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[Mertz]

I have a 72 3/4 with 350/350 and pull a 5000 lb trailer once or twice a year. I have some trouble getting up a long 7% grade. I am thinking about going back to a Qjet from my Edelbrock 650. I have headers, MSD ignition, 1.52 roller tip rockers and Edelbrock EPS intake. Can I use the adapter to go from Square Bore to Spread Bore or should I change the manifold to get best performance? The carb guy I talked to said I might want to switch the jets and put the secondaries in place of the primaries. He also suggested adding spring loaded needles to help prevent fuel starvation on the hill.

[mnunn454]

Last point 1st,

7% grade isn't enough to create fuel starvation.

Switching primary jets with the secondaries is exactly the wrong answer. Should you go that way, your truck will run too rich 95% of the time and too lean when you need it most.

Swapping carbs and/or manifolds is an expensive solution to a simple air/fuel metering problem.

The answer is in your Edelbrock's "power mode" setting. That's easily adjustable (and cheap too) by replacing the two springs that surround the metering needles with stronger ones that'll lift the needles out of the jets at a slightly higher vacuum level and or going with slightly smaller needles that'll let more fuel in when the springs are lifted. This has the same effect as a Holley's "Power valve". This is one of Eddy's really nice features. In less than 10 minutes, and without spilling fuel all over the manifold, you can change springs, needles or jets to get the mixture setting you need under both power and cruise settings.

On Edelbrock's website you should be able to locate a technical article that'll explain all about adjusting your carb to run richer in power mode without going richer in cruise mode.

The article's at http://www.edelbrock.com/automotive_...ers_manual.pdf

I got there by clicking on Installation & Tech, then FAQs. It's behind the link in the 1st FAQ. Whole article will be helpful, but the settings you want start on about page 10 or so depending on your particular carb type.

One caveat: What R&P ratio are you using? If it's a 3.08 almost any engine and carb would struggle to pull 4-1/2 tons up an extended 7% grade.

Good luck. Let us know how you make out.