Y-block trips.

R

reddog565

Senior Member
Hi guys! I know I posted this before, but I'm back to having some issues with my trip set up.the issue I've been having all along is I have to run with the choke about halfway closed. My center carb has a manual choke with a power valve. The two outer ones are just there to supply fuel! No power valves, no idle mixture screws. I had the two outer ones redone by the guy in Vero Beach. He did a good job. But, I'm still having the issue of having to run the choke about halfway closed. If I don't do that it will stumble and won't accelerate. I'm almost positive I have no vacuum leaks! So in essence, since I have to run the choke about halfway closed it means I have to give it more fuel.I have a pressure regulator I've read it all the way down to two pounds and all the way up to seven pounds. Right now it's set at about 3 lb. So what's everyone's thought about why I have to continually run the choke? I have about 20 pounds of vacuum at idle !As always, I appreciate the feedback from you guys you all are very intelligent.
Thanks..
 
It sounds like you have a carb. that is somehow partially plugged internally or a vacuum leak somewhere. What is the history on the center carb? Was this set up running good before then suddenly took a turn for the worst? If heads have been surfaced several times there may be a leak there at manifold to head area. Complete gasket kits may have 2 different style intake manifold gaskets. One with smaller ports and one with larger ports. Mistakes can happen. 3 lbs fuel pressure on a Holley 94 is pushing the envelope hard. Are all vacuum ports on the intake plugged including the one in the back? I think I would focus on the center carb. and a possible vacuum leak first.
 
I had the same issue on my '55 Vic...until the Holley stock (supposedly) main jets were replaced with the next larger ones. Ran fine after that.
 
To start with, is your condition only when using the center carb, or when you open up the front and rear carbs ? I'm assuming you have progressive linkage. Going from a 52 to a 54 jet is not enough to make a drastic over rich problem. 52 sounds in the ball park for the center carb if it's from 1939 thru 1953. The later carbs with larger venturi's used different jet sizes ('55 and '56 272 engine).
If the rear carbs have blocked out power systems, then the jets should be larger than #50. Maybe 54 or 55. Just my opinion.
Also, once plugs turn black, they take a little while to change color again. Best to clean or replace them to be accurate on jet changes.


Sal
 
Great input guys! It's progressive linkage.
And the"problem" is only upon initial accelerate ion.
I "inherited" this "issue", when I purchased car.
It's annoying, because I have to constantly adjust
Choke..
 
Have you verified the accelerator pump is functioning properly by peering down the throats of the center carb and seeing streams of gas as you advance the gas pedal linkage from the rest position?
 
Nice fuel squirt! When I posted this
Last time, the "issue of sucking air"
On outboard carbs was brought up.
So, that's when I sent them to Vero
Beach. They were reworked to make
Sure throttle plates are completely
Closed! Correct me if I'm wrong, but
When I close choke some, I'm in effect
"Riching". Giving it more fuel. I've tried
All the usual check's for vacuum leaks.
Either, soapy water, carb. Cleaners.
 
Yes when you close the choke plate it richens the fuel mixture. Scicala has good advice. It is very hard to trouble shoot this type of problem from afar. It still seems to me that there is an internal problem with the center carb, or a vac. leak but that does not seem to be indicated with 20" of vac.. if you could block off the end carbs with block off plates and run only on the center carb. and then get that to work correctly, then go back to the two end carbs. that would be best
 
I still feel the center carb. is somehow partially plugged. Having to run with the choke partially closed will turn plugs black.If using ethenol fuel and storing the car over the winter can create issues. If the outer carbs. needed rebuild the center one probably did also. After rebuilding the two outer carbs. did the car run well for a while then suddenly start running badly? What model carbs. are you running? 7RT)8BA)ECG?? Some of them have a vacuum port for distributor on rear. Sometimes when these carbs. are internally clogged they need to be professionally rebuilt because the carb cleaner we have today is almost like dish wash soap. (useless). Do you know anyone with a good carb. you can borrow just to rule out the carb. issue or try your carb on another running engine?
 
So when the center main jets were increased to 54, did you still need to run with the choke on? I agree the center carb may still have a clogged passage. Do you know anyone who has a smoke machine? That will tell you for sure if you have a vacuum leak somewhere.
 
reddog565 said:
Love your chopped top!! The center carb.
ECG.(good one). Both outers- model # 59
Click to expand...

Thank you....Yes ECG is a good one. That ECG does have a vacuum port on back side. Just want to rule that out. You also may want to drop fuel pressure down to about 2 1/2 pounds.
 
Last edited:
When I changed jet's to #54. It didn't
Help. All it did was make the plugs
Turn black. Any thoughts on a home
Made smoke machine? I don't know
Of anybody around here that messes
With old cars like me.
 
Hi guys! Latest update on trying to find a vacuum leak. I made a smoke machine. This is what I came up with. I taped the center carburetor off, So no smoke would escape. I connected the smoke machine to the port on my manifold. I found smoke coming out of the center carburetor top hat. That's a hole where the accelerator pump lives.I also found smoke coming out of the front carburetor there's a vent tube in it . Found no smoke either on front or back throttle plates. So what's everyone's thought on this? Remember I'm trying to run down a vacuum leak..
Thanks
 
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