3x2 idle/adjustment issue/vacuum

[Michael F.]

several questions....should I have a strong suction when I place my had over one of the end carbs (gas lines not hooked up to end carbs) seems to me I must have a vac leak as timing too advanced and idle must be high or car will die....it is getting fuel to center carb and squirters have good stream. Note: the rear carb has a very strong suction is that normal? what would happen if I didn't have center carb vac line hooked in with end carbs?
Would not having fuel hooked up to the front and rear carb cause any idle/running issues? should I be able to use a hand vac pump and hold open or open the secondary carbs throttle blades when not running? carbs have been thru and everything appears good. WHAT AM I MISSING?

[Timothy B.]

Re: 3x2 idle/adjustment issue/vacuum

Michael,

My thought is there is a large vacuum leak in the end carburetors and you should not have a strong vacuum signal at fast idle. That is probably why the engine does not idle, the problem could be incorrect gaskets or a sealing surface leaking.

Who did the rebuild on the carburetors.

[Robert M.]

Re: 3x2 idle/adjustment issue/vacuum

Hi Mike;

Try disconnecting the linkage from the center to the end carburetors, if that linkage is not set properly per the AIM one or both of the end unit throttle plates may be slightly open.

[Michael F.]

Re: 3x2 idle/adjustment issue/vacuum

I have the end carbs linkage disconnected as well as the fuel lines. I had a leak on the front carb bowl and the center carb bowl. I rebuilt carbs several years ago with holley kits, just to note that I have been doing mechanical work on my cars for over 30 years and did take rear apart and put in new gaskets and such but still does it. I felt it was vac leak also but ....

[Stuart F.]

Re: 3x2 idle/adjustment issue/vacuum

What part do the vacuum dash pots play in this. I'm referring to the vacuum diaphragms on the end carbs that actually open them at low vacuum (WOT). I know they have return springs in them as well. My interest is due to having recently rebuilt a set for my son (put kits in them) as they too were leaking. I had never touched a Holley Tri-power before and, by choice, prefer to stay away from Holley carbs altogether. But in this case it was necessary. His set is on a 69 L-89. The kits came w/o any instructions, pictures, or parts lists so I was flying blind using my basic common sense (which isn't quite enough with Holley's).

His car runs like a bear every where and any time except when you come to a stop light or want to shut it off. It stalls and diesels, and I know I can fix these problems given enough time and research, but my son is an airline pilot and our schedules rarely are compatible. I want him to get an AIM, but it would help if someone could point me to where I can download the sections that I need.

Stu Fox

[Michael F.]

Re: 3x2 idle/adjustment issue/vacuum

stu, I think that is where my vac leaks are....I took off back carb and bolted a plate over the holes and it improved alot, on to front and I am sure the pod with vac diaphram is leaking so I will replace both and find out. lastly I can't get the timing to where it needs to be, may be my dist is off a tooth and will check for that also. if I turn dist to take out advance it won't run...more testing tonight. I think I am just getting old and forgetting everything that was second nature to me back in the day.....

[Joe R.]

Re: 3x2 idle/adjustment issue/vacuum

Michael,

Don't forget that the two end base gaskets are upside down compared to the center carb base gasket.
Sounds like you have more problems than just a gasket but the gaskets will cause a huge vaccum leak.
The end carbs should have no suction at idle when you hold your hand over the center.

JR

[Timothy B.]

Re: 3x2 idle/adjustment issue/vacuum

Michael,

I THINK the end carburetors have a idle circuit to keep the fuel fresh so there will be a small vacuum pull through the transfer slot or that little hole under it. I would pay attention to the correct base gasket as stated in the post above plus make sure the carburetor metering plate and throttle body (both sides) are flat.

[Michael F.]

Re: 3x2 idle/adjustment issue/vacuum

I replaced the base gaskets tonight but misplaced my fuel line so will have to find it. I think my other problem may be a timing issue but will find out after fuel lines back on for all 3 carbs and I crank it up...will update next week.