slimbobaggins

I asked this in the 3rd Gen truck section with 0 responses, figure I'll get more of a response here since a lot more of you have carbs.

After rebuilding my stock Aisan carb w/ some assistance on here, I got my 22R idling pretty good on cold idle ~1250 rpms, and warm idle was 700 rpms with ~21 inches of vacuum.

The last task now that I had a stable idle was to set the ignition timing, which I hadn't messed with. With the vacuum advance lines plugged, it was advanced past the 12 mark, not a whole lot, I'll guess around 15 degrees. I set it to 0* BTDC like the underhood label says, and it barely idles, running really rough, and vacuum is down to 19 inches. Bumped it forward to 5* BTDC, and it smoothed out a little more, but still not great. Started to rain, so I called it quits for the day.

This morning, I crank it over, and depsite the choke being closed and the fast idle cam engaged, the cold idle is way low, didn't have the tach hooked up, but nowhere near 1250... it eventually sputtered and died. I assume this is a result of me retarding the timing yesterday.

So I don't know why it's running so poorly, but my question is if it runs good at 15* BTDC, and it's not pinging, is there any reason to not leave it there? Before I messed with the timing I drove it around the block once, didn't get on it hard or anything, but it seemed to run okay.

slimbobaggins

Never mind, looks like I found my problem.

Pulled the timing cover, and looks like I'm off by 1 tooth. I swear I checked this multiple times, but oh well. What a heartbreaker.



Cam is at TDC, crank timing mark doesn't line up:

Stetson_md

Is piston#1 at tdc?

jimbyjimb

iTrader: (1)

Even though you solved your problem I'll answer your question.

As long as you aren't pinging feel free to advance your timing as far as you like. Octane will have a huge effect on this. Tune on the fuel you typically use.

LCE recommends 10* BTDC for performance applications. Their guidelines are pretty good considering the wide body of experience they have tuning these engines. Your mileage may vary.

andykrow

Cam might be fine. With the timing mark at zero at tdc the dimple on the cam gear should be just to the left of straight up. 11:55 rather than noon... Don't worry about the bright link on the chain as that doesn't line up most of the time. It's only for initial setup. Looks to me like if you line up the timing mark the cam mark will sit right where it should.

If you aren't pinging and the truck runs good at 15 degrees just leave it there. Plenty of people advance until the truck pings, then back it off until it stops and leave it there with no ill effects. And that's usually more advance than factory spec.