Vintage Tech Advice September 2013 Heater
Bob Aliberto
January 10, 2014

Heater Core Sizes

I am replacing the heater core in my '64½ convertible (built June 1964). I'm thinking that there is a difference in the heater core size for '64½ versus '65-'66. Can you confirm?

Chris Jenkins
Fairfax, VA

The heater core for a '64½ Mustang is essentially the same as '65-'66. Any differences are slight, basically due to different manufacturers of replacement cores. A 2-inch thick core is listed for the heaters up to the '68 model year, although I find that current replacement cores are a bit thinner than the originals. However, they are easily sealed to the heater case with extra foam insulation.

Fixing a Leak

My daughter and I are restoring a '68 Mustang hardtop. Our next step is the interior, which we plan to gut and replace with new parts. At this point, we've discovered a leak in and around the front windshield, which we replaced previously. We have tried various caulks to isolate the source. At this point, our project is dead in the water; we cannot proceed with replacing the interior due to the leak. She's discouraged and I'm frustrated. Can you offer a solution to the situation?

Howard Klein
Via the Internet

Resealing a Mustang windshield is a tedious and messy job at best. The only method should involve removing the chrome moldings and as much of the old caulk as possible. The glass is held in place by the thick rubber weatherstrip but requires lots of pliable sealer between the weatherstrip and the car body to be water tight. This area can only be accessed with the moldings removed.

A special tool is needed to release the clips that secure the moldings. Thankfully, the tool is inexpensive and easily obtained at a local parts store or mail-order via Mustang parts companies. I usually use two tubes of 3M Bedding and Glazing Compound (part number 08509), along with an ordinary household caulking gun. It will take practice to locate the molding clips and learn how to use the tool. Clean the moldings completely of old sealer for easier reinstallation.

Be sure to apply new sealer deep into the channel between the weatherstrip and car body, and also around the molding clips as they extend under the weatherstrip.

An experienced glass shop can do this job more efficiently than you or I. There is no shame in obtaining an estimate from the pros.

Six to 289

I have a '68 Mustang with a six-cylinder engine and automatic transmission. Will a 289 V-8 bolt to the same transmission if I use the V-8 bellhousing?

Bud Crosby
Via the Internet

A V-8 bellhousing for a C4 transmission will bolt up to your current six-cylinder. That, along with the correct torque converter, will allow you to bolt the transmission to a V-8 engine. Be certain to rebuild the trans with as many clutch plates as possible. Some six-cylinder transmissions have fewer clutch plates. See the May 2013 issue of Mustang Monthly for Jim Smart's excellent article about automatic transmissions, which will help you identify your unit.

Factory Discs?

Last year, I acquired a '65 hardtop that has some strange options. It's a C-code 289 (two-barrel) car that appears to have its factory Pony interior because the instrument panel has the correct cut-out for the five-dial instrument cluster. However, this car also has factory disc brakes and a 9-inch rear end, although I guess it's possible that the rear end could have been swapped. However, the brakes look factory with the single master cylinder and Kelsey Hayes proportioning valve in the correct locations. Could the disc brakes be original to the car?

Tony Albanese
Via the Internet

Disc brakes were a stand-alone factory-installed option for V-8 Mustangs. At $52.70, it was affordable! I believe your hardtop came with disc brakes since the system looks factory and is still completely intact.

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