Putting in a weiand mini blower in the elco its a 350 9.5.1 compression, question what size lower pulley should i get, and where can i get this pulley at. also what kind of carbs are you guys running on these mini blowers i was just gonna use my extra edelbrock performer 600cfm carb stock hei dist with either an crane hi 6r or msd 6btm box. how much boost can i run with kb hyper pistons, stock crank and connecting rod, lsa is 112.
Jon

 

9.5:1 is too much compression for a roots blower using pump gas, trust me. I tried 9.2. Then I tried 8.6. If I had it to do all over again I'd do 8.0 or lower.

It WILL work but you will be flirting with detonation all the time. Detonation and hypereutectic pistons don't mix. I don't know what your complete cam specs are but if it's a very mild cam (it better be to work with the little 142) you should stick with the stock 6" bottom pulley. That's the one that comes in the kit. The larger 7" bottom pulley you can get from Summit or any place that sells Holley stuff.

You really don't want to run more than about 4 PSI of boost into that motor on pump gas. Even the stock pulleys will likely provide more than that (again, depending on your cam). Doesn't sound like much but it is- it's a heluva rush of torque compared to running N/A. DO NOT LISTEN TO RECOMMENDATIONS FROM GUYS WHO RUN CENTRIFUGAL BLOWERS OR TURBOS- they will be dead wrong about a roots blower. You can get away with a lot more with a centrifugal or turbo than you can with a roots blower. Then again, they don't give full boost from the instant the pedal hits the carpet!

If you want to try it anyway here's a couple of gudelines:

1. Don't ever run lean. Things go "bang" when you run lean. More fuel pump than you could ever possibly need. Make sure the carb is in good working order and jet it up 3-4 jet sizes to be safe.

2. You will need to stay VERY conservative on spark advance. For your engine I wouldn't go over 26* total advance maximum at WOT until you get used to tuning one of these motors. Yes, you can run vacuum advance on top of that (I do, too) but at WOT you will run it with significantly less spark advance than you do now on your N/A application. I run 28* total in my motor and that's about the detonation limit with 8.6:1, aluminum heads and 6 PSI of boost, just to give you an idea.

 

wow thanks for the info damon, the cam is a crower race cam, but is very mild its a lsa 112 like i said with 210/216 exh .296 .296 at .o50 lift. with my rr of 1.5.
for the pulley i should get a 6in one, can i get this at summit or jegs, as i am getting this through ebay, also any idea on where i should get the gaskets from as he took off the plate and gaskets to take pictures of the blower gears. also what kind of box are you running? will a stock hei do also will it fit behind the blower?
Jon

 

I didn't realize this blower was used. Did he disassemble the thing? Like actually take the front gear case and/or blower snout off of it? If so, you're into territory I haven't gone into yet. I assume Holley sells these gaskets as service replacement parts.

The pulleys you can buy from Summit or wherever- Holley doesn't sell this stuff direct to my knowlege. The only things they sell direct would be service replacement parts. Make sure you also get the longer bolts you need to attach the bottom pulley to your existing crank pulley. You need 3 pulley bolts and a longer crank snout bolt.

 

sweet do you by any chance have pictures of your engine. Yes he said he dissassembled the blower so he could see the rotors. Are you running any kind of ign box? Also how much boost are you runnng? thanks

jon

 

A picture of my setup (old, before I had aluminum heads, but still the same basic setup today) is in the sticky thread at the top of this forum.

I was running an MSD 6A before (no boost retard- feel free to ask how I'm doing that) but the box went flaky and I yanked it. Right now I'm just running a home-built HEI with an MSD module and coil. Plugs gapped at .035". Still seems to run just fine without it.

 

so do you believe i can get away with just a 6a or 6al box i think i may just go crane hi6r for the box as its 100 cheaper and im sure just as good.

 

Actually, my brother used that Crane box on his GTA (not with a blower) and I was very impressed with it. Lotsa standard features, small size, threw big fat lightning bolt sparks and never gave us a minute's trouble. I'd say you could definitely use it in place of the MSD box.

 

sweet looks like ill be using that. even though he doesnt have a blower does he still use the retard control?

 

No, no reason to.