Cobra style UD pulleys and smog delete

AnthonyA1234 · Nov 15, 2022

Thinking of putting on the cobra style under drive pulleys that lmr sells on my car along with deleting the smog pump. I’m thinking of the cobra style because from what I’m reading lmr says that they aren’t arent a big enough reduction to cause charging or cooling issues. Does anyone have these pulleys on their car and could tell me if you notice a difference when driving?
In regards to the smog delete, is there any negatives that go along with doing this? My car does not have cats. Also, I believe I know everything you have to do when doing the delete the only thing I was curious about was how you go about plugging the vac lines that would normally go into the vacuum operated valves in the smog pump plumbing.
Also does anyone run this setup with the lmr cobra pulleys, and a shorter belt that bypasses their smog pump and could tell me what size belt is needed?

AnthonyA1234 · Nov 15, 2022

https://lmr.com/item/LRS-8221C-K/mustang-93-cobra-pulley-kit-79-93

slow84lx · Nov 15, 2022

The only difference you will notice is that your wallet will be lighter. No real advantage and many disadvantages on a street car.

Potomus Pete · Nov 15, 2022

Plus you are going to have to match up a new belt. Trying to find the right size will take while

nickyb · Nov 15, 2022

Keep the smog stuff and get a catted mid pipe, or do it later when the smell gets to you.

sd331 · Nov 15, 2022

AnthonyA1234 said:
Thinking of putting on the cobra style under drive pulleys that lmr sells on my car along with deleting the smog pump. I’m thinking of the cobra style because from what I’m reading lmr says that they aren’t arent a big enough reduction to cause charging or cooling issues. Does anyone have these pulleys on their car and could tell me if you notice a difference when driving?
In regards to the smog delete, is there any negatives that go along with doing this? My car does not have cats. Also, I believe I know everything you have to do when doing the delete the only thing I was curious about was how you go about plugging the vac lines that would normally go into the vacuum operated valves in the smog pump plumbing.
Also does anyone run this setup with the lmr cobra pulleys, and a shorter belt that bypasses their smog pump and could tell me what size belt is needed?

i have a 93 cobra and bought lmr cobra pulleys because i was to lazy to refinish the oem ones i had plus pulleys do wear out a little...the new pulleys seemed to cure a slight vibration i had...i gutted out the smog pump by breaking the vanes and removing all the small clips inside..so the pump is now an idler pulley...there is no problem with cooling or charging.

General karthief · Nov 16, 2022

sd331 said:
pulleys do wear out a little

The wear on a pulley is so little as to be almost nothing, proof of that is on my truck, 600k+ miles, countless belts, several bearing swapped but never a pulley change.
just say'n.

Mustang5L5 · Nov 16, 2022

I have them on my car.

They aren't true underdrives in the sense that they don't reduce the speed of EVERY pulley on the system, but only the smog pump, power steering and A/C pullies. It's an 11% reduction. The water pump and alternator do not get reduced at all. They spin the same RPM as a stock pulley set. These are the same diamters that the 93 cobra used which is a street driven car, so it's not like a pulley set from March.

No issues with them on my car. At idle, with the A/C on, alternator output voltage is still over 13v. No cooling issues, but again, there shouldn't be because there isn't any reduction in WP rotational speed. Power steering feels like it did before. I don't have the smog pump anymore.

I've only put minimal driving mileage on them, but have idled quite a bit in 90+ temps with the A/C on and havent had an issue with them.

AeroCoupe · Nov 16, 2022

I do have aftermarket underdrive pullies on the alt, water pump, and crank on both of my cars and have no issues but I run a Mark VIII fan and Fluidyne radiator on one and a Mark VIII and Griffin radiator on the other so that helps a lot. Idle the voltage reads right around 13.5ish volts and off idle 14.4ish volts. I do not have a smog pump on either car so the belts are not factory length.

Easy way to measure for belt length is to use a piece of string and run it around the accessories with the tensioner in the middle of the tension range then measure that piece of string. When you go to the parts store you can ask for a serpentine belt for your car and the part number on the belt has the length in millimeters (I do not believe they are in inches anymore). Once you know the part number on the OEM length unit then you can use the length you measured in lieu of the last numbers of the part number and that should get you the right length belt for your application.

As an example, “8PK2515” is the PK number found on an OEM serpentine belt. The first digit indicates an eight-rib belt, followed by “P” to identify metric belt sizing, and a “K” showing that this belt conforms to the SAE standard for rib sizing (3.56 millimeters wide for automotive-type serpentine belts). The final series of numbers is the effective length of the belt, given in millimeters.

So with that if you measured 2450 mm then you would see if they had a belt with a part number close to 8PK2450. With the tensioner in the middle of the tension range when you took your measurement I would tend to error on the shorter side of a belt length if they do not have a belt with the exact length you measured as they will stretch a little bit.

Probably more than anyone wanted to know...

sd331 · Nov 16, 2022

General karthief said:
The wear on a pulley is so little as to be almost nothing, proof of that is on my truck, 600k+ miles, countless belts, several bearing swapped but never a pulley change.
just say'n.

so we are in agreement... that pulleys do wear out just a little

slow84lx · Nov 16, 2022

sd331 said:
so we are in agreement... that pulleys do wear out just a little

Steel pulleys, not so much.

General karthief · Nov 16, 2022

sd331 said:
so we are in agreement... that pulleys do wear out just a little

I stated 'almost nothing' so I 'almost' agree
Actually I measured a new pulley I have with the old one still on the truck, I have had this new one for like 10 years, and I could not see any measurable wear, but the cheap tool is not like a micrometer type that can measure thousands or smaller numbers, I'm sure there is wear but again close to nothing.
What amazes me is I have the original pulley on my adjuster for my mustang with 150k on it, now picture that bearing spinning for that many miles and still being good. Think about how fast that bearing is spinning, and how long it does it. Revolutions, distance and time math crap.
Now I have a headache.

Cobra style UD pulleys and smog delete

AnthonyA1234

AnthonyA1234

slow84lx

clean it good before insertion

Potomus Pete

I'm still waiting for the fully nude shots

nickyb

I gotta say i never painted my nuts, Never Ever

sd331

Member

General karthief

wonder how much it would cost to ship you a pair

Mustang5L5

That is…until I whipped out my Bissell

AeroCoupe

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

sd331

Member

slow84lx

clean it good before insertion

General karthief

wonder how much it would cost to ship you a pair

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Cobra style UD pulleys and smog delete

clean it good before insertion

I'm still waiting for the fully nude shots

I gotta say i never painted my nuts, Never Ever

Member

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

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

Member

clean it good before insertion

wonder how much it would cost to ship you a pair

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