Quote:
Originally Posted by Bobby Zlatkin
Rich B., you are correct about the replacement cam for the 270 hp and 283 hp 283 engines not being accepted by Farmer. It was called the 'green stripe' cam by some and the 'Duntov cam' by others.
Farmer Dismuke knew that the posted specs. were short and bounced a few guys that he knew were running the cam right out of the tube. (That's how they used to come from GM)
Supposedly he did it to get GM to submit the correct specs. to the NHRA. I would have hated to have been one of the sacrificial lambs.
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A few thoughts:
1) Wade, I agree with you that this whole "any valve job" issue needs to be clearly stated and addressed by NHRA.
2) Relevent to the "any valve job" issue, when NHRA started the Super Modified classes way back when, they allowed any combustion chamber mods without welding and any valve job or work in the valve seat/port that did not extend more than 1" into the port. Can you believe they still had people who got thrown out? It will happen here, too.
3) Alan, your explanation of the characteristics of a legal valve job will never fly. I'm not saying you were not told that, but if that's their (NHRA) assumption, it needs to be in writing. I see nothing in the current rule book that gets even close to the description you gave. We are way past having a written set of rules and then the tech men's rules the way we have raced so much in the past. We approach the technical sophistication of NASCAR cars and they would never survive with such an approach to this.
4) I asked and was told that we are limited to 1/4" below the top of the valve seat, 1/8" greater than the diameter of the valve head. Anything goes.
5) It is the suff outside the valve job that generally is a judgment call. I give that total call to the tech people. As long as we are basing our definition of "legal" on no modifying the port, that's their judgment. I know it puts the issue of right-ness in somebody else's hands and that allows for all kinds of corruption, but so be it. Everytime someone on this forum opens their mouth about insinuating that a racer has bogus stuff, that person does the same thing. If anything, we should develop some way to inprove the quality of that tech person's judgment.
Finally, an interesting bit of history. The whole Junior Stock camshaft flap that arose in the Jenkins era and carried on into modern Stock Eliminator racing has an ugly twist. The original camshaft specs sent to NHRA by Chevrolet were "functional specs", that is camshaft specs based on at-that-time industry standard .004" lifter rise on mechanical lifter cams and .006" on hydraulic cams. When it was found that NONE of the off the shelf GM cams would pass that spec, first Jenkins and his crew got General Kinetics to grind camshafts that would and add a bit of "juice" to the grind. Then another "advantage" showed itself when somebody got hold of "design specs" for those cams. As an example, the original '57 283 hydraulic cam, the 398 pn cam that was used up thru 1966, had "functional specs" of 250 degrees. Compare that to "design specs" which showed 300 degrees it was an obvious benefit to get those numbers submitted. It became the standard from then on that design specs were sent to NHRA from Chevrolet. That is how you ended up with the 929 cam being 310-320, the 30-30 cam being 346 degrees, etc. Then came the flap of "how much lifter rise do you allow before you start measuring?" because the design specs were what was on paper and did not have anything to do with valve train movement. It was later (in the 1970s) established at .001" on Chevrolet hydraulic cams and some other GM makes. (I got bit on that deal, having a CD cam measured at .000" liffter rise.) Unfortunately, Ford, Chrysler and AMC never caught on to what was going on. So, even in the Stock Eliminator era we had a 289 Ford with a 244 degree camshaft, a 390 AMC with a 266 degree camshaft, etc. Other makes never stood a chance against the advantage Chevrolet had, especially before wholesale factoring was introduced for attempts at equalization.
For grins, I still have a hand written tech sheet that Farmer sent me from 1965 that shows a 1957 283 with a 398 camshaft and it states 250 degrees.
Your history lesson for the day. :-))