The Stovebolt Site Forums The Shop Area Engine Shop Advance or Retard?

My dad and I finally got out there in the cold to track down that silly BB on the flywheel. Our truck seemed to be running ok, but we weren't able to see the BB with the timing light. We finally found it, cleaned it up, and started messing with the distributor for the first time in order to set the timing "on the BB". Initially, the distrubter was retarded about 8 degrees. Mind you, the truck was running ok. The plugs were charred black, which I'm told means the engine was running lean. Anyway, after setting the distriber back to the "0" mark, the engine wouldn't fire up. So given all that, my questions are 1) where do most people running stock a 235 have their distributer set, advanced or retarded, and how much? We'll get it fired up tomorrow--it is just too cold out there right now. Thanks!

I'm running 15 degrees advanced. However, I am running a distributer that does not hava a vacuum advance unit on it.

gjberche,

I could be wrong, but I don't think any engine made is timed to fire ATDC...retarded. Opening the points BEFORE the piston reached top dead center is sort of like leading a duck with your shot gun sights. It takes time for all the ignition stuff to happen as well as the fuel/air mixture to ignite and burn. The firing has to "lead" the pistons arrival at TDC to maximize the process.

I think there are two schools of thought. Use marks or BB's, or time it until it runs the best with no detonation or abnormal heating.

The marks will get you in the ball park, and they should be accurate, but it isn't against the law to fiddle until you are happy with it.

When you and your dad timed it, did you remember to disconnect the vacuum line at the carburetor and plug the port into the carb...maybe this is why it won't start now.

How did you determine it was 8&deg ATDC...did you use a advance timing light?

Stuart

Thanks for your response Stuart. You'll have to forgive me, as I think I posted before thinking, and this is the first time I've fiddled with a distributor.

What I really want to know is how to set the "octance selector". When I said our distributor was 8 degrees retarded, I really meant to say that the "octane selector" was 8 marks off center (towards the "R"). I assumed "R" meant retarded, but now it seems clear that "R" means "rich". Is that correct? What does the "A" then mean ("leAn" ?).

I also didn't know you need to diconnect the vaccuum advance when setting the timing. To my knowledge the shop manual doesn't say that. It seems like it wouldn't advance much at idle, but maybe it makes a difference?

Thanks for helping out a new guy. The only way to stop being green is to get dirty!

The octane selector is not used to set the timimg. It's original use was to tailor the timing to either higher or lower octane fuels for the best performance without pinging. You can't find fuel with low enough octane to ping in your truck; the engine will fight the starter before it will ping. Apparently the previous owner advanced the distributor timing too far and fine tuned it with the octane selector. The selector should be set to zero when you unclamp the distributor and time the engine. The "A" is for advance and the "R" is for retard. Sooty plugs indicate a rich condition or incomplete combustion, not an excessive advance condition.

I timed my 261 right on the BB and was not pleased with my fuel mileage. I decided to experiment with the advance (since that is easy) and I have ended up almost at the end of the advance slot. I run E-10 gas exclusively.

I can get my motor to ping when 'lugging' around a corner, say around 1200-1400 rpm. I suspect that if I put in heavier mechanical advance springs I could get this problem to go away. I only turn 2000 rpm going down the road 68 mph and I really think I need full advance by 1700-1800.

I have not taken my pickup on a long enough trip to check highway fuel economy since advancing the timing, but it seems like I have to fuel up less often around town. I try very hard NOT to lug the engine in the rpm range it pings in. Even with the timing at this level the engine NEVER fights the starter. I noticed that the tailpipes are burning gray now rather than the black when the timing was on the BB.

Greg,
As Baldy sais loosen the bolt to the left of the distributor and slowly move the dist and marks to be set in the middle, not A for advanced or R for retarted. Then carefully lock down the bolt. Then disconnect the vac advance at the carb and plug the carb with a short piece of tubing and a bolt. Have you taken the flywheel cover off and turned the flywheel to where you can clean the little ball and the first mark clockwise on the flywheel? After cleaning take a little white paint and paint the ball and first mark. Just a little so you can see it with the timing lite. You are almost ready to set the timing. Install new points set to .019, new condenser, new rotor and cap an wires and plugs. On the right side of the dist there is a screw, loosen it very slightly just so you can just turn the dist a little. Start the engine let it warm up some and shine the timing lite on the opening on the bellhousing. The engine needs to be running very slowly 375-475 rpm so the centrifical advance is not engaged as you are setting the base timing. If its running fast turn the idle screw on the carb to set the idle down. Don't turn the air fuel ratio screw on the carb yet. If you have a vacuum guage get it out and hook up to your intake manifold what is it reading 19-21" of vac your timing is close to where it needs to be. You should be using #1 spark plug wire. Can you see the ball or first mark you painted? If not, turn the dist one way or another slowly til you see the ball line up with the pointer. Check the vacuum reading did it get better 19-21" when you turned the dist. The idle may go up when the timing gets close. Set the idle down again recheck the timing. When you get the timing set on the ball, shut the engine down and without turning the dist tighten the screw on the dist, that will set you timing. Restart the engine and adjust the rpm by the carb and adjust the air fuel ratio using the vacuum guage to highest reading. It will take some back and forth to get it perfect. Give your self time to learn the engine.
Good luck.

52pu

Wow 52pu! Thanks for a really detailed explanation and procedure. The shop manual does not go in to such detail, but perhaps that is because the intended audience for the shop manual was the service techs at the dealerships, who probably knew the procedure details by experience.

We cleaned the BB on the flywheel but haven't painted it yet. Should I use any old white enamel paint? Also, how can you tell the engine RPM? Our truck seems to idle slowly, but I don't have any quantitative way to measure the RPM. Any thoughts? Thanks again for the replies!

you can hook up a dwell-tach and use it to watch the rpms.... a dwell-tach is an instrument that measures your engine rpm and also reads the dwell of your distributor breaker points.

put the dist back to where it was get to run disc the vacum line to dist use vacum gauge with eng at idle adv dist to highest vac then retard dist until vac is 2 numbers lower eng will be time very close to correct...doc

I found that the best way to time the engine was to forget about the timing light I bought and tune it by ear (or better by RPMs, dwell-tach as suggested by cjoe). I painted the ball on the flywheel, using a bit of krylon white paint applied with a Q-Tip (it does not really matter, just any paint that reflects light well) but I found that to run efficiently that I had to advance the timing beyond the opening that is available in the housing.

52pu has a good system there, but again I looked for max rpm at a given carb setting to establish a baseline. This setting was done at low rpms to ensure that I had not engaged the vacuum advance. Once I tuned to this point, I re-adjusted the carb for best mix and rpm.

While not the most scientific way, or possibly even the best method, it suffices.

Good Luck,

Thanks guys. I just need to wrassle with this rusted distributer clamp and then we'll be able to time it up! As with most things, there isn't really one single way of doing it. All this info is very much appreciated.