Originally posted by StudeRich
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Not sure what difference the heat riser would make in a hot engine bay when it's 90+ degrees outside, but it's a thought. I can try reconnecting the spring and seeing what happens if the new gasket doesn't have any effect. A pressure regulator is something I might look into as well. -
It's the stock setup for a 1960 Lark VI: 170ci flat-head six, Carter AS carburetor and a mechanical fuel pump. I can try adding photos once I've got it all back together.Originally posted by az64stude View PostComment
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Does it have electric wipers and no vacuum boost fuel pump? The only way I can figure cooling the pump could make a difference would be a vacuum leak at pump when pumps hot.Comment
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There's nothing on the car the runs on vacuum; manual brakes, manual steering, electric wipers. The pump is the normal cam actuated variety. But as I said, I traced a vacuum leak at the manifold gasket so we'll have to wait and see if the new gasket corrects the issue. I won't have it put back together for a few days... Just waiting on a second valve chamber baffle.Originally posted by kxet View PostComment
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Since the OP said the carb had been rebuilt, I would concentrate there. These old carbs can be finicky. Linkages wear and come out of adjustment, and that's true if the rebuild wasn't done right. I think the guys suggesting the choke fast idle are on the right track. The fast idle sets the throttle plate open a tad to help with a cold start. It could be the fast idle cam and or linkage is binding. So after driving a bit, the throttle plate is staying open. That would give high rpm's on a hot start. My two Honest Abe's.Comment
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If you have the intake manifold removed check it for flat with a straight edge, it may need to be resurfaced.Comment
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This is one I would like to see in person. My first thought when reading the initial post was the linkage binding, or the fast idle cam coming back up some way.
The real head scratcher here is pouring cold water on the fuel pump apparently solves the problem. Running the different analyses through my little pea brain is giving me a headache.
Any chance that just opening the hood results in normal idle on re-start? Even assuming Jack's posit that the fuel in the bowl is heated enough to raise the float level, one would expect that increase in fuel supply to lug the engine down without a corresponding increase in air flow some where. I am really doubting there are two separate causes happening simultaneously to create more fuel and more air. I also can't imagine (unless the fuel supply is already way over rich) that a mysterious vacuum leak is making it idle fast on hot re-start. Most vac leaks get better as the parts expand under heat, rather than worse. Besides, if a vac leak is causing this, how would you explain cold water on the fuel pump curing the problem?
Did it do the same thing when the electric pump was on there? I have electric fuel pumps on three vehicles with carbs, and have not issues with either of them. Using a fluid cooler of some sort may solve this problem, but you won't know without installing one.Comment
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Next chance you get look closely at your carb linkage with hot engine and no water on pump.especially the fast idle cam. when installing manifold gasket a THIN skin of ultra copper silicone will help the seal and wont burn out.if this problem goes away by it self i will tear my hair out! Luck DoofusComment
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Lynn, when an engine is operating at a given temperature say 170 - 190 range and is shut off the block temperature will rise substantially possibly to boiling point for a short time and then start to cool back down again. If the intake manifold does have some irregularities and is prone to leaking while at this increased temperature and the engine is restarted while still hot a slight vacuum leak could develop resulting in a temporary lean mixture and an increase in idle speed. I have half dozen manifolds in my supply, intake and exhaust and all of them were not flat and required resurfacing, some were .003 - .005 and the worst was .022. With the age of the engines and the number of times these manifolds have been on and off, the probabilities of a non true surface is relatively high and hence vacuum leaks become an inherent issue.Comment
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Ok, replaced the manifold and exhaust flange gaskets, verified heat riser works, installed valve chamber baffles, new inspection cover gaskets and filter element for crankcase breather. I also double checked the carburetor adjustments for fast idle and unloader and the float.
So...
The engine now runs much more smoothly, and the high idle for hot starts is corrected. Now I've got cold starting problems:
It took me fifteen minutes of trying to get my car started this morning and it's only 60 degrees Fahrenheit. The choke is set to the leanest mark, but I still get flooding if I start per the manual (completely press the accelerator once and then turn the engine over). Even if I hold the throttle open, to disable the choke, the engine takes forever to start, and runs rough for about twenty seconds before clearing up. If I take the air filter off, and adjust the choke plate manually, I can hold it completely open and there is no change in the idle... Not sure what to make of that. I would think I could just not use the choke ever then, and simply set the "choke" to get fast idle on startup, but that just makes me think the jetting is way WAY off.
To eliminate the variables:
New plugs
New cables
New coil
New condenser
New batteryComment
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If the engine runs smoothly and pulls fine, it's unlikely jetting is the cold starting problem. Jetting is the least likely cause of the problem. It's rare to find a 1-bbl where jets have been changed. Your suggestion to work with the choke adjustments is the best science. Once that's as it should be, then if curious, have someone with a wideband O2 sensor and meter tell you what your idle and cruse air/fuel ratios are.Originally posted by MrBulldops View Post
Excellent procedure. The majority of carburetor problems are cured by a completely new ignition system. The Champion is especially prone to plug wire problems inside the metal loom which holds all the plug wires tight together.To eliminate the variables:
New plugs
New cables
New coil
New condenser
New battery
jack vinesPackardV8Comment
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