Sure is purdy Guy!

I fired mine up today. After many stupid problems that appeared out of the blue, it fired up within about 2 seconds and purred immediately. So far, the new MSA exhaust sounds great. I went with four hangers and it really helped the alignment. Other than the muffler hanging lower than I'd like, the rest fits really well.

I have an ignition timing question. I *thought* I remembered checking the idle timing with the vacuum hose removed, but the '78 FSM didn't say anything about the vacuum advance when setting timing. When the distributor is at mid-slot, it idled at about 1300 RPM (pulled the carbs from my race L26 and didn't touch them) sounds great, but the timing light shows a ton of advance. It was something like 20° or more. I adjusted the idle screws to get the idle down to ~800 and then turned the distributor and got the initial timing down to about 14°, but it started running rougher and had a delay in throttle response. When I clamped the vac hose, it wanted to stall. With the vacuum advance in place, I checked the total advance at 2800 RPM and it was 46°. I am running the stock '82 NA distributor which, according to the distributor advance curve excel file, that dizzy should be at around 55° total advance. I'm really shooting for a lower number like high 30's with the higher compression.

So, my question is, how do I set the initial timing with that distributor? What am I doing wrong?

Jeff....I plug the vacuum advance and run 17 degrees advance at idle. It seems with the higher duration camshaft, you almost must run more advance at idle. I have no idea what my total advance is, but I run the stock European distributors or the stock Datsun distributors on all mine.

Jeff,

Not sure if I've ever seen timing checked WITH VA attached. The 55 you are seeing is probably with 17 degrees vacuum advance. I think that dizzy adds 17 degrees mechanical. Is this a race motor? If so , I would forget that VA and run around 17 initial. How much mechanical advance does the spreadsheet show?

Steve, I thought exactly the same thing about pulling the vacuum hose, but the FSM never mentioned it. I reread the instructions several times and it wasn't to be found.

It makes me feel better that 17° initial is normal. I can probably get it to run there. The chart shows 8° static, 17° mechanical and 30° vacuum for my '82 distributor.

So, I should run the 17° initial, and plug the vacuum advance? I have never studied timing, so I'm at a bit of a loss as to what the vacuum does. I understand the mechanical better, but not the vacuum part of it.

Hope Guy doesn't mind this thread diversion. VA is to help with emissions and MPG . It should only be involved during low load high vacuum situations. That's why I asked if this is a racing motor. Running a street dizzy on a race motor is a compromise anyhow, but having the VA working will probably limit total timing under full load( using OEM figures)- which you don't want .

Vacuum Advance- how is it supposed to work? - ChevyTalk --The Social Network for Chevy Fans

If that could help, with my Rebello cam & Megajolt system, I have to run 20° to 22° at idle to be good. With overlap on aggressive cam, you need a lot of timing advance compared to stock unit at low rpm.

I run 49° at cruise under low load.

I am with Mathieu. I ran 40 advance at idle on a triple weber 240z and could get momentum from stop with no ping if gently accellerating..too much pedal made it ping. It was a quick experiment when setting the timing. I ended up with 20 at idle and 38 at max.

Wow, thanks guys. I never realized that I needed that much initial with the cam.

Just remember......much better to run a little less advance if in question. Detonation destroys engines!

Installed the L24 crank in the L28 block......spins like a top!

Installed the .040 over ITM pistons. Torqued the main and connecting rod caps. Looking good. BTW Madkaw...the pistons are flush with deck.