Smaller Pulley = less boost???

[Mach1]

Honestly I don't think I'm getting much slip. My biggest question is why the large jump in boost from 5000-5500 RPM. Is it going up so fast because the engine is getting restrictiive due to the small heads and small cam, or is it just in the perfect efficiency range of the S-Trim? At 5000 RPM it would be at 44,000 and at 5500 it would be at 48500.

yeah, 1/4" aint shit, assuming it didn't just spin a bunch and land 1/4" from the orig mark

[shumpertdavid]

If it's the same style bracket setup my buddies 1st gen has, if you try to tighten the belt too much, the bracket will flex and throw the belt. We ended up adding a bracing bar below the head unit, cutting a plate to bolt to the rear of the cylinder head, and using a turnbuckle with heim joints to brace the blower bracket. Now he can get plenty of belt tension to keep from having slippage and throwing the belt, however it now needs the crank to blower brace to help support the bearings and keep seal leakage under control.

[Diabolic]

Yes the original bracket actually bent and stayed bent. I made another bracket out of .500" 7075 aluminum and now I can hang off the pry bar and it doesn't flex at all.

[Diabolic]

I'm going to have ASP make me a custom hub so I can run a Gen 2 style blower pulley in 8 rib. This way I can run a larger 3.33" blower pulley and run a 9.5" crank pulley at the track and swap to an 8" for the street. I'm also on the lookout for a Novi 2000. I should have the Intercooler installed by mid Sept. I just hooked back up the nitrous kit the other day, and I will have meth injection by the end of September.

[CJ]

Belt had moved about 1/4" from the mark on the pulley.

Like Tyler said it could have moved a hell of a lot - even a little slip at 4000rpm can mean the belt literally does 20 complete rotations before it settles. I would mark it a few times with different colors and repeat until you're confident it's only moving a little. Once that's out of the way, it could be that your blower is just clapped out, it does happen. Have you ever disassembled it to look at the impeller? I had some debris get into my blower once and it chewed the shit out of the impeller (it was just a small piece of rubber that came off a coupler) and I lost about 1.5lbs of pressure permanently.

[Diabolic]

Well the thing made more than 15#'s this morning. It was just that it was at 6000 RPM instead of 5000, and it took the limit of 50,000 rpm to get there. I believe that's about right since this is on a 351 with AFR heads and not a 302. I think I will see the boost I want at the RPM I want(5000) once I get he correct pulleys on there. I want to shift where most blower cars are just getting up to speed. How many blower cars shift at 4800-5000 RPM?

[CJ]

Well the thing made more than 15#'s this morning. It was just that it was at 6000 RPM instead of 5000, and it took the limit of 50,000 rpm to get there. I believe that's about right since this is on a 351 with AFR heads and not a 302. I think I will see the boost I want at the RPM I want(5000) once I get he correct pulleys on there. I want to shift where most blower cars are just getting up to speed. How many blower cars shift at 4800-5000 RPM?

oh well hell man, I didnt know that.

[Diabolic]

I've decided to relocate my tensioner like the ones in the photos above. I'm going to try a Reichard Racing 2.93" blower pulley. I am currently seeing 12.3 #'s at 5200 with a 3.13" so I think the 2.93" will get me to 14 #'s by 5200.