RacerX wrote:


Although I have not checked I believe the top of the pistons comes darn close to the top of the block. So shave the block and you may just have the piston hit the head.

RacerX wrote:


I just checked my new engine and its has a 7R head as well...marked 7/84. It was from an early 85 car FWIW.

Updates:

Better pics of the early vs. late head:

6R head:





8R head:



The shadows in this pic give the appearance of a sharp angle where the raised shelf around the spark plug plateaus out. In reality, it is a smoothly cast radius, in contrast to the sharp, machined edge on the 6R head.



I also checked the port volume - used some clear plastic to define "full" (see pic below), which gave me very consistant readings of around 110cc, for both the 6R & 8R heads, so there does not seem to be a difference there that I can find. I can see that different types of valve guides could change this number a bit, depending on how far they protruded into the intake port. Exhaust ports also measured the same on the early, and late heads - around 114cc for both.

Awesome work Eric! Did the 6R head that you have the dimples in the intake runners?

Just for reference, I found my post on NASAforums where I had measured it. I had 109cc for the early and 117cc for the late.

I'm going to call Mike Lindsey and ask him, because he actually marks the intake port volume on the heads they rebuild. I'll see what he has to say on the subject.

-bj

Sterling Doc wrote:

BJ, no, my 6R head did not have those dimples. I thought about that at the time, and double checked that it is a 6R, and that it was stamped a 1983 build date. Odd. Even more odd, though is that my measurements all correlate with your 6R head, and not the 8R head. Let us know what you find from Dave Lindsey - and thanks!

As part of the future, it appears that we will begin to need to use more "after market" stuff on our cars, such as front valences. Does it make sense to provide for a way to have a specific list of "after market" replacement parts for things that are not free but have approved "after market" parts as legal replacements? I know that the rule for valence's is something like "exactly the same as stock". I am told that there is only one source, at the moment, for a new replacement but it might be good to call out what any legal replacements are in a supplemental schedule. I know that I would have a hard time determining if some new valence met this rule and I suspect others would have as well.

We could provide for folks submitting a request to add a part to the list by supplying appropriate information to a "tech working group". The list could be updated at any time, by the group, as the need arose.

To keep this from getting out of hand, there could be a process where a request was submitted and the tech working group would determine if there was a shortage developing that creates a need for such an approval, such as the potential for lifters. If a need was determined, they could then review data to determine if a specific manufacture/part was "equal" and publish an approval and add it to the list. This would make everyone aware of "legal" after market bits and pieces as they become necessary. Even it this is determined to not be necessary, at this time, perhaps provisions should be made so that it could be implemented in the future, when determined that it is necessary. It would eliminate issues as the class goes forward.

As for BJ's suggestion that the rules "require" all timing to be stock, I suggest that the dyno test program include determining if stock is reasonably best. If so, make timing free. That allows each person to determine if they want to spend money to change their timing or not rather than requiring it. My reason for this is heads with various amounts of shaving should not have to have custom timing figured out as not everyone that shaves a head will immediately go to the minimum, or even close to minimum, as that makes the head harder to rebuild in the future and remain legal. Charlie had this issue of his head being legal but thinner than the new, thickness rule. Another head lost to our group.

Jim Foxx