sc overdrive pulleys

davec73

SCCoA Member
Guys I have been thinking of adding a pulley drop to my sc to push a little more boost. However I am going to be replacing the stock blower with a rebuilt ported early model blower with gtp coated rotors in it. I am going to add headers soon but until then is it safe to drop pulley sizes with this combo to around a 2.8 pulley or should the coated rotors and porting add enough boost for now and do the pulley drop when I add the headers? All the members on this site refer to them in% value but the drop mm sizes are 3.0 2.9 2.8 2.7 2.6 2.5 and 2.4 and anything under a 2.8 you have to machine your snout so it doesnt rub. Also do I have to run a smaller belt if I drop pulley sizes
 
i'd recommend you keep the stock size pulley and get an overdrive on the crank or jackshaft, that way you keep more belt wrap on the blower and you don't have to machine nothing

im still looking for a 15% o/d and 25% u/d on a crank pulley, don't think anyone makes one though, that would be ideal


also note, that with that much overdrive it would probably be wise to upgrade the injectors, ford went to 36s with the gen2 blower for a reason, im sure it wasn't cost effective on their part

then lastly you have a problem with heat, these eatons sure do build it, i'd recommend meth and you can really turn the wick up, its so cheap theres no point in not getting it
 
the coated rotors help a ton with the heat issue and also form a tighter seal for more boost. Im supprised more sc owners dont perform this upgrade I am wanting to ad headers to the motor before I put the pulleys so I wont build up as much pressure in the engine and blow head gaskets. so I guess I should buy the pulleys headers and injectors and do them all at the same time. If anyone has any of these parts let me know.
 
If I understand right the coating can come off and cause issues is why more people don't use them.
 
to clarify everything with the coated rotors, most blower shops and many people from this forum believe this to be true.
if running stock size pulley or maybe a 5% od at most then coating the rotors can/will help with heat and sealing. however if the rotors are coated and you apply od pulleys they will crack and chip the coating off after a short time thus losing efficiency and clog up your ic. thats why most people dont coat them being the fact that most are running atleast a 10% od or more on there blower. if you want to run higher od on the blower the best rotor pack is from an 89-92 blower. the rotors are slightly tighter than the 94/95 rotors. they took very little material off of the 94/95 rotors so they could coat them and allow the coating to form the perfect seal with less effort on there behalf.

as for a 15%od blower side and 25%ud drive side crank pulley, i to have not heard of one out there. if indeed someone could make one and the blower side has enough room to allow 15% od then that would most likely become the most wanted pulley for our blowers given the fact that 15% is the most common od ratio. this topic has come up before and it is being looked into. however dont expect anything soon.

Stephen
 
to clarify everything with the coated rotors, most blower shops and many people from this forum believe this to be true.
if running stock size pulley or maybe a 5% od at most then coating the rotors can/will help with heat and sealing. however if the rotors are coated and you apply od pulleys they will crack and chip the coating off after a short time thus losing efficiency and clog up your ic. thats why most people dont coat them being the fact that most are running atleast a 10% od or more on there blower. if you want to run higher od on the blower the best rotor pack is from an 89-92 blower. the rotors are slightly tighter than the 94/95 rotors. they took very little material off of the 94/95 rotors so they could coat them and allow the coating to form the perfect seal with less effort on there behalf.

This is not entirely true. I ran 20% overdrive with coated rotors for quite long time and so have others, and never had a problem of the coating coming off of the rotors. There is no difference between rotor pack years dimensionally, all they did was coat the rotors in the 94/95 versions.
 
the coated rotors help a ton with the heat issue and also form a tighter seal for more boost. Im supprised more sc owners dont perform this upgrade I am wanting to ad headers to the motor before I put the pulleys so I wont build up as much pressure in the engine and blow head gaskets. so I guess I should buy the pulleys headers and injectors and do them all at the same time. If anyone has any of these parts let me know.

The coating is nice to have but once it starts to chip it will eventually come off. Most people do like to take that chance and put the uncoated packs in when running high amounts of overdrive.

