VancouverL71

I am working my way through getting my holley tripower operational on my 1969 big block and have a couple quick questions as I work my way through it.

1. I get the car all happy starting well and running and then go back a couple of hours later when its cold, still no problem. Then I leave it for two days and it seams that that fuel has completely disappeared out of the float bowl. Any ideas? Eventually I get it running again but the accelerator pump stops giving the car a good shot and the bowl seems to have emptied. Nothing seems damp around the carb.??
Any ideas what to change out. I have now had the carbs off/on 3 times in the last week.

2. Choke on holley
Can someone explain how to set up this little tab that sits next to the green thing (see pic) I assume it has something to do with the engine kicking down to a lower RPM on warm up but it doesn't seem to do anything.

babbah

1. The Center Carb bowl should store fuel for at least a week, or longer. I would check to see if when parked the fuel is dumping into the engine.
If you don't see anything damp around the carb throttle shafts your issue is internal to the carb.
Or your issue may just be evaporation. The ethanol fuels tend to evaporate more quickly than the non ethanol blends.
2. That metal "tang" with the slot in it is to limit the fast idle and choke setting for initial cold starting. It's a mechanical adjustment and you can bend it in to provide the "stop" to the plastic choke cam.

VancouverL71

Thanks so much babbah,
re: fuel disappearing, i have been guilty of reusing the same base gaskets so I will order a new set and try to keep this float bowl sealed once and for all.
re "Tang" very much appreciated,,,, your help once again has be great. I will try to adjust it and let you know the results.

One last think since the carbs are sitting on a pretty expensive original aluminum manifold,, I have not been torquing the bolts but just purchased a torque wrench. Do you happen to know the specs to torque the carb bolts down onto the aluminium manifold?
Maybe this would help with float bowl leaks??

Thanks, Pete

babbah

You're welcome Pete.
1. The spec for the carb mounting bolts are:
Carburetor Nuts 5/16"-24 12 ft. lbs.
Note: I NEVER torque carb mounting bolts down, especially on a aluminum intake such as ours.
I guess since I've rebuilt the 3x2 carbs a zillion times over the past 49 years, I simply hand tighten them with a socket wrench. I periodically check them to make sure they are still tight.
If they are not tight the carb base plates can and will warp.
2. For your intake manifold bolts they call for 35ft.lbs. and must be done in GM specified sequence.
And yes, regarding the slotted tang and green plastic choke cam, that is used when the engine is cold and you first press the gas pedal to set your initial choke/ fast idle setting.
More detail can be found in your chassis manual if you have one.
3. I am assuming that your BB idles fine after it warms up, yes? And your only issue seems to be that after a few days your center carb bowl is empty? that's very strange. Mine go dry in about a month being not used, which I think is normal.
I'm not sure if your base gaskets would have anything to do with your problem. doesn't seem likely.
It would make more sense if you saw some external visible fuel leaks, but you say you don't.
So keep me posted on that one? What type of fuel do you run? E10? or ??
PS-Tri Powers rule!

pltmgr

Do you see any leaks inside the after engine shutoff? Gas fumes coming up from manifold? Is the power valve tight and the gasket on perfectly?

VancouverL71

Well I finally got back to my tri power babbah.

Good news on centre carb. I replaced the base gasket and put a new needle valve in the float bowl. Car now starts and runs fine even after sitting for several days. Yeah

New issue which I found, when I disconnect the two outside carbs and open either of them up at idle, the back one accelerates the engine as I would expect. The front carb nearly instantly kills the engine.

Would anyone know if this would be too much fuel or not enough fuel.
Maybe I need to pull the front carb apart now. GRRR, I have had these things on and off too many times already! I need to move onto my other 100 issues I am dealing with.

RE fuel, the best we have here is 94 octane with no ethanol, thats what I run but saying I run that is a bit misleading. The car has been out of the shop garage once and all I got was another 10 things I needed to do.

Anyhow, its coming slowly

Thanks, Pete

MelWff

have you checked the float levels of the front and back carb and are they set the same. The front and back are vacuum operated and have no accelerator pump and normally wouldnt open till you have a strong vacuum signal coming from the center carburetor. You simply do not have a strong air flow through the front and rear at idle so not enough fuel maybe drawn causing a lean condition and stall. Under normal conditions are you having a lack of power problem?

VancouverL71

Thanks Mel,
I realize the vacuum operates the two outside carbs. I will take off the front carb tomorrow and see if it is set up properly. Seems strange that the engine quits as soon as I manually open the front carb so I was just curious if it was too much or too little fuel. I will change the float bowl needle valve and new gaskets and see what happens.

Thanks, Pete

MelWff

why cannt you just remove the two sight plugs on the front and rear carb with the engine running to compare float levels?

Solid LT1

The slot in the metal tab that rests against the fast idle cam is used to set fast idle speed by inserting a screwdriver into the slot and bending the tab into the plastic cam to set the cold fast idle speed, after the choke pull off has activated the cam falls away discontinuing the fast idle speed. It isn't uncommon for the fuel to boil out of a Holley float bowl on a HP Chevy motor due to latent engine heat. That is one of the reasons why there was a service package heat insulator made for the 4BBL Holley carbs. This is just one of the many "joys" associated with owning a HP Chevy. Luckily one of the joys is when the throttle is floored that more than makes il for some of the others.....

VancouverL71

Thanks solid LT1. I think I can set up the choke as you mentioned.

With respect to the float bowl. turns out the needle valve was stuck shut so now working as it should. I took time to clean out the carb well after having 15 year old fuel gumming up carb etc.

Carbs finally seem to be running as they should and starting the car easily and reliably. Next up, windshield washers! Not a single windshield washer item left on the car, this should be fun!
Thanks guys for the help.