[rac43]

Need some advise. I just put a new Edelbrock 650 Thunder with vacuum operated secondaries on my 350 T-Bucket. Have a HEI ignition so no vacuum hooked to the carb and all vacuum inlets plugged. Now, my question. How wide should the secondary butterflies open? Under WOT and my looking down the throat, the primaries go wide open and the secondaries only open about 1/8th inch. Is this normal? It runs like a raped ape but need to get the best out of this 650. Thanks lots

[DoubleVision]

Your lucky they only open that far, Vac Sec carbs usually don`t open any or much when not under load.

[onovakind67]

Edelbrock describes the secondary operation like this:

A mechanical secondary air velocity valve in Performer Series carbs senses air-flow according to demand and automatically regulates a smooth transition from part throttle to wide-open throttle.

These carbs have mechanical secondary throttles that should open wide when you rotate the linkage all the way.

[spinn]

i agree with double.. isnt it a vac secondary ?

*edit* on a holley
vac sec wont open just revving the engine in neutral. there has to be a load. the secondary idle enrichment comes from the amount of transfer slot showing in the secondaries.

on a stockish engine i use boxes. the slot is as long as is wide... or .020 whatever it sez.

on a mild or hot build i like a box and a half.

[onovakind67]

The Holley vacuum secondary carbs have secondary butterflies that are operated by the vacuum developed in the primary venturis, the more vacuum in the venturi the farther they open. If you rotate the throttle mechanism completely, only the primary butterflies will open until the vacuum is sufficient.

The Edelbrock carbs have mechanically operated secondary butterflies, when you rotate the throttle mechanism fully, all four butterflies will open. The amount of air drawn through the secondaries is controlled by an air valve above the secondary butterflies. On the Performer series carbs the air valve has a fixed counterweight and the opening rate is not easily adjustable. On the Thunder series carbs the air valve is spring controlled and is easily adjustable.

[spinn]

i guess they are not vacuum operated. thanks for the correction.

is this the one with spring rod down the center, and the doors open 80% ? i thought that was vacuum controlled.. oh well sorry for the confusion.

[rac43]

Originally Posted by onovakind67

Edelbrock describes the secondary operation like this:

A mechanical secondary air velocity valve in Performer Series carbs senses air-flow according to demand and automatically regulates a smooth transition from part throttle to wide-open throttle.

These carbs have mechanical secondary throttles that should open wide when you rotate the linkage all the way.

I guess you all are trying to answer my question but I don't have a Holley, nor do I a have a Performer. I have a Elderbrock Square Bore Thunder carb. The secondaries DO NOT open more than 1/8th inch when the throttle is wide open. I thought someone here with experiance on a Thunder carb could offer me an answer. From the answers above, I now know what a Holley and a Performer card do. Anybody know anything about a Thunder Carb?

[Mr. Wormy]

ONOVAKIND. did answer your question your thunder edelbrock is easily adjustable.look on edelbrock web site. Wormy.

[spinn]

hold that thought

right on , that will explain it

[onovakind67]

Originally Posted by rac43

I guess you all are trying to answer my question but I don't have a Holley, nor do I a have a Performer. I have a Elderbrock Square Bore Thunder carb. The secondaries DO NOT open more than 1/8th inch when the throttle is wide open. I thought someone here with experiance on a Thunder carb could offer me an answer. From the answers above, I now know what a Holley and a Performer card do. Anybody know anything about a Thunder Carb?

The Performer and Thunder series carbs share a lot of features, including mechanical secondary butterflies. The Thunder series isn't a new concept, they're a copy of the Carter AVS carbs that came on the 60's Mopars. I had one on my 68 Roadrunner that I bought new in 1968 after returning from Vietnam. You can see the features here:

http://www.edelbrock.com/automotive/..._features.html

If you read closely you will see the statement that I copied for my earlier reply. If your secondaries don't open fully when you rotate the throttle linkage to its limit, you should investigate the linkage for a problem.

[woodz428]

I'm wondering if you are confusing the air valve butterflies that are above the secondary plate with the secondary plate. You shouldn't be able to see the secondaries unless the air valve is opened. If you are seeing the secondary air valve butterflies only partially open, that is normal. Much like a Holley, it won't open fully unless under load. If you manually hold the air valve open so you can see the secondaries, you can open the throttle fully to see if they are operating correctly(engine off,of course). It is highly unlikely that the secondaries are only opening the little amount you are seeing, it would have been caught at the factory. I suspect you are perceiving the air valve as the secondaries.

[rac43]

Got is fixed! The linkage for the secondaries on the side of the carb had a tiny screw wedged between the linkage and the carb that were keeping the secondaries from opening all the way. A small black screw, no telling where it came from but now the secondaries open all the way under full open throttle. Thanks to all that tried to help with this. Problem solved!