1968 273 2bbl Engine Timing

[TheAstroImager]

Curious what mechanical timing any '68 and later 273 owners are running. Currently, I'm following the fender tag recommendation of 2.5 degrees after TDC. I'm still running the original engine (57K miles) on 87 regular, no hardened valve seats. Before I go tweaking anything, has anyone here had luck advancing to maybe 5-10 degrees before TDC mechanical? I'm just trying to find a good starting point. I'm assuming with vacuum advance, it should be around 30 degrees total? My google searches on the subject keep coming up empty.

Thanks

 

[413]

2.5 ATDC? That sounds like a bad idea, a 273 2 bbl is already lame, advance it and see how it responds. Doubt it will hurt anything. Doesn't cost anything

 

[AJ/FormS]

Just remember that whatever changes you make at idle, those will telegraph into your Power-Timing.
That is to say ; if you add 10 degrees at idle, it will add 10 degrees to your Power-Timing, which, if that is already on the edge of detonation, now it's gonna want to cause big trouble.

 

[Dana67Dart]

2.5 ATDC? That sounds like a bad idea, a 273 2 bbl is already lame, advance it and see how it responds. Doubt it will hurt anything. Doesn't cost anything

Why all the hate?

The 2 after is due to smog regs. The advance curve is way faster than non smog cars.

My 67 dart 273 2 BBL FSM says 5 after but the mechanical is all in by 1500 or there about, 273 4bbl is at the same point at the same rpm

I run mine at 5 before it seem to like it there, no hesitation on launch and I can do an 18 second quarter mile!

 

[413]

No hate, just that a 273-2bbl is not a powerhouse and not much compression ratio either so advance it and tell us how it likes it. I've owned a couple, not impressed as far as power is concerned. But they are a good reliable slug engine.

Yes adding 10 is at all RPM's

 

[Bewy]

I think 5-10* BTDC would be a huge improvement: better tip in response, better idle, cooler running.
However, by what ever amount you advance the initial timing by, you would need to shorten the centri curve inside the dist by the same amount. Or find a 318/273 dist that came from the factory set up for 10* BTDC initial timing.

Certainly, as a quick test you can advance the timing to 10* BTDC & do a test drive, but keep the rpms & no WOT.

 

[67Dart273]

You need to learn to check total advance to be sure it is not OVER advancing if you bump up the timing. Both vacuum and mech. NOT that hard.

It's a good idea to check the stock mark with a piston stop to be sure. And then you know

Then wrap a flexible tape around the balancer and then do it again, get an ACCURATE circumference. This will give you a figure you can calculate degrees vs inches. For something like this, you can almost get by with every 10* and estimate the rest, or every 5*

Use a square and scribe and it won't take long to mark the wheel. I usually calculate 20* and make those two marks. You MUST use a tape. Then you can check one mark against the other with dividers. You can also calculate the tape measure figure for 40 and recheck that way

Then you can divide those in half for 10 and then half again.

You can get an idea of checking this by referencing one mark on the wheel at TDC then matching the new marks you made against the 10* index on the timing tab

Get the specs from the service manual, and you can download them from MyMopar.com, free

Bear in mind that the distributor advance specs are in DISTRIBUTOR degrees, which are HALF crank degrees. AKA if it says the mech advance is 11*, that should advance 22* at the crank.

 

[413]

How about move the distributor around and find the position it runs best, then check the timing.

And WOT doesn't mean much for timing, it mechanical advances by RPM and manifold vacuum at part throttle.

 

[jeff alder]

Us old farts have always done it by ear. It's a hard core 273 2 bbl... turn it a bit lock it down throttle it by hand. What do you hear?> Advance or Retard>Repeat