Tuning for altitude
 

I'm planning on taking my 382/220 stocker to Bandimere in July. I have typically been running in the 1000 to 3000 foot altitude range, but I expect that going to 5800 feet might require some changes. I will only have two or three qualifying runs so I won't have much time for trial-and-error.

So should I go down one or two jet sizes? Should I add a degree or two of timing? I'd like to start with a good guess before I hit the track for Q1.

Re: Tuning for altitude
 

Dave, put in the loosest converter you can find. I would go down 2 jet
sizes and leave the timing for the second run. Every combo is different
of course, but I have found that the less crank you have, the more effect
it will have in slowing you down. You don't see many people from the
area building too many lower class cars. There are a lot of A,B,C cars &
a lot of stick cars. The locals know how to give themselves a better
mousetrap. Hope this helps.

J.R.

Re: Tuning for altitude
 

If you are going to the Mile Highs in July you can expect to see air 8000 to 10000 ft corrected depending what time of the day you run, last year Weather conditions: air temperature 79 degrees, relative humidity 34 percent, barometer 29.81 inches, adjusted altitude 8,869 feet, track temperature 70 degrees. This track has a cooled starting line, the track temperature on the non-cooled area is 90 degrees and down track it is 94 degrees.
. You will lose .8 in et from the air you are in now. Also you will be pitting a good mile from the starting line, give your self some time for cooldown. Mind you, you can be fast on the mountain with the right combo. Starting line temp can get really hot but with a low hp combo you can add air to your rear tires. Go with lower gear trans [ three speed ?]. Shorter rear tires? If you are the only N car you just have to get under the index. Just drive the car and have fun. Depending on how safe you are with jetting at home down 4 to start with. Your car will feel like its broke, Good luck Tom

Re: Tuning for altitude
 

6.14's ;-)

Re: Tuning for altitude
 

The car will definitely feel like it broke the first pass. Haha. When we ran there a lot and went fast. We changed gear 6.14s to 6.50s put in a looser converter, also ran a shorter tire then we normally did, changed timing a couple degrees, we ran a q-jet but made a multi step adjustment to the rods and when we really wanted to go fast also changed camshafts from what we ran normally. As Tom said if you are the only one in the class and can run under. Change the jetting and call it good and drive it

Rick Ryan

Re: Tuning for altitude
 

Thanks, guys. I'm not prepared to change a lot for this, but these suggestions are helpful. I don't think the budget will allow buying shorter slicks just for this one event, or changing gears. I think the 5.86s will do. But I will try the tuning changes.

I did run at Rocky Mountain Raceway a few years ago and with no changes at all ran under the index, so I should be okay from that point of view.

Re: Tuning for altitude
 

I see from a 30 tall to a 28 tall slick about 150 rpm gain. I have moved cam forward 2 dgrees added timing and 2 steps leaner on carb. All of this using weather station to compare any gai s showed around .15 gain

Re: Tuning for altitude
 

Here's an excellent article from David Reher, Reher-Morrison Racing Engines.
https://rehermorrison.com/tech-talk-...-with-bad-air/

Re: Tuning for altitude
 

I run 6 Degrees more timing in Denver than Wild Horse in
the wagon.

Re: Tuning for altitude
 

First pass ever in Denver = I shifted from 1st to 3rd because it was
so long in 1st gear - I thought it was already in 2nd gear.