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ignition timing with vac gauge

Posted: Wed Apr 10, 2019 11:37 pm
by steve00136
Well i have read a lot about how you should ignore manufacturers settings which was based on a totally different 1970s leaded fuel and use a vacuum gauge to set timing and not a strobe. I connected my Gunsons vac gauge up after slackening the distributor clamp and as soon as started engine the gauge was showing retarded timing (even though it was set at the prescribed 10deg). I advanced the timing bit by bit. Vac went up and so did tickover speed until it levelled out at 20" so retarded it 1" on the scale which measures in inches. Disconnected and went for a run and a massive difference in acceleration and sounds smoother. On return out of interest i connected my timing strobe and found it was now 20 deg advanced. Seemed a lot to me but will run it and monitor for any pinking.

Re: ignition timing with vac gauge

Posted: Fri Apr 12, 2019 11:11 pm
by steve00136
I did a compression test today again with the Gunsons tester and got 180+-3psi which i think is quite high but guess due to a PO doing 40thou rebore and skimming the head 55thou. Also K&N filter with AAA needles so engine is not really standard for standard settings to apply.
Is more advance better for a higher compression? Is that why engine seems to run better?
PS it's a 1975 RB with HIFs and 41610 distributor.