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Vintage Ford Mustang Tech Advice - December 2014
Beyond the Basics
Rough Running ’66
I have a ’66 Mustang with a 302 in it. It has an Edelbrock 600-cfm carb. The car runs smooth until it gets hot, then it’s not smooth anymore. The car is driven on nice days and has never seen any wet or bad weather. I have checked the fuel line, including putting a pressure gauge and a regulator on it. I have checked the vacuum and reset everything. The car just started doing this recently. I put fuel additive in because of the ethanol I’ve heard can have water in it. Could there be something wrong inside the carb? Any help would be grateful! I have a friend who is a mechanic, but he’s not sure on these older engines as he is a young guy.
Via the Internet
It could be several different things, but we can check a few things that have happened to me in the past.
Choke: It is possible that it isn’t opening up all the way. The older the carb the easier it seems that the choke sticks, even on a good rebuild. Other carburetor issues could be the metering jets and rods not being right for the carb, or the idle mixture not set. If it has been a while since the last rebuild you might be due.
Coil: I have had coils misfire when they got hot. They usually go bad all at once, but I have had it happen. Get it on a machine and see if you are losing spark at temperature.
Wires: I had an abrasion on a plug wire that allowed it to arc against the engine, and it only happened when it got hot and things expanded. Check the location of your plug wires against headers or exhaust too—if they burn, they arc.
Thermostat: Check and make sure you engine is staying in the correct operating temperature. A hot running engine will stumble.
Tune-up: The tune needs to be checked for many reasons, and it’s more than just setting the timing. Fuel, air, and spark have to work together.
There might be a half dozen other things to check but those are your biggies. It is possible it might be the distributor. Find someone with a good old-fashioned Sun machine and take a look at the engine when it is hot. I hope this give you a starting point.
Trunk Torsion Rods
I purchased my ’66 Mustang convertible completely disassembled. I am in need of the two trunk torsion rods. I took a pair from a ’66 coupe and they are not the same and will not come close to working. I found one Mustang parts store that says in the catalog that they are the same. Do you have a part number for the convertible torsion rods and do you know of a supplier? Also, did all ’66 Mustang GT cars have front disc brakes? If the cars had the dual exhaust brackets under the rear seat, does that mean anything?
John S. Cowart
Via the Internet
The torsion bars for the trunklids on the coupes and convertibles are different. The convertible version is smaller due to the convertible boot. Take a look at the picture—the hinges are the same but the rods fit in differently. The final version of Ford’s Text and Illustration only lists the part number for the coupe, so I don’t have a number for you. The Triple R Mustang Ranch provided the rods for these pics, and they have a set if you still need them. Contact Delonzo at (317) 926-3418.
All ’66 GTs came with disc brakes. GTs also had the reinforcements in the back seat areas, but so did all cars with dual exhaust from the factory. If you are looking to see if your car is an original GT, a quick check list to look for: wiring harness for the foglamps, steering box tagged HCC-AX or AW, and two factory holes in the rear framerails on each side to mount the exhaust trumpets. Stick your finger in the factory assembly hole located inside the trunk and feel for reinforcement for these holes—if it isn’t there it wasn’t dual exhaust from the factory. Of course, it needs to be an A- or a K-code engine too.
The torsion bars for the trunklids on the coupes and convertibles are different. The convertible version is smaller due to the convertible boot.
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