At 10:57 PM 7/29/97 -0600, you wrote:
>I am no expert in MGA Twin Cam engines, but this is what I foresee as a huge
>problem. Your MGB block (and pushrod MGA blocks as well) is machined with
>oil galleries to oil the cam. With no cam, this would be a major loss of
>oil pressure, and would not work. Now, if you could make something to plug
>off the place where the cam is, that might work. I am not sure, though, how
>you would drive the distributor, or where the distributor would be mounted.
>On the A Twin Cam, the distributor was mounted on the left hand front side
>of the engine (not on the right hand back of the block). This would be
>another hole to plug. Also, you would need the twin cam timing chain cover
>and tensioner. This is really not as simple as just bolting a different
>head on the same block, like a cross flow is.
===Reply===
Not quite that difficult - the Twin Cam used a jackshaft in place of the
camshaft, to run the oil pump, distributor, and tach drive. The overhead
cams were driven by a chain from the jackshaft. The distributor and cam
chains were located in a casting that fit over the front of the block.
Instead of the pressed-steel timing chain cover, there was an aluminum
casting which covered the drive to the jackshaft, the timing chains, and the
bottom end of the distributor. The distributor stuck out of the left side,
forward part of the engine. On a conversion, you could leave the
distributor in place, and just accept that it's going to be a hassle getting
at it, since it'll be under the intake manifold and carburettors (sound
familiar, Jaguar owners?).
The problem with this idea is that, in addition to casting the head, that
you'd have to have the timing case and cam covers cast, design and have cast
a jackshaft (although I think you could probably use a standard camshaft,
but you'd have to figure out some way to attach a timing chain drive to the
front of it), as well as casting the intake and exhaust cams, sourcing
tappets, valves, tappet guides, cam bearings, cam bearing caps, cam chain
tensioners etc., etc., etc. A lot of this (cam bearings, bearing caps,
tappet guides and shims) could be cribbed from XJ-engine Jaguars, but this
is the sort of project that would require a very healthy R & D budget, and I
doubt that, even at $2,500 a pop, you'd sell enough to recoup your investment.
Mark Moburg
MarkMoburg@mindspring.com
New York, New York
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