I bought a used blower kit Sunday and am trying to figure out what the boost may be. It has a 4.00 pulley and is a SN89..any help? TIA

 

I can't remember all the ratios for the old paxtons ( i used to run them on my 5.0 stangs in the early 90's) but either way on a stock 350 you won't see more than 6-7 PSI tops with that blower. 9 if you overspin the heck out of it.

 

And you should not overspin the SN89 if you want it to last.

 

Roy,

Tariq sent me a PM that you bought the Carroll Kit. I was the previous owner of it. I never did install it, because of rich running problem. (Turnout out to be a improperly machine TPIS intake) I did do a lot of research on it at the time.

I did all the calculation and you do not want to spin that SC any faster, its geared properly for safe maximum RPM for upto ~5250rpm. It is alteast 6 psi blower. If it has the high output impellor its closer to 9psi. Sometime in the late all 90's paxton rebuilds all come with the high output impellor.

The previous owner who had it installed had it rebuilt at sometime, but just prior to my purchase it was checked out by Paxton. The notes on the test sheet led me to beleive it had the high output impeller, but I wasn't a 100% sure.

 

The high output impeller is called the VR4 upgrade, VERY rare and expensive. But it will give you upto 15psi.

I had a paxton SN60r older but better model, which gave me 9psi at 5400rpms and I was not overdriving the rpms. Stock pulleys, and it did not have the VR4 upgrade.

 

thanks guys, I guess the good news is that I won't require a whole lotta tuning and other modifications. I was looking for a mild setup that I can use for now with a stock(kinda)350 and then bolt to my 383 when I de-tune it from 11:1 to whatever I need in this application. I'm looking forward to getting this one done. I have always wanted to be blown

 

Its was not technically vr4 thus you wont see 15PSI.. The SN units... with the vr4 impeller would hit roughly 10 psi if you were lucky...I had an sn93 with impeller upgrade.. I used pullies and the Paxta Trac fluid.. Best I ever got to was 11psi... the thing ran sooooooo hot you could fry an egg on the case... but mine lasted 4 years without a rebuild...and according to the guy who now owns it the thing still works fine..

The VR4 did have that impeller but it also had different internals.. Hardened shafts, I want to say the ball drive unit was beefier>>Like more ***** or something like that... Also the Discharge housing had a bigger inlet in it... Plus a different pully setup...


However mine was a FREAK... I knew people at the time that would trash those units almost as soon as they bolted them up... They were very finicky... From what I heard at the time If you got an ORIGINAL paxton unit(Which mine was the last of the original units) you were much better off than the later owners.. Yours being an sn89 would be an original company nit as well..

The downside to that blower is the ball drive is EXTEMELY parasitic... Heck take your hand and spin the compressor pully... Good luck spining it...its hard enough to just turn it... Then take a gear driven vortech S-trim... Spin it.. its easy to spin untill its building boost... thus not as parasitic on the low end.. Withmy paxton I could tell you If I had the belts on or not by merely starting the car.. the Paxton really used some amperage when starting..because its so difficult to turn and you HAVE to keep the belts TIGHT... to get 11psi I had the belts soooo tight to keep them from slipping that it wore a slight groove in my front main bearing @ 2:00 ... LOL

Paradise Wheels in CA now owns the rights to the ball drive blowers.. they handle all the rebuilds now as well as carrying the parts for it.. Last I heard they can do the upgrades as well..

Sorry I dont have the phone number.... But If I stumble across it Ill post it up.. Ive not used one of these blowers in quite a few years... But still remember all about the tricks and tips... PAXTON OIL COOLER IS YOUR FRIEND>>

 

And all those tips and tricks are as valuable as the supercharger itself to a guy like me who is lost. Thanks for all the great information about the setup. I guess I should have investigated before I bought but what fun would that be?

It looks like I need to use that oil cooler that comes with the blower, I saw that it is not part of the original assembly so I was going to plug it, you saved me Kenwood. And you are sure right about the amount of pressure required to turn the blower, I may have to beef up the 350 so it will idle Is there a source that would tell me about maintenance required on the unit?

I have a 383 on the stand and a choice of miniram or suprerram with 58mm bbk,etc....Is this a good choice for this motor? With the Rpm restrictions on the blower(more great essential information)I guess the superram gets the nod here. Is there a formula for power increase as it relates to pressure under boost? And Kenwood, I have alky/water injection, do I need a BOV?

