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Discussion Starter · #1 ·
Does anybody know the diameter of the Metco lower pulleys. Somebody was telling me that the 6# lower was equivalent to a 3.0-3.1 upper. Is this true and why are they selling it as a 6# pulley if it only really does 4#. I figure it was crap, but just checking before I purchase.
 
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Well, I am not home to measure my lower 6 lb pulley...but I do know this..I went from 14 lbs to 20 lbs of boost when I put it on with my 2.80 upper. Its a JDM unit that is only 1 of 2 so far custom made by Jim D'Amore himself. One is on his car ..one on mine. The pullies are the ones he sells for his Lightnings and then the stock pulley cage was made to work with the 4 and 6 lb pullies. He mainly sells the Metco Lower system though.

Harry
www.HotRodHarrys.com
2003 Cobra (20 lbs of boost and Nitrous) 112 Octane Fuel
 

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Here you go...

Stock = 7.4" OD
2 lb lower = 7.9" OD
4 lb lower = 8.5" OD
6 lb lower = 9.0" OD

I hope that helps !!!
 

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My understanding is that the 6# lower will get you between 13 and 14 lbs of boost. It seems to be close to what a 2.93 upper will give you. I'll let you know for sure as soon as Rick convinces DiabloSport to sell me a preditor! ;)

Good Luck,
Kevin
 

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Discussion Starter · #5 ·
Obiefox said:
My understanding is that the 6# lower will get you between 13 and 14 lbs of boost. It seems to be close to what a 2.93 upper will give you. I'll let you know for sure as soon as Rick convinces DiabloSport to sell me a preditor! ;)

Good Luck,
Kevin
That is what my track is also.
 
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I use a Gates 774 (I hear the 775 works also)...so whatever the ending part number means with them in inches...thats it.

I have the Billetflow Idler mod and Billetflow Billet 100mm Idler and 92MM Idlers with the 2.80 upper and 6 lb. lower.

Harry
www.HotRodHarrys.com
 

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Thanks Harry.... I don't have the Idlers, however. So wouldn't I require a smaller size belt than with the idlers ?

I just have the RR 2.8 and 6# lower.
 

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DAMN! What am i doing wrong. Im running (now) 2.75 upper and 6lb lower w/ 100mm upper idler and 100mm idler on driver side and 90mm on pass side w/ a 3.2 in alt pulley and the only belt i could get to fit was 81 7/8 inches long! :confused:
 

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Bluesmobile
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03Venom,
You may be able to install a smaller belt by removing the stop block on the tensioner bracket IF the tensioner is now close to the outside end of the travel and you want to run a smaller belt.
A Dremel tool will make short work of it.

I have a 4# lower, 3.0 upper, 3.5 inch alt pulley, two 100mm idlers, and the Biletflow 3rd idler w/90mm pulley. I am running a Gates belt 80.25 inches.

The position of the lower idler next to the crank pulley may have a little something to do with belt length also. Not sure how much though.

Dana
 

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right now I have a napa 780 on and it began shredding shreading after 1 day. I might try a Gates 774 or 775 now that I see this post. (77.27 to 77.5 inches I think will do it) I suspect the napa 780 is 78 inches. You can see the damage that I have done in one day to the 78 incher... ouch... moral of my lesson learned I think is if you are going to use a RR ultra grip then be extra careful you get the right size belt. Other than that I think you guys have already seen my right up on how (and dyno proven)



 

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Is it me or is something not right w/ the way the pulley is on the snout! ??? Looks to far back. but what do i know. Jamie

I am running Napa 25-080797 Belt. 81 7/8 inches.
 

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updates

I put on a napa 774 (78 7/8 inch OD) and it runs much better... but only lasted about a day before it began slipping aga not as bad this time... but yesterday I noticed I could break loose the tires all through second gear... today I can't.... and I have some dust build up. If I put an upper idler pully on do you guys think that will be enough ? or am I going to need the 100mm and the 92 mm too ?:shocked
 

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Bluesmobile
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Skorost,
I would do it in stages. I would install the upper (3rd) idler first. If you still feel slippage, then install the larger idler (92mm) on the left (Passenger) side. The lower right one won't help your problem.
I would also check the alignment of the blower pulley, if you haven't already. It looks like it is just slightly too far onto the blower shaft. This is not good.

Dana
 

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A Metco idler kit is a great way to wrap the belt around the upper pulley helping in belt slip. This is done because of the way the idler kit wraps the belt around more of the upper pulley.

Check them out here:

Metco Pulleys
 
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