Strange clicking when I put the car in gear

[bradartigue]

Little thingy on firewall is there for a reason. Helps prevent pop bang pow on decell. Smoother shifts.
Does not hurt anything. No reason to remove it.
There is no soleniod on carb that trips it to stay open.
Mine on my 72 works wonderfully.

Bear in mind though part of that reason is the way the USA cars were sold - smaller carbs, ignition timing on the lean side. You can tune that decel pop out and a larger carb usually won't do it. Twin carbs almost always do it (whole different set of issues there). I like that pop on the twins.

[majicwrench]

Decell pop bang pow means you are running unburnt fuel thru engine, washing down cylinder walls.
Little thingy is there for a reason. Your choice what to do with it.

[mdrburchette]

I don't get the popping through the exhaust even with my dual 40s. I don't know if I could even install it to work with them.

[bradartigue]

The logic going around this thread is wrong - the thing keeps the fuel flowing on decel (it keeps the throttle locked up just at or above the first progression holes), it does not stop or reduce the fuel flow in any way. When engaged you would be in gear with your foot off the gas, decelerating. Manifold pressure holds the throttle plates open by air passing through the fast idle connection on the carb through the (now open) fast idle capsule on the firewall. After manifold pressure drops to a certain point (which YOU set via a button at about 1600 RPM IIRC) the capsule closes and the throttle linkages drop to their normal idle setting (850 RPM).

If you're going to run the thing I can send you a copy of the how-it-works guide. I scanned it at some point in the past.

So yes, it is there for a reason, that reason being the carbs sized on the USA cars were anemic except in 1974 and 1967. You get a lot more low idle/downward progression control with the larger carbs. Still though you can tune out the pops if you have them with some jetting, mixture tuning, and ignition tuning.

[majicwrench]

With all due respect, the thingy keeps the throttle open to keep the AIR flowing into the intake so it will burn the gas that is getting sucked thru the idle circuit.
When you decellerate, the throttle plates slam shut and the pressure under the plates drops drasticly, sucking for all it's worth on the idle circuit, pulling FUEL into the intake. Without AIR the fuel WILL NOT BURN and ends up washing down the cylinder walls, contaminating the oil, and going bang pop pow in the exhaust when it finally encounters some oxygen.
The thingy holds open the throttle plate so some air can get into the intake, thus burning the fuel, and so the pressure does not drop so drasticly below the throttle plate.
The fuel flows REGARDLESS of the thingy. The thingy only controls the throttle plate. THe thing does NOT keep the fuel flowing on decel as you stated.
Keith

[mdrburchette]

And here I thought it was to keep rpms up a little for smoother shifting and to set the fast idle.

[bradartigue]

With all due respect, the thingy keeps the throttle open to keep the AIR flowing into the intake so it will burn the gas that is getting sucked thru the idle circuit.

I deserve none!! Too many mistakes over the years, like that Alfa I bought last year...geez...

On the inlet of air - carburetors don't work that way. You can't set the throttle to position "x" and get only air. You CAN do that with a fuel injection system. With a carb the throttle always admits both. We're really debating apples and oranges; if you let in the fuel/air mixture on decel the popping goes away as the ignition cycle never stops (thank god they never tried to disable that on decel...)

[bradartigue]

Oh and hey the debate over this stuff is what makes these cars run better. FIAT sure as hell never described anything well enough for understanding.

[majicwrench]

Well said, and yes, apples and oranges.
I am very aware of how a carb works, and what the infamous "thingy" was designed to do. By holding the throttle open a bit, it help insure an air/fuel mixture in the cylinders that will burn in the cylinders, not in the exhaust.

And certainly respect is due.

[bradartigue]

And thus consensus is reached.

Let's now talk about the function of the seat belt interlock device.

Kidding. I don't want to talk about that thing, ever.

[majicwrench]

Oh that would be a riot! Talk about things that needed to be eliminated...

We did kinda hyjack this thread...so sorry.....what was the clicking noise??

[Zippy]

Whew, that was close. Glad you guys worked that out. I would hate to lose more great contributors to this forum. Respect