Square bore to spread bore adapter

[Vanderstel]

When I built my 318 engine I installed an Edelbrock performer intake, which is a spread-bore style intake. I then installed an Edelbrock square bore 650cfm carb. I had only installed a spacer but no adapter of any kind.

I was watching Derek Bieri revive an old 50 Chevy also with a spread bore intake and square bore carb. He used an Edelbrock adapter #2696. With my engine since my rebuild I always had a roughness off idle and not so smooth throttle response. I didn't know what it was, it wasn't too bad, so I hadn't done much to correct it. After watching what Derek did, I thought that would be an easy test to see if it helped my problem.

I went down to Advance Auto and picked one up. Oh my gosh, what an improvement! So much smoother and throttle response is so much better. The only change I had to make was adjust the idle speed up just a skosh. So happy with the results.

 

[Don67Satellite]

Yeah old Derek "sparkolator" has some good info now and again.

Without that adaptor you've likely been suffering from a huge vacuum leak from around "the fuel-make-it-happener". Congrats on fixing it.

I used to run the Performer 440 which also was a spread bore, and also had to acquire one of those adapters.

I now run a Performer RPM square bore.

 

[ckessel]

When I worked at the speed shop, this is the unit we used/sold for the Performer intakes. Gives you enough to seal out vacuum leaks and not raise the carb up.
Edelbrock Carburetor Adapters 2732

 

[Dave6T4]

That's what I used on mine, and they work. Motor idles well, and responds well to mixture screw adjustments. I went around my carb base with my open propane torch and found no vacuum leaks.