underdrive pulleys

I installed Steeda underdrive pulleys on my 08 Mustang GT a month ago, and I'm happy with them. They free up a few horsepower and make your accessories last a little longer.

Seat of the pants is a notoriously inaccurate measure of power driven by confirmation bias. Nevertheless, my car does seem a little stronger. I was expecting a small improvement in fuel economy, and it's possibly in the 1/10 mpg range. The engine runs smoothly.

It's winter in Michigan, but the temperature has never moved above the normal operating range. The generator is fully charging the battery. The power steering feels the same. If you're concerned about cooling, perhaps you should hold on to your old water pump pulley. If you have a problem, you could reinstall that pulley and run a shorter serpentine belt. The new water pump pulley is quite large. There have been no leaks and no problems so far.
Much easier to install from above the car than below it. If you move the air intake tube and the coolant overflow, there's adequate room to work.

With a manual transmission, leave your car in 5th gear with the emergency brake applied and chock your wheels. In lower gears, the torque necessary to remove the balancer bolt was moving the whole car. I used a 15" breaker bar with a cheater pipe to loosen the bolt.
The OEM Tools 7 ton puller from Autozone absolutely will not work - it's way too long to fit between the balancer and the radiator/fan. A Ford dealer mechanic let me borrow his Blue-Point®/Snap-On YA6490A, and the balancer was much easier to remove.

The directions said to apply "a dab" of high temperature silicone to the keyway on the balancer. There was a lot of silicone on the key and the old balancer, so I scraped and brushed it off as best I could and applied a healthy dose of silicone to the new keyway. I don't think it's there to keep oil in the engine. The crankshaft front oil seal is there to keep oil from leaking out. I speculate the silicone is there to keep water and dust from migrating past the balancer in toward the engine. Installing the balancer definitely required a cheater pipe for the last step.

Belt tension wasn't enough to hold the water pump pulley in place while loosening and torquing the bolts. A drift punch through the pulley hole around 8:00 kept the pulley from turning. You might also try rotating the tensioner counter-clockwise to increase belt tension.

You have to remove the stud at 4:00 as you look at the generator. The snout has a 5mm hex on it, and it's easy to remove and replace with the bolt in the kit.

Two months after I bought my car bone stock, I installed a JLT 3 CAI with Brenspeed 91 octane tune and they made a night and day difference to the car.
Three months later I installed Steeda underdrive pulleys, DIY charge motion delete plates, and a revised Brenspeed 91 octane tune as my next mods and I was even happier. There was a definite SOTP performance increase with the second round of mods and gas mileage also improved by ~1mpg. The Steeda UDPs have been on my car for six years with zero issues and I'm very happy with them. They also enabled me to raise the rev limiter to 6500rpm.

I went with Roush Pulleys to drop the Accessory Speed with 4.10 Gears. Works Fine for about 2 years...

Master, that is a well written, thorough thread. Would be very valuable to anyone considering this modification. Kudos.

Well and for those that are looking to save parasitic HP from the accessory drive, folks always seem to skip one of the best mods you can do and that is to install an electric water pump. I've gone electric on just about every build I've ever done. There are only advantages in running one.

07, that's a great idea. What's your estimate of the current draw? I can see the advantage of an electric pump both in warming the engine from cold and cooling it when it's hot.

How much hp we talking with a electric water pump? N/A vs Boost?

Saw a YouTube video by Richard Holdener today who ran a GM stock 5.3L engine on dyno using OEM stock accessory drive & stock exhaust manifolds then removed each part of the OEM accessory drive & dyno'ed again to measure the parasitic HP difference. When he removed the stock water pump & installed an electric water pump he measured a +10HP difference by going w\ the electric water pump vs the stock water pump so approx 10HP. This may differ w\ a 4.6L due to differences in coolant flow thru the block\heads\crossover but it shouldn't be much difference at all IMHO so the 10HP difference is relevant.

Gives 07Boss's post some credence & from seeing Richard's video has got me thinking bout this as well.

Hope this helps.

Interesting information, thanks. Meziere claims 12-15 rwhp with their electric pump, that sounds pretty optimistic personally. Still an improvement.