Thanks again to everyone, I really appreciate all your time and input. I found paradise wheels website, not very complete, I think maybe they are working on it but there is a phone number...

 

I did not run a BOV.. although it would have been a good idea.. That will help keep the discharge tubes from blowing off..

The tips would be to change the blower oil EVERY OIL change... DONT use paxta trac fluid.. USE FORD BRAND TYPE F ATF automatic transmission fluid.. Its BETTER to use the ford brand than valvoline or others because they put different additives in..>>Suggestion given to me by a tech guy at the original paxton..

Recognize that whatever intake you choose a 383 with a superram and mini ram the system will create LESS BOOST.. because your consuming a lot more air faster... so the blower has a harder time keeping up.. Im not saying it wnt work...It will..Ive seen similar combos run in the past.. ALKY injection... DO NOT rely on washer fluid.. the instructions say you can use washer fluid for the alky injection.. I SAY NO WAY.. the washer fluid clogs the nozzle.. when that gets clogged your air temps go waaayy up and you Preignite.. when you preignite your pistons take a beating..

the car will run fine with it..Dont get me wrong..but Im just saying the first time you start the car...you will see/hear the thing change.. the car sounds like the batery is dying...

Maintence log was nothing more than oil change list... I THINK>>I might have the sheets and booklet from when I had mine... Ill check tonight.. If I do I will post back up and then I can fax the trougnbleshooting manual and other stuff that came new with it.. I believe I still have the decals that came with it somewhere as well...LOL..

other tips are DO NOT OVERFILL the blower with oil...thats bad for the seals.. and there is no such this as too many oil changes... I changed the blower oil every 1-2000 miles... Mine was on my car for 30,000 miles.. I never had a rebuild...never had a problem.. Keep the oil cool.. Keep the oil fresh.. Keep the belts tight.. Dont put pullies on it...

FWIW the belt issue is like thaton many superchargers.. I see BIG HP vortech guys running a ball bearing spreader bar from the center of the SC compressor down to the center of the crank.. So they can really crank the belts down without deflecting the crank or bending the SC bracket..

 

I guess I need to be educated on the entire issue of belt tightening. The blower has a 4" ribbed pulley on it and it appears that once mounted it takes a belt in the normal manner, just longer. That would make it self-tensioning but I gather that this is not the way to go?

Also a concern is the heat produced by the blower, the clearance to the hood is awfully close, is there a paint blistering issue here and if so what do I do to alleviate that?

Thanks again for all your help Kenwood

 

On those belt issues Im not 100% sure.. Reason is My system was in a Trans Am GTA with a 355 TPI. on the trans am the belts were for the blower only... Ive never seen one that uses the factory belt to drive it.. The tension you need to spin it would KILL a waterpump after about 30 miles.. But to give you an idea of the pressure I put on mine so they would not slip..>> The kit had a crank pully>> a sliding Manually adjustable tensioner> then the compressor pully... I would take a LONG Crowbar and pass it through the mount against my steering box... Then I would cantilever the middle of the bar against the slider tab.. I would pull back with 1 arm to tighten it... Then with the free hand tighten the tensioner bolts.. >> My vortech I would put a breaker bar on the tensioner.. Pull on that the same way...then tighten.. If I did not do that the belts would slip and you had little black shavings all over the bracket.. Thats why all of the higher PSI setups use COG pullies instead of serpentine or v belts..

the hood blistering... I doubt it.. Mine sat really close to the hood and it was METAL which would transfer more heat to the paint than fiberglass.. so Im 99.999999% sure your good..

 

I read about the problems with Paxtons. Someone told me their were goods and bad ones. They put a good perspective on them, if still working it one of the good ones, if the bad ones were really bad and should be weeded out by now.

Roy (the original poster)

I am pretty sure I had an oil cooler for that Paxton. Also Paradise Wheels is who tested the Paxton out before I bought it, they wrote 8.5psi on the test sheet.

 

The oil cooler is in the package. I just worry because where there is a line and a connection there is the potential for a leak and catastropic failure, what do they say, if it can happen, it will. I'll install the cooler and just be careful to make it all leakfree as possible. There is also a pump included that looks like it might be part of the oil cooler system, does that sound right?

I like that whole if it still works its a good one thing

 

I have an SN 93 unit on my 89 Vert.
Like you I had a lot of questions about the set-up.
I bought the car with a 355 in it, and was set up with the water/ alki injection. It made 6 psi on the 355, and still makes 6 psi with the 383.

