pulley. Sometimes in summer congested traffic it was sketchy giving concerns with cooling and charging. I went back to stock accessory drive speed. Its best for my driving conditions in my location. Underdrive is not worth the minimal gain in useable power for my situation. The crank pulley change also slowed the supercharger down but I have partially compensated for that with a smaller supercharger pulley.

Did you change the rest of the pulleys back to stock? Electric fan?

JD1964 · Feb 8, 2026

The crank pulley is stock and has the entry level 6” Vortec supercharger drive pulley inside of it. I have a 2.62” driven pulley on the supercharger. Water pump, AC and alternator pulleys are all stock. Smog pump has been deleted.

JD1964 · Feb 8, 2026

Electric fan? Yes, Contour dual fan setup with DC controller

Mindseye007 · Feb 8, 2026

JD1964 said:
The crank pulley is stock and has the entry level 6” Vortec supercharger drive pulley inside of it. I have a 2.62” driven pulley on the supercharger. Water pump, AC and alternator pulleys are all stock. Smog pump has been deleted.

I guess your running aftermarket gauges for everything?

JD1964 · Feb 8, 2026

Mindseye007 said:
I guess your running aftermarket gauges for everything?

All the factory gauges are still functioning in the cluster. I have a mini shift light under the cluster bezel. Single PLX on the pillar currently with two modules. Wideband and Vacuum / Boost.

I know the factory gauges are not always dead accurate but I ran the accessory under drive long enough to know its drawbacks. This car is not a trailer queen. When I’m 150 miles from home at a car event stuck in traffic on a hot summer day, the e fans are going full speed and the Mrs wants the AC blowing, no more accessory under drive for me.

JD1964 · Feb 8, 2026

Forgot to add pic to last post

Mindseye007 · Feb 8, 2026

JD1964 said:
Forgot to add pic to last post

Do your mats ever slip underneath the pedals?
I put those claws and they still slipped as i was lifting my foot off the gas and shifting quick into 3rd gear the mat pushed the gas peddle to the floor and it redlined its my dam size 13 feet lol I got so mad and threw the mat in the garbage nothing works for me . So no more floor mat for me on the drivers side.

JD1964 · Feb 9, 2026

Yes, I’ve had a few incidents where where the floor mat interfered with the gas pedal releasing. At first I thought it was the linkage binding. I checked all that and found no problems. Then I discovered the floor mat will slide down over time and cause the pedal to hang up. Since then I just make sure it’s pulled all the way back when I get in the car and I have not had any trouble since. I should probably seek a permanent solution.

93gtmustang · Feb 10, 2026

Mindseye007 said:
Are you running underdrive pulleys ?
I'm running March underdrive pulleys with a 200amp alternator so sweet I could feel the hp power increase after they were installed. That was one of the first mods i did years ago. Wonder how the cobra pulleys are? But after watching this I think I might upgrade to the SVE pulleys.going to check the size specs for the March pulleys first.
View: https://youtu.be/Nkwg3lyZB_A?si=8A0-Kvz61jwboeAu

I have the BBK underdrive pulleys.
When the car was street driven, the underdrive pulleys were a problem when stuck in traffic in the heat.
The underdrive pulleys would affect the water pumps performance, which would start the electric fan to run endlessly, which put a drain on the battery, and then the alternator couldn't keep up.
It had the stock alternator which probably didn't help. If I had kept it on the road I would have switched back to the stock pulleys.

Engine Underdrive pulleys

Mindseye007

AeroCoupe

lube between the nut and the face. I know my lubes

Mindseye007

Mustang5L5

That is…until I whipped out my Bissell

nickyb

I gotta say i never painted my nuts, Never Ever

AeroCoupe

lube between the nut and the face. I know my lubes

Mindseye007

Mustang5L5

That is…until I whipped out my Bissell

gkomo

now i can hopefully expect to receive the shaft

AeroCoupe

lube between the nut and the face. I know my lubes

JD1964

there is enough sticking out to grab on to

Mindseye007

JD1964

there is enough sticking out to grab on to

JD1964

there is enough sticking out to grab on to

Mindseye007

JD1964

there is enough sticking out to grab on to

JD1964

there is enough sticking out to grab on to

Mindseye007

JD1964

there is enough sticking out to grab on to

93gtmustang

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Engine Underdrive pulleys

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

I gotta say i never painted my nuts, Never Ever

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

there is enough sticking out to grab on to

there is enough sticking out to grab on to

there is enough sticking out to grab on to

there is enough sticking out to grab on to

there is enough sticking out to grab on to

there is enough sticking out to grab on to

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