Dennis,
>
> Dear Tim,
> When you said "at the blistering pace at which you get things done",
> I hope you were being sarcastic, as I really don't get things done very fast
> at all. This Spit engine has been in pieces since last January!!
No sarcasm. One minute you were talking about it, the next you had already
tried something. That's impressive.
I looked abit closer at the set up for the A series. Basically the engine
> front plate is unaltered. The timing cover is very shallow (actually it is
> flat against the front plate except for where the cam protrudes from the
> engine block and where the crank comes out so oil can flow from the top
> just above the cam down to the sump via the front of the crank) and has two
> holes in, one for the can wheel and one for the crank wheel. Then there is
> a cover plate to protect the belt drive.
> I'm wondering if one could simply make the existing timing cover very
> shallow, machine a hole for the cam wheel (I say wheel to diferentiate it
> from the sprocket) to bolt onto the cam and find seals of the appropriate
> size. The real problem will be finding the wheels. I don't see why one
> could not use those available for the A series. The important thing is that
> the crank wheel be half the size of the cam wheel so that each turn of the
> cam is caused by two turns of the crank. Then one would need adaptors to
>allo
> w the cam and crank wheels to couple to the cam and crank. This should not
> be too hard if it were cut from a blank piece of aluminium on a laithe (?).
> I'll have to mull it over some more as the above might work, but it would
> look untidy. If only I had the welding gear to weld aluminium, then I'd
> be in buisness! Then it would a cinch to fabricate covers.
>
> Cheers Dennis
>
Sounds interesting. I had a look in my shop manual over the weekend, and
did some thinking about this. I think you are generally right, that a shallow
cover that allows oil to flow and contains two oil seals is what is needed.
I see some issues:
* The cover is not a very good seal as is; I think it's too flexible. What if
you made the cover out of two pieces of 1/4" aluminum plate? One would be a
spacer, like a thick washer shaped like the periphery of the cover, and the
other would be continuous and contain the oil seals. These two pieces
would share all bolt holes and dowel holes; some sealant between them would
prevent leaks. The expensive way to do this is to sculpt the equivalent out
of solid 1/2" aluminum plate. (Welding the two 1/4" plates together might
distort the mating face too much. Then again, it might not.) Oil seal
mounting holes would have to be machined into the plate.
* How far does the camshaft protrude from the block? Would the camshaft itself
run in the oil seal, or would the pulley bolted onto the camshaft have a bushing
that runs in the oil seal?
* What would be the effect on the camshaft bearing areas of the load arising
from the belt tension cantilevered over the increased distance from the block?
Is this load negligible?
* Does the "oil thrower" serve any useful purpose other than to lubricate the
timing chain? I suspect not, but don't know for sure. Would it have to
be retained?
One final thing: you ARE going to have fine cam phase adjustment by way of
movable belt idler pulleys, aren't you? If the cover is made of 1/4" aluminum,
there is enough strength to mount the idler pulleys conveniently.
If you pick any dimensions off the front of the block, especially bolt and
dowel hole locations, I'd be grateful to have those.
Regards,
Tim
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