I've been running underdrives for...geez I dunno, 7 years now? Never had any issues with cooling or charging as far as I can tell.

07 Boss said:

Well and for those that are looking to save parasitic HP from the accessory drive, folks always seem to skip one of the best mods you can do and that is to install an electric water pump. I've gone electric on just about every build I've ever done. There are only advantages in running one.

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You could install a Steeda underdrive crank pulley AND run a Meziere EWP for a combined gain of 12rwhp. Just make sure you get a shorter drivebelt (Gates K060990).

The electric pump will keep your motor a little cooler which we all know that heat is the enemy. If you hook it manually you can warm your car up faster. At the track I have the pump and high speed fan hooked up to switches and run them with the motor off.


You can cool your motor down in 20 minutes instead of waiting an hour between runs. If your belt breaks or your alternator goes out you can drive your car miles on a good battery without overheating and possibly get home or somewhere safe to do repairs. Done this a few times. One time drove like 24 miles to the next town on a road trip when my alternator bugged out on me on my way to California. I snapped a belt last time and drove about 14-15 miles home.

I have had one failure in the last couple of decades and that was just recently but continue to praise them and their benefits. I had a regular electric Meziere on there and then switched to an HD model that had a heavier duty dummy pulley for the added belt tension required by belt driven SC's. It was supposed to prevent bearing failure due to the added stress. Ironically it was this HD pulley that failed and seized up snapping the belt. The pump still works and I made it the 15 miles home. I have just swapped back in the regular Meziere and will be sending the HD one back so they can investigate and repair it.

Forgot to add that the electric water pump Richard used was a Meziere EWP for the GM 5.3L engine.

07Boss, does Meziere include a wiring diagram w\ their pump? What is the most common method used? Manual wiring or can it be wired so that the PCM can control it? Was thinking bout using the now unused CMCV connector at back of engine along w\ the pigtail off my CMCV actuator to supply power to the pump thru the engine valley under the intake manifold then pull the CMCV wiring pins at the PCM connector & rewire the pump from there.... Or is it better to run a new separate wiring harness setup for it using heavier gauge wire than 16 ga?

Asking due to myself thinking to do as what Dino has posted....to use a Meziere electric water pump in tandem w\ my Steeda Underdrive Pulley set to free up even more parasitic HP.

Thanks for posting the drive belt info, Dino.....was gonna be my next question to ask but you answered it.
I'm assuming that this Gates belt size given is to work w\ a std NA setup, yes?

PS---Just got off Meziere's web site. They actually make a EWP for these Ford Modular 4.6L using a larger WP idler pulley than the std 5" pulley to work w\ aftermarket underdrive pulley systems (WP348S is the SKU#). I submitted a request to Meziere to confirm that this SKU# WP348S will work w\ a Steeda UDP system & use the stock OEM belt. I'll post back on their response. Also have their wiring diagrams so it appears that I "could" have used the existing CMCV wiring but since it is 16 ga it would be pushing it to provide constant 11A-15A across it over extended time intervals as Meziere recommends (also provides the wiring harness w\ the pump) using 14 ga to the pump fused to 20A so I'll just make a separate OEM looking harness complete w\ relay & bring it down along the alternator's B+ cable to the pump.

GlassTop09 said:

PS---Just got off Meziere's web site. They actually make a EWP for these Ford Modular 4.6L using a larger WP idler pulley than the std 5" pulley to work w\ aftermarket underdrive pulley systems (WP348S is the SKU#). I submitted a request to Meziere to confirm that this SKU# WP348S will work w\ a Steeda UDP system & use the stock OEM belt.

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Here's your answer (basically yes).

https://www.meziere.com/Products/Co...mp-Ford-Modular-with-Large-Pulley-55-GPM.aspx

This EWP has a 5.5" pulley whereas the regular WP346S has a smaller 5.1" pulley.

GlassTop09 said:

Saw a YouTube video by Richard Holdener today who ran a GM stock 5.3L engine on dyno using OEM stock accessory drive & stock exhaust manifolds then removed each part of the OEM accessory drive & dyno'ed again to measure the parasitic HP difference. When he removed the stock water pump & installed an electric water pump he measured a +10HP difference by going w\ the electric water pump vs the stock water pump so approx 10HP. This may differ w\ a 4.6L due to differences in coolant flow thru the block\heads\crossover but it shouldn't be much difference at all IMHO so the 10HP difference is relevant.

