: Edelbrock 1411 Carb for 472. Need help with Adapter Plate!

05-10-10, 02:30 PM
Hi everyone,

I am trying to install the 1411 Edelbrock Performance Carb on my 472, 1969 Cadillac Eldorado. I called Edelbrock and they recommended the 2697 Adapter Kit. When I placed it over the intake manifold, it is not an exact fit. I've placed some pictures of the intake manifold and the plate and show the area that would create a vaccum leak. Can someone please help me understand if this is the right kit, and if so, am I placing it incorrectly? Thanks everyone.

05-11-10, 10:45 AM
I hate to say this, but going from a Rochester QJ to a Carter or Holley derivative square bore carb on that manifold is NOT a performance gain - it's a performance loss.

Much better to either tune and do some metering rod work your present QJ or have the guys out at JET Performance build another street tune QJ for you. www.jetchip.com. Find the 8x11 paperback Rochester book by Doug Roe, HP Books.

JET builds the QJ's for my marine Olds 455 rebuilds and I have no complaints.

05-11-10, 11:32 AM
Why is it a performance loss?

05-11-10, 03:16 PM
The QJ installed on your engine uses mechanical secondaries which are flow-controlled by that air valve in the top of the air horn. The QJ automatically adjusts itself to the maximum airflow needed by the engine at any given instant and load requirements: and it's a spreadbore. That's why the primaries are relatively small (economy and quick part-throttle performance); the secondaries are huge and allow the carb to flow up to 850 cfm if the engine can use it.

The Edelbrock #1411 is a 750 cfm Carter AFB derivative - a square bore with purely mechanical secondaries. Your adapter necks down the larger AFB primaries to the QJ original primary bore diameter in order to maintain low and part-throttle driveability, BUT the secondary bores in the AFB and adapter are smaller than the QJ bores in the manifold, so the aftermarket carb will NEVER flow as much as the OEM QJ.

"Yeah, but with the AFB the mechanical secondaries slam open faster than the QJ air valve......so I get more power faster....." yes, they do, and no, you don't. Slam open the secondaries at low and mid-engine speeds and you get a stumble and bog because the fuel metering won't come in with low airflow through the wide open venturis - that's the beauty of the QJ: the air valve keeps the carb tuned to airflow requirements and the hanger and cam on the air valve bring the mixture in as secondary airflow can use it.

05-11-10, 03:35 PM
It does look like a restricter plate since you are going from large secondary ports to small ones. Quadrajets are the best carbs ever designed (for street cars) but I get tired of saying it and I assume people get tired of hearing it. That's why I didn't have the heart to post anything earlier. I don't have a suggestion about the ill fitting restricter plate anyway but they must make different models or versions because that one obviously doesn't fit right.

05-11-10, 04:08 PM
I appreciate the feedback regarding the QJ Carb. In all honesty, I think the performance that the Edelbrock Carb will rob will be minimal and probably unnoticeable. I went with the Edlebrock #1411 because of looks. I am going to have a painted and chromed engine bay and think the Edelbrock Carb complements that. Anyone looking to drive this car already knows it's heavy and has terrible gas mileage, and is not looking to optimize performance by 5 to 10% using the QJ carb. Instead, they want a car that looks nice on the outside, looks nice under the hood and runs strong. I think you both have an excellent point regarding the QJ performance compared to other After market carbs, and certainly appreciate your input. Thanks again!

05-19-10, 10:09 AM
Looks over Function? :banghead::thepan::thepan:

05-19-10, 11:14 PM
I like Qjets too. But if you must use the adapter, you could cut an aluminum plate maybe 1/16" thick to cover your manifold with the proper openings, and use your original gasket. Then put the square bore adapter on top with an appropriate Qjet or home made gasket. Bruce Roe

05-20-10, 07:20 PM
Looks over Function? :banghead::thepan::thepan:

I can see using a nice shiny carb on a nice clean engine and living with a little less efficiency, but an ugly Qjet can be hidden pretty well with a chrome drop base air cleaner. That's what I do anyway. You have to bend over a little if you want to see the carb. Here is my ugly Qjet: