Supercharger heads...but what did Paxton McCulloch do?


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By Daniel Jessup - 15 Years Ago
Thanks to Frank Lydell up in Rockford, MI, I am well on my way on the blower build. He had the crank pulley, a good bonnet, and a vintage cylinder air cleaner. Ironically, Jerry Christenson put a copy of classified ad in the latest Y block mag issue (#95) on page 5 from a "bunch" of years ago about a guy looking for 312 parts, superchargers, etc. The ad just happens to be the same Frank Lydell stationed on an aircraft carrier in port at SanFran at the time. 

But I digress. My question alludes to the VS57 and how Paxton McCulloch addressed the situation of FoMoCo heads in 55 and 56 Fords (and maybe even 57's) on their aftermarket kits. Most of know that you want to run the large valve, low compression heads on a blower set up. But how did Paxton get away with putting a VS57 on a 292 or 312 with C heads, or worse still G heads? Am I reading too much into this, or is the boost just not enough to make a big difference because the VS57's were limited?

By Ted - 15 Years Ago
Daniel Jessup (1/10/2010)
My question alludes to the VS57 and how Paxton McCulloch addressed the situation of FoMoCo heads in 55 and 56 Fords (and maybe even 57's) on their aftermarket kits. Most of know that you want to run the large valve, low compression heads on a blower set up. But how did Paxton get away with putting a VS57 on a 292 or 312 with C heads, or worse still G heads? Am I reading too much into this, or is the boost just not enough to make a big difference because the VS57's were limited?
I think you’re reading too much into this.  The poorer the head flow, the higher the boost is the simple explanation as pressure builds up before actually getting into the cylinders.  The exact same kit being used on a 292 and a 312 would have the 292 running a higher boost pressure simply due to the cubic inch being smaller.

A simple pulley change slows the blower down on a higher compression engine so you don't have as much boost but many of those early engines were already in the 8.0-8½:1 CR range so the limits were far from being pushed.  I'll suspect that the kits for the cars were designed as such but maybe someone else with some real 'kit' knowledge can add some more.

By MoonShadow - 15 Years Ago
I've been running the G heads with a VS-57 for several years now. I think the compression theory has changed a lot since the 50's. I don't think the compression is nearly enough to hurt anything. Some of the modern systems run a LOT more pressure with no problems. Chuck in NH

PS: by the way I never did find that spare crank pulley. Sorry I didn't get back sooner and glad you found one.

By Daniel Jessup - 15 Years Ago
Aaaaahsoooo, young grasshopper Daniel learn much from white haired guru of Y block knowledge Hehe

Thanks Ted, wasn't giving too much consideration to head flow either. A nice "Duh" moment. Does make it interesting though, because in my hunt for parts through Craig Conley and some other fellas who have dealt with original Paxton Mcculloch equipment for the Y blocks, part numbers, different crank pulleys, bracketry, and other items pop up all over the place with no explanation as to what the piece might fit, etc. I would be interested to read up on any original company info on the kits and what parts came with each one.

I would be most probably be safe to assume that I could run an otherwise stock set of C heads (I have a good set in the garage here) on a 292 with the VS57. Chuck, from what you said, it looks like I could run them with no problems as long as I watched my CR. By the way, no problem on the crank pulley. Finding all 3 of those parts from the same fella gave me a better $ deal than buying piece meal.

By MoonShadow - 15 Years Ago
When I first visited the Y-Block online library (this site) I also had questions about CR, head work etc. One of the things I learned was that with the supercharger the flow is pressurized all the way through. So a charge of fuel with blower pressure is just waiting to pop into the open intake valve. All the "getting there"  stuff, porting etc, becomes less important. Sounds good to me. Not that headwork won't help it just won't help as much as on a naturaly asperated engine. ????? Chuck in NH
By Don Woodruff - 15 Years Ago
Moonshadow:

I have to disagree, porting and other head stuff becomes even more effective when supercharged. Also an effective exaust port and system becoms more critical. All depends on the performance level you want to achieve.

By John Mummert - 15 Years Ago
I think people worry way too much about CR with the McCulloch blowers. First of all they only make about 4#s of boost. Secondly, they don't make any boost to speak of below 2500-3000 Crank RPM. Detonation is the only real concern so if you do experience some in the 2500-3000 range the ignition advance can be delayed.

IMO: wide lobe center cams (112-114) are a waste of time with the McCullochs. 109-110 seems to be a better choice. The wide lobe center rule really applies to positive displacement Rootes blowers that make boost immediately.

What has been recommended to me, and I think this correct: Build it as if the blower wasn't there and the boost will make it that much better. In others words: 9.0-9.5:1 CR and cam with 110 separation or less.

BTW: the original F-Code cam was ground on 109 lobe centers.

By Daniel Jessup - 15 Years Ago
John, thanks for chiming in. Valuable info to look at and consider. I am not building an all out race car. Just a 55 Sunliner with a 292 and McCulloch setup hooked to a T85 R11 unit. Would you recommend a vintage teapot or a later model carb like a Mighty Demon Jr? I have both intakes A and B...