Altitude Vs Compression Vs Ignition timing question

The funnycar team I work for has recently stepped up to a class with and overdrive restriction on the blower and I'm curious as to what people are doing to compensate for major changes in DA, yesterday for example there was over 3500 ft difference between the 4 tracks we normally race at, we have plenty of head gaskets to make changes and currently we are at 11.35-11.85 (staggered piston heights) with an .080 gasket. I'm also wondering what affect the altitude will have on the maximum timing we can run?
526 Hemi with Muscle heads 14/71@ 40 over maximum

 

We run HH8's limited overdrive on BBCs, but I'll give my thoughts anyway. This season our density altitude varied by almost 5000 feet! So its on my mind also.

According to this formula, Corrected Compression Ratio = FCR - [ (altitude÷1000) x 0.2 ], your compression should change by .7 when changing 3500 feet in altitude.

On our engines, we would need .030" thicker head gaskets to reduce the CR by that much. Maybe I could get things setup so the pushrods still worked? But what worries me is losing the squish clearance. Maybe its not as important as I think? Your thoughts?

As far as timing goes, I do think varying DA and GoW effect the optimum timing and I am working on proving it by running on the dyno in these different weather conditions. Its going to take a while though as high humidity will likely need to wait until next August

I currently compensate for DA by only changing the main pill.

 

Thanks, that is exactly the kind of formula I was looking for.
As for your squish clearance someone smarter that me will probably be able to explain this better but I believe the more squish you have (the closer the piston is to the head) the more turbulant the mixture becomes which leads a better mixed mixture and a faster flame speed which will also have an effect on how much timing you can run, I guess trial and error is the only way to tell how much difference .030 will make.

 

Patrick Hale

Is this the kind of information talked about in Patrick Hale's weather book?