Holley Carbs

[Edm]

I am trying to learn more about carburetors and wondering if someone can help. Whats the difference between a spread bore and square bore?
The parts numbers are also confusing. With the 650 cfm whats the difference between the 4777and the 4150? Those seem to be the most common. Is the 4777 just a street version of the 4150? What difference would it be if you were to put in the better secondary springs in and a better power valve?

[andre]

Spread bore: 2 small butterflies and 2 large one like a quadrajet.

Square bore: 4 equal butterflies.

4777: is a carb number

4150: is a carb series which included 4776, 4777, 4778 and so on.

Power valve have to work with vacuum at idle, has to be about 2 under idle vaccuum. If you have a 6.5 vacuum reading at idle, you put a 4.5 power valve and you should be fine.

For your spring for secondary, I assume you are talking of a vacuum operated secondary carb, a stiffer spring will make the secondary open slower, which in some cases will get rid of a dead spot, or on the other side can become a lack of instant acceleration.

Hope it helped

André

[Edm]

Thank you, that helps a lot. Now what about the numbers similar to 80541-1? Is that just another series of carbs? Or would that be one particular carb?

[dnsno]

?

You ever heard of a three barrel holly, Andre?

[andre]

http://www.jalopyjournal.com/forum/s...=189863&page=2

There is a picture of one of those 3 barrels there.

I heard of those but never had one in my hands.

80541-1: carb part number.