All dressed up with no less than four Honda Keihin carburetors, the little six-banger was able to produce 125 hp at the rear wheels at 4800 rpm. With this setup the car performed almost as if it was fuel injected.

photography:Bud Lange

Welcome back, all you "six--cylinder fans," to the continuation of our report on subsequent alterations to the 200 cubic inch Mustang six! For the benefit of you new readers, we started with a standard Mustang 200-inch six, recording 65 horsepower at the rear wheels on a chassis dynamometer, in subsequent changes, we installed a larger Ford carburetor from the 240 cubic inch six-cylinder engine, milled the head .060 and Installed stee1 tubing headers with a dual-muffler setup. We wound up with 100 horsepower at the rear whee1s, and in the process lost none of the economy or smoothness of operation inherent in this particular car. At this juncture, we decided that since the engine responded so well to minor enhancements we would dig a little further and see what we could come up with In the way of more performance goodies.
 Automatically, our first thoughts were of the cam-shaft, which in the case of the stock unit is designed strictly for maximum torque and economy. In this area, it just can-not beat. However, the horsepower range comes to a screaming halt at 4000 rpm, , and since we were desirous of going on up to 5500 rpm, we

consulted Mr. Ed Iskenderian. We told Ed we did not wish to destroy the inherent smooth-ness and tractability of the little six and would like a hydraulic action cam to maintain valve train silence. He responded by placing in our hands just exactly the cam we had asked for. The specifications are as follows 260° dur-ation, .408 lift, 42° overlap, in-take opens 21° BTDC, intake opens 21° ATDC, exhaust opens 59° BBDC, exhaust closes 21° ATDC. By comparison, the stock cam has 256° duration. .368 lift and 28° overlap.
  After changing the cam, we had to add a little more spring pressure for the added rpm. So we came up with some stock Ford items that are not only dirt cheap, but are perfect for this combo. We used the valve retainers from a 1962 260 Ford (part number C20Z-65I4--A, 12¢ each). We also used the standard springs from a 289 Ford (part number B6A-6513-A, 43¢ each). Multiplying these prices by the six cylinder, you can see what we mean by a reasonable price for springs and retainers...all from your friendly Ford dealer.
  Spring pressure worked out at 90 pounds (valve closed) and 190 pounds open. Having installed the cam and springs, we observed a 5 horsepower increase. However, we were running the engine at 4500 rpm. Then we noticed a favorable by-product of the change; we were now able to rev the little six up to 5500 rpm with no hydraulic pump-up. At the same time we put the cam in,

On the left is the standard 200 cubic inch cylinder head with stock valves; head on right is fitted with 1/8-inch oversize exhaust valves.

A cam change and Honda carburetion (plus a few other tricks) bring the six-cylinder galloper into the mid 80's and low 16's

we also installed pushrods (part number CODE-6565-B) and adjustable rockers (part number CODZ-6564-A) from earlier Falcon engines. They are of the same ratio, but gave us a handy method of adjusting pushrod lengths when changing cams, I would certainly recommend this change-over.
  During the test on the cam, we noticed that the ignition (in its stock form) was rather unwilling to cope with anything over 5000 rpm since point float was encountered. We cured this situation by adding more point pressure with the installation of dual springs tailored to 36 ounces of tension. This stabilized the points up to our desired goal of 5500 rpm.
  At this time, we felt the lit-tle six was crying for more fuel so we decided to investigate the possibility of adapting vacuum control slide-type side‚draft carburetors. We hoped these would cure the low hood line problem, as well as take care of the inevitable flat spots encountered when using large venturi areas on small engines. Since the cylinder head employs an integrally cast manifold, it was absolutely necessary to do some work in this area. We decided to remove the head and secure some stock exhaust flanges with short pieces of attached tubing. We then proceeded to the local boneyard and came up with two 1 3/4-inch SU British carburetors from a Jaguar, noting that the cast aluminum air cleaner (manifold and all) could be placed into the engine compartment very nicely. So we cut the steel tubes off approximately 1-inch (in length), mounted the SU's on these tubes, and centered the whole setup on the intake manifold. Then we scribed a pattern, drilled out the necessary holes, and brazed the flanges onto the intake manifold. Since the manifold is of thin-wall casting, the brazing was a very simple job, and anyone (even in East Snowshoe, Montana) could perform the same operation with dispatch.
  We also wanted to try some other slide venturi carburetors; namely, those used on the 450 Honda motorcycle. Since they are only 37mm in size, we decided to try four, so a couple more flanges were added for the subsequent tests.
  Meanwhile, back at the barn, we had the setup all ready for the tryout with the two SU's. After installing two carburetors rebuild kits (for $13.00), we were ready to go racing. By the way, the used SU carbs cost us $20.00. New they are $55.00 each.
  The throttle hookup was relative simple. We merely clamped a 5/16-inch throttle arm onto the SU shaft, ran a direct rod to the standard Ford bellcrank and everything worked out nicely.
  Our first test with the SU's indicated a lean mixture condition, so a visit to our local Jaguar dealer turned up some SY needles that worked out perfectly for this installation.

