Q&A / Tech

Mailbag: How to Avoid Loss of Acceleration at Higher Gears

Got questions?

We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re curing a potential fuel delivery problem.

B.L. Vale, NC

Q: I have a 350 Chevy (bored .030 inches over) with 10.4:1 forged pistons, 292-degree duration cam, and Corvette heads with 2.02-inch/1.60-inch valves. The engine also has an Edelbrock intake and 750 cfm carburetor. The car is a 1979 Camaro with 4.11 rear-end gears with positraction.

The problem I’m having is with acceleration. The engine will pull really strong in first and second gear (I have an M22 four-speed manual transmission), but is weak in the other two gears. Is my carb too big? Is my intake bad? Is my clutch slipping? Is my fuel pump weak? If you stand behind the car, the gas fumes from the exhaust are so bad your eyes burn.

A: It sounds like you have a fuel delivery problem. The first thing you should do is check your fuel pressure. You didn’t say what kind of fuel pump you have, so I’ll assume it’s a stock mechanical unit. The problem is that when the car first takes off, there is plenty of fuel in the carburetor’s float bowls. But when they empty, your pump can’t supply the fuel the engine needs.

We’d recommend replacing the mechanical pump with a Holley electric pump equipped with a fuel pressure regulator. Set the regulator at 7 psi and you should have all the fuel you need.

It sounds like the air/fuel calibration is way too rich at idle—that’s why you smell so much gas in the exhaust. An Edelbrock Calibration Kit can help you dial in your carburetor properly.

Tags: , ,

Leave a Reply

Your email address will not be published. Required fields are marked *

*

This site uses Akismet to reduce spam. Learn how your comment data is processed.