Scott, that is a very interesting question. For those who may be wondering about the Ford V8 hybrid heads used on the sixes here is a brief history as I remember it. Please allow me to briefly expound on its history. I'm sure a complete book could be written on this fascinating aspect of drag racing. Early racers recognized the advantages of the Ford six over other inlines of the day. Seven main bearings 12 port head Forged crank Large 4" bores standard strong block intake/exhaust on the opposite side of the steering linkage However, the stock production cylinder head was designed as a low speed, high efficiency unit with emphasis on fuel economy, not performance. Racers soon realized the head was the biggest restriction to making big HP numbers with that motor. It didn't take long for racers to look to V8 heads to adapt to the 300 six. The bore center spacing on the 300 are 4.480". The bore centers on the small block Ford V8 are 4.380". So early on racers got two V8 heads, chopped off the end cylinders, centered the remaining three cylinders over the #2 and #5 cylinder bores, elongated the outer bolt holes to amazingly match up to the six's block holes, brazed the two pieces together, and had a crossflow head design that was vastly superior to the original six. There were a couple of issues with this method though. First, the intake / exhaust valve arrangement was backwards from the original six, necessitating a custom ground camshaft. This was no biggie, as a custom cam with lobes in the .700" lift range were needed to take advantage of the big valve, big port, canted valve design of the Cleveland V8s anyway. (Stock cams gave less than .40" lift.) The second issue was the offset of the four chambers that did not perfectly align with the bore centers by .100". So the next step was using three heads with two chambers each to offset all six holes by only .050" each. Better. But moving the chamber by as little as .050" can affect maximum flow potential by as much as 10%. The next logical step was a six-piece welded head made from six individual pieces of V8 heads to get the bore spacing perfect. Look closely at the picture of Bruce Sizemore's head you posted and you can see six distinct chambers welded together. Other stages of evolution included the use of hi-port exhaust plates as developed by Jack Roush and Wayne Gapp and Bob Glidden for their Cleveland small block Pro Stockers which were equally dominant and then using NASCAR aluminum heads. A common concern with all these hybrid heads was the weld / braze joints on the chambers. They were prone to cracking necessitating much between-race welding maintenance. To that end racers petitioned NHRA to allow their heads to be cloned into a single piece billet head, manufactured by Alan Johnson of Top Fuel / Funny Car fame. Once they were approved reliability issues were solved. To answer your original question I think only a few racers had the technical moxie and expertise to pull off this conversion - maybe a dozen teams or so. So if a dozen teams went through this process that would mean maybe four or five dozen hybrid Ford V8 heads got built. And let's not forget those who tried other heads, like our dearly departed good buddy John Peto who grafted Mopar W6 heads up to his very rapid Ford six. I'm going to wrack my brain and try remembering some of these teams. Maybe some of them still have their hybrid heads. Here is my list of racers I would ask about the whereabouts of them: David Majors Joe Williamson Ambrose, Argenta, and Huettman Bruce Sizemore Bob Andrews Mike Nahan Lou Olynick I'm sure I'm forgetting several teams so anybody feel free to add to this list. Some of these teams, Like Steve Ambrose and Bob Huettman (who, incidentally, are the longest competing sportsman team in NHRA history at 41 years with a Ford six!) are still at it. Race on Boys!
There is at least one of the hybrid headed engines left. It is out in my shop and as soon as I can get my son to post some photos we will. It is a 292 Chevy with ford Boss heads fabrecated to Chevy. I start it every now and then to bring back memories.
Thanks Greg for the history lesson, I would like to find one... Christmas tree, That's awesome, I had heard that they ran one on the mister crude anglia chevy 6, and that Sissell even tried one...
Hybrid headed engines were legal in the /Gas classes and /Altered classes and /Dragster classes. But never in the /Modified Production classes or /Econo Altered classes or /Econo Dragster classes which require "stock" head castings be used.
We heard about Sissel doing one and took photos to the nationals and he said he should be asking us questions as he had done blew his up. Something about a 90 degree mag drive had failed.
This one was recently put back together out here. All original except for the valve cover. It was first raced in '61 in Delaware area.
^^^^^^^^^^^^Starter placement is determined by the size of the flywheel, so having a starter in your FED 6 cyl powered digger wouldn't be any easier than a V8, correct?
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