bmw2nv2000
Enthusiast
I am planning on adding an underdrive pulley when I install my X-metal TB. Just wondering if they are really worth the money and effort. Looking for experienced answers. 
Underdrive pulley... Worth it?
- Thread starter bmw2nv2000
- Start date
Define: "Worth the money and effort."
If Viper Race HQ opinion matters, they put em on Comp Coupes.
Will 1.3 lbs less rotating mass help a 1/4 mile? Nope.
Will they help a 45-120 minute race? Yup.
Worth ~$200? Probably to a racer....
If Viper Race HQ opinion matters, they put em on Comp Coupes.
Will 1.3 lbs less rotating mass help a 1/4 mile? Nope.
Will they help a 45-120 minute race? Yup.
Worth ~$200? Probably to a racer....
Phoenix SRT
Enthusiast
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Pardon my ignorance, but what does an underdrive pulley do?
bmw2nv2000
Enthusiast
So JonB you are saying they do not produce extra hp or improve throttle response enough for a street machine?
Tom F&L GoR
Enthusiast
If you get an underdrive set that slows down the power steering pump, you will avoid the much discussed autocross power steering reservoir eruption and underhood fireball. Spinning the pump slower will be easier on the fluid, the pump, the temperatures...
Shandon
Enthusiast
True but the power steering pump runs the hydraulic fan also? Not sure what effect that would have?
Tom F&L GoR
Enthusiast
My Gen 1 has a simple two speed electic fan, sorry, and the one underdrive crank pulley slows down everything - PS pump, AC compressor, water pump, and alternator.
In your case if the engine (or the engine controller) needs to see the fan spin at a certain rate you would have to get a package of pulleys such as a smaller crank pulley and a larger fan pulley.
In your case if the engine (or the engine controller) needs to see the fan spin at a certain rate you would have to get a package of pulleys such as a smaller crank pulley and a larger fan pulley.
Frankster
Enthusiast
Had a 67 Camaro set up with serious HP. 454, Steel crank, dimple rods, Donovan gear drive, plasma ceramic rings, square port high flow heads, stainless valves, Holly 850 double pumper, Wyand intake, TCI Trans with 2000 RPM stall, dual point Mallory........
And it had an underdrive pulley to drive all the accessories.
Total with nitrous was better than 900 HP.
I got stuck in traffic on the 110 FWY in LA. The engine overheated, ran like hell and was a bear to manage. Only when I was moving at a decent clip did the engine return to normal temps.
Avoid the underdrive pulley.
The underdrive pulley is good if you're at the track with limited run time.
But when you are streeting the vehicle my advice is to avoid it at all costs. The small HP gain to be had by going to an underdrive pulley is not worth it if you drive on the streets.
That, my good man, is the voice of experience.
And it had an underdrive pulley to drive all the accessories.
Total with nitrous was better than 900 HP.
I got stuck in traffic on the 110 FWY in LA. The engine overheated, ran like hell and was a bear to manage. Only when I was moving at a decent clip did the engine return to normal temps.
Avoid the underdrive pulley.
The underdrive pulley is good if you're at the track with limited run time.
But when you are streeting the vehicle my advice is to avoid it at all costs. The small HP gain to be had by going to an underdrive pulley is not worth it if you drive on the streets.
That, my good man, is the voice of experience.
bmw2nv2000
Enthusiast
Thanks for the input guys. I think my car will live on without an underdrive pulley.
Speedfreak
Viper Owner
I could not disagree more. Your problem sounds like a very poorly scienced out cooling system. I have a 68 Firebird with a "serious motor" in it too although not nitrous and that wouldn't matter for this analysis anyway. I found no difference in the cooling of the motor but I did find it picked up almost 1.5 tenths in the quarter mile with the underdrive pulleys system. The key to making a first gen firbird or camaro run cool has alot more to do with the radiator (must be aluminum), fan size and heavy duty fan clutch, shrouding and sealing of all of that than the underdrive system. Mine sits in Florida heat with the aftermarket AC on all day long an maybe hits 190.
In a viper with an electric fan the underdrive pulley is going to have NO effect on the cooling of the motor or overheating. But I am sure it will increase horsepower as virtually all of them do and most only reduce accessory speed 20-25% to avoid any issues with charging and cooling. I would put it on, there is virtually no downside unless you plan to idle the motor for 2 hours with headlights on and the stereo full blast.
29OUTLAW
Viper Owner
I've had one on my 2005 for so long I forget it's even there. Don't know about any benefit but it hasn't caused any issues.
Frankster
Enthusiast
You've hit the nail on the head when you said "problem sounds like a very poorly scienced out cooling system".
You see, Dodge has millions to spend on vehicle issues like cooling. They aren't going reduce the cooling flow to below what their engineers have determined as best.
So now someone like you comes along and says it's OK to reduce cooling flow because it gives you a few more HP. But are you one of the engineers who designed the coolant system in the Viper?
I doubt you are. So why are you second guessing the designers? Don't you think they did all that was practicle to eek out the maximum HP for these vehicles? Do you know better than the engineers at Dodge? They have millions to spend on problems like this. How much did you spend on this problem?
If an underdrive pulley was a practicle option for a Viper they would have included it.
