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MG Midget and Sprite Technical - 1500 decommissioned emissions

I have owned my 1275, 1971 midget since it was new but am working with my neighbor on the restoration of her 1500, 1976 Midget.

We decided to remove emissions equipment to reduce weight and improve access to the engine compartment. The tag in the compartment indicates a 2° ATDC timing adjustment. At 5,000 Ft. above sea level, we usually advance 3°. I assumed that a straight configuration without emissions was more aggressively timed.

What is UK timing spec for 1976 1500? Is 6° BTDC OK?

At 6° BTDC set with vacuum to advance disconnected, timing advances to about 18° upon connection of the vacuum line at idle. On the 1275, there is no perceptible advance visible with the timing light or increase in tick over RPM when the vacuum line is reconnected but the change is radical on the 1500. It is such that the idle speed must be reduced at the carb to compensate once the vacuum line is back on place.

If anyone with a UK spec or a decommissioned emissions 1500 could indicate the proper timing setting, I would appreciate it. Also, should the timing be set with the vacuum disconnected as is standard practice with the 1275 (even though it hardly matters)?
Glenn Mallory

Im thinking Deb evans is going to be your best friend on this one.

Curious... How does she perform now that she can breather ...what might be cool is going to the Uk HS4 set up, but to get really cool, and better performance (well torque anyway) perhaps a UK 1300 spitefire intake with HS2 carbs..

Yeah I just learned about this little gem of a mod last night, apperantly HAP of acme speed shop Is a fan of this set up on the 1500.
Prop

Does the 1500 have ported vac like the later 1275s? This might help explain lack of vac adv at idle...

Vac adv at idle isn't nec bad.

A
Anthony Cutler

Set the advance to 10 BTDC @ 800rpm with vacuum disconnected as an intial setting & see how it runs.

I've got my desmogged '78 1500 up to 14 BTDC now & it runs absolutely great!

Set it & don't fret over the vacuum advance, as long as you have no detonation (pinging), you're fine!

It also likes Premium 93 octane, I've tried 87, no detonation, but a little sluggish...
Dave Rhine ('78 1500)

What Dave said.

My desmogged '79 1500 is set to 16 BTDC, vac disconnected and runs pretty well. Also, some of the NA 1500's have a vacuum retard distributor as stock equipment for emissions control.
Richard Reeves

Yep, you're right Richard...my original distributor had a vacuum retard.

I replaced it with a pertronix distributor with vacuum advance...it perked the little engine right up!

:)
Dave Rhine ('78 1500)

A pic of my setup:


Dave Rhine ('78 1500)

This thread was discussed between 23/10/2010 and 24/10/2010

MG Midget and Sprite Technical index

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