Are there any easy trick to makeing my 400 auto run better at hige elevations .it,s a dog @ 8000 ft and wont pull a small encline above 8000 ft . it runs and idles fine but as soon as you put a load on it NO POWER almost stalls out .would like to find a remedy before this fall hunting seoson . Oh ya It,s a 2004. thanks Chuck.

 

i think you have to rejet, and possibly clutch it,

 

Aye, rejet and reclutch should help you out a bunch.

 

LOL...had an 03 AC 400 auto...no power at any altitude! Sold it and bought a Rhno!

 

Rule of thumb... 3% power loss per 1,000'. So... 8x3 = 24% less power anyway, properly jetted or not. Now add jetting that is too rich (assuming jetted for sea level) and you are jetted about 24% too rich. That means unburned fuel (is your plug wet and/or black?) and it can't make power if it doesn't burn. Unburned fuel also cools the mixture and combined you'll notice a real loss of power. You are NEVER going to get all the power back at altitude, but proper jetting can help a lot. Sounds like you need to do it.

You can also install a clutch kit. This will allow the engine to run at a higher RPM for any given speed. The RPM will then be better matched to the torque curve for the altitude. Call EPI and explain what you are trying to achieve and they'll help you pick the correct spring combo.