Memories of a Motorhead: Bob Scott interviews his brother George
(George Scott is my brother. As long as I can remember he was interested in internal combustion engines. He was tinkering with motorbikes and motor scooters at a very young age. He built his first motorbike by mounting a Clinton engine on his Schwinn bicycle and designing and building a clutch using belts and pulleys. He bought his first car when he was fifteen years old, worked on it for a year with money earned from part-time employment at a gas station, and had it ready for the road when he turned sixteen and got his drivers’ license. He then went through a succession of fast and fancy cars, working on them constantly in our family garage. He graduated from high school in 1954 and had no interest in furthering his education. He was working at an equipment rental store when our neighbor, Merle Noftz, who was an engineer at Chrysler Research offered to get him a job at that facility. He worked there for several years and accumulated a wealth of information and other interesting anecdotes, which I am narrating in this article. After leaving Chrysler, he went into business for himself and is currently living in Costa Mesa, California, where at the age of 68 is still self employed as a salesman with no intention of retiring or slowing down. )
Rob, you got me going on the old days at Chrysler. It was certainly an interesting time for an eighteen-year-old motorhead who thought he knew everything and wound up being humbled beyond belief by all the brainpower at Chrysler Research.
When I was hired in December 1955 my supervisor took me on a brief tour around the facility as a sort of indoctrination to the mechanical research lab where I would be working. After showing me development on disc brakes (not in use by any American auto company yet, I also saw a catalytic converter and assumed that is was a performance enhancing device due to the name,) gas turbine engines, hemi engines with Hilborn fuel injection using Chrysler mechanical control systems, and other interesting projects, we stopped at a dynamometer cell where an engine was running at 3600 rpm.
I asked what kind of testing was going on and Roger (my supervisor) told me to look at the beam. That, I was later to learn, was the Toledo scale face about two and a half feet in diameter that was measuring engine torque. The engine on the stand, with exhaust manifold glowing orange, was producing 1200 ft. lbs. of torque because they were supercharging it with shop air pressure of two atmospheres, approximately 30 psi. It was a 360 cubic inch “B” engine. I knew right then that this is where I was supposed to be.
I worked for a year on the fuel injection program and during that time I was involved with the single cylinder testing I was telling you about. The single cylinder test stand was a 354 ci Chrysler hemi that had all but one piston, rod and valve set removed. The thinking at the time was it would be easier to work on one cylinder, make changes and get answers before making parts to test on a complete engine. The single cylinder engine had a means of advancing and retarding the camshaft while the engine was running and we could remove the cam lobes individually (exhaust and intake) and try different combinations and indexing on an almost infinite basis.
The intake was one perfectly straight tube that slid over another with close tolerance (like a trombone slide) so it could be lengthened and shortened to find the best possible length for the speed the engine was running. Intake runner tuning is the result of finding the point where the sonic resonance is maximized. When you put your hand in front of your bass stereo speaker you notice there is an air push. The same thing occurs in an engine. You can hear the induction resonance when you step on the gas with the air cleaner removed.
This intake resonance is very pronounced on a single cylinder engine, particularly when recorded and played back at a slower speed, which we used to do. It sounds like Bop, Bop, Bop. By the way, we also took high-speed films of the valve train and watched them in slower motion. All sorts of weird things that would never have been normally visible were discovered and fixed in this manner.
Someone, I think a brilliant engineer by the name of Bob Graham, deduced that if we tuned our intake runner to the point where the resonance was greatest, it would give the maximum push to the air and fuel when the intake valve opened at any given speed. The theory proved correct in the tests on the single cylinder and the results were reduced to a formula that was used from that day forward for ram manifolds on Chrysler engines. The runner as measured from the valve seat to the plenum (the open area where they normally meet under the carburetor,) can be determined by dividing 84,000 by the length of the runner = the speed the runner will work the best. An example is:
84000 (constant) = 5250 rpm
16 (runner length)
The formula worked with all camshaft designs tested, engine displacements, compression ratios, and bore and stroke combinations of the time.
An exhaust tuning formula was also developed on the single cylinder test stand. An example is:
205000 (constant) = 5256 rpm
39 (length of exhaust runner to collector)
On the exhaust tuning we found that we could flatten out the torque curve by adding length to the collector (the point where all the runners meet.) The collector on an engine with all cylinders operating was usually a tube measuring about 20% smaller than the total of all the exhaust runners.
When this was going on in the mid to late 50s we were all so excited over the findings the department was buzzing about how best to use the information. The first resulting engines to take advantage of this information were the 1960 Chrysler 300F, the Plymouth “Sonaramic Commando,” and the Dodge version with the same engine, the D-500. And, of course, the Hyper-Pak Valiant that we have been discussing lately.
You might be interested in knowing that Tom Hoover calculated to get a 392 hemi to breathe as good as a stock 170 ci Slant Six it would have to have three inch intake and exhaust valves!!
So, we had some good information and data to start the Hyper-Pack development before the funding for it came down. Lots of cam and intake combinations were tried, but the best was the “Squid,” so named for the sea creature that it resembled. With its long runners it was tuned for 5500 rpm. We tuned runners for speed less than the point that the engine produced max power so as to give lots of power when rpm was down coming out of the turns at Daytona. Maximum power was at 6500 rpm. It produced 260 hp with the 276-degree camshaft (Duntov/Porsche design,) 10.5:1 compression pistons and cast iron headers of untuned length. (We were running out of time before race day.)
During the single cylinder testing we found a good valve spring with a surge dampener that was used on the 1958 300D Chrysler, so we used those on the Hyper-Pack. I still remember the part number. It was #1944554. The Hyper-Pack had valve gear stable to 7200 rpm and sounded like a banshee screaming at full song on the dynamometer during power runs. It was policy to leave the dynamometer cell door open during power runs thereby allowing operator quick exit in case of an engine failure of magnitude. At the end of the power runs on the Hyper-Pack where max speeds and noise were reached, there were always crowds of curious onlookers jamming the doorway wondering what the hell was going on in there.
An even better camshaft (this time stolen directly from Porsche,) was tested, but too late for the race. It was the 284 degree with .450 lift, 60 degrees of duration good for another thirty horsepower. This cam profile was later used in the 413 and 426 Max Wedge motors like the one in my 63 Plymouth.
In closing, I would like to say that the Slant Six or “G” engine as engineering and production referred to it, was a terrific engine to work with. More or less by happenstance than by planning the fact that the engine breathing was extraordinary came completely as a surprise. The leaned over installation was requested by Body Design Group to make hood clearance. (They only saved about an inch.) But, it left all that room between the cylinder head and the inner fender panel, without which the key to the Hyper-Pack, the “Squid” intake manifold would not have had space. The 170 cubic inch slant six not only had remarkable breathing capacity, but also was a very low friction engine. And best of all, it was extremely strong in the lower end, due to among other things the short stroke design. I fully believe that with the right valve equipment it is capable of turning 8500 rpms.
Later note: I noticed that Clifford Performance sells an original spec. long runner Hyper-Pak intake manifold for the 170 Slant Six. Clifford mentions a certain conventional bodied Six Pack car that turned in 12.34 seconds with their equipment.