Intermediate discharge tubes

[Rob V]

I have a question which I hope doesn't cause too much discontent.
I have 2 4150 main bodies that I wish to add a third circuit to.
My question is.....is there an ideal spot for the tubes?
eg....How far above the throttle plate and in the centre of the throttle bore or to the outer?
Thanks in advance for your help. Rob.

[bigblockmark]

OK, Ill bite. Just curious why you need to do this ans what the whole combo is that requires this.

I run a 4500 1250 dominator with just 2 circuits on a 582 pump gas engine. 3 circuits just made it rich at part throttle and seemed redundant. Just pulling the intermediate air bleeds out of the top was a step in the right direction. So get metering blocks that had the 2 circuit or 3 circuit option. Sometime less is more.

I believe Dambest and Braswell do make 3 circuit 4150 carbs.

[Rob V]

Bigblockmark...Thanks for the reply.
The combo is a SBC small cube 317ci Comp Eliminator style engine with 2x4 4150's
I have 2x BLP Billet bodies but not drilled for the intermediate tubes.
I like a challenge and figure if Braswell, Ray Edwards and others build 4 and 5 circuit carbs for these applications then a 3 circuit deal should be a step in the right direction.
I thought this topic might not be received that well as there is a wealth of information on converting from 3 circuit to 2 circuit but nothing for going the other way.
Again thanks in advance for any help. Rob V

[jmarkaudio]

I reworked a set of 1000 oval blade carbs for a small inch comp engine like yours. They used mini annulars, and the intermediate was not used. In the end picked up about .04 over someone elses 4150 carbs. You do not need an intermediate circuit in your case, changing to a good annular or mini annular booster with the appropriate sized carb will net the best power. The 4 and 5 circuit stuff is an attempt to atomize the fuel better at the expense of a proper fuel curve. Annulars do it without disrupting the fuel curve.

How big are the bodies you have?

[Rob V]

jmarkaudio, Thanks for the reply.
My venturi size is 1.405" with Braswell downleg boosters.
Throttle size is 1.750"
It was my intention to add the intermediate tubes to these bodies and test on the dyno.
It is not that I don't believe you guys.....I just like to see it for myself.
I was hoping for an ideal location for the tubes to enter the venturi then as a worst case I can block off the circuit if it is untunable.
Some people are stubborn and hard headed and need to see things for themselves...... I am one of those people.
I do appreciate your advice though and look forward to yours and others replys
Thanks Rob.

[mike laws]

[Rob V]

Thanks for the reply Mike
What are your thoughts on their placement horizontally?
Aim for centre of the bore or are they better placed to the outside of centre?
Thanks again for the advice Rob

[mike laws]

[Rob V]

Mike....Thanks for taking the time to reply.
Yes... I have 2 sets of BLP metering blocks to try....both 3 circuit.
I am guessing the hardest part of drilling for the tubes will be calculating the downward angle to end up in the correct location.
I was going to aim for 5/16 - 3/8 up from the bottom of the body.
Any advice on installing the tubes?
My thoughts were an interference fit and green loctite, am I on the right path?
Next time I order my main bodies from BLP I will remember to ask for the tubes to be drilled.

Thanks for you advice. Rob

[mike laws]