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Poor running 68 500GT KR

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I am dealing with a poor running 68 GT500, I had the carb restored and it runs much better but still not great. The problem we are having after we shut down it will not start. I am getting fuel to the carb but after it sits for 30 min it starts and runs. This was about 6 weeks ago. I tried to start it yesterday and now the car barely runs and will not idle. I replace the coil think this would help. I ran an Ohm meter on the old coil across the Batt /- terminals and got a reading of 1.6 and across the center coil to either of the other post and it was 1.4. The new coil didn't help
A couple of other items - The original choke heat tubes are not installed. It currently has and Electric choke ( a wire runningn from the negative post on the starter relay) not sure if this is working and not sure how this works. I'm thinking about going back to using the original type choke tubes but how does it install and attach at the exhaust manifold and at the carb??? is there supposed to be a heat shield at the exhaust manifold that the tubes attach to?? There is no heat shield on the exhaust manifold at the moment. I purchased an electronic assembly manual on line and it's hard to see any details on the drawings.
Also I am thinking about replacing the original points distributor with an electronic ignition distributor that looks original - Any suggestions?? I also want to replace the plug wires and spark plugs. Not sure how you accomplish this? it is crazy tight especially on the drivers side - how are you guys doing this?

Thanks for all your suggestions and help.

Terry
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Discussion Starter · #7 ·
Its my friends car
Have you checked the condition of the points, their gap, and tested the condenser?

How old is the fuel and does it contain ethanol?

When you run it and then shut it down, does it crank over at the same speed as it does when it's "cold"? If not, have you performed a voltage drop test on the starting circuit?

Assuming you have the OE Holley carburetor, have you checked/adjusted the float levels?

As for the OE-type "Hot Air Choke", the tubes attach at the rear of the RH exhaust manifold as shown by the arrows....
View attachment 869141

I havent checked the point gap yet. I will check tomorrow. How do you check the condenser? and perform a voltage drop test on the starting circuit? The float levels have beed checked and its the original carb. Thanks for the exhaust pictures. How doest the tubes attach to the carb? I can see were the one treads into the choke housing, does the other tube attach to tube at the top of the carb?
 

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Discussion Starter · #11 ·
Mike Butler restored the carb. I haven't removed the spark plugs yet, I am still trying to figure out how to get to them. I under stand you would need to remove the brake reservoir and crossmember on the driver's side.
 

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Discussion Starter · #16 ·
Bart Thank you for your response, very helpful - i will keep you posted on the results.

I am familiar with the smog system on 70 corvettes and camaro's - is the ford similar as far as the install of the smog tubes. The exhaust manifolds on the GT doesn't appear to have threaded holes for the smog tubs. Sorry for all the questions, This is the first ford i have ever worked on.

Where vendors do you recumbent to buy parts?
 

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Discussion Starter · #18 ·
He purchased the car at Barrett Jackson in 2022. It appears to have been sitting for a while before he purchased it and It hasn't ran well since he purchased it.
We did drain the fuel tank and fill with fresh VP 94 octane fuel. The carb main body looked to be original with correct part number and date code but the meeting blocks were not correct. The carb was restored with the correct metering blocks. Once we installed the restored carburetor it ran much better but not great. He drove it some this summer with an intermittent issue of restarting after he shut it down. We haven't touched the car since the summer until this weekend. It barely runs now and will not idle, seems like it's not firing on one or 2 of the cylinders. We have not tuned it yet, but I will work on it this week, time permitting. I plan on check timing, points gap and starting system. I know the plugs and plug wires should be checked and or replaced ( I don't know the age of these) but I am not sure how you remove the plugs and wires to inspect on this car. You can barely see the plugs much less replace them. I read the best way is to remove the valve cover and crossmember on drivers side and may consider removing the brake master cylinder also to gain access to the plugs and wires. This looks like a daunting task and can open a can of worms. The brake lines from the master cylinder look chewed up already so these will need to be replaced sometime
The car looks like a nice driver with a repaint sometime in the past, the convertible top looks good and the Interior looks original. The engine is missing the smog system. Is there an expert on these cars near Louisville KY that would be willing to inspect it?

Thanks

Terry
 

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Discussion Starter · #20 ·
Sounds like it is still needing all of the tuning/checking of everything, but, you might simply have picked up a piece of garbage in the carb. Seems like it needs to come back apart to inspect, and check filters, tank, etc..

I remember my dad accomplishing a plug change on our KR without removing anything, just some creative ratchet/socket pivots and extensions, and my older sister's small hands to get the #8 plug "started" into the head. She would've been maybe 12, as I remember this being around 1976 LOL.. So if you've got any kids who know how to start a spark plug by hand, it's possible. ;)

I've found with FE's, every aspect of the tune needs to be right on point for it to run right. Which of course makes "duh" sense, but the standard deviation is a tight window.
Good Point and replacing fuel filter, add this to the list

Thanks
 

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Discussion Starter · #29 ·
It also appears like you dont have any vacuum lines on the thermostat housing. I suspect if thats the case, you probably have a bunch of other vacuum related issues.

i also see a-number of non stock parts on the engine. I dont think the builder did you any favors.
i notice the vacuum ports on the thermostat also. Going to work on replacing all the non correct parts.

Is there a good diagram on the routing of these vacuum lines. also a good wiring diagram?
 

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Discussion Starter · #38 ·
Should not be necessary. The GT500KR was a straight-up CobraJet engine. Of course, it might need all sorts of items to bring it back to stock. Mansfield Mustang is the best single-source for such parts. Oh, and send the distributor to Dan at the Mustang Barn for calibration. Pretty good bet it is way off.
Thanks for the response
 

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Discussion Starter · #46 ·
II have been looking at the engine bay and it looks impossible to change the plugs and wires without removing stuff and lifting the engine. Did you jack the engine from underneath? or lift from the top side? Jack points or lifting points. Do you remove any of the transmission bolts or crossmember?
 
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