Boost gauge with 4# pully?

[Sweet35th]

Now I know the stock boost gauge isnt incredibly accurate, but my truck with the stock pully on a cool day would see right about 10psi in top of 2nd and 3rd gear.

Now with a 4# pully on it, it barely is over 10psi, and not to the black.

I drove my buddies 00 with a 4# pully and his is WAY into the black. And my other friends with a 2 pound pully would run about where mine is....

Im wondering if I realy have only a 2# pully. I have a 670 belt on it and it fits snug. I havnt measured the pully yet, but what should it be for a 4#??? Its a JLP pully....

What do your guys boost gauges do with 4#?

 

[amfernandez]

pulley size

There was a thread a few weeks back on the size of the diffrent pulleys. Metco #2lb=7.75. #4lb=8.25 #6lb=8.625. Asp/Psp #2lb=7.9 #4lb=8.4 #6lb=9.0. and JLP #3lb=8.17. #4lb=8.5. #5lb=8.75. #6lb=9.0. Hope this helps.:read:

 

[LIGHTNING LARRY]

Casey, what brand is your pulley? My #4 pulley slammed my gauge.

 

[crazy4ink]

My PSP 2#er along with my Stage1 will peg the hell out of my boost gauge. Possibly your gauge is messed up?? Just a thought

 

[Sweet35th]

How can one companies 4# pully be 8.25, and anothers be 8.5??

 

[Sweet35th]

BTW is a JLP 4#

 

[crazy4ink]

Maybe the different sizes has something to do with rotating mass?? If a pulley is physically smaller, but a little heavier, it would have to make the engine exert more to get it around just as fast.

What I said may have absolutely no basis in reality, but it sounded good while I was typing.

 

[LIGHTNING LARRY]

Originally posted by Sweet35th
How can one companies 4# pully be 8.25, and anothers be 8.5??

Because one company BLEW IT!

 

[crazy4ink]

ROFLMAO!! Once again, L.L. with the jab...good one! :beer:

 

[Road Racin']

The main reason is that boost depends on a number of factors and the pulleys should be measued in inches not psi! The pounds could be used as averages. That would get rid of the metco size problem.

 

[Helix]

To be 100% positive. Get an aftermarket boost gauge. The stock gauge is junk. Good for stockers, but junk after that.

Helix

 

[LIGHTNING LARRY]

Originally posted by Helix
To be 100% positive. Get an aftermarket boost gauge. The stock gauge is junk. Good for stockers, but junk after that.

Helix

Yep. :thumbsup:

 

[Helix]

Originally posted by crazy4ink
Maybe the different sizes has something to do with rotating mass?? If a pulley is physically smaller, but a little heavier, it would have to make the engine exert more to get it around just as fast.

What I said may have absolutely no basis in reality, but it sounded good while I was typing.

The lower pulley runs off the crank. When you make this pulley bigger it makes the smaller pulley turn faster giving it more leverage but it also makes the motor work harder unless the amount of boost your adding conpensates. Just like a 12 speed bicycle. When you move the chain up to a bigger sprocket at the pedals you pedal slower yet the bicycle goes faster in return making it harder for you the motor. I'm sure theres more to it then that.

Helix :burnout:

 

[FordSVTFan]

Damn, Helix spouting forth the Physics :thumbsup:

 

[CrashTestJimbo]

My truck is stock down to the filter, and just last night I put the gauge into the black. Crosses fingers Come on factory freak,come on factory freak.