Help with high alt. calibration on Edelbrock 1405
 

I am rebuilding my 1405. I live in Wyoming and need to change the stock
application to high alt., I think I got the jets and metering rods figured out
per. the Edelbrock calibration chart. The thing I'm unclear about is the step
up spring, it has the orange one in it. Should I change that too? Am I missing
anything? If anyone has done this kind of rebuild, I sure would like some advice.

Re: Help with high alt. calibration on Edelbrock 1405
 

The step up spring controls the point at which the power circuit comes into play, or when the metering rod starts to rise up out of the primary jet. If you notice a bad hesitation just as you accelerate (but your accelerator pump is OK) then you need to switch to a stiffer spring. Try the one you have now, the go from there.
The best advise I can give is get a wideband Oxygen sensor to use as tuning aid. Ever since I got mine, I won't tune a carb without it.

Re: Help with high alt. calibration on Edelbrock 1405
 

Thanks, I hope i'm not going to jack things up leaning this carb out. It just seems to be getting too much fuel and I assume the stock set-up is too rich for 6000 feet in elevation.
I was also told to make sure my mech. fuel pump isn't putting out more than 5 psi. I don't have the tools to check that, maybe where I bought it they can tell me what it's putting out.

Re: Help with high alt. calibration on Edelbrock 1405
 

The 1405 is calibrated rich from the factory as it's a performance oriented carb. (The 1406 is basically the same carb but calibrated leaner for better fuel economy.) So, you're on the right track by leaning it out a bit for higher altitude, provided it still has the factory jets/ metering rods etc. Here's a link to Edelbrock's site http://www.edelbrock.com/automotive_...carb_faq.shtml which says to compensate 4% for every 3000ft.

Here's a simple and inexpensive fuel pressure gauge. http://www.summitracing.com/parts/SUM-G3122/

and inline hose adapter
http://www.summitracing.com/parts/SUM-G1710/

Re: Help with high alt. calibration on Edelbrock 1405
 

Thanks, all that is a lot of help.

:gmc2: