The concave washers made it in from Germany!

The head that needs to be rebuilt again after 3 short years, due to these washers failing, is an early head, it is a 6 something, maybe 6A, so rumor has it they don't flow as well as the later 8A head. Also my 6A head is shaved about 47 thousands to increase compression to get closer to the 88 motor, the down to that is the timing is retarded as a result and you can't change the timing to make it equal to an 88 motor. I have access to an 8A head and rebuild cost is the same.

SO THE QUESTION IS, would it be best to build the 8A and lose the compression but gain on the flow and timing? Or just put the 6A early head back on with lesser flow, retarded timing but...with more compression??? I suppose another option is to build the 8A head and shave it, keeping the retarded timing issue but not the flow issue or compression??????? hmmmmm

Eric, any ideas on equalizing the early cars with this issue, I know this isn't the first post on this, but I am at the point in building another head and maybe it will be best to put the 6A back together if we can change the timing to match the later cars for the purpose of equalizing.

Thanks to all for your thoughts in this.

Norman, when I cc'd my 6R head, it was identical to the 8R head I had. The strongest motor tested at Nationals last year had a 6R head, so they can make good power. BJ (Texas Region) found that a few of the very early 6R heads seemed to test out less, but this has not been confirmed. The heads BJ had, had a dimple in the intake, and seem to have '82 build dates. Strangely, both versions are "6R". The 6R heads shape leds itself to more quench area when heavily shaved, so they may work better on low compression motors, when you can shave them down until they look like this:


So Norm, if your 6R head is true, and the valvetrain is in good shape, I would not hesitate to use it.

We should get another round of dyno data at Nationals again soon. Unfortunately, one of our planned test bed low compression motors suffered an engine fire on its maiden outing, so that has delayed formal dyno testing. In my travels this year, I've gotten quite a bit of good feedback, and information on power issues, and will be putting this all together for rule change discussion time, after Nationals.

Thanks for the information Eric, I had heard that the early heads have more torque and the later more HP. I do notice that my car really does well with race starts and average on long straights, so maybe there are advantages to a 6R on certain tracks. I gave Joe my last dyno sheet and can't remember exactly the numbers, but I am thinking 135hp and 132 or so torque. So maybe the numbers don't always display how the cars really work. But I am leaning towards using the 6R with more compression and retarded timing.

Thanks, let me know if you get some dyno results and I will see if Joe still has mine from a year ago.

My last fresh Low compression motor made 134.5 HP, and 141 ft/lbs. with a 6R head.

Norm,
I believe there is no reasonable difference in heads. Any power differences are more due to parts and actual build than which part number the head is.