a-trim pulley upgrade
 

I was thinking of getting a new blower pulley to pump some more boost out of my a-trim. I was thinking of 2.87 6 rib pulley from ASP. Is this a good idea or is a crank pulley better for more boost? Would I need a bypass valve or would I still be in the safe boost range without one?

I don't have an A-trim but here are my gains from adding a 7" crank pulley to my 6lb Powerdyne. The stock crank pulley is 6.5". I was unable to run up to 6000rpm due to spark blowout but you can see the hp/tq gains throughout the rpm range. http://www.msnusers.com/MustangMembe...hoto&PhotoID=6

Thanks
That made quite a difference. I imagine it would be similar to the Vortech. Did you have the powerpipe on before you did the crank pulley?

i run an A-trim with the S-trim impeller upgrade (still an A-trim housing). i put on the 2.95" pulley and was getting around 10-11 psi in hot weather with the crappy stock plastic intake hose and no bypass. i just put on a 10 rib 2.5" pulley, race bypass, and intake tube i cut and made for about $30. just got it running last week, so no dyno, but so far its putting out a little over 18#s. if you do get a smaller pulley or even keep the one you got, shot peen the surface that the belt touches to make it a little more abrasive and you can gain boost by preventing slipping at high rpm. its not bad for the belt at all, and the crank pulley i got from vortech for the 10 rib was already done, dont know why they dont catch on and do the blower pulley

To answer your question, no, I didn't have the powerpipe yet. After putting the powerpipe on and correcting for the spark blowout (gapping the plugs to 0.35), I was able to pull to about 6200rpm. The powerpipe shifted the curve to the right. I'm assuming your gains with the A-trim might be similar. Here are my last three dyno pulls with the powerpipe:

http://www.msnusers.com/MustangMembe...hoto&PhotoID=7

I did the crank pulley on mine for warranty reasons. Take the pulley off the blower and it voids your warranty.