Zenith Fiddlings

[gmask]

Okay i have blocked the heat riser on the rear carb so that it is not allway sopen and currently the car stalls after warming up for about 5 minutes if I drive to a stopsign and then try to move forward.

Once it gets to normal temp it is fine. I try to wait for it to warm up but it takes too long. Could it be the idle mixture? I didn't really test it? I tried adjusting the choke cover that that has not really helped much.

[ctaylor738]

The best solution is to get the rebuild kits for the heat risers (I got mine from a dealer). The next best might to be to turn the fast idle up a bit to see if you can get past the stalling. This is on the front carb, and you need a mirror to do the adjustment. Should be in the Haynes manual

You have made great progress!

[gmask]

Originally posted by ctaylor738
The best solution is to get the rebuild kits for the heat risers (I got mine from a dealer).

You have made great progress!

How much aprox for the rebuild kit? Can this be done with the manifold attached?

Oh yeah I did play with the fast idle a bit before so it's probably whacky right now. Offhand is clockwise on the fast idle raising the idle or lowering it?

I'm pretty satisfied with my work on the engine and carbs. I do need to retighten the head bolts soon. Do I just loosen each one at a time and then retighten tio the corrct torque in the standard torque pattern. Or do I retorque them each close to spec and then incrementally retighten each in the torque pattern like when installing them?

[240 Ed]

Hey, Hey-Whoa, Whoa!

If you only turn up the idle on the first carb, you will throw off the synchronization of the two, and it will run crappy!

The secret with these two carbs, IMHO, is to adjust both carbs so they react the same.
A simple way to do this;

Disconnect the linkage between the carbs.
Disconnect the linkage between the throttle pedal actuator and the carb linkage.
Now you have each carb isolated, both from each other and from the throttle pedal.
Now adjust the mixture. Set both to 1.5 turns out to start.
Cover the idle-air hole on each in turn and see if the drop in rpms is the same. Adjust until they drop rpms the same ( or as close as possible).
Then adjust the idle speeds. Each carb has one with a star wheel on it.
I would visually set them at the same "thread count", then try to balance them with the same method of covering the idle-air hole.

You can gently rev each carb from idle to see if they respond right away.
Then when they are reacting the same, you can adjust the linkage between the carbs. Adjust so they just fit without changing the set.
THEN adjust the throttle pedal linkage in a similar manner.
THEN you can adjust the whole idle speed up or down with the thumb wheel on the throttle pedal linkage.

The other thing to check. If your thermostat is old and yucky and slow, or stuck open, the engine will NOT warm up quickly, or at all! Car runs like crap.

[ctaylor738]

the kits are kind of pricey - about $60. The issue is getting the shaft unstuck, which usually requires pulling the manifold - a true PITA. I would think that in sunny LA you could get by with the flaps shut.

Actually, the fast idle adjustment is made only on the front carb. It is separate from the balancers and does not affect the synchronization. It opens both carbs.

I believe that clockwise will increase the idle speed.

I have always just re-torqued using the inside-out pattern.

[240 Ed]

NOPE! Sorry Chuck,

If you change the fast idle on the front carb, you WILL upset the balance between the carbs.

You might be confusing the throttle lever adjustment with the front carb idle speed adjuster, and therefore we are talking about the same thing.

Are you talking about the round thunbwheel thingy??? Then yeah.

[240 Ed]

On the flap issue, you don 't need these to operate in LA. Just make sure they are as closed as possible and have someone tack a weld there to keep them closed.
You can't get them to close all the way either, but don't worry.

[ctaylor738]

Ed -

The fast idle adjustment is only on the front carb and uses a screw and a stepped cam. It is completely separate from the balancing adustment and the hot idle stop. It is made with the rod connecting the carbs in place and thus opens both carbs equally. It is the same effect as holding the throttle open a bit with your hand.

[gmask]

Yeah it is the frotn carb only as I have removed the screw from the rear as reccomended in the manual.

BTW I sold the engine out of the parts car to a guy who's gonna stick in a Unimog.. cool!

I noiced something odd or maybe not so odd but different than my car which is that the 71 has a box around the downpipes with what appears to be an outlet for heat to rise into the air filter and aid in warming up the carbs? Maybe I could get this work on the 72 in place of fixing the heat riser flaps?

[ctaylor738]

That would work, but make sure the valve in the air cleaner works so you are not sucking hot air into the engine after it has warmed up.

[240 Ed]

Chuck,

Hmmmm. I guess my '68 is different, sorry!
Mine has the thumb wheel on the linkage, which I thi n k you call the hot idle adjustment.
And both carbs are essentially the same for idle adjustment.

Gmask,

I took my "box" off. On the air cleaner snout, you can wedge the flap open by tucking the lever under the seam of the snout. You will see what I mean when you start messing with it.