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  #1  
Old 05-24-2007, 02:29 AM
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Join Date: Sep 2006
Posts: 55
two zenith ?'s

Hello,

Now that I've got my carbs apart and on the bench, I've got a few questions....

1st, of the two barrels, I can move the left one (standing at the front of the engine looking aft) with the throttle actuating lever. The right one barely moves. Looks like this has something to do with the secondary diaphragm? Is it supposed to open fully? If yes, how do I move it safely?

2nd, My local indy garage postulated that a stuck heat riser butterfly may have caused warping in the carb body and suggested grinding the mating surfaces flat. I have seen that advice repeated in this forum as well. I thought this would be a bit more straight forward, but in looking at the carbs, am I going for the surface that has the mounting studs in it? necessitating removal of the studs and the fairly stuck on insulator plate? or is it a different surface I should be concerned with. Should I do the top of the intake mani as well?

a bit scary being this far into a carburettor.......

Thanks for any guidance.

Marc
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  #2  
Old 05-24-2007, 12:51 PM
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Posts: 758
Marc:

As you lean over the carbs on the engine from the PS fender, the barrel nearest you is the primary and its throttle is actuated by the lever. The rear, or secondary, is actuated by the diaphragm and its attached actuation rod. From your description, yes, the left one is the primary and the right one is secondary.

Stuck heat risers could warp the carb body. This is usually the soft aluminum body of the carb, but could also be the iron throttle body. You check each carb surface with a metal straight edge to see whether the surface is warped. Remember, the gaskets are usually able to accomodate some minor surface imperfections. Machining should be a last resort, and would likely be difficult to do anyway. Usually carb surfaces are trued by fixing a sheet of emery paper, 180-240 grit, maybe rougher, to a sheet of plate glass. Then you carefully abrade the whole flat machined surface against the flat paper until it is even.

You should consider that the top is a thin casting while the man body is complex and more bulky. Therefore, even with some significant irregularity, a careful and even tightening of the body screws against fresh gaskets can usually seal vacuum leaks. Now, to check true in an easy way: with no gaskets between the parts, simply fit them back together and see how the bare metal surfaces fit against each other. Any fatal flaws will be obvious, because the gap will be greater than the thickness of the gaskets.

Carefully clean all the parts, blow out the passages with air, check the surfaces for true fit, assemble the internals, check float heights and adjust with a spacer/sealng washer (use only one, they are available in different thicknesses from 0.5mm to 2.0mm, usually the standard washer is OK) at the needle valve, and if things look good, button'er up with fresh gaskets. Your biggest headache will be adjusting everything once it is back on the car. Lots of great info on this site for adjusting and trouble shooting, tools, etc.

With the carbs off, this is a good time to free up the heat risers, or fix them closed if you live in a temperate clmate and don't mind a possible cranky motor when it is warming up. Heat risers can be a PITA in these motors.

Tip: Always wait for the motor to cool before removing the carb screws...the warping potential will be minimized.

Best of luck,

230/8
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  #3  
Old 05-24-2007, 05:20 PM
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I agree with all 230/8 said. Make sure that the vac. line leading to the secondary diaphram is free from build up. The passage is small and the need for vac. to move the diaphram is high. You may need poke with toothpick and cleaner (dont poke anything else like jets). There is a post where I detailed how to modify the INAT secondary to ensure that it opens every time. You may want to consider doing that while you have them apart.
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  #4  
Old 05-24-2007, 06:10 PM
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excellent! But Im still not sure if the butterfly for the secondary is supposed to be fixed??( I kinda doubt it but.....) even moving the secondary rod that controls it will only make it wiggle, not open.

Should I dissassemble that 'middle' part of the carb, ie between the part with the bowl and where it mates to the manifold? The upper surface of this is what would require surfacing?


I should have done the heat risers when I had the manifoldsoff, now it looks a bit tough to get to with out removing them, is it possible still?

Sorry for the questions, but I'd rather do it slowly and right then rush through and do it over....

Marc
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  #5  
Old 05-24-2007, 06:46 PM
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Marc:

There is a rod connecting the diaphragm to the secondary linkage. Simply remove the ball end from the linkage and try to rotate the linkage to confirm the butterfly in the throttle body moves freely. It should.

The heat risers can be freed on the car, and if you have the carb off you should have good access to them. Go to the Dodge/Chrysler dealer and ask the parts man for for a spray can of their manifold heat valve lube. It contains solvents and a graphite in suspension that will penetrate the shafts to free them up. You can carefully wiggle the counter weights to get them loose and then rotate them back and forth with plenty of the heat valve spray lube. It is tedious, but will work. Use this spray, it will not gum things up when heated. Keep using it regularly after you have freed the valves. I give mine a blast every time I check the oil.

If you have dipped the carbs to clean them, then you should have separated all the main pieces to do so. The throttle body is screwed to the metering body and with the joining surface sealed by a by a fat gasket. Your kit should include this. There are two very thick heat insulators on each carb and gaskets for them. A heat shield separates these insulators.

You know, Marc, you should consider the CD ROM manual. It is only $20. The 114 series manual has all the meaty carb data in it, and the 108 manual also has data for older models, some similar to the stuff in the 114 manual. This will be very valuable to you. If you have not already been referred here, check the Jaimie Kop site for some zenith manual data.

http://www.jaimekop.com/


230/8
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  #6  
Old 05-24-2007, 07:31 PM
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Ive been religously looking at the Jamie Kopp manual. Its a great help.

I got the throttle body and metering body (thanks, didnt know the proper names) apart, cleaned and checked surfaces and all looks good and straight.

Indeed, secondary butterfly does move with the rod disconnected.

turning the corner, going back together now!
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  #7  
Old 05-24-2007, 08:57 PM
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Ok, so with throttle and metering body back together, secondary diaphragm replaced, Secondary butterfly doesn't move again. Also vacuum test ie pushing up diaphragm rod, plugging the two holes in the barrels and letting go, rod still comes back down. I thought it was supposed to hold pressure and stay up? sounds like its pumping though...

Last edited by Neubie; 05-24-2007 at 08:59 PM. Reason: more info
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  #8  
Old 05-25-2007, 01:59 PM
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Sounds like there is a leak.

230/8
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