I suggest you put one on your own personal Viper and then come back and report your results to this forum.
bmw2nv2000
Enthusiast
Thanks for the comments. I am told it does noticeably help the throttle response. Who knows I may try one after all. But still thanks again all
dave6666
Enthusiast
Why not try the other end of the crankshaft first... the flywheel? Put a lighter flywheel on and it affects nothing on the other end like cooling, alternator output etc.
bmw2nv2000
Enthusiast
Good point.. Actually Ive been looking at Lightwieght flywheels, any idea where I can find the best price on one? Looks like the range is $400-$500 but which is the best?
SilveRT8
Enthusiast
IMHO Guys who have changed gears to 3.55 or 3.73 are already running the rpm 15 to 21% higher, for those the UD pulleys will bring back the accessories' to stock speed.
My SRT8 Jeep with stock 3.73 gears already turns 3000 rpm at 80 mph in top gear, so I run the -20% UD pulleys with a slight hp increase and no drawback.
My SRT8 Jeep with stock 3.73 gears already turns 3000 rpm at 80 mph in top gear, so I run the -20% UD pulleys with a slight hp increase and no drawback.
bmw2nv2000
Enthusiast
Well I may regret but I dropped the hammer and ordered my Underdrive.....
Frankster
Enthusiast
How much HP do you gain with the underdrive pulley?
Canyon707
Enthusiast
I installed my X-metal TB It looks nice and thats about it. Dynoed less power Less torque. A different day but no matter still less across the board. I am thinking of going to the bbk 67mm I think the single bore may take away some of the low end torque. Disappointed yes....
Speedfreak
Viper Owner
Give me a break. If we used your method of analysis there wouldn't be a single aftermarket supporter of Viper products for anythying as the "engineers" obviously thought of everything. Certainly the exhaust system, computer tune, air intake system, head airflow, brakes, gearing (shall I go on) are all PERFECT since the engineers thought of everything (and spent millions) and it can't be improved upon. The fact is engineers are forced to compromise on a litany of issues in vehicle design to take into account scenarios that have a 1 in 1000 chance of happening on the the street and they also have to warranty the product. They also have to comply with governement regulations, which we promptly throw out the window with half our mods. THAT IS WHY they don't push everything to the limit.
And as I recall, GM spent "millions" on my 68 firebird too. I put and aftermarkedt pulley system on it and it was a major improvment in horsepower and no cooling problems. Mystery solved, test over. You really should call Vic Edelbrock and tell him that that billion dollars in sales he does for aftermarket products that attempt to improve on the factory engineers (intakes, carbs, head, cams, etc.) are all crap and none of them work.
I am just begining to mod my 06 but you can bet a pulley will be on it. Its a no brainer. March Performance makes hundreds of these systems for many different vehicles. I guess the millions they spent don't count and a few gazillion buyers must be wrong.
VicTxV10
Enthusiast
Canyon707, PM sent.
Dads Toy
Enthusiast
Not a viper but I know for fact that a few of my f-body buddies did before and after dynos swapping out the underdrive pulley as the only change and they averaged between 3-5 rwhp.
again not a viper but its a number from dyno pulls.
again not a viper but its a number from dyno pulls.
Frankster
Enthusiast
Dads Toy I think got it right.
The HP gain to be had with an underdrive pulley really isn't worth it if you're streeting your vehicle. Let's face it, there are all kinds of snake oil merchants out there who will sell you anything to make a buck. Been there, done that, bought the T shirt and got kicked in the ****.
I figure Dodge has struck a good balance between streetability and performance with the design of the Viper. Sure, you can get extra HP with an underdrive pulley but it's been my experience that it isn't worth it. Go with an electric water pump and get almost the same HP gain without the potential of cooling problems.......and cooling problems are something you really want to avoid in an aluminum block engine. I've seen too many warped blocks because someone thought they could second guess the manufacturer.
The HP gain to be had with an underdrive pulley really isn't worth it if you're streeting your vehicle. Let's face it, there are all kinds of snake oil merchants out there who will sell you anything to make a buck. Been there, done that, bought the T shirt and got kicked in the ****.
I figure Dodge has struck a good balance between streetability and performance with the design of the Viper. Sure, you can get extra HP with an underdrive pulley but it's been my experience that it isn't worth it. Go with an electric water pump and get almost the same HP gain without the potential of cooling problems.......and cooling problems are something you really want to avoid in an aluminum block engine. I've seen too many warped blocks because someone thought they could second guess the manufacturer.
HI-NOS-Viper
Enthusiast
I street mine every day. I have the pulley kit and love it. Absolutely no problems here. Do I regret the mod, absolutely not. Talk to big brake Dave, he has them.
bullish
Viper Owner
I have a UD set for sale, give me a call 630-669-5853
Darbgnik
Enthusiast
OK, I obviously don't know, but couldn't the crank pulley be decreased, the water pump pulley be increased, and all the rest left alone, that way the parasitic losses from steering, alternator, AC, ect, be lowered yet coolant flow be unaffected?
bmw2nv2000
Enthusiast
Thanks for the offer to sell me one guys, would take you up on it but already got my new one in the mail. Thanks JonB
How much UD cost and how hard is it to install? Mechanic job or can it be done in the garage with instructions? If mechanic needs to install it what will be the total package UD plus install cost? Trying to figure out if additional 5Hp increase worth the money and effort?
bmw2nv2000
Enthusiast
Call JonB @ PartsRack $225 with new shorter belt. Very easy install with hand tools, remove air box, remove belt, un bolt factory pulley, bolt on new UD pulley, slip on new belt, bolt air box back in place. And let her
. Easy as that
