low boost #s

[mkhalil83]

i have vortech y-trim with powerpipe on a 331 stroker with h/c/i, the heads are ported. i got the blower on and its only making 6 to 7 pounds of boost with a 3.00 pulley on it. is this normal because mybe i need to spin this type of blower higher to get more boost i checked for leaks but i didnt see any. i am trying to get 10 to 12lbs out it do i need to go with a smaller pulley or is there another problem

 

[mkhalil83]

can someone help

 

[91 HATCH]

use a 7 inch crank pulley

 

[Jack's95gt]

Because the engine is stroked and has more displacement, your boost pressure will be lower. The volume of air moved is the same so the effect is the same. I have also noticed this with my 342.

 

[Modular2v]

boost is a measurement of retriction.....when you ported the heads you allowed the forced air to flow through the motor at a less restrictive rate.....are you making less power?????? NO! You are making power more effeciently!

 

[mkhalil83]

i understand the part about the heads and stroke but i went from a 3.33 pulley to a 3.00 pulley and there was no change in boost. and mind you that this is a V-7 Y-trim bigger than a S and T trim.

I think i am using the 7.00 crank pulley because its the double pulley and i the 6.87 pulley is the single one that u bolt up to stock. do you all think there could be boost leaking out somewhere? do you all think it could be still the heads and stroke. And i know you have to spin this blower a little higher to get boost out could it be that?

 

[MattZ281LE]

i have vortech y-trim with powerpipe on a 331 stroker with h/c/i, the heads are ported. i got the blower on and its only making 6 to 7 pounds of boost with a 3.00 pulley on it. is this normal because mybe i need to spin this type of blower higher to get more boost i checked for leaks but i didnt see any. i am trying to get 10 to 12lbs out it do i need to go with a smaller pulley or is there another problem

What are you spinning the motor too RPM wise.

I made 16# with a 2.95 and 7" crank on my 331, good for 660 at the wheels.

I had a ported gt40 lower downs for upper, stock Vic Jr's, power pipe, 75mm TB 1 3/4 LT

 

[mkhalil83]

6000 rpm

 

[ninety15.0]

Im not too familiar with the y trim...what are the specs. If I recall correctly, those blowers really need to be spun up to make peak boost. How much boost are you seeing at say 3-4000 rpm? and how much from 4-5000 rpm? How much vacuum are you pulling at idle?

 

[mkhalil83]

i dont know the exsact specs but its bigger than a t-trim is suppose to support up to 900 horses is it possiable i could have a leak somewhere or do i need to put a smaller pulley on it at 4000rpm its at 4 to 5 lbs at idle its at 12 to 15 vac

 

[Foxfan88]

stroked engines will make less boost than advertised. but its not a bad thing, its good. your getting all that air in there with less pressure pushing back. with added displacment you could stuff more air in there.

 

[ninety15.0]

Those idle vacuum numbers seem perfectly acceptable for a bigger motor with a decent cam. What rpm do you generally run the blower up to? i would think you would need at least 5500 rpm to see peak boost numbers.

 

[mkhalil83]

about 5800 rpm i think i should be getting at least 10lbs of boost with my set up i think theres a leak with my blowoff valve i put a blowoff valve on it and i have that those cheap blowoff valves tend to leak so i bought a bosch one that comes with the s-trim kit i am going to hook that one up and hope it works but if it doesnt i am out of ideas

 

[Yellowpnoy]

Hey man, look for belt dust around the blower bracket, that is a sure sign that its slipping. Also, its not good to do all the time, but put some belt dressing on the belt and see if the boost numbers rise, if they do, that is sure sign there is belt slip. Sometimes depending on the belt you use, you cant hear it squeal. Also, that is a lot of blower for that motor if you arent planning on upping the boost to at least 16# or above to get the true capabilities of the blower, you would be better off with a s or t trim at those boost levels.

Anthony
dart blocked 427w