Scott is correct in saying that the 1500 lump in a Midget body is undercooled
because of the reduced air flow over the engine in this engine bay. This can
cause the already less than satisfactory half circle thrust bearing to wear
out and put a rod through the block. The usual answer is to fit an oil
cooler, or /and use synthetic oil. However, when you really start to tune
this motor for MAX power, using 13:1 CR etc it generates too much heat
locally within the engine so it fails. Thsi would happen in these really
tweeked motors no matter what car they are in, in fact it happends on the
engine dyno. Why? Because it is big lump of iron which because of its mass
and architecture of the cooling passages within the motor cannot disipate
fast enough the heat generated at high sustained revs with high CRs.
The A series engine on the other hand can disipate the heat generated when
very higherly tweeked, so it is possible to tweek it higher and higher without
the heat problem being the limiting factor.
Don't get me wrong, you can produce a fast, powerful, tractable STREET motor
out the 1500 and even a very fast powerful race engine BUT, it will never be
as powerful at full "tweek" as the A series can be. I would think that in
terms of a STREET motor, one you can drive in traffic, will have good
longevity and reliability, they are about even. The A series might have the
edge because of all the R & D done on this lump but the 1500 does have a
larger capacity (although the A series will go to 1600 I think) so might
have the edge in that department.
For the street, then, I think they are comparable, so Marcus, stay with the
1500. With all the other mods involved (gauges, coupling to the tranny, or
fitting another tranny etc etc etc) you will be better off modifying the
existing motor. After I've spent the $3500 it will take to do mine, I'll tell
you if it worked or not!
To finish, you can machine the 1500 to have full circle thrust bearings,
reducing the tendancy to throw out the half ones and toss rods out the block.
And a request, of which this is the second. Does anyone have a set of con
rods for the 1500 they will part with?? I need a set.
Cheers Dennis
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