2x4 Edelbrock Carb tuning
 

Hi Guys,
I've got a 428 SCJ, Edelbrock Performer RPM Cam, and Heads, vintage F262 intake, a pair of 1404 500CFM carbs with progressive linkage, and super custom home made 2" primary equal length headers. Compression is about 10:1, and it's all polished to a mirror finish, except for the headers. I'm pretty sure that none of that matters, except for the progressive part......

I called the Edelbrock tech line today and was told to set the carbs up exactly the same, "mirror image" was the term the guy used. What I don't get is why the carbs would be set up the same if the motor only runs on the rear carb until the front one kicks in at something above 1/2 throttle. The guy on the phone sounded like he was not born until well after Vic stopped making 2x4 intakes for FE's. Is he right about setting the idle mix and speed with both carbs?

After reading the carb manual I think I'll leave the jetting to someone smarter than me, and who has more dyno jets than I do. Just for the record, I have exactly zero dyno jets, so all I need is a guy with one dyno jet to do whatever needs to be done to make the stupid thing run right.....

Tell me again, how much does injection cost?

Thanks,
Jon

I put a bolt in the slot on the linkage to make it "un" progressive linkage...worked out mucho bettero for me. basically, I have a double pumper (2x2 barrels) with vac secondaries (the other 2x2 barrels)

Jon - Attached is an image of the dual Edelbrock setup on my personal car. It is a non-progressive straight-pull. The engine is a 403 FE(390 +.060) and the carbs are a pair of 1405's (600 cfm). The car is an outstanding performer.

The tech at Edelbrock is correct. Mirror the carbs. When you are off the idle curcuit and on the main jets the fuel flows proportional to the air flow. It doesn't matter if you are flowing more air through one of the carbs as in a progressive setup. Each carb will feed fuel according to the volume of air passing through it.

I have built two other cars for resale. The first was a 302, Edelbrock f-28 manifold, twin 1405's and progressive linkage. The second was a 289, high rise intake(from Branda), twin 1405's, and non-progressive linkage. In each case the carbs were jetted to their engine's fuel requirements, but all carb pairs were mirrored. Once you match the fuel/air requirements of your engine you can feed it with one carb opened 1/4 inch or two carbs opened 1/8 of an inch. The progressive linkage never really impressed me. As you may have noticed, I do like the twin carb setups. While you may lose a bit of volumetric efficiency with the twin setup, You can't beat it for looks and bragging rights. You've got a gut wrenching 428 in a very lightweight vehicle. Getting 2 more mpg cruising around town on progressive two barrels just isn't an issue. Cruise around on four primaries at 1/2 the throttle opening.
Keep in touch with Edelbrock support, start adjusting with the jetting on the rich side, and you can get the jets/rods close with a good ear and "seat of the pants" feel. Fine tune it on the dyno after your up and running. Study the carb manual. The carbs are relatively simple.
- Geary