jackson 63

I have a 63 SWC 340hp with a Carter AFB. Engine starts ok when its cold, but it starts hard when its hot. When it does start I get a lot of smoke and fuel smell. I had the carb rebuilt last winter because of this problem but that was no help. The engine itself does not run abnormally hot. Around 170 deg.

65 vette dude

Sounds like you might have percolation, or starter drag. Next time it won't start, take off your air cleaner, and look down the throat of the carb for fuel boiling or leaking(floats adjusted too high). If you have an IR gun shoot the bowls, they should be under 140º. Starter drag is when you try to start a hot motor, the motor turns over very slowly, almost like the battery is bad. Some say it's the heat on the solenoid, and or the starter......some say it's a bad battery, or ground. Whatever the cause, the problem goes away when the motor is cold. I had this problem when I was a kid, and replacing the starter and solenoid took care of the problem.

MOXIE62

What do you mean when you say the floats are too high. According to the manual they should be 5/16" with air horn upside down and 3/4" when air horn is in the up right position. Which one of these dimensions is to high. And I agree, Jackson's problem is when engine is off there is fuel leaking from the primary cluster or the pump discharge nozzle causing flooded engine.

jackson 63

I do not have a starter problem. Something is causing my fuel to percolate. It did this before and after my carb rebuild.

aaronz28

Your problem is everyone's problem - ****** Gas! Even on pump premium.
The boiling point on today's fuel is so much lower than it used to be - when the engine shuts off - the residual heat from under the hood is boiling the fuel out of the fuel lines and out of the carburetor.

FI cars are even worse

you could verify this with a tank of 110 octane race fuel - which has a much higher tolerance for the heat - plus it smells good.

NOW - if you are running race fuel already - then I don't know what to tell you.

tbarb

If you 340 hp engine has it's original heat riser valve wire it full open. Also, how much idle timing are you running, the factory distributor is set up for 24* centrifugal degrees so you can run approx 14* initial timing plus a vacuum advance providing another 15* for a total of approx 29* idle timing. That will cool it some along with the open heat riser.

If the engine has it's original 201-15* vacuum advance control get a replacement that pulls full at 8" vacuum, I can't remember the part # but someone else will probably post it.

Frankie the Fink

If you search the forum you will see the many solutions to tackle this problem:

Lowering floats, wiring open passenger side exhaust heat riser, blocking intake manifold intake heat runners using F/I gaskets, adding phenolic or spacers made of other material under the carbs and several other things...

I've done ALL of these things on both my '61 and '63 cars...

To confirm percolation get one of those Harbor Freight $23 I/R temp guns and aim it at the carb bowls when you are having the issue; if the temps are north of say, 140* that's your problem...

MikeM

I have never had to put my IR gun on my float bowls. I just drive on my merry way. Maybe I'm just tolerant of an engine with a carb on it compared to FI and just don't worry about it or maybe, I don't have a problem at all with my 89 octane E 10 gasoline in this area?

I am not a natural born worry wart so maybe I have a problem and don't know it. Or just don't care.

Frankie the Fink

Nobody said anybody HAD to put an I/R gun anywhere. The OP has asked for a diagnosis of his issue and that tool can help. He can then decide whether or not he considers it a "problem"...

MikeM

I ain't tearin' my hair out over something that doesn't amount to a hill of beans is my point. If it starts a little hard when it's hot because the engine is flooded, big deal. It's like everyone elses carbureted car, plus or minus.

No need to joust with the windmill.

Frankie the Fink

Opinions vary.

jackson 63

Frankie you are right. Thanks for the tips. I, unlike Mike do not like to grind away on the starter and finally start in a cloud of smoke.

Lou64

My original engine had percolation problems as well and I'm on the same gas as MikeM. Even with the spacers and electronic fuel pump it would percolate, and worst was on hot starts. I would be stuck places like gas stations for 20-30 minutes while I sat and let the car cool down.

MOXIE62

Did you ever find a fix or did you just swap engines.

MikeM

When my '63 still had the 327/300 (stock) engine in it with AFB, I never had problems on a hot restart.

There is a "hot restart" procedure in the owner's manual. Wonder if anyone knows about it? It's in the same section as a "cold start" and they are both different.

And both of them are different than starting your newfangled, modern FI car.

Lou64

Never fixed, apparently my car had these same problems since the 80's according to the guy who used to work on it.

Frankie the Fink

Not counting washing your cylinders down with the over-rich mixture...in any event there are 'hot start' procedures to deal with it that are less stressful than the 'hold it on the floor until it fires' method and don't require you to wait 20 minutes for things to cool down:

"Difficult starting of a hot vehicle from 5 minutes to an hour after the engine has been operated, can be caused by the volatility of modern fuel. If you have this problem; try using the following method to start the engine: DON’T touch the footfeed (VERY important). Crank the engine over from three to 5 seconds (different vehicles will respond to different times); and then GENTLY (so as not to activate the accelerator pump) press the footfeed approximately 1/3 of its travel. The engine should start, and may run rough. Run the engine at a high idle for about 10 seconds."

When I do this the engine does not run rough when it starts and I can just drive away...

MikeM

http://www.thecarburetorshop.com/Tro...m#Hardstarthot

There is some good information on that site where you got that starting procedure and there is some bad info including that hot starting procedure.

The fuel system engineers from GM provided input for hot starting procedure in the owner's manual and I'm almost positive, if they'd recommended wearing out the starter motor every time you hot started the car, the electrical guys would be all over them.

Besides, I don't know how you sneak up on an accelerator pump and cycle it without squirting unless it's broke.