if you were to run there what changes would you make

1.Torque converter 400 rpms looser

2. Gear

3. Cam

4. Tune

Rusty for a boosted motor I was told put on the fastest pulley you have, maybe add a degree or 2 of timing and take away about 20% fuel.The air was about 9400 feet at last weeks D5 race

I was just there for the first time last week. I asked a couple gas carb guys and they both told me they go down 4 jet sizes and add 2 degrees of timing.

On my alcohol carbureted car, I did absolutely nothing and it ran great.

My mechanically injected car, I added 2 degrees of timing and needed to go 20 sizes leaner with the pill before it would get on the chip or down the track. It was recommended to go 3 sizes smaller on nozzles instead of the big pill change, but I didn’t have those available.

My dragster converter was 400 rpm tighter there, if that’s a concern.

If you rely on smaller portable generators, don’t expect them to handle the same loads they can at home.

quote:

Originally posted by Lenny5160:
I was just there for the first time last week. I asked a couple gas carb guys and they both told me they go down 4 jet sizes and add 2 degrees of timing.

On my alcohol carbureted car, I did absolutely nothing and it ran great.

My mechanically injected car, I added 2 degrees of timing and needed to go 20 sizes leaner with the pill before it would get on the chip or down the track. It was recommended to go 3 sizes smaller on nozzles instead of the big pill change, but I didn’t have those available.

My dragster converter was 400 rpm tighter there, if that’s a concern.

If you rely on smaller portable generators, don’t expect them to handle the same loads they can at home.

He also forgot to mention he won the darn thing in Super Comp too. Pretty good trip to the Mountain.

We take two jets out and add two degrees in. We also see roughly the same amount of decrease in Converter stall. If you've got a smaller carb to throw on, that'll help as well.

congrats on win,i thought gary wombolt won all of those ,congrats. thanks for ideas.will carb bowls change in fuel height

It was a fun weekend. I went out first round in td, mistake on my part. Live and learn!

Rusty, Just throwing this out for consideration.

(BTW, I was running the exact same jetting last weekend at XRP as I had in the car at Denver).
Like Tony's car, NA/Alky. But when I was there full-time, I ran 2* more timing, more gear, looser converter. Same carb tune other than idle mixture. Obviously you have different combo & car, but just saying you may not need to change a whole lot.

By David Reher, Reher-Morrison Racing Engines

“Some racers wear out the threads on their carburetors trying to adjust for weather conditions.”

As I write these words, we’re loading our Speedco Pontiac Grand Am into the transporter for the annual trek to Denver. Preparing to race at a mile above sea level brings home the reality of racing under adverse conditions. While we make many adjustments for Bandimere Speedway, one of the items that is definitely not on our to-do list is to change carburetor jets.

Read entire column here:
David Reher article on altitude/bad air

This message has been edited. Last edited by: FootbrakeJim,

thanks jim,good read

This message has been edited. Last edited by: rusty,

That is a good thought on the generators I did not think of that.

As for jetting on the carb if it is right at sea level it should be close to good at higher altitude but will make less power due to less oxygen. I agree with the Reher and Morrison article and Footbrake Jim on that. Booster squirter nozzles on a carb is purely mechanical so that will not be perfect but your main jets are more or less self adjusting to density of the air. Idle mixture is somewhat effected by air density so it may require some changes and idle mixture is more critical than many think. The Holley books say it does nothing over 1100-1200 RPM that is not true. Your idle mixture will effect the motor up to maybe 3500 RPM and could effect how it goes up on the converter if it is far enough off.

With Mechanical injection you are going to have to make big changes and some testing to get it right. There are a few here who are good with numbers and smarter than I (Not going to mention any names sr4440)than can do the math and get you very close on pills.

"Will carb float bowls change in fuel height?"

That is a good question to and something I would definitely put on a check list to check when there. I do not think it will change much but float level is critical on a carb so I would certainly check it once there for any changes. There is a significant pressure change at that altitude and I would like to hear any real experience if it changes float level a noticeable amount.

I have raced at 7500 DA and even below sea level but never up in Denver and I understand the challenge to run the number or index in different conditions.

I was lucky enough to slide by Wamboldt first round. He is a tough customer. Might have gotten by Lenny too if I had just left the throttle on the floor. Notice I said "might have."

quote:

posted June 26, 2021 10:20 AM Hide Post
I was lucky enough to slide by Wamboldt first round. He is a tough customer. Might have gotten by Lenny too if I had just left the throttle on the floor. Notice I said "might have."

lol

I had Dave Ones in the first round...did the dumb thing of not having car in first gear....brake won't hold in second.....my car was a zerox machine all weekend, and my lights were there....stuff happens though....


Vern came by after the round and said "did you forget to put it in first again?"....Same thing happened the first time I entered the event several years ago in the gamblers race....ugh....

In case anybody is wondering about tune, my stuff from sea level is two sizes smaller on the nozzle jets, went from a 78 main to a 94, and added 8* of timing.....Took me several passes in testing to get it happy..

quote:

posted June 28, 2021 10:28 PM Hide Post
In case anybody is wondering about tune, my stuff from sea level is two sizes smaller on the nozzle jets, went from a 78 main to a 94, and added 8* of timing.....Took me several passes in testing to get it happy..

wow and thanks

Mark's car was a Xerox machine. I thought he had a shot at the whole deal but a brain **** got him again. My friend Kevin Wright was on the tree also and then he and Dave Oones were both late I believe and he came up just short.

The guy who won, Bradley Johnson was on another planet though. Man, that guy is tough!!

I have raced at Denver quite a bit and it can be very humbling to say the least.

I change converter and jets and leave chip. I don't change timing because basically I'm too lazy.

thanks vern