What method do you use to set your initial timing?

[Casenator]

The other day I was speaking with an long-time racer about my attempts at timing my BBC and trying to find out what it likes. I've read many different theories and suggestions on how to do it, but his method was completely new to me. I've never heard of it before and I'm curious on what your thoughts are about it.

He said to NOT depend on a timing light or AFR gauge because they can mislead you. Reading plugs is the only way to do it properly (which I kind of agree with).

If I'm remembering correctly, he told me the vacuum advance must be connected and then rev the engine to about 2000 RPM and hold it steady. Next, turn the distributor one direction until it starts to lose RPM and then go back the other direction until it does the same. Then center it and lock it down.

I can envision how this method may work, but I also see how some things may be overlooked doing it this way (like when mechanical advance becomes fully engaged).

Have any of you ever heard of this method, and what are your thoughts about it?
What are your recommended methods for timing an "unknown" engine combo?

 

[cadillac_al]

I'd say that gets you "close enough" and then you can tune from there.

 

[CorkyE]

If that was the preferred method, then oem's would have no reason to publish timing specs. Reading plugs can tell you a lot about your timing, but there are too many draw backs for it to be effective for the average car owner. How to is the main one, then even trying to read a plug where the fuel is E10 no lead. And don't forget, you need to cut the threaded portion off so you can see the complete insulator.

 

[tom3]

Old guy I used to run around with always unhooked the vacuum advance, revved the motor up pretty good, advanced the timing until the engine ran the fastest, then backed it off a little. Then hot started the motor a couple times to see if it kicked back on the starter. This guy was pretty well known for fast small block Chevys without a big wad of cash. One other thing I remember he would test a motor by putting the trans. in neutral, floor the gas pedal and hold it. If the motor fluttered and died, new valve springs. i(f it really revved, maybe new rods and bearings?) But I saw this quite a few times with no damage to anything - but this was with old school small blocks.

 

[1980RS]

If you are not going to use a timing light then make sure you look at the ground strap on the spark plugs close to see where the strap changes color as you just want it to color on the strap bend. Years ago we used to advance the timing until the engine wouldn't pull anymore than back it down a few, we were to poor to own a timing light. These days I use a regular old Sears Craftsman timing light and lock my timing in on my race car. Some BBC's like 34° and some I have used like 44° and I also found that the better the air is the less timing you need. On my street cars (Chevy's) I run as much initial timing with less in the mechanical timing in the distributor. On my Vortec engines, they won't even tolerate any vacuum advance and if they do it's only like 5°.

 

[carhead22000]

myself for a quick set up i turn it till it revs up and drop it back a hair till idle drops.but thats only a good place to start.

 

[Casenator]

Carhead, was that with the engine at idle or revved up?

Tom3, that sounds very similar to what this guy was telling me.

Being that all these methods are performed with no load on the motor, I guess the only real answer is to see how it drives after each adjustment.

I had my BBC set at 24* initial and 12* mechanical (with no vacuum advance), all in by 2000 (maybe even 1700). I randomly dropped it back to about 16*, connected the vacuum (fixed to about 14*) to ported. It seems to run better and smoother driving around the neighborhood, but haven't really checked other things like WOT from a stop or from a cruising speed.

To me, 28* seems to be on the far low end for timing, so now I'll advance it again, little by little, and see how it responds. I might just end up in the 40's like 1980RS has seen. Road testing with a GPS drag-app and the "seat of the pants" feel are the only methods I have and that really sucks in this 95* to 105* heat.

As CorkyE mentioned, I'm not practiced at reading plugs, but I probably should try. Color changes on the bend of the strap (thanks 1980RS) and the porcelain color itself, etc. I think once I find the timing the motor wants, I should be able to eliminate the extreme lean condition that appears with partial-throttle at light-loads that I'm seeing. It's a challenge to get the carb matched with timing curve for what the motor wants.