Altitude setup??

I'm hoping to get some opinions on a static compression ratio for a high altitude engine.

Our track has an average density altitude of about 9300' during the racing season. Today our raw pressure was 23.2hg (11.39 lbs) for example. Seems like most guys are running 11.5-12.5 on their blown deals at typical altitudes, so I'm just curious what you guys think would be an appropriate increase to compensate here. I only run the engine here, I don't go down the hill.

-Scouder

 

Ya on the moon?

I run 12:1 at sea level. The more static, the less boost you have to run. info on the motor?

 

Compression

At that altitude I would make the compression ratio as high as possible, and would close the intake valve as early as reasonable.


Noel

 

We look down on the moon from here!

Track is 6600'. SW Wyoming.

This motor is 511, 4.375 over 4.25. Heads don't flow real well, but they're the best I can get at 380/260. BBC rods at 6.7. As soon as I find the right price on a used setup I'll be putting a Littlefield 14HH and Bird or Buzzard setup on it.

If I was at sea level I'd probably be setting it up at 11.5, but with the reduced static pressure I thought it might be better to give it some head start. Maybe it's not significant. It's starting out 3.5lbs down on cylinder pressure, but I only plan on putting around 20-25lbs on it, so maybe I just spin the blower a little faster to compensate and forget about it. Whaddya think?

-Scouder

 

I am thinking 12.5 - 13 as static. How fast do you want to go?

 

Hoping to make 1500 on an easy tune-up under 8000rpm.

-Scouder

 

track?

there's a drag strip in SW Wyoming?

or is this Sand Drags? ....just curious...

 

About 5 miles north of Evanston, Wy. 1/8 mile only. Abandoned airport leased from the county. Community effort thing. Very grass roots, family oriented and fun. We call it Hypoxia dragway because of the lack of air.

-Scouder

 

For many reasons, i think i would build a 12.5:1 motor, and make the rest up with the belt. 1500HP should not be hard to get to. 25-28#s of boost, and 12.5:1, you'll be makin lots of noise.

 

Thanks much. I appreciate the input.

-Scouder

 

If this is a conventional headed BBC I would probably not go over 13:1. The dome sticking in the chamber gets ugly, ignition timing wise. After that, make up for it in blower.