To refresh; 1275 from about 73 or 74 with a dizzy from 68, pair of HS2's
without ported vacuum, the vacuum port on the manifold. Manifold vacuum
measures 15 in Hg at idle.
Here is what I have measured; vacuum disconnected and ports plugged and
timing set about 6 BTC at idle. Connect vacuum hose from manifold port to
dizzy and now it is advanced nearly 25 degrees and idle is rough.
Mechanical advance inside dizzy is marked 14 degrees. I decided that
perhaps the advance was actually retarding under foot to the floor, because
manifold vacuum decreases, causing stumble until the mechanical weights
kicked in. So I took it for a ride with no vacuum advance connected and
ports plugged. The stumble is now only very slight until the weights move
and then it runs great and pulls strong. Idle is smoother, and car runs
great, why do I need the vacuum advance anyway??
Now if I really should have ported vacuum think I can tap off the "Y" pipe
the attaches to the oil separator? Maybe make something to reduce the
volume inside the tap like a plug with a small hole?
Another thing, I am measuring 175-180 psi on a dry compression test on all
cylinders. My Healey 100 measured 90-110 and my TR4 is about 150-160, on
the same gauge. It is higher than I would have expected, especially with a
"L" 1275. Was it a different piston that made the late 1275 lower
compression?
Mark
Nashville
http://www.arrestmered.com
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