David Stribling
February 4, 2014

Boosted Brakes

I have a '65 Mustang fastback with an SSBC disc brake conversion on the front and drums still in the rear. I also run a four-speed Top Loader (if it matters). My cam profile only provides 14 inches of vacuum at best. What is the smallest diameter vacuum-assist power-brake booster needed to provide better stopping ability?

Greg Plubell
Sherman, TX

In general, disc brakes require about 1,000 psi of pressure to operate. The smaller 7-inch boosters only provide about 900 psi, so you're still hard on the brake pedal trying to stop the car. All power-brake boosters require 18 inches of vacuum in Park/Neutral to operate properly, so you will experience a hard pedal if you're only making 14 inches. I've experienced issues with some of the aftermarket small-diameter boosters too.

I just had this problem with a customer's '66 Mustang GT coupe. It had a dual-diaphragm, 7-inch booster that wasn't working at all with the factory disc brakes. I solved it by going to Mustang Steve (www.mustangsteve.com) and using his 9-inch booster kit. The fit was great, and it works better than the dual diaphragm unit I pulled off the car.

If you need to generate some additional vacuum, SSBC sells a small electric vacuum pump should you need it (ssbrakes.com/i-10093987- electric-vacuum-pump.html). I highly recommend Mustang Steve's kit.

Lastly, if you have power steering, you could always convert your power assist to hydraulic with an assist unit from www.hydratechbraking.com(shown here on Modified Mustangs & Fords' '68 Mustang project car) and leave your vacuum worries behind.

Overdrive Six

I have a '66 Mustang coupe that currently has a 200ci inline-six with a C4 automatic transmission behind it. I've enjoyed driving the car for a few years now, but freeway driving is not as fun as I would like. Do you know if it would be possible to swap out my C4 for a later model overdrive automatic, like the AOD found in the Fox-body Mustang? If it's possible, what potential problems might I run into doing this swap on my '66? Do you know of any complete installation kits for doing such a swap on an inline-six?

Raymond Jones
Santa Clara, CA

I looked everywhere for proof that Ford put an AOD behind the 200ci/3.3L inline-six and I struck out. I thought some of the '82-'86 T-birds and early inline Fox Mustangs may have come with them, but I think they used the C5 automatic instead. The C5 was basically a C4 with a lockup torque converter for improved economy.

The literature tends to say an AOD in those years was possible, but I don't think so. Even so, it would be very difficult to locate one today. Until one of the bigger distributors makes an adapter, the only overdrive option right now is the manual transmission five-speed conversion using a Borg Warner/Tremec T-5 through Classic Inlines (www.classicinlines.com) or Modern Driveline (www.moderndriveline.com). If you really want to put the AOD behind your 200, Bendtsen's Transmission Adapters (www.transmissionadapters.com) can probably make one for you, but it would be pricey. If we could get one of the bigger suppliers to work with Bendtsen, we might be able to get a product that could get these inline-sixes in the 30-plus-mpg range.

Feeding a 408 Windsor

In your Oct. '13 issue, I read the story "Fueling Around." Your story covered single four-barrel applications. I'm in the process of building a 408ci Windsor with Jon Kaase P-38 heads, 11:1 compression and a Comp Cams hydraulic roller camshaft with 631/619 lift, 241/247 duration at 0.050. I would like your input on how to proceed with a dual-quad carb setup? My original thought was to use a pair of Holley 1848-1 465-cfm carbs. Keep in mind I'm looking for both performance and street ability? Thank you in advance for your help!

Tony Bogus
Akron, OH

The engine you just spec'd out is anything but streetable, and my initial thought is that the 465s are too small for what you are doing. A 408 stroker Windsor with 11:1 compression, a roller cam with 600-inch plus lift and 240-degrees plus duration with Jon Kaase P-38 heads that flow more than 300 cfm at 0.600 lift is not exactly a street engine. There are guys who have engines like this on the street, but "streetability" isn't why they have them.

I could not find a camshaft in Comp Cams' current list of cams for any of the Windsor engines that matches your application, so perhaps it is a custom grind or an older grind. Either way, the engine is going to idle very rough and will want lots of fuel. You would think 930-cfm would be enough to fuel this beast, but the accelerator pumps and smaller venturi of the 1848 model Holley is probably not well suited for this particular engine. You're going to need a single-plane manifold (not good for street applications) and some bigger carbs.

The Edelbrock dual-quad Air Gap manifold has a range of 1,500-6,500 rpm—your engine is capable of more rpm than this. Edelbrock recommends a pair of 500-cfm carbs for engines less capable than yours. After that, you're probably looking at tunnel rams if you want multiple carburetion. To get the maximum out of this engine, you might consider a Victor Jr. single-plane intake and a bigger carburetor, but I know it isn't as good looking as the dual four-barrels.

If you have already purchased the Kaase heads (www.jonkaaseracingengines.com), my suggestion would be to contact them and ask them where to start with the carburetion. With that kind of money wrapped up in the engine, spread some dough and buy some really good engine dyno time—you're going to be doing a lot of jet changes before you're happy and king of the streets of Akron.

On The Road Again

I have a '65 Mustang fastback that I would love to put on the road again. I'm always looking for ways to modify the car to make it better. One way, as you well know, are subframe connectors. I've been told they do stiffen the body quite a bit with a minimum of metal and weight. But, I read with great interest, that an old racer's trick was to weld in another set of floor pans underneath the car with the originals still there. That, in turn, stiffened the car. Considering weight and stiffness gained, which do you think would be better? Whichever you suggest, how about a recommendation? I would like to road course this car at some point in time.

James (last name withheld)

Go with the subframe connectors. Welding in an additional set of floor pans may help the stiffness of the chassis, but it is extremely heavy and is only helping in the same plane you are already stiffening. The subframe connectors go a long way in reducing body flex. If you plan to do a lot of road racing, I would consider welding up all of the body seams before adding them. Remembering that the Mustang sheetmetal is only spot-welded together; completely welding the seams greatly improves the rigidity of a race car.

As far as a recommendation on subframe connectors, I generally build them myself because of the body contour. Even though they do work, try to stay away from the cheaper ones made out of a straight piece of tube steel. Look for ones that contour the body or are designed to not be impeded by the floorpan sheetmetal. Global West (www.globalwest.net) and Total Control Products (www.totalcontrolproducts.com) both make good pieces with Total Control Products' weld-in subframe connectors shown here.

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