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SS/VX engine combo.

Posted: Mon Sep 24, 2018 1:05 pm
by OFP857

There was an SS/VX racer at an NHRA national event that I attended recently, and I thought that it looked like fun.

At the risk of redundancy, I'll give a brief synopsis of the engine-related portion of the NHRA rule book as it pertains to the SS/VX class:

12 pounds per cubic inch, including driver.
2444cc (149 cid) max engine size, which at 12 pounds per cubic inch, would require a minimum weight of 1,788 pounds.
1,600 pound minimum weight, which at 12 pounds per cubic inch, would require an engine no larger than 2180cc (133 cubic inches).
94.1mm maximum bore.
Roller lifters are not allowed. Max valve lift is .630". Max valve sizes are 44.1/37.5mm.
Stock intake manifold flange pattern is required, although porting and welding are allowed.
Max throttle plate size 52mm, max carburetor venturi size 44mm.
Racing gas from the NHRA approved fuel list.

I believe these rules closely mimic similar classes run by other sanctioning organizations, including the "Pro Gas" class that requires serialized CB Performance CNC-ported "Pro Gas" 044 heads, the Jaycee Super Stock class, and possibly others.

The NHRA SS/VX national record was previously held by Doug Gonzalez and Anthony Chicca of D&A Racing with a 10.49. I watched an in-car video of Chicca- it looks like he's launching it off about an 8,800 rpm chip in the two-step, shifting at about 9,000 rpm, and going through on the top end at about 7,500 rpm or so. I would not be interested in pursuing the national record in this class, I would just like to be able to comfortably run under the current 11.60 index.

I'd be interested in learning what kind of an engine combo would be appropriate for this class.

Re: SS/VX engine combo.

Posted: Mon Sep 24, 2018 1:49 pm
by OFP857
Here's the video of Chicca:

Is that an RLR/MSE vertical-gate shifter?

Re: SS/VX engine combo.

Posted: Tue Sep 25, 2018 1:22 pm
by OFP857
I'm playing with the math here, and it looks like crankshaft strokes from 78mm to 88mm will fit this class, when combined with the 94mm bore.

All things being equal, I would think that a smaller engine would be less hindered by the rule restrictions relating to the 44.1/37.5mm valves, .630" lift, stock intake manifold flange pattern, and 44mm carburetor venturis.

But then again, a larger engine would probably have less trouble overcoming the large gaps in gearing, when trying to use only four gears to get from 0 to 120+ mph.

Re: SS/VX engine combo.

Posted: Wed Sep 26, 2018 9:03 pm
by gbaker770
80mm would probably be a great place to start.