How much boost should I expect?

Just a side note... I know at my track, they limit OD to 20% in top sportsman which is the class I will be running.

 

Std. vs HH

My understanding is that the standard helix works pretty well at low overdrive/rpm and that you really don't see a lot of benifit from the 120* twist till about 7500 and up. Is this correct or bad information?

Richard Gavle

 

Thanks for the reply Mike,

If you reread my post, that is what I was saying. That the Standard twist rotor works good at low speed and the High Helix needs to be spun fast to show its advantage.

Thanks again for the reply.

Richard Gavle

 

Are you talking about NED?? There is no such rule in Top Sportmans there

 

Yeah, NED.... I was thinking they went by the IHRA 20% rule...

 

Well i wont pretend to know anything as im still new to blown alky cars myself.

I will give you some input from my setup tho, it is very similar to yours:

this is my setup:

cbb 555

14/71 std helix littlefiled striped fairly fresh running at 11.1% od

11:1 static compression

just under 0.800 cam

buzzardcatcher

doorcar, powerglide.

this produces just under 25 psi in the current setup

 

at idle it sits at about 10 - 15 psi.

max boost is reached at 7500 - 8000 rpm

 

Aahhh...... WHAT?????? 10-15 at idle??? i'm lost
Jason.

 

Are those readings coming from a gauge or a datalogger? I had an autometer gauge that read 10 psi when the car was off and would bury it at 50psi during a run. Installed a racepak shortly after and less than 40psi during the run was recorded.

 

those are from a gauge, i don't have a datalogger installed

 

Just replaced my guage for exactly the same reason!
Racepak one day!!

 

Long time ago we ran BBC 540's, 10.5:1, large rect. port Chevy heads with std helix LF 8's at 45% over. We would run about 6500-7000 RPM and make about 15-20 lbs boost.

 

Just an update... we ran 26 pounds of boost at 6800 rpm at 20% over.

 

The track was pretty bad.... We blew the tires off on the line, got on and off the gas, shifted at 6500 and coasted thru the traps with a 5.33 @ 101 mph.

That was letting off around 500 feet

 

what top and bottom pulleys you running?build a engine close to you..was told my heads will flow in that area of 400..my cam is smaller..a 746 lift..piston bigger at 11.5--to--1..running a std. rotor 12-71 blower that littlefield just fresh up for me.