At left is the valve spring and retainers from a standard 200 cubic inch engine, and on the right is the Isky spring and the Ford retainer No, C20Z-6514-A.

Here's the setup that netted 115 rear wheel hp at 4800 rpm. Head makes use of two 1 3/4-inch SU Jaguar carbs, Quarter-mile speed was 81 with this combo.

  Our theory about the slide valve carburetion netted us a very fine batch of horsepower plus a couple of big carburetors that you can stick your foot in anytime and any place. They don't cough, hesitate or spit back...they just GO!
  For a good all-around setup, it would be difficult to beat this one. When making the changeover, it is advisable to use the manual choke setup which is operated most easily by a Bowden cable.
  Our final rating showed an additional 10 horsepower. The added carburetion was letting the engine really come on in the higher rpm bracket, and we were belting out a solid 115 rear wheel hp up at 4800 rpm. Translated into a 0-60 time, this amounted to a 9.4-second clocking (or close to a second off our previous time at the end of last months alterations). A trip down the quarter-mile netted 81 mph in the low 16-second bracket. One further benefit here; the gas mileage was beginning to show decline, but not as much as one might suspect as the car was still capable of consistent 18 to 2O mpg at normal cruising speeds.
  With the carburetion and cam changes, the engine still had a more-than-reasonable idle at a steady 600 rpm, leading me to believe this setup could be used very nicely with the little C-4 automatic transmission.
  When we had put on an additional 1000 miles or so with this setup, the urge to go to the four Honda Keihin carburetors became too strong. Having previously brazed the four flanges onto the manifold, the transition was only a matter of two or three hours work. When installing the Honda carburetors, we noticed they did not care too much for high pulsating fuel pressure (due to their small float assemblies), so a regulator was installed to limit fuel pressure to 3 pounds. This did the job very nicely. The first run-up on the dyno indicated lean mixture conditions in the medium rpm range. This was cured by removing the .028mm jets and replacing them with .042's. The main jets were subsequently enlarged to .070, and a set of adjustable needles were installed. These are available from Honda agencies. The metering rods have five notches for adjustments, and we found the "number two" notch (from the top) to be the ideal setup.
  These changes seemed to bring the air-to-fuel ratio into balance, so we decided to give the little six a full blast on the dyno and see what we could get in the way of additional horsepower. I was also very interested to find out what the small carburetors would do for horsepower in the lower rpm ranges, so we took a reading at 2800 rpm and netted 75 hp at the rear wheels. At 3800 rpm we had l05 hp, and we reached the top of the ladder at 4800 rpm, with 125 hp. This proved to us that our idea on the soundness of this type carburetion was right. When you jump on the throttle with the little bears, it is just like having fuel injection. It feels like all the horsepower unloads at once. In driving the car on the road, we found we could still stabilize the idle, very nicely at around 600 rpm. As a matter of fact, the idling adjustment on these Keihin carbs proved to be something to behold. This setup came with a smoother idle than 99 percent of all the stock cars I have ever played with. We did, however, encounter flat spots in the extreme low end of the rpm range, but, after all, when playing around with 5.8 square inches of carburetion on such a small engine, one must learn to expect that all cannot be "peaches and cream." To offset the flat--spot disadvantage, the price of these units is only $25.00 each.
  Exploring still further the possibility of using side-draft carburetion, we decided to check a couple of the Tillotson diaphragms used on the American Harley-Davidson motorcycles. This is a very simple, straightforward carburetor of 1 5/8-inch venturi dimensions. Testing proved this arrangement to be capable of equaling the SU's in all-out horsepower, but having more flat spots than a thief would encounter in robbing a banana factory.
  The general behavior of the car in normal stop, go, and cruising ranges was a most pleasant surprise. Later tests proved this car to be capable of 84 to 85 mph in the quarter-mile. With 4:1 gearing and 27-inch rubber, 5500 rpm could be had at any time, and this is 110 mph. This performance proved more than equal to several versions of the 289 2-V and 4-V jobs that we found willing to try us on for size.
  We also tried the 4:1 gearing in conjunction with the four-speed tranny, and our conclusions would be to forget this setup since it wreaks havoc with gas mileage and is certainly not conducive to good smooth road speeds at 70 mph. Instead, stay with the three--speed synchro with the 3.20 rear gear set. As for the remainder of the work, take your pick. It all proved very exciting and rewarding for us since we have always felt that true hot rodding is venturing into the unknown or unusual.
  I have personally gained a tremendous respect for the latest version of the seven-main, six-cylinder engine and sometimes wish one could purchase such a Package, call it a GT Six, and add some minor heavy-duty equipment to the chassis. This combination would give a good accounting of itself when compared to many foreign sporty Jobs that cost considerably more.
  So as we close our hood and roar off into the setting sun. We can only say come on and join the six-cylinder parade for more fun with less money than you ever could imagine!

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