Hello All:
I am one of the fortunate few who tried out Jim Swarthout's roller rocker
kit. I thought I would contribute to the list my observations of the process
and results of installing the kit as there had been much discussion on the
list as to the benfits of such an alteration of the engine.
Installation
The kit as it arrived contained a set of 12 shiny aluminum rockers and all
the washers and nuts required for installation. It also contained a small
book of a colour printed manual, a laminated reference sheet for valve
adjustment and a nice little shim for adjusting the rocker-valve stem gap.
The rockers are nicely polished aluminum with bronze inserts for turning on
the rocker shaft and dowel rollers for contacting the valve stems. I liked
the fact that the kit included new nuts for the adjusting ball-screws that
link the rockers and the pushrods. The kit uses the original ballscrews.
I have to say that fitment aided by the manual was very much as expected and
went well. The kit is very well put together and the instructions are the
best I have ever received for any mechanical component.
The worst part of my install was removing the components from the old rocker
shaft. This was at first puzzling because I remembered that the last time I
did this in the 80s it was very simple to get everything apart. The manual
states not to use a twisting action to get the pedestals off the shaft. Well
I kept that to a minimum, but I can tell you that filing a workhardened
steel shaft is slow. Those pedestals were on that shaft quite tightly. Once
I had the shaft free, I took a look at the oiling hole. I was puzzled to see
that it seemed to be blocked off with an orange rubber-like substance, Then
I looked in the #6 pedestal that contains the oil passage mating with the
hole in the shaft. I found a pea-sized lump of orange sealing silicone stuck
in the pedestal. I remember that in an earlier life I used to put silicone
between the head and the block around the water and oil passages to help
seal the passages since I was forever having water leaks. This resulting
blockage is one reason why you're not supposed to do this. That little oil
passage got a blob of the the silicone squeezed into it as the head was
bolted down and then the oil pressure pushed it up into the pedestal where
it quite effectively blocked off all internal oiling of the shaft. I never
noticed it during the last rebuild when I replaced the shaft and didn't use
any silicone on the head. But it was still there in the pedestal. Even with
the splash lubrification it was not enough and my shaft was worn in almost a
millimetre after only 4K miles! Doh! I had tested the day before as the
manual suggested and purchased a new rocker shaft.
Since the aluminum rockers are more "square" than the original steel units
some have less freedom of movement than the originals. I had to do a bit of
dremelling on the outer pedestals to solve this. Although Jim's manual
indicates this may be necessary in the lower outer corners, I discovered
that if I rounded the vertical edge of the upper arm of the "Y" in the
pedestal to a radius of perhaps 1/8" (probably less), I ended up with much
increased of freedom of movement for the rocker. The work took no more than
5 minutes with the dremel and a file and in no way seemed to compromise the
strength of the pedestal.
The valve train follows an odd-logic form of assembly of pedestals, springs,
rockers and spacers, so the good reference diagram in the manual was very
helpful. With all the bits laid out in order on the bench, I counted the
order of parts about 10 times before actually feeling comfortable. I was
careful to keep the adjusting ballscrews in the original order with the
optimistic idea that the pushrods would already have been worked in to those
specific screws. Perhaps it helps, who knows. I discovered that the threads
on the original nuts were quite chewed up and had left bits of metal in the
ballscrew threads. Careful cleaning there is very important because the
ballscrews are a lot harder than the alumuminum rockers they screw into. I
made sure the screws were very clean and then everything fit together nicely
with no thread handups at all.
Results
I have a stock engine with a recent rebuild. I have a 6:1 header leading to
the Moss sport stainless exhaust. I also have the Crane Cams electronic
ignition. Carbs etc. are all original. The kit changes the geometry of the
engine by changing the lifting ration (cam vs. valves) to 1.75:1 from the
original of 1.51:1. As promised by the manual I have definitely noticed a
change at the low rev torque. Before when I had any variation at all between
the damping in the carbs the engine would have to be quite warm before
starting from stop was smooth. The engine would start the car moving using
the angular momentum of the flywheel, but right when the motor should have
taken over it would starve out and I would do my best to make a nose-print
on my horn button. A smooth take-off involved revving the engine just a bit
before slowly letting out the clutch and using a slipping takeoff to get her
going. Once warm it was fairly OK, but very very noticible if the carbs had
lost any damping action.
With the increased valve lift, the car no longer needs to be revved and
seems to pull smoothly from very low rpm. Basically I start pressing the gas
and release the clutch simultaneously so the takeoff is right from idle
speed. That's a noticible difference.
On the top end I do feel that the improved breathing has let the motor rev
higher without having to use a ton of gas to do it. The acceleration does
not peak out, but seems to increase with a crackling roar. However here a
dynomometer would be of more use than simple observation. A racer would
bemoan any acceleration that doesn't go to 7000 rpm. I never accelerate past
5000 rpm and thats with Born To Be Wild playing on the radio! I can say that
with a good push on the gas she has a much smother acceleration feel at 3500
and up whereas before I noticed that I was definitely starting to see some
real non-linearity before. A very subjective observation of course, but I do
know the feel of my car, and I feel it has improved.
Conclusion
The kit is impressively put together. The quality of the components seems
excellent. The parts are beautifully machined and have no amateur feel at
all to them. The manual is absolutely first rate. I thought the addition of
the adjusting shim was great. I had forgotten my feeler gauge kit in the
basement and was going to tramp back inside when I considered the
thoroughness of the manual and meticulous individual bagging of the washers
by type and checked again. The manual mentioned an included tool so I looked
in the box again and spotted a nice shim complete with nail-hole sitting
right there waiting for me. The laminated valve adjustment guide is now
sitting in my box of TR tools as a useful reference. Much less messy that
fighting with the Haynes manual while turning the engine by hand.
I feel that my car now accelerates better from stop and the engine seems to
turn more freely at high rpms. How much of the effect is due to the
increased valve lift vs. friction reduction? Probably most of it. But I can
feel sure of one thing; the reduction of friction due to the rollers and
improved bearing surfaces will mean that the parts wear less and the
adjustment will stay put for a long time. Combine the change in breathing
and the reduction of friction and the roller rocker kit becomes a worthy
addition to the engine.
One comment I would make is that I do not think that a new rocker shaft is
an option, it is essential. It is nonsense to fit a high quality set of
components like this kit to a worn shaft when the shaft costs so little
compared. Perhaps the kit could also include the cotter pin necessary for
the rocker shaft. Fortunately I had a nice SS one on hand, but I would have
been forced to use a nail otherwise.
I have not compared Jim's roller rocker kit to other offerings because I
have never used them. I can say that I have never seen a setup which led me
so well by the hand through altering a part of the motor that is considered
terra incognita to most week-end mechanics. I enjoyed the experience. I have
rarely felt I got so much benefit out of a few hours work.
So thanks for the kit Jim and well done!
Mark Hooper
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