Thread: advice on 489

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Originally Posted by cvfb97

I was also wondering how you felt about centrifugal super chargers? Would the stock crank hold up to 6-8 lbs of boost? I looked up the 3610 heads you suggested, the first ones I found were 112cc if I remember correctly. Using a cr calculator I found online, if I used the 112cc heads my ratio would be around 9.8. would that ratio work for pump gas with no intercooler?

Centrifugal superchargers are probably the easiest to package in a tight engine compartment and it shouldn't be too difficult to mount an intercooler in a 3rd Gen Camaro if you wanted to. You would want hood space to bolt a bonnet (or bonnets) to the top of the carb(s) and space somewhere else to mount a filter system. You'll also need blow-through carb(s).

The size of carb(s) or CFM required for a given application can be calculated by the following formula A: {(CID x RPM) ÷ 3456} x {Boost ÷ 14.7) + 1} = CFM required.
Let's plug in some values and see how this works....
798.61 X 1.544 = 1233 CFM
This would probably require a 2-4 intake manifold with two 650's and a split supply pipe with two carb bonnets. I've never seen it done, but that would make the most sense to me.

It is my opinion that 8 lbs of boost would be no problem with a stock 454 crank up to 6200. It's revs and detonation that kills cranks. By the way, find a quiet time to really pay attention to this, read and heed......
http://www.contactmagazine.com/Issue...ineBasics.html

Chamber volume depends on extent of CNC machining.....
#3610 CNC bowl blend, Partially CNC Chamber w/ Hydraulic Roller Springs 109cc
#3610-1 CNC bowl blend, Fully CNC Chambers w/ Hydraulic Roller Springs 112cc

A blower on pump gas will want somewhere between 7.5:1 and 8.5:1 static compression ratio, depending on amount of boost and mixture temperature. Some guys will tell you to use 9.0:1 or 9.5:1 with a blower, but the higher the SCR is, the less blower boost you can blow into the motor if using pump gas. If you are using straight methanol or ethanol, heck yeah, run it up to 11:1 if you want to. You will be able to buy pistons to accommodate ~8.00:1 for use with pump gas. Not sure of your elevation, but if you live in Greenfield, Indiana, your elevation is about 882 ft above sea level and you would want to limit the boost to about 8 psi so that you could run the motor on pump gas without detonating it.

Take a look at this Final Compression Ratio Chart from Blower Drive Service......
Technical Charts
Across the top is boost in psi, down the left side is static compression ratio. The shaded areas are OK for pump gas. The unshaded areas will require a better fuel such as E85 or straight ethanol or methanol or race gas.

Here is the formula for figuring Final Compression Ratio
Final Compression Ratio (FCR) = [ (Boost÷14.7) + 1 ] x CR
8 divided by 14.7 = 0.544
+1 = 1.544
1.544 X 8 = 12.35:1, rounded off on the chart to 12.4:1

I'll look around and see if we can juggle pistons with 109 and 112 to figure it out to around 8.0:1 SCR.
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