Something has worn, moved or broken with my engine and now it runs better.
I say "something" because I haven't opened the hood to check it out. I did notice the mechanical advance was a little sticky the last time i did a tune-up (June04) but I didn't pay it any attention. I didn't even check the timing. Actually I haven't checked the timing for a couple of years. Anyways, I've been so focused on the SU style Hitachi carbs that I haven't bothered the check or adjust anything else. I've been messing around with the damper springs, damper oil, needles, idle speed, blah,blah,blah. The car ran ok, but something just wasn't right. Even after I upgraded the exhaust. I had more power, but still, it barely idles with the headlights on and still feels sluggish going up long hills.
Well something happend the other day and now the car idles at a solid 1800. It's also pulling 16in.hg at idle with the headlights and heater on and feels all around better, even on the hills.
I can't imagin a vaccuum leak causing this since it's running real lean to begin with. My guess is the mechanical advance has loosened up and is functioning or has gotten stuck in the advanced position. What ever the case, I plan on cleaning up the dist and resetting the timing. Probably with a little more advance.

Any one have any ballpark figures for setting timing? This cam won't let it idle below 1500 and starts to pull from about 4000. Duel SU's, oval port nonGX head, header.

I have had the mechanical advance shaft lock on me. At the best possible time. Had just put twin Hitachis on and put the car on the dyno, pulled an awesome(not) 45HP. Frustrating as hell!

You'd be suprised how much timing these things need in the topend. I preloaded the springs in the dizzy to stop them from advancing as early. Also elongated the slots to give more total.

Have a play by advancing the static timing and driving above 4000rpm until it feels/sounds/smells right. Bring the revs up to where full advance is in, put a timing light on it. Now set the static timing to normal. Play with the advance until you recreate what you saw with the timing advanced.

The problem we had with the timing advancing later was the temp increasing on the highway. 4000rpm with no advance causes a lot of heat to be retained in the combustion chamber. The engine had a heap o' compression and would detonate at low revs if we advanced it too early.

If you're running a ton of compression, the A series head doesnt seem to like much more than about 32 degrees advance all in.

You need about 10 or 12 degrees at idle.

The slots in the dizzy allow more than the 20 degrees we need, so they need to be shortened, or you need to find a SSS dizzy.

The springs dont let all the advance in until reasonably high in the rev range, so the best scenario we found was to make them a lot weaker.

This gave us 10-12 degrees at idle, and all the advance was in by about 2000rpm..

It wouldnt be super satisfactory for a road engine, you'd need some way of mapping engine load in there too, to make it driveable at high throttle/low RPM.. Vacuum advance does nothing when you're running one throttle body per cylander, there just isn't any vacuum...

Umm, I just realised, I am not using a datsun distributor.
Maybe I should put this in "Crimes I've commited"?

And keep an ear open for that death rattle, it means lift thy right boot. And knock the timing back/add more fuel.

your charge prob sounds like a dodgy earth - which could also be sapping power from the ignition system.

wire brush them all back to bare and shiny metal and put some vaseline or engine oil on them before you tighten them up.

With recurving a distributor for a race engine, is it just important to have idle timing right, then have all the advance in before the engine gets on the cam, after which it's just max advance (ie 32deg BTDC) all the way to redline??
I don't really understand it, I want to get my distributor recurved but don't really know what to ask for
I have an A15, a shade under 12:1, pretty big cam but not full race, 45s,
There aren't any dynos in Taupo to be able to tune for hp

Thanks for the reply's.
I've got about 10-12deg at idle without the vac advance and around 25deg from about 3000 and up. With the vaccuum advance hooked up at idle, the timing jumps to 25deg and it sounds like its enough.
After I clean everthing up, I'll try and add about 5deg to static timing and see how it feels and sounds at higher rpms.

If your timing advances this much just by reconnecting the vacuum hose at idle, then you have it hooked to the wrong place.

There should be NO vacuum signal in the line at engine idle if you have it hooked to the correct ported vacuum fitting on the carb. It sounds to me like you have it hooked direct to the manifold, or to a carb fitting that sees full manifold depression at idle.
There should be a correct fitting on the carb, so see if you can identify it & use that one instead.

Yea, it's hooked up straight to the manifold. I do have a port on one carb for the vaccuum advance. I'll change that around as well. Maybe I should do that first.
Is this where the vac.advance should ALWAYS be hooked up? Or is it just because i have SU's?

Direct to manifold,.... never
To ported vacuum on carb [any carb]... Always