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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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Since it hasn't run very good since purchase you really have no baseline to try to figure what has changed/gone wrong. It could be one or several problems. I second the advice of taking it in to an experienced professional.

If it were me I would start with the basics fuel filter, points, condenser, plugs, cap, wires, timing, carb tune vacuum leaks. I would use good quality parts.
 

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Since it hasn't run very good since purchase you really have no baseline to try to figure what has changed/gone wrong.
This.

Do you know how many miles are on the car? If it's a high mileage engine, it could easily have multiple bad valves and leaking piston rings. No way to tune that.
 

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You dont need to remove the booster to change the spark plugs. You just need the correct combination of extensions and swivels.

1968 Shelbys sent to Canada did in fact, have smog. Shelby built all the cars to the same specifications.
 

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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.
 

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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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On removal/installation of the #8 spark plug for an FE,yes, it can be a bear. While it is possible to snake one's arm under the brake master cylinder, once my then 12 year old started growing, it made sense to remove the brake master cylinder for those infrequent plug change intervals. When these cars were new, the general consensus was change plugs every 12K miles or once per year. Fast forward to now, many of these cars often take several years to rack up 12K miles so the pain is less frequent!

To put plug changes into perspective,consider changing out header gaskets on a set of Hooker Super Comp full length headers. It is a blood letting experience and makes the plug changes seem like a walk in the park

With some modern gasoline formulations,fuel percolation can be a recurring problem under the hood of a FE Mustang. Insulating the fuel line and the carb base from engine heat during a heat soak might make a difference when you experience hard hot starts.

On the smog systems from that era, Here's a link to Mansfield Mustang's site containing some helpful photos of the typical PCV and Thermactor smog components::


Good luck.
 

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“….. Is there an expert on these cars near Louisville KY that would be willing to inspect it?
I suggest posting on the SAAC forum


and inquire about a Shelby / Mustang oriented restoration shop in your city. Most cities of that size have at least one shop or person that would be well known for their work. Another time tested method of research would be to find a local vintage car club and ask them for a referral. The people in those clubs will welcome your inquiry and have a inside scoop when it comes to local talent who can be trusted to give the car the care it deserves.

Usually I’m all for the DIY approach. But in the case of your friends car, it might be a money and time saver to call in a Mustang / Shelby authority. I’m sure the car cost well into the 6 figure range. A few more hundred $$ spent is a good way to keep the investment safe.

Z
 

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I appreciate your advice - any Shelby specialist willing to chime in.
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.
 

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I know this isnt helpful to you now, but its always a good idea to check these things out before you spend $200k.

maybe someone following this will benefit from that advice.

The other suggestions are good. I dont think there are a lot of CJ/AC cars, but it does add a different dimension with vacuum and pulleys, etc
 

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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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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?
a) Properly set up, a point distributor will work as well as any electronic. In daily use, points will gradually go out of adjustment. Will you be driving it to work?
My '55 still has points. I have not adjusted them since about 2002. Not a problem.

b) Plug wires are tricky, but doable. The plugs are the hard part, requiring exotic tools. Back in the day, a lot of guys would lift the motor off the mount by pulling the horizontal through-bolt. Some would just skip it. You may have some of the latter going on.
 
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