I used to actually have in my possesion the august '73 issue of Road and Track
which described tuning the Spitfire/Midget 1500 engine. Well, the article was
specifically about the Spit engine, though the two are the same as far as I
know. Okay, to be honest with you the article was actually about tuning the
small Triumphs, and never mentioned MG at all! There are some neat things in
the stroy, like the 0.745g the GT6 delivers on 165-13 radials, and the list
showing 4.55 limited slip diff for $203.50!
I am not extremely familiar with this particular engine, but if I end up using
a DSP Spitfire for autocrossing I might know a LOT more about it this time
next year. At any rate, here's some figures from Jim Coan's testing:
Horsepower at RPM x 1,000
Config | 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5
---------+-------------------------------------------------------
Stock | 26 35 43 50 57 60 61 60 59
|
warm | 27 36 44 53 60 66 69 71 72
|
hotter | 26 36 45 56 64 71 77 80 80 78
|
hottest | 27 37 39 59 68 74 79 83 84 83
|
[Why do all my technical articles end up with charts in them??]
Description of configurations
------------------------------
Stock - right out of a normal Spitfire 1500
warm - tube headers, dual 1.25" SU carbs from Spit Mk. III. Gives 13% boost
in max bhp over stock.
hotter - as above, but head milled 0.150" ( = 9.7:1) with racing valve springs.
Here we have 32% increase in power (or is that 25% less weak?)
hottest - as above, with better cam. Gee, can YOU tell when the cam kicks in?
Finally, we have a 38% boost in maximun grunt. Not bad.
There were other tests given, 16 in all. If you want I can photocopy the
article and mail it off. But basically it says that with a streetable engine
one can indeed get 80 bhp out of the thing. This was with the dual 1.25" SU
carbs, I would imagine a single 40 DCOE Weber or 40 Sk carb would be roughly
the same, a dual carb setup a bit more, especially if you port the head and
go to larger or better shaped valves. Perhaps bringing the max power up to
around 90 or so, and still being a very driveable engine.
By the way, I could get either new SK or Weber setups (1 or 2) for a lot
less than Paeco if you decide to go that route. A rough price guide is
$200 for each carb and $150 for the manifold and linkage.
mjb.
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