'73 Intake Manifold & vacuum

[BadDog]

I have '72 carbs on my '73, and I assume i have a '73 intake manifold (smug stuff is long gone)... there are a few (3? 2 behind each carb?) vacuum attachment points that aren't plugged on my manifold, with 1 being used by my distrib's vacuum advance. Am I right in assuming these should be plugged? And if so, what should I use? Any other ones that I should check for? My engine runs great once warmed up now that it's tuned up a little, but still runs like crap when cold...

[2ManyZs]

Plug em if you aren't using them. Most if not all can be plugged off with pipe plugs after you remove the hose nipples. Some of them can be a PITA to get out though. If you can't get them out you could try using vaccuum plugs from the auto parts store but it would be better to put pipe plugs in so you don't have any vaccuum leaks. Just go to the hardware store and pick up a couple of each size 3/8 and 1/4 in pipe plugs and plug away.

[BadDog]

I actually have just the holes there now... here's a pic (from my "choke issues" post, but with new circles drawn ).

And oops, the distributor advance isn't hooked up there, it's on the carb...

I'm guessing the "leaks" would contribute to rough running when the engine is cold, as the air is coming in behind the throttle plate...

I *think* I might have some pipes that go in those holes, I just received a box containing the original carbs, smog crap, A/C & heater parts (what a mess).

And do you like the holes cut in my air cleaner? I guess that's a "kludge" to get around the vacuum-operated door for the "heat riser"(?) at the bottom of the air cleaner... as Homer Simpson would say "those are *speed holes*"

BTW, disregard the routing of my choke cables... that has been corrected

[2ManyZs]

I don't remember where they used to go, and I also don't remember there being so many. I remember there being only two. Yeah, they need to be plugged, just not sure the best and easiest way. I guess you could try the old JB Weld in them, or tap them out for a small machine screw or use a self tapping screw, but then you might have to take off the carbs to make sure no cuttings get in the intake.

[BadDog]

I think I'll try something temporary first, like duct tape to see if it'll help the cold performance problem, then JB Weld them (I really gotta get some of that stuff) or find the pipe fitting that went in the holes, then block them off. Thanks!

[Daniel]

Although Z's are cold natured .There is a foil hose that connects to the heat shield then the air cleaner.It sucks hot air off the exhaust manifold when cold.From your photo I see that missing. Daniel

[BadDog]

Yep, and so is whatever vacuum hose operates that little door at the bottom of the air cleaner...

[visionary]

Baddog, I have to go to a meeting, but when I get back I will detail your manifold for you. I also have '72 SU carbs on my '73 and have disconnected all the smog, etc.. I also removed the "box" aircleaner and replaced with individual aircleaners. these cars are not cold running cars, especially after the smog system is removed or is in poor condition. It is a must for all of the holes in the manifold to be plugged for several reasons beyond engine performance...

Be back soon....

Keith

[Daniel]

I would install the hose and prop the door open.My 72 air cleaner has no door,It's always wide open.I do have a flap on the front I can close but I rarely do. Daniel p.s. In your photo the carb on the left has a metal pipe attached to the overflow on the bowl of the carb.The right is rubber and attached to the air cleaner as both are on my car.My question is where does that metal pipe go?

[BadDog]

The "metal" pipe on the left is actually a clear plastic tube that has yellowed ... it leads to the air cleaner also.

And when my timing was *way* off, and the car dieseled when shut off, I found that gas shoots straight out the top of the fuel bowl, 5 feet into the air and all over your car At least I took those hoses off with the air cleaner assembly, and gas didn't shoot out the hose onto my exhaust manifold :eek:

Other evidence of poor tune can be seen in the lower left side of the picture, on the inside fender opposite the mouth of the carb: burn marks!

[visionary]

Baddog,

You have a '73 manifold with '72 or earlier SU carbs.

The two holes you have circled on the front manifold are not holes per say. They are screw threads that mounted the idle speed hose crossover tube for the flattop hitachi's that are no longer there. There should be two identical thread holes on the rear manifold. If the cosmetics bother you, simply fill the threads with appropriate screws.

The two nipples that are coming out of the manifold next to the thread holes were for vacume hoses connected to the Throttle opener control valve that was linked to the flattops to allow air-fuel mixture into the engine to minimize the unburned hydrocarbons in the exhaust. These should always remain pluged. I would put pipe plugs with teflon tape on them to ensure you don't get a vacume leak. Any leak here will affect your vacume advance to the disrtibutor dramatically.

The "hole" on the equalizer tube I cannot see very well, but if it isn't a mounting or thread hole plug it because as you can see, the vacume boost for your brake master cylinder comes from the equalizer tupe and good pressure here ensures your brake master cylinder booster doesn't fail.

The breather tubes from your float bowls you can join with a "T" fitting and then send to the air cleaner or if you decide to run individual air cleaners you can run them into the appropriate one. Do not plug these as it will cause the float bowls to overflow and gas will run out of the front of your carbs.

The "winter" setting on the stock air box is forward or closed on the intake baffle and the "summer" setting in rearward or open.

I have elimiated all of these issues by using individual cleaners, putting a valve cover breather filter instead of the hose and disconnecting the hose to the flow guide valve from the carburetor.

You also need to check the PCV valve from the crankcase breather hose....

good luck

Keith

[BadDog]

Wow Keith, thanks for all the info... it's such a nice here in NY state I actually drove the car into work this morning for the first time (35 miles or so). She took about 5 miles or so to warm up, even though it was about 70 F. Not seeing your post first, I found screws to go in those 4 holes, and of course, it didn't make a lick of difference .

I'll make sure that those two nipples towards the front are sealed tight... I think the hole on the balance tube is just a mounting point, but I'll look at it again more closely. Maybe I'll also get some clamps to make sure there's no possibility of a leak on the distrib vacuum advance... If the PCV valve is on the valve cover end of the crancase breather hose, then I don't think I have one