Gives 07Boss's post some credence & from seeing Richard's video has got me thinking bout this as well.

Hope this helps.

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It is actually the impeller diameter that determines horsepower consumption.

GlassTop09 said:

Forgot to add that the electric water pump Richard used was a Meziere EWP for the GM 5.3L engine.

07Boss, does Meziere include a wiring diagram w\ their pump? What is the most common method used? Manual wiring or can it be wired so that the PCM can control it? Was thinking bout using the now unused CMCV connector at back of engine along w\ the pigtail off my CMCV actuator to supply power to the pump thru the engine valley under the intake manifold then pull the CMCV wiring pins at the PCM connector & rewire the pump from there.... Or is it better to run a new separate wiring harness setup for it using heavier gauge wire than 16 ga?

Asking due to myself thinking to do as what Dino has posted....to use a Meziere electric water pump in tandem w\ my Steeda Underdrive Pulley set to free up even more parasitic HP.

Thanks for posting the drive belt info, Dino.....was gonna be my next question to ask but you answered it.
I'm assuming that this Gates belt size given is to work w\ a std NA setup, yes?

PS---Just got off Meziere's web site. They actually make a EWP for these Ford Modular 4.6L using a larger WP idler pulley than the std 5" pulley to work w\ aftermarket underdrive pulley systems (WP348S is the SKU#). I submitted a request to Meziere to confirm that this SKU# WP348S will work w\ a Steeda UDP system & use the stock OEM belt. I'll post back on their response. Also have their wiring diagrams so it appears that I "could" have used the existing CMCV wiring but since it is 16 ga it would be pushing it to provide constant 11A-15A across it over extended time intervals as Meziere recommends (also provides the wiring harness w\ the pump) using 14 ga to the pump fused to 20A so I'll just make a separate OEM looking harness complete w\ relay & bring it down along the alternator's B+ cable to the pump.

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Dino Dino Bambino said:

Here's your answer (basically yes).

https://www.meziere.com/Products/Co...mp-Ford-Modular-with-Large-Pulley-55-GPM.aspx

This EWP has a 5.5" pulley whereas the regular WP346S has a smaller 5.1" pulley.

Click to expand...

The larger diameter Meziere ideler pulley would also slow bearing speed.

GlassTop09 said:

Forgot to add that the electric water pump Richard used was a Meziere EWP for the GM 5.3L engine.

07Boss, does Meziere include a wiring diagram w\ their pump? What is the most common method used? Manual wiring or can it be wired so that the PCM can control it? Was thinking bout using the now unused CMCV connector at back of engine along w\ the pigtail off my CMCV actuator to supply power to the pump thru the engine valley under the intake manifold then pull the CMCV wiring pins at the PCM connector & rewire the pump from there.... Or is it better to run a new separate wiring harness setup for it using heavier gauge wire than 16 ga?

Asking due to myself thinking to do as what Dino has posted....to use a Meziere electric water pump in tandem w\ my Steeda Underdrive Pulley set to free up even more parasitic HP.

Thanks for posting the drive belt info, Dino.....was gonna be my next question to ask but you answered it.
I'm assuming that this Gates belt size given is to work w\ a std NA setup, yes?

PS---Just got off Meziere's web site. They actually make a EWP for these Ford Modular 4.6L using a larger WP idler pulley than the std 5" pulley to work w\ aftermarket underdrive pulley systems (WP348S is the SKU#). I submitted a request to Meziere to confirm that this SKU# WP348S will work w\ a Steeda UDP system & use the stock OEM belt. I'll post back on their response. Also have their wiring diagrams so it appears that I "could" have used the existing CMCV wiring but since it is 16 ga it would be pushing it to provide constant 11A-15A across it over extended time intervals as Meziere recommends (also provides the wiring harness w\ the pump) using 14 ga to the pump fused to 20A so I'll just make a separate OEM looking harness complete w\ relay & bring it down along the alternator's B+ cable to the pump.

