360 Rough Acceleration

BDR529

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Again with hoping I explain this well enough. My '75 Monaco has a 360 4-Barrel in it. When i'm at a dead stop, the car idles great, as soon as I put it into drive and step on the accelerator (gradually) the car will start to go, and then bog down a little bit, and then start going again just fine. Once it's up to speed I don't notice any issues. I took it over to my mechanic to let him take a look and we did some troubleshooting. Once moving along at a decent speed (35 mph) I would stomp on the gas, and the car would react great. He said this proved that the accelerator pump in the carb was working fine. Then e started playing with timing and vacuum. All he documentation I have shows that the timing is supposed to be set at 8 degrees. When we checked it, it was up at 15 degrees! However, once we bumped it down to 8, the car would idle ok, but it didn't sound as good as with the timing up at 15, and the problem with the acceleration got worse. Then he checked the vacuum with a gauge and even with the timing set at 15 the vacuum pressure was low. Tomorrow I'm going to go over and we're going to tear the carburetor apart and look at it's insides. One thing I noticed in one of his books about the carburetor was that it supposedly has a a stage pump inside. one possibility he mentioned that I thought made sense might be that one of the "stages" isn't operating correctly. He also said that if we didn't find anything there that we cold check out the timing chain, just to be safe. Anyone here have any ideas about what could be going on? Just looking for any advice.
 
I'm assuming your Monaco has a Thermoquad. They are excellent carbs, but can be tricky until you understand how they work.
 
The first thing I would do is make sure the accelerator pump is working correctly.

You can check that with the engine shut down, removing the air cleaner, opening the choke butterfly, and while looking inside move the throttle lever back watching the accelerator ''squirt'' nozzles. It should be a smooth and even stream of fuel to the primary's.
 
Your factory timing specs are given for sea level settings, with added elevation you will increase the amount of advance. Also be sure you are disconnecting your vacuum advance to check the timing. You could also change the setting on the accellerator pump lever to a hole closer to the fulcrum to increase the rate of fuel, and be sure the initial setting height of the pump shaft is correct at closed throttle. Your pump could be getting a late start.

Timing chain???... If your timing chain jumped a tooth, you would have to advance the timing just to make it run, and it wouldn't pull a sick hoe of a p**s pot.
 
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I'm sitting at about 1100 feet, so that shouldn't make too much of a difference. We did ensure to plug the timing advance as well. Thanks for all of the info, definitely gave me some great ideas to check out today!
 
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