I also would not waste your money on headers, they have not been proven to be much of an improvement and there are better things to spend your money on if your just getting started modifying.
 
I was under the impression headers added 25 - 30 hp and even more with supporting mods?

i to can say i did not notice any hp improvement with headers. i got them anyways due to making it much much easier to work along the sides of the engine. they will help free up space.
plus they look cool. thats about it.

some say headers are better for the heads because they dont collect heat and keep heat at the head.
others say the stock manifolds are better for pulling the heat away from the head.
i dont know if any are true but sure enjoy the extra space and look of the headers.

ding ding ding, this was my 1500th post lol
 
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I guess rotors can be recoated with blower rebuild? I have stainless headers on mine, took them off of a previous car i bought. I should have had them jet-coated as well...next time....i will
 
So the SC i just bought came with a 3.0" pulley so percentage wise, what would that be considered. sorry im totally new to the SC world and have been reading article after article trying to learn as much as possible
 
the coated rotors help a ton with the heat issue and also form a tighter seal for more boost. Im supprised more sc owners dont perform this upgrade I am wanting to ad headers to the motor before I put the pulleys so I wont build up as much pressure in the engine and blow head gaskets. so I guess I should buy the pulleys headers and injectors and do them all at the same time. If anyone has any of these parts let me know.

This is the first I've heard about the coated rotors helping with heat :confused:

David
 
This is the first I've heard about the coated rotors helping with heat :confused:

David

thats as i have been told from a blower rebuild shop, and thats if only at stock speeds and yes there is very little heat drop but it still measurable on there flow bench. as it was told to me, its not worth it. go with the stripped or clean rotors. especially if you intend to go with alot of od. weather people believe or even know or not the rotors will still move just enough to make points of contact while rotating. if coated and overdriven the coating will come off. the more od the faster it will come off. for those that believe in and like coating the rotors, all the more power to you, as for me. if a blower shop tells me im better off not coating them, then so be it. my rotors will not get coated. also in such they are losing money by not getting to charge for the coating. so in such case they must truelly believe that coating is not good for overdriven blowers.

also the reasoning i was told for the coated rotors at stock speeds helping with heat is due to less blow by at the tips of the rotors. allowing for less already heated air to slip back and remain in the case allowing for more cool fresh air to be moved into the case.
 
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Have any shops set a threshold for % OD where they don't recommend coating? More than 5%, more than 10%?
 
I own a gtp and an sc and all gtp rotors are coated and no one says a thing about the coating coming off the rotors in chunks? The blower is still an m90 on a gtp although it is not ic. The main cause of coating loss on the gtp is running meth it will strip them clean. I will do a little build up test by adding the coated rotors to see generally how much it increases boos then I will add my ported blower to see if that adds even more. then I am going to drop pulleys and add a bigger tb injectors and maf.
 
so with the coating and porting maybe three to four and it should pull harder earlier and throughout the rpm range?
 
so with the coating and porting maybe three to four and it should pull harder earlier and throughout the rpm range?

im not sure anyone can tell you truthfully if it will or will not dave. with certain mods, tunes and what not no 1 system is going to react the same. i can say if you really feel like you want to coat them, then coat them. if it goes bad and it cracks off later down the line well ic's are dime a dozen since most people are going to fmic's and other forms of ic's. so you can always take them out later on, strip them and replace your ic. all of which wont cost you very much for any of that. the chances of any damage happening is slim to none as the ic will likely catch anything that might flake off. just keep an eye on your act's. if they go up then take a look. if they dont then dont worry about it.

as for the additional 1-2 psi of boost from coating the rotors i to have been told that is true, yet i have not tested that myself.

any and everything i tell you is from what i have seen, done, been told, or researched about and is only 1 side of the perspective. others have and will do other things that will have worse or better outcomes. so only take this as a reference and continue to collect info from everyone else and then proceed with your own perspective. there is yet to date very much debate over whats good and whats bad for blowers and there will continue to be much debate.
 
Porting really won't "make" any more boost, it simply lets the air flow easier thru the supercharger making it more efficient.
 
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