Mustang MonthlyHow To Tech Qa
Vintage Tech Advice - September 2013
Beyond The Basics
Shelby 351 Power
I’ve been wondering about the horsepower rating for the ’69-’70 Shelby G.T. 350. Given the modification of the aluminum high-rise intake manifold, is the Shelby engine making the same 290-horsepower rating as a garden-variety 351 Windsor? Or did the Shelby 351W make more horsepower and Ford just wanted to understate the rating for the usual reasons?
Victoria, British Columbia, Canada
The addition of the free-flowing high-rise aluminum intake did add a few extra ponies but not very much because, otherwise, the engine was stock, including the restrictive exhaust manifolds. The slight increase was felt more in driveability than in horsepower figures.
Vehicle manufacturers did indeed manipulate published horsepower figures to suit their needs. When the ratings were lowered, it was usually to satisfy insurance companies. And, of course, to get a vehicle into a certain class for racing, as was done with the Cobra Jet Mustangs in 1968.
Brake Retracting Spring
The April issue of Mustang Monthly had an excellent article about improving drum brake performance. The one component that I never see addressed or available in the kits is the shoe retracting assist spring on the 10-inch front brake assembly. This spring installs in the same position as the rear parking brake link, however it is a spring that shares the holes with the primary and secondary shoe-to-anchor springs. Does anyone make these? Years ago, I rebuilt my brakes and threw away the old springs before the new kit arrived, only to find that the springs weren’t included. I was able to locate a used pair. Will the brakes perform as designed without this spring?
Lehigh Acres, FL
The retracting spring is not an absolute necessity and was not included in replacement spring kits. The brakes will perform normally without it.
Back when disc brakes were optional, the majority of vehicles were equipped with four-wheel drum brakes. They had to work smoothly and quietly to satisfy car owners. Brake squeaks or other noisy operation was not tolerable. Lots of time and money was spent on drum brakes. However, as time passed and materials improved, some brake parts were deemed redundant and no longer used.
A similar example is an anchor plate located on the large pin that the retracting springs attach to. The plate was included on early cars but was eliminated later on.
Correct ’67 Radiator
I have a ’67 Sprint hardtop with factory Select-Air air-conditioning. It’s a late production car that was built at San Jose and delivered to the Phoenix, Arizona, sales district. At some point, the A/C equipment was removed from the engine compartment. The only remaining items are the vacuum canister and the water valve. My question is about the factory radiator. When I purchased the car, it had an aftermarket two-core radiator with skinny tanks. I am currently using a 20-inch, two-core radiator with block-off plates on the sides and a seven-blade fan, same as the 390 fan, but the engine still overheats here in South Carolina. I want to keep the factory look in the engine compartment. I’m willing to go with a three- or four-core, but I’ve been told that ’67 Mustangs with the 289 and A/C had the 24-inch saddle-mount radiator. I know the 24-inch was used on the 390 GT, but there is no evidence of a saddle-mount ever being installed in my car. What is the correct factory radiator?
Jon A. Davis
The 20-inch wide radiator with block-off plates is the correct radiator for a ’67 Mustang equipped with a small-block and air-conditioning. The larger 24-inch saddle-mount from the 390 GT was not used on A/C small-blocks until ’68 production.
The original radiator and shroud should be adequate to cool the car. Any issues from an otherwise clean system are usually related to air flow. I find the fan clutch to be quite troublesome and difficult to diagnose. The factory shop manual test procedure utilizing a strobe timing light can be difficult and inconclusive, so I usually substitute a known good fan clutch or simply replace it with a new one.
I have a problem (or will have one someday). The number four spark plug in my ’66 Mustang’s 289 engine is stuck. It is not cross-threaded. I am afraid to try too hard to get it out because I don’t want to break the plug off in the head. I took it to an auto repair shop but they wouldn’t touch it. Do you have any suggestions?
Palm Coast, FL
There’s really no easy method or trick to help remove a stubborn spark plug. The possibility of breaking off the hex area with the threaded portion remaining in the head is a real concern.
Try loosening the plug while the engine is hot to see if it will budge at all. I usually find that if the plug moves even just a little bit, it can be coaxed out with a liberal application of penetrating oil, then rocking the plug in and out by alternately loosening and tightening. Should the hex area break off, the head must be removed so the remaining threads can be drilled out.
Let us hear from you.
Send your ’65-’73 Mustang questions to: Beyond Basics, c/o Bob Aliberto, P.O. Box 205, Salt Point, NY 12578. Send email to email@example.com.