> Kelvin,
> Thanks for clearing up this issue for me..as for
> the cast crank and "softer cam".. I drove my Morris
> Marina TC over 200,000 miles, most of them at 5500 rpm
> or better. I had no problems with the crank or cam. On
> the contrary, my MG roadster,the 1977 in particular,
> has had several flat cam lobes develop. Did it have a
> Marina cam??Did my Marina have an MG cam???hmmm.
> Howard
Howard:
There is no question that the cast cranks hold up well. Even with the
typical lack of oil changes in Marina motors, they usually have little wear.
Not so the blocks and cam train. The blocks tended to taper, perhaps due to
the short skirt press fit pistons. The cams and lifters were only good for
40,000 miles. At the time, my father and I were researching the additives
used in US oils. One of the adatives ZDP (Zinc diethyl something, can't
remember) is used to increase longevity of flame hardened components, but
can prove detrimental to chilled cast iron. We never did come up with a
definitive answer. I have heard that Clancy Bros. the manufactures of the
short tappets did have problems, but again nothing definite.
The UK cars did have different cams and advance curves. Back in the 80s my
dad and I played a lot of mix n match with engine components to build
drivable Marinas'. The typical build included 8.8:1 pistons, UK cam, UK
advance springs and the smog equipment removed. The high point was 11:1
Aries pistons, Isky cam; lifters, springs, pushrods. Cross drilled, nitrided
crank. Fed by a Weber DCOE with a shaker hood scoop. The car ran great but
was ill-fated. On the engine break-in trip the front left fender was ripped
off by a pickup making an illegal left turn. 4 days later with a replaced
fender, I lost control of the car on a Pro-Rally special stage after a tire
went flat in mid air.
The engine ended up in my 1970 MGB, where it lived for many a happy mile
until the Isky cam lost a lobe and trashed the oiling system.
Kelvin.
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