Modified Mustangs & FordsHow To Tech Qa
Garage Q&A - Tech Answers, December 2013
Keep Those Classic Ford and Mustang Tech Questions Cominng!
Q: I recently had a 1966 Mustang fastback modified and the 289 engine sits at an angle -- the motor mounts are two different heights. The individual who did the work said that it was done that way because of the torque of the engine. I have checked with numerous people, NPD, and more and no one else has ever heard of such a thing. Can you help me clear this up and will this present a problem if I don’t change it? Thank you.
Ann Arbor, MI
A: The engine shouldn’t be sitting at an angle left to right when you look at it. It should be angled down toward the transmission about 4 degrees, but side-to-side, it should be level. What exactly is happening may be one of several things:
On November 1, 1965 (early into ’66 production), Ford changed the style of motor mounts from the earlier vertical post to the later horizontally mounted bolt to hold the rubber insulators to the frame mounts. It may be possible, (though unlikely) that you have one style on each side of the car and it is not allowing the motor to sit level. You want to check to see if this may have been done.
For 1966, Ford lists three different mount bushings for both before and after the crossover date: one for convertible, one for 289 Hi-Po, and one for the rest of the cars. The convertible bushings are shorter, and it’s possible you may have a mismatch of bushings. Simple solution would be to buy a new set of bushings you know match and switch them to see if this solves the problem.
The ’67-’70 bushings are similar (and sold generic to all small-blocks after 1/11/65), with Ford having a different bushing for the ’68 convertible.
There is a possibility the frame mounts could have the holes in the wrong place. There are two different frame mounts for the horizontal bolt engine mounts; one is known as the “big-block” mount. This is not terribly accurate as the “big-block” mount was used for ’68-’70 289, 302, 351W, and 351C convertibles, as well as the 390-428 big-blocks. The other mount is used for 289-351C cars that are close. It’s possible you have two different frame mounts. Check the forward hole on your mount and see if they are in the same place (see arrows in photo). If you can’t find a difference in the mounts or frame brackets, you may want to have the car checked for previous collision damage. It doesn’t take much to tweak the engine out of place. My guess is a mismatch somewhere in the motor mounts or frame brackets.
Starving For Fuel
Q: I have been battling a fuel starvation issue in my 1968 Mustang since last fall. My car is a 302 with an Edelbrock intake and 600-cfm carb, MSD ignition and distributor, and a mild cam. When operating under a moderate load, such as when climbing a long hill, the car sputters and dies. Ten minutes later, it fires up and runs normally until I encounter another hill. I removed the fuel line at the carb during one of these incidents, and there was no fuel in it. I have replaced the carb, fuel pump, fuel filter, fuel lines, and sending unit. I have also drilled a small hole through the fuel cap to make sure the tank is vented. None of this has helped. The only option I can come up with at this point is to install an electric fuel pump. Any advice you can provide would be greatly appreciated.
Via the Internet
A: Without knowing your carburetor model number and going by the fact that you have replaced everything and still have the same problems, here are my ideas on what I think is going on, from least likely to most likely:
Make absolutely sure the pickup in the tank is facing down at the lowest point in the tank. I say this because some of the new reproduction sending units do not stay in place, the tabs are not wide enough, and they will spin on you as you are trying to get that annoying O-ring to seat properly. It’s possible that you are starving the sending unit when going uphill when the fuel level is low.
I want you to install a fuel pressure gauge between the fuel pump and the carburetor. If you’re running a stock-type fuel pump, you may be starving the carburetor. Most carburetors want 5-5½ psi of pressure to run, and if you get down to 2 psi, you start having problems. It’s possible that under load and heat, the stock fuel pump can’t keep up with the load demands from the carburetor. The next time it occurs, note the pressure while cranking the motor. You may need to go to a heavy-duty pump.
When you said there was no fuel in the line at the carb, my first thought was vapor lock. Vapor lock occurs when the mechanical pump and lines get hot enough for the fuel in them to boil, which means the pump can no longer force more fuel through it until it cools and turns back into a liquid. Likewise, vapor lock in the carburetor turns the fuel in the fuel bowl into a vapor, and the vapor won’t make its way through the carb -- it usually vents through the top of the carb into the venturi area. When your engine is under load, like climbing hills, it obviously creates more heat, and your 10 minute restart is pretty fast (my car had to sit for an hour), so it sounds like you’re just on the hairy edge of vapor locking.
Along with the aforementioned fuel pressure gauge, look at the following:
Isolate the pump, fuel lines and carburetor from the heat of the engine the best you can. Running fuel lines close to the engine might look good, but causes problems.
If you’re running a stock-type fuel pump, you may be starving the carburetor
Make sure the bowl vents on your carburetor are free and clear. Some air cleaners can block the vents and the vapors can’t escape the bowl.
Make sure you’re running good fuel. Winter blend fuels can cause vapor lock in the summer time.
Note the temperature of the engine and the outside world when this occurs. Does this happen mostly on really hot summer days, or do you potentially have a cooling issue with the motor like a blocked radiator?
Higher altitudes can affect the boiling point of fuels. Does it only happen at higher altitudes? You can tune the carburetor for such conditions.
As you know, an electric fuel pump may help since the pump is off of the engine and not getting heated. This solves a bunch of problems with vapor lock, but you need to confirm that you in fact have that problem first. Start with the regulator and check the fuel pressure when it occurs and the temperature of the engine. You may just need a better fuel pump, or a little cooling system tweaking.
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