Building a holley tri carb set up

luvmyclassics

luvmyclassics

Senior Member
The more I read the more I am confused

I have a 239 V8 with a mild cam. Would like to have a tri carb on it for show and not performance.

Looking at a Edelbrock intake with Holley 8BA carbs.

Need help with power valve selection, jet size, and idle circuits.
 
If you want show and not performance block off the outer 2 carbs. It will run on the center like stock and be much easier to tune.
 
luvmyclassics said:
The more I read the more I am confused

I have a 239 V8 with a mild cam. Would like to have a tri carb on it for show and not performance.

Looking at a Edelbrock intake with Holley 8BA carbs.

Need help with power valve selection, jet size, and idle circuits.
Click to expand...

Know someone who did the same thing ( two outer blocked off, running on center) The carb settings were pretty much stock. Get it running and then determine what's required, if anything.
 
Edelbrock 1109 (for 8BA) 3x2 manifold is a good choice. Best price is Amazon. It will accept 3 Ford/Holley 94 carbs without grinding off the front of the carbs. Also GM CS130 alternator will fit in front of them without modification to the carbs (offset alternator mount not required). Don't wimp out - get progressive linkage and use all 3 carbs. It is a little more work, but well worth it when you get them right (satisfaction). Good luck.,...jack

Note: outer carbs do not have to open all the way. About 75% might work mighty fine.
 
Last edited:
I've got my outers blocked off with Uncle Max's ultra thin plates, hard to tell they are there, at least till I get the engine break in period over. Then I'll open them up!
 
jack orchard said:
Edelbrock 1109 (for 8BA) 3x2 manifold is a good choice. Best price is Amazon. It will accept 3 Ford/Holley 94 carbs without grinding off the front of the carbs. Also GM CS130 alternator will fit in front of them without modification to the carbs (offset alternator mount not required). Don't wimp out - get progressive linkage and use all 3 carbs. It is a little more work, but well worth it when you get them right (satisfaction). Good luck.,...jack

Note: outer carbs do not have to open all the way. About 75% might work mighty fine.
Click to expand...

Good advice from Jack Orchard. If you decide to go to a real tri power set up, then do not block off the power systems in any of the 3 carbs. If a mild cam and the manifold vacuum is a little lower than stock, then you might need to go to a lower vacuum rated power valve. For example if you're warm idle manifold vacuum is 15" you would want to use a 7.5" power valve. (about half the manifold vacuum).

Stay with stock main jets until you run it and see if others are needed.

Also on the front and rear carbs, just turn in the idle adjustment mixture screws until they are seated (not real tight) and turn back the RPM screw for idle until the plates are seated, then out just enough to keep the plates from sticking in the bore. This way you idle only on the center carb and still have idle progression holes in the end carbs to better avoid a hesitation/stumble when you open them up.

Sal
 
I go for blocking off the end 2 carbs. I just went through setting up a prgtessive linkage system on a built 294ci engine, and after much putzing around, great expense and the help, of Uncle Max. It runs great. Use junk caarbs on the ends with NO GAS. A rich running engine kills the cylinder walls and the list goes on. Read JWL's book an you'll find out, there is little or no benifit to running More carbs on a stock engine. I have a friend that has been running a 284ci Ardun engine on ONE 97 for the past 10 years. The other two just look nice. Good luck.
 
luv,
#1 use Strombergs if you can because these carbs don't rely on vacuum oper-
ated power circuits. They are just easier to tune.
If you stay with 94's block the PV's in the end carbs, use 5.5 PV in the
center.
51 jets in the center and 49's in the end carbs. This will get you started,then
read the plugs and/or get A/F readings under actual driving conditions and develop
jet sizes from there.
This is only my opinion based on real world experience. I'm in complete agree-
ment with Scicalas' advice regarding the idle circuit and idle speed adjustment.
Charlie ny
 
I may have been too harsh, I just din't know why you would want to do this to a stock engine. If you don't get it right, you can do allot of harm.
 
Charlie gave us advice on progressive linkage set up and provided a 5.5 valve for our 284 engine. All problems eliminated.Thanks Geoff.
 
I agree with Ol' Ron here, Ive seen many cylinders washed from guys putting too much fuel to a stock motor just for looks.
 
I could never get a multiple carb set up to work correctly. I finally asked myself the question: Do I want to fiddle with this set up all the time or drive and enjoy the truck? I went back to a single 94 on a stock engine and have not had a problem since.
 
Charlie and Scicala have it right. There is no idle jet change for the 94 or the 97. By doing what they say you are leaning the idle. The adjustment screws are all you have.
 
If I was to block off the two end carbs what is the preferred method. Plugging the two end fuel lines or tracing out gasket material with no openings to the intake manifold on end carbs? Or both. To make it authentic looking you'd need to see the three fuel lines and the tri-power fuel block.
 
You must log in or register to reply here.
Back
Top