[Spits] 79 Spitfire with SU carbs

[Jim Muller]

On 30 Jun 2007 at 22:25, David Woerpel wrote:

> If an engine has 
> been de-smogged, would the plug gap be different?

No.  Nor would the point gap (i.e. dwell angle).

My 1500 has been demogged and it has the 1976 head with 9.0:1 
compression ratio, original carb.  I've experimented with the timing 
to get it to accept modern gas, and no change (within reason) in the 
timing would make it behave the way you describe.  I don't think your 
stumble is due to using North American tuning specs.

You need to make sure your coil, points, condensor, and plugs (and 
wiring connections) are good.  I've never experienced a bad coil but 
if I recall correctly it might cause a high-speed stumble.  Another 
thing to consider is that your plugs might be getting fouled, which 
is why the rpms of stumble onset seemed to come back down after you 
got it raised.  That could be the result of a bad mixture.  Given the 
carb-swap I suspect that.  But first try swapping coil with a known 
good one.

-- 
Jim Muller
jimmuller at rcn.com
'80 Spitfire, '70 GT6+



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