new jack with a 350 performance q

[shackleton]

I just signed up and was hoping someone could shed some light on an issue I have with my '80 High Sierra 25.

I bought the truck with a 400 in it and soon blew that motor.  I replaced it with a 350 from Marshall (some local shops advised me this was not the best choice but I was in a bind and needed something quickly as the truck was out of state when it met it's maker).  This truck is sheerly a work horse and to be used for hauling a horse trailer and various menial tasks.  It doesn't get much road time(<2000 mi/yr) but I'm not happy with it's performance.

It has an Edelbrock intake, is linked to a TH 400 and a 14 bolt rear end (the t-case is a 205 for what it's worth).  It's bogging on the low end almost like it's loading up with fuel that won't clear until I put it in neutral and rev for a bit.  Also power gets sapped quickly when pulling the trailer through the hills.  This leads me to think I'm having a carb issue combined with incomplete combustion.

I was thinking of a Holley avenger or truck avenger at 670 cfm.  Also I want to bump up the ignition and am wrestling with the HEI upgrade or going full bore with the MSD 6AL.

The other wrinkle is that I live in the foothills outside of Denver at ~8000' above sea level. I tried to give you the whole picture but I started running long and tried to rein myself in.  If there is any other info you need let me know and I will try to provide it.   Does anyone have any thoughts about this?  Thank you in advance for your input.

[VileZambonie]

At higher elevations the last thing you need is more fuel since there's less air pressure. DO NOT over carb it. I would go through and perform a tune up - set your timing and rebuild your carburetor. If your carburetor is shot and you don't have the carb overhaulin skillz pick up a reman'd Q-jet for about $250 bucks.

[shackleton]

Thanks for the reply.  I was looking at a new carb basically to make sure I had the go power necessary when hauling.  I believe that carbs sold for altitude come with a different needle and spring kit to compensate.  I've never bought a carb up here so I don't know if the different configuration works or not.  Is it your opinion that adjusting it won't work and just play it safe with a lower flow?  Do you think the Holley options will be ineffective or that I won't get the return on my dollar or both?

Thanks for the input

[VileZambonie]

Basically any performance carb out of the box is going to be rich in all modes of operation so they will just bolt on and work for most applications. In a high elevation there is less air pressure therefore you need to step down the amount of fuel being meterd in slightly. A stock Qjet should work just fine. As far as it's ability to perform - Those Qjet carbs have huge secondaries. When you stomp on it you'll now it.