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Author Topic: 67 GT350 warm starting issues  (Read 1051 times)
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stangman39
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« on: October 04, 2017, 08:11:37 AM »

When I got my 67 it had a 600cfm Holley on it that wasn't running well.
To get the car mobile I put another 600 on it I had.
Cold start no real issue but once warm it'd crank and crank (same cranking speed as when cold).  I'd have to floor the gas and hold it to eventually get it to fire over.
This past weekend I finally put on a correct 715.
Same issues when warmed up.

I also noticed the alt is not working so I need to replace that and when idling there is visible smoke coming out the exhaust and it burns the eyes.
When driving the car has good consistent power.

Probably a good overall tune up is in order and compression check.
Any thoughts or tips to try to diagnose the warm starting issue?

Thanks for the help  

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67 GT350 #2647
67350#1242
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« Reply #1 on: October 04, 2017, 09:24:45 AM »

Having to hold pedal to floor for it to start indicates a flooded condition.    Exhaust fumes that burn the eyes indicate a rich idle condition.    Probably most common causes would be leaky or bad power valve or too high fuel level. (misadjusted floats).    Same problem with 3 different carbs doesn't seem likely but it is possible.    The 715 Holley is known to have spec'd at too high fuel level for today's fuels, and the quality of today's power valves is certainly questionable.

I would first make sure the initial timing is in the right range, then troubleshoot the two causes mentioned.   Check at idle no fuel dripping from boosters which might mean too high fuel level or sticking needle/seat problem.
Kurt.

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Dan Case
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« Reply #2 on: October 04, 2017, 10:04:31 AM »

Having to hold pedal to floor for it to start indicates a flooded condition.    Exhaust fumes that burn the eyes indicate a rich idle condition.    Probably most common causes would be leaky or bad power valve or too high fuel level. (misadjusted floats).    Same problem with 3 different carbs doesn't seem likely but it is possible.    The 715 Holley is known to have spec'd at too high fuel level for today's fuels, and the quality of today's power valves is certainly questionable.

I would first make sure the initial timing is in the right range, then troubleshoot the two causes mentioned.   Check at idle no fuel dripping from boosters which might mean too high fuel level or sticking needle/seat problem.
Kurt.

Depending on what fuel is available where you are you could be suffering fuel that boils as low as 115°F to 124°F even without ethanol in it. Boiling fuel in the bowls raises the effective fuel level. On a recent long tour (over 1,000 miles over a few days) we got one fill of fuel in a little town that our car ran very poorly on.  These days when I set float/fuel levels I go to the low side of specifications or even lower depending on the car and what it is used for.

I will second the comment on Holley® brand power valves. I have bench tested every one for decades to make sure they seal. Several years ago quality went down on genuine Holley valves.  While servicing a friend’s Boss 302 carburetor I ended up buying eight (8 each) new Holley packaged valves from two different sources to find one that sealed when closed. That was the extreme, as most work okay or it takes sorting through just a few.  So far the valves in aftermarket kits for the R-3259 / R-3259-1 Holley models from Branda have worked fine.

You didn’t mention whether or not you serviced carburetors you swapped in. Depending on what brand and material they are made of gaskets in Holley 4150/4160 carburetor shrink a little or a lot if they are exposed to fuel and then allowed to dry out.  Lots of shrinkage can cause functional and leakage issues.
Dan


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Dan Case (a.k.a. rr64)
1964 Cobra owner since 1983, Cobra crazy since I saw my first one in the mid 1960s in Huntsville, AL.
stangman39
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« Reply #3 on: October 04, 2017, 11:27:49 AM »

Thanks for all the info.

To be honest I have never rebuilt or taken apart a carb in my 20+ years of tinkering with old Stangs!  (I've change accel pump diaphragms, that's about it!) With my luck I'll mess something up and have more problems than I started with!
I have recently been referred by a buddy of mine to a well known carb builder here in GA.  For the little overall money it probably can't hurt for me to have him go thru the carb.  Then I'll know it's not part of the problem.

Regarding fuel.  I really don't know how long the fuel in the tank had been sitting when I got the car about 6mo ago.
I do try to run 90 octane ethanol free with a little mix of 110 Sunoco.

It'll take me a week or 2 to get the carb gone thru, I'll report back after I do some adjustments/checking all around.

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