Anyone know what size pulley for radix to get around 8 lbs boost?

 

On my 6.0 I get 7.5 psi using a 3" pulley. I think on your 5.3 you will need a 3.2" pulley..

 

3.1 on mine yields 9psi with a bigger cam, LT's, and true three inch duals (no cats). 'Bout halfway between stock and mine ought to get you close.

 

What size pulley do you have now that makes 5.5lbs? Boost is a measure of resisitance at the manifold, some mods will increase or lower boost like intake, heads, cam and exhaust.
A .20" smaller pulley will increase boost ~1.5-2lbs.

I use a 3.2" to make 8.5lbs.

 

I have a 3.4 right now

 

It is highly recommended to pully down only .20" at a time so go for a 3.2" pulley, tune and see how that works. I found it to be a major difference going from 3.4-3.2"...Boost comes on sooner too!

 

Thanks for the info guy's.

 

If I go to a 3.2 pulley now and add heads and a cam later could this then add more boost because less restriction?

 

A less restrictive intake might increase boost levels but better flowing heads/exhaust will actually drop your boost level while power levels increase. Heads or head work would be a last mod, the right cam can make a significant increase in performance in an FI application.

 

My 5.3 with longtubes and k&n makes between 8 and 9 psi with the 3''.