View Full Version : are aluminum pullys good

10-21-2006, 07:29 PM
I just bought a 2003 cobra and I what to upgrade the psi. I want between 15-17 psi as long as I can still use pump gas. I have a prediter tuner on it now. Is there a big differance between brand names? What is the best one and what all do I need to do? other than retune it? Do I need a new belt or am I ok with just a smaller pully?

Any input would be appriated.

10-24-2006, 07:22 AM
I thought I posted on this thread yesterday but ?????

Since the factory pully on the Eaton is a press fit pully assembly, you should not use aluminum unless it is part of a DUB system (steel hub mounts to the supercharger, pully mounts to the hub ).

In addition, the Eaton consumes 8hp to spin it with the 3.6inch stock pully (reference; Kenn Bell), by reducing the leverage of the pully (smaller pully) the belt will have more of a tendancy to slip. To increase belt grip would be to add idler pullies so that more surface area is in contact with the supercharger pully. Richard Racing offeres a patented pully design that reduces belt slip.

You may as well replace the remining pullies at the same time to prevent bearing failure since the stock units tend to fail (as some have suggested).

Billut Flow, Richard Racing, and I think Metco manufacture good quality parts for the Cobra With a reduced diameter SC pully, and larger idler pullies belt length will be different than stock. To gain more than 14psi, the crank shaft pully may also need to be changed as well as the alternator pullie so that the alternator speed does not exceed its maximum RPM.

Also, the heat exchanger will need to be changed to one with a larger capacity and better efficiency. Along with higher flow injectors, and possibly higher capacity fuel pumps.

off topic:
The Eaton does have its limits. Two main factors that limit the amount of power achived are; heat generated by compression, and volume of air flow.
The Eaton can be ported but that will not increase the volumetric air flow to achive high power or even maintain a stable boost at the high end. The faster the Eaton spins over is maximum RPM the higher the air discharge temperature becomes which will result in loss of power as well as a shorter engine life.

In my opinion, I would rather spend the money on a Whipple or Kenn Bell unit in the 2.2L or above and run it at 10psi than push an Eaton to its limits at 15psi.

10-24-2006, 08:45 AM
I have been using the Reichard Racing upper pulleys for a few years now. And as far as the lower pulleys, Metco rules the world! I am fixing to install a 3.1 RR upper and a Metco 6 lb lower on the Terminator that I just bought. I have had a lower pulley set-up on all three of my Terminators. The torque increase is totally amazing! If you exceed 12-13 lbs, your Predator pulley tune will not be adequate to handle the extra boost! YOU WILL NEED a custom tune!!! The longevity of your engine depends on a good tune!! If you change the upper pulley to anything smaller than a 3.1, I would recommend changing the belt and adding a snub idler pulley to help with the belt slip. Most people will tell you not to exceed 16.5 lbs on an Eaton. On my last snake, I had a ported Eaton, a 3.1 upper/ 4 lb lower and I would see 16.5 lbs on my boost guage. If you run more boost than that, you will be just blowing hot air! You will need a cooling mod!! I also suggest a good aftermarket heat exchanger! Without this, your IAT temps will rise and cause your engine management unit to pull timing. This will result in a loss of HP and torque!~ I have seen this happen on dyno runs and dyno tuning! Good luck with your decision!:thumbsup:

10-24-2006, 02:19 PM
I realy appricate the help I'm gonna hold off on the smaller pullys till I put a wipple on. All your info has been very helpfull.

10-25-2006, 03:44 PM
I realy appricate the help I'm gonna hold off on the smaller pullys till I put a wipple on. All your info has been very helpfull.
i just went with the whipple and i love it.. i think a kenne bell can make more horsepower though. strictly here in houston is in the 900 rwhp range w/kb.

i got the new whipple w140-ax hp version with stock 3.5 upper pulley... metco 6lb lower kit, alt idler pulley 100mm, 2) 100mm pulleys and 1) 90mm pulley from lfp, 3.2 alternator pulley from lfp, k080839 belt , accufab tb, c&l 95mm maf and cai kit, lfp heat exchanger, 60lbs injectors, kenne bell boost a pump, bassani xpipe w/cats, diablo custom tune, made 17 lbs of boost, 605 rwhp 595 rwtq

runs perfect..pulled 1.67 60ft time at track on bfg 315/18 drag radials, 7.2 sec 1/8 mile and 10.9 sec 1/4 mile. very safe for 93 octane.. been running for 3000 miles already with no problems. a/f was 11.7-11.8 all across the range.

remember when you go to 4 or 6lb lower you should always put a 3.2 alternator pulley to keep it from over spinning. i had to replace all my front pulley bearings including the tensioner bearing with non contact 6203 bearings. the stock bearings almost locked up (2 days later) from over spinning after i first swicthed to the metco lower kit. i found this out when my 839 belt was squeeling and jumped off while i was getting on it. then i bought the new pulleys above from lfp-lightning force performance and have had no other issues.

10-25-2006, 10:49 PM
Good choice on the Whipple.......I had 2 Kenne Bell's and will never have another one even if someone gave it to me.......just my .02 cents :D

My Whipple running 5psi LESS than the KB I had makes about 20rwhp MORE so I'm happy where I am now :thumbsup:

10-26-2006, 06:45 AM
I have seen issues at the track that someone else was having. They had a much smaller pully on their Cobra and while at the track it kept loosing boost. It would just open up the boost bypass valve and was probably retarding the timming as well. He started off fine, then all of a sudden half track just shut down. I caught up with them not too long after that since the group of people were under the hood. They had a smaller pully on the Eaton but what size I did not ask.

Another issue I have seen is people placing ice directly on the supercharger casing. Since the Eaton is made of cast aluminum, rapid cooling of the metal could result in a crack. If your Eaton is suffering from overheat, let it cool down with the hood up naturally since the rotors will be as hot if not hotter than the casing. Cooling down the case will not cool down the rotors.

One of the better methods to cool down discharge air temperature is to replace the heat exchanger as well as increase the resivior capacity especially with one of the type that has the fuel cell type cap. They can be stuffed with ice and just plain water would work more efficiently than placing a bag of ice on the supercharger. Another method would be to use mentanol injection. Evaporation of alcohol will chill the air temperature considerably.