Need Advice On Blower Pullies & Belt Size
 

509ci
AFR 315 full cnc , inconel exhaust valves and roller spring package .
8.4 cr
Diamond flat top blower pistons .
Callies Ultra H-Beam 6.385 rods .
4" stroke forged crank .
Bore 4.50
Standard deck 9.8
I have no cam specs yet .
Spinning to 6000 rpm .
Should make around 625 to 650 n/a
871 BDS blower no chiller .
Two 850 quick fuels .
BDS competition blower intake .
CMI Sport tube dry exhaust .
Looking to make 850+ hp 91 octain fuel .
Many call's to BDS to no avail . Need to know what size blower pulley's and belt to reach my goal . Any help from my brothers would be greatly appreciated . Looking to use 8mm stuff .


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Not too sure exactly what your question is. Are you asking how much boost you need to get the extra 200 hp you are looking for. Of all the info you have listed one critical thing you have not stated is static compression ratio. The BDS catalog will give you "general compression ratios" based on the static compression ratio and the boost you are running. Probably the safest place to start I would think is same pulley top and bottom. The BDS catalog will tell you what size belt is needed for a total "X" number of teeth. I guess just make your choice of pulley teeth where you are safe initially, but still have room to run a smaller pulley on top for a bit of overdrive if need be to get to your desired horsepower. I hope this helps!

the Deep, did you mean a 4.50 Bore? and as bejen asked, What is the Comp Ratio? what cam are you looking at getting for this set up?

Yes 4.50 bore 8.4 cr . Madara cam , I have not seen the card yet . Will know more Monday .

Question is : This blower gig is all new to me . I'm thinking I need about 6# of boost to get me to my goal with no chiller and 91 fuel but have zero idea how to select pulley's . Lake elevation is 820' above MSL . Looks like I would be 5% under-driven @ 6 lbs boost . :picard1: :readinghelp:

Well if this makes 625 NA than 1/2 of atmoshere is Appox 7 lbs. so take 1/2 of 625 (312) and add 625 + 312= 937 at 7 LBS. you dont need much boost it looks like to get your goal.

Those heads flow real good, looks like 380 int and 296 ex @ .600 lift.

Correct me if im wrong but that is what BDS has told me in the past.

^^^^Need to consider parasitic loss. It takes HP to drive the blower, air temps , etc.

5 under would be a good starting point. If going to be dynoing id bring some extra pulleys if u can borrow some. I wouldnt be afraid to run 7lbs on that setup. Call the guys are good vibes racing for belt and pulley setup

850hp sounds like a reasonable goal.

Here you go, http://www.goodvibesracing.com/
This is what they do as MT mentioned.

Ok , yea this is where some of my parts came from so I have the book . I'll call em Monday . Never being around blower motors much (except here) sucks . Thanks guys for the help . I think Mike Tkach built one similar , called and left a message but he must be out enjoying the water . Yea Mild this things going to the dyno . Can elevation be accounted for as far as tune at dyno time ?

Here is a good tech article from Holley with a lot of reference charts of what to expect with various blower sizes and Comp ratios.
http://documents.holley.com/techlibr..._tech_info.pdf

Thanks Griff .

I had a very similar build just put on the dyno
509ci
Flat top blower pistons
Brodix bb-2 plus heads no Cnc work
Bds competition intake
Bds blower that was rebuilt by dpms 0hrs
Pair holley dominators
Don't have cam specs in front of me same cam made 550hp with gm steel rectangle port heads
I made 7.25lbs boost
Pulley at crank 52. 53 at blower Motor was dynoed at boyds racing engines in Norman Oklahoma

What did she make for power ?

What size supercharger and are u running an intercooler ?

sam,why 91 oct fuel,i am thinking that is all u can get on your lake.if that is the case 6 lbs boost will be a good place to be.that is a non stripped blower so it will need to be spun a little higher than a stripped one.i would start at 10%over.those heads flow a ton of air and will not have the restriction a gm iron head will have.i have a ton of pulley,s that i use for tuning on the dyno.after you make some pulls i can send you pulley,s to try on the dyno.good vibrations is a good place to call for pulley,s and are fairly priced.

Thanks Mike , 91 oct mainly because these birds have been known to dump 87 into the other tanks so I wanted to build in some safety . Could just keep some Boostane handy I guess . How do you guys combat fuel that may not be up to snuff ? Am I over thinking ?

871 no cooler .

15-20 gallons of leaded race fuel every time you fill up is good insurance. It will lower the egt's a bit. Smell good when you pull up to the local watering hole and keep the tailpipes nice and white. It is however a little hard on O2 sensors if your running them.

I plan on O2 sensors in the new tails for tuning purposes on the water . Fuel tanks 35gal a side .

110 unleaded. Don't get the smell though.

When you do that math you also have to deduct the parasitic loss of turning the blower, keep that in mid. Roots type blowers use a considerable amount of hp to turn so he would prob end up around 850. Bsfcs around .600 to .650 give or take are common w roots blowers which agains points to the extra hp used to make thar boost, smitty

sam,get me the measurement from center of crank to center of blower drive and i will tell u what belt&pulley,s to start with.if your engine is tuned properly i see no need to mix fuels,that is what a lot of guys do when they don,t have the correct tune,kind of a bandaid.