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Spitfire MK3 Vacuum Advance


Mad4classics
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Suffering from a good deal of pinking with the vacuum advance connected!!! No amount of retarding the ignition cures it, but just disconnecting the vacuum advance and things are fine. I can run at the stock 6degree static setting.

Can anyone tell me the Delco number for the MK3 Spitfire Vacuum advance? The number underneath on mine is 7952875.

According to Triumph Spitfire & GT6 - A Guide to Originallity; the Vacuum advance should be 0@5inHg and 7.5/15@12 inHg, but with a quick check with a vacuum meter I've already got 6degrees at less than 5inHg. Also from the attached picture you can see that the "nose" is fairly long compared to what I expect.

Began to think I was suffering the same problem as Brown&Gammons describe on the MGA:-

https://www.ukmgparts.com/product/mga-midcat-5-submga4-ignition/vacuum-pipe-assembly-inc-clips-mga-1h919

 

image20171104_142804006.jpg

 

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Its most likey the internal spring has fractured and there is no longer any vac calibration .

Vac units are avalable , a slower might help, 

You are running on 97+ ron fuel ???

The vac unit is a economy device to advance more at cruising , it has no addvance when accelerating

The vac is generated at light throttle plate openings if the spring has failed then you get too much instant advance as soon as any vacuum in the line is developed 

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The spring hasn't failed, it passes the usual noddy tests; holds position on vacuum - no leak, and returns consistently to the original position, when the vacuum is released.

Running shell+ nitro ALL the time.

Need to confirm the correct vacuum advance is fitted. 

Using a vacuum meter and the advance control on the distributor to bring the plate back to the same position, I plotted the the characteristic up to the range limit on the meter (need a better meter). Extrapolating the line it will hit 15@12inHg but it's not 0@5in aand is consistently higher than the book figures I've got until the end point.

I'm having difficulty finding any information regarding delco distributors; even though, as I understand it, they were made at a factory in Dunstable.

 

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spitfire3 in my wsm shows dizzy as delco D200 7953557    standpart 214799

no vac advance 0-4ins hg

starts at 6.2 ins hg

7.7 - 10.7 ins hg    gives 5.5 dizzy advance  =  11 crank

20ins hg  max  gives 7.5 deg   15 at crank

centrifugal at 3200    25 - 29 deg advance 

need to add vac to centrifugal 

http://vitessesteve.co.uk/Servicemanuals  will give all the centrifugal     easier than pasting n here 

Pete

 

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53 minutes ago, Pete Lewis said:

 

spitfire3 in my wsm shows dizzy as delco D200 7953557    standpart 214799

no vac advance 0-4ins hg is already advanced by several degrees. It's consitent and will hold that position under fixed vacuum.

The vacuum unit number is stamped on the underside of the unit; need a mirror to read it unless your a contourtionist or take the nsf wheel off.

David

 

Thanks for that Pete,

My advance unit just starts ramping from zero and by 4in Hg is advanced by several degrees. It will hold this position under constant vacuum.

The Delco number is stamped on the bottom face of the vacuum unit. Need a mirror to read it.

David

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