I run the stock tensioner and have no noticable belt slipage with a 3.75" pully.

The blower does hit the hood support tunnel a bit bud does not seam to be a problem.

These blowers have some limitations that you need to keep in mind.

Run a blow off valve!!!!
You will reduce low speed MAT by 50+ degrees.

Do not exceed the blower max RPM
These units are designed for 38,500 Max at the impeller!
You will have to do some math here.

The blower is geared at 4.4:1
You have to factor your crank and blower pully ratio and multiply it by 4.4 to get the impellar drive ratio. Multiply that by the MAX RPM that you will spin the motor and you should not exceed 38,500

IE: If you are using a 7" crank drive, and a 4" blower drive
Your Max engine RPM will be limited to 5000.

I have a problem with my set up because my 3.75" pully will not let me go above 4700. I need a 4.5" to get up to 5600+
If I belt down the blower I will probably loose boost.

Just be conservitive on what you expect these units to do.
The best set up would be ,
Leave your compression up , and dont build the motor for high rpm.
Build it for torque. That is how my 355 was set, and it made 380 RW HP.

If you want more, (we allways do) get a bigger blower.

I wish I would have found all this out befor I built the 383.
I installed a 530/550 cam AFR 195's Big mouth intake. 8.5:1
FAST ecu, 44# injectors. I make 400RW becaus I can't rev the thing.
Lots of money and work for 20 more HP!

The other posts have given you great advise.
Change the fluid every couple thousand.
It gets metal in it, and will ware the unit out. Even if the fluid looks clean.
Take the blower off and turn it upside down to get a good drain.
It will last if you take care of it.

Good luck

 

The PUMP is for the cooler.. Basically the kit was just a pump, some hoses and a special dipstick..I cant rmemeber exactly but I believe it had a resivour as well... Im not sure if it came with it or if we added one..

they are right about junk versus good... A buddy of mine Bought a later year paxton unit... It lasted 1 pass at the track...He sent it back on warranty..they gave him a new head unit.. We installed it... Drove the car to the gas station... During the trip it failed... He got it replaced again>>Failed>>>Got another new one and sold it immediately without opening the box... Mine I drove the car daily.. beat mine at the track on weekends.. I even drove it from Cincinnati to Oklahoma city...raced it... and drove it all the way home... again I never had a rebuild..

the boost going less only happens when your engine is close to using the max amount of cfms the blower puts out... the closer you get the lower the boost level..

 

This is some great info....
I just bought MrNukes SN60 Carroll setup. This thread has been quite enlightening, and now I really can't wait to get it on and going!

I think I will need to invest in the oil cooler, as I don't believe this kit includes one.

Sorry to hijack!

 

Not entirely true. Boost is a byproduct of backpressure created in the system. You can have a boost drop from simply changing the heads. In stock form the car is all choked up which will create more boost in the process. If you make it easier for air to enter and exit the engine the boost will decrease as well. People get hung up on boost numbers when they really don't mean much. 9spi on a stock motor is not near as good as 4psi on a good flowing motor of the same displacement.

 

As long as the centrifugal supercharger is in a normal operating range ( flow and RPM ) boost is mainly a function of impeller RPM. Look at this compressor map from Vortech V-1 A-Trim.



Look at the 30k line. ( 30.000 RPM on the impeller )
At 10 lb/min the pressure ratio is about 1.28 = 4.1 psi boost.
At 40 lb/min the pressure ratio is about 1.26 = 3.9 psi boost.

What does that tell us?

A change in the restriction after the supercharger ( Engine CFM capability ) will affect the flow a lot but the boost will be about the same.

With a displacemet supecharger like an eaton it is a totally different story.

 

I do not agree. I know for a fact if you decrease the friction loss inside the intake tract you will see a boost pressure drop. I can prove it with formulas as well as real world experience. Not saying I disagree with compressor maps, as I am sure in the tests they conducted to get them they were correct, but I know what I said to be true as well.

Lee

 

If you look at the graph to the right of about 40 lb/min, you will see that the RPM lines has a downward slope. If you are in that area you will see a pressure drop as the flow increases from less friction loss inside the intake tract.

If you the intake is VERY restrictve so you are near the surge line, then the boost will actually increase if you reduce friction loss inside the intake tract.

In either case the power of the engine will increase.