Click to expand...

I bought their relay kit so I used whatever power wire came with it. I used a hot with engine running circuit to trigger the relay (I think it was the cruise control circuit). Then I wired my manual switch to the same relay. This way the pump only runs with the engine running or when I flip the switch. At least that's the way I remember doing it but it was many moons ago, like 10 years or so.

5.0 Mag did the Meziere install on a 2010 4.6, and the improvement was a meager 2-3 hp..which baffled em, since they had done the same install on several 05-09 cars with great success..typ 10-11 hp. The oem 2010 water pump is different than the 05-09 oem water pump...it's a different design.

Pentalab said:

5.0 Mag did the Meziere install on a 2010 4.6, and the improvement was a meager 2-3 hp.

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That's because the engine was already fitted with underdrive pulleys before they installed the EWP.

07 Boss said:

I bought their relay kit so I used whatever power wire came with it. I used a hot with engine running circuit to trigger the relay (I think it was the cruise control circuit). Then I wired my manual switch to the same relay. This way the pump only runs with the engine running or when I flip the switch. At least that's the way I remember doing it but it was many moons ago, like 10 years or so.

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10-4....thanks, 07Boss. I already have all the proper relays (have them w\ a 5-pole connector so can make it look OEM), 10 ga inline ATP fuse holder, an add-a-fuse connector to jump switched power on a mini fuse slot in SJB & plenty of 10 ga, 12 ga, 14 ga & 16 ga wire along w\ all the accessories on hand so the only items for me to get is 1-pack of 1\2" split loom & 1-pack of 1\4" split loom to dress it all up. The pump comes w\ the 14 ga fused wire loom w\ 2-pole weatherpack connector to connect to the EWP, just don't know how long it is....assume it's 3' long. I got copies of Meziere's wiring diagrams after posting yesterday so have already figured out the way I plan on doing it but I appreciate you posting.

Dino Dino Bambino said:

Here's your answer (basically yes).

https://www.meziere.com/Products/Co...mp-Ford-Modular-with-Large-Pulley-55-GPM.aspx

This EWP has a 5.5" pulley whereas the regular WP346S has a smaller 5.1" pulley.

Click to expand...

Yeah I found that right after I posted yesterday. The Steeda UDP WPP dia looks to be larger than 5.5" (tried to get a measurement off mine last night but too much stuff in the way...the resonators on the FR Bullitt 85mm CAI air tube won't allow me to get a good measurement but it appears to be somewhere around 6"-6.5" dia so if I do get this I might still need to use the Gates # belt you listed...assuming that it will make up for the extra .5" dia of the WP348S as the WP346S has the OEM 5" dia pulley size) but I got a response from Don Meziere himself to my question which he gave me the same info that I had gotten off their web site. But he did ask me about the size of the Steeda pulley & I informed him that I had sent a request to Steeda to inquire into the dia of their UDP WPP for the 4.6L 3V V8 so who knows.....might get a good result here if Meziere does come thru w\ a dummy WPP sized to fully replace the Steeda UDP WPP I'll definitely buy it from them to reward the effort (gonna get 1 most likely either way) as parasitic HP/TQ gain is HP\TQ gain, yeah the price per HP may not be worth it to some but I like this prospect & there are some distinct advantages to having 1 of these installed as 07Boss has laid out & if Meziere can provide a 6"-6.5" dummy pulley this will make the pulley bearing last longer as well due to slower bearing rotational speeds as well as being able to reuse the stock OEM belt as Steeda designed for.

We'll see...……….

PS---In keeping w\ the OP, this is a good setup as this Steeda UDP setup was the 1st "power" mod I ordered for my Stang just 3 days after buying it (along w\ a set of FR SVT 07-09 GT500 18x9.5 wheels & Gorilla lug nuts) & for the reason that Steeda went into partnership w\ Ford to build their UDP HB using the same supplier than Ford used to build the OEM HB's so the Steeda version is built from the same materials Ford spec'd for the OEM HB's for the 4.6L, engineered to the exact same Ford engineering design\manufacture process so it is pretty much guaranteed to work w\o issue. Excellent write up!