Pix for engine idle setting

[rutger kohler]

I have just worked my way through the excellent instructions, from the manual, on how to tune the engine idle.  I took a photo which may possibly help others on how to connect a vacuum gauge. (Note this is a RHD car)

The attached shows how I used a push on a tube Tee to get a connection for the vacuum gauge.  The existing nylon vacuum hose is removed from the rubber connector to the manifold and a short length of tube inserted.  This connects to the Tee and then the existing nylon vacuum hose is fitted to the other leg of the Tee.  The third leg of the Tee is connected to the vacuum gauge via another piece of nylon tube. (Note in my case the vacuum tube is 4mm and I spent quite a bit of time trying to fit 1/8" and 3/16" tube before realising this).

I got about 14.5"Hg which matches others and I would have to say I am happy with the compression and performance of my engine. The final RPM is 750.  There is a small surge which is interesting, you can hear it more than see it on the Tachometer, the frequency is about every 5 or 7 seconds, however this is small beer and I am really chuffed with the results.  Thanks to those who wrote up the manual. (the vacuum gauge

[jameshoward]

Interesting. Couldn't you just use the blanked (by a bolt) opening on the intake manifold?

I am wholly familiar with the surge. I would recommend a revisit to the linkage tour again - and again, if necessary - to sort it out.  I think the problem you may have is the balance between too lean and too rich, and the cars response to that situation.  Personally, i found that ditching the vacuum gauge after achieving an initial sense of what it shows is the way forward. I found the way to stop the surge was to achieve balance by adjusting the idle air screw and enrichment on the FI pump. Note that you must not adjust the FI pump screw with the engine running. I had my pump fully leaned out and then slowly enriched from there. I hit a sweet spot and the car runs brilliantly. Near 30 mpg on a long run and no surge.  Its a 230 running on points and the original coil.

Have you checked the compression of the engine using a compression gauge? If not it may be worth doing.  Mine is rubbish, incidentally.

JH.

[w113dude]

James,

30 MPG on highway? that is very impressive!

[ja17]

Check the ignition timing at 3,000 rpms after set-up with a vacuume gauge since max vacuume setting could result in the ignition timing being too far advanced.

[IXLR8]

30MPG on the highway--

James, is that per Imperial gallon or per a four quart Colonial gallon?


the other Joe

[jameshoward]

Here was the post I made at the time. It was 32 Miles per proper British Imperial Gallon at about 70 MPH on the motorway. As such it wouldn't be representative of normal combined driving, but it was interesting for me nevertheless.

http://www.sl113.org/forums/index.php?topic=16594.0

[rutger kohler]

Hi James, in reply to your query about why I didn't use the plug at the other end of the manifold, firstly I didn't want to disturb it have just had my manifold bead-blasted and coated, and secondly my method was a very quick changeover with no nuts or bolts etc.  Finally I want to use this setup when I check the advance/retard on the distributor,at higher revs, as another poster has suggested.  I would like to see what the vacuum going to the distributor is.  I may revisit the sticky linkages tour at a later date but at present the surge is so slight I going with it.