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Timing by the vacuum method

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bigjones

bigjones

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I've just re-timed the 1500 by the vacuum method that was brought up recently over in the Triumph forum.

It went surprisingly well. (Before I went through all that business with the dizzie, the car was running, I believe, very well). After re-fitting the dizzie I get the engine up to temp - the reading on the vacuum gauge was 14 (inches of Hg, I think).

I slowly rotated the dizzie clockwise until the reading showed a max of 20. (Engine revs also went up from 800 to 1300). Then I backed off to 19 and set the idle back to 800 rpm using the idle screw on the carb.

I checked with a timing light on the crankshaft pulley marks and this new setting was about 13 BTDC at 800 rpm.

I'm quite pleased about this because the engine now is operating more efficiently.

During this set up I had plugged the vacuum retard at the dizzie with a golf peg.

I'm wondering if there is any benefit re-attaching this vacuum line.
 
Adrian, I don't remember seeing pictures of your distributor. Am I correct that your 1500 has a vacuum advance distributor? The late TR-1300s and early 1500s had a vacuum retard capsule for emissions purposes.

Disconnecting and plugging a vacuum retard port will not affect anything but emissions and change your idle speed. Plugging a vacuum advance port will only rob you a bit of part throttle cruising fuel economy.
 
Doug,

Hi there!

Yes, it is a vacuum retard - thanks for the info - I'll go ahead and re-connect then.

Searching the archives, I see you yourself are a big fan of an onboard vacuum gauge - I'm thinking the same. There's already a hook up on the inlet manifold! It seems straightforward enough - is there anything folks should know before they install a gauge in the cockpit.

Cheers!
 
The only caveat I can offer about an onboard vacuum gauge is make sure you route the hose away from hot places and pinch points. I'm partial to VDO gauges and they are affordable through eGauges.com. If you want an older looking style gauge, chrome bezzel Sunrpo vacuum gauges are available from Summit Racing. If you want an original Smiths unit, they show up on eBay fairly often but typically sell for $40 to $60 depending on their condition.

The retard capsule on the dizzy isn't a big favorite with most people. My 1300 came with a Delco dizzy with a torn diaphragm in the retard capsule. The previous owner simply disconnected and plugged the line. I had so many other issues with the 1300 I never worried about it... especially when I learned it wasn't going to help me with fuel economy like an advance would.

Connect your retard unit if you want but if the retard capsule is working, expect the idle RPM to plummet when you connect the vacuum to it. That's normal and corrected by running the idle screw back in.
 
bigjones said:
Doug,

Hi there!

Yes, it is a vacuum retard - thanks for the info - I'll go ahead and re-connect then.

Cheers!
Click to expand...

Don't. At the spridget 50th, Jeff Schlemmer advised me to leave it disconnected and plugged. He siad it would run better and, more importantly, cooler. I trust Jeff on this one and as far as i am concerned it does run cooler.
 
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