Good day all,

Just learning about doing a basic tune up on my 66' Toro's 425 engine and I'm having a bit of trouble interpreting the charts in the Olds CSM. I see that the initial timing is set to 7.5 degrees at 850 rpm but there is another spec listed below:



Just curious as to what this second parts of the chart is telling me? For example, on mine I would set the initial timing to 7.5 degrees at 850 RPM, which is easy enough, and then what? Am I done? Or do I have to follow the chart and check the timing advance with a vacuum pump at the 900 and 2100 RPM settings? I know this is a very noob question so bare with me, I'm learning bit by bit.

Thanks!

 

Before you set the timing, you need to deal with the points. Replace them if needed and then hook up a dwell tach. While the car is running, use a 1/8th inch allen key though the door in the distributor and turn the screw on the points to set the dwell to 30 degrees. Note: the fiber block on the points that rides the cam in the distributor wears down over time, so the dwell changes. So you can't assume just because the points are good that the dwell is correct. Always adjust the dwell first before adjusting the timing (unless you have some electronic points, which don't wear).

To adjust the timing, you have to remove the vacuum hose from the vacuum advance on the distributor and plug the vacuum hose (I usually use an old spark plug, the end that the spark plug wire connects is a perfect size). Then up the idle to 850RPM and set the timing to 7.5 degrees BTDC. When you are done plug the vacuum advance hose back in, and reset to the correct idle speed.

The other specifications are for the vacuum advance and mechanical advance, those would be used if you rebuilt your distributor. So no, they are not part of a tune up.

 

Ok thanks, that is great information. Yes, I have a new set of points and condenser here and my timing light/dwell-tach is on it's way. I will be sure to check that stuff first.

I've been doing a bit of youtube watching, etc trying to learn the basics and pretty much everyone talks about "total timing" etc but there's no spec in the manual (well, not obvious anyway) for total timing, only initial. I'm assuming this is just a starting point? The engine is older (bone stock - never rebuilt), running on Premium 91 and may still need a few timing tweaks or should I just stick with the 7.5 degrees?

 

You'll probably also find a note in there somewhere telling you if engine pings with everything set to spec, to reset base timing to 5° BTDC.

The 7.5° BTDC spec is based on 1966 premium gasoline which was leaded (except for AMOCO) and typically in the 100 to 104 octane range.

Don't be concerned with the distributor specs on a simple tune-up. They're in there to help diagnose distributor problems.

 

Ah yes.....I never thought of that leaded gas thing. I guess I'll just keep an ear out for the pinging and dial it back as needed.

 

So many things to think about with the modern gas.......do I need to retard the timing a bit? do I need to add a lead substitute? Do I need an octane booster? Do I need to add fuel stabilizer because the car sits a lot? How many additives do I need to put in this thing anyway??

Sheesh, can't I just go get some 100LL at the airport?

 

Your Toronado would love you for it.🙂

Depending on the flight station you might be able to buy a 5 gallon can of it. Put it in the car's tank and then fill it with premium unleaded and the car will run close to how it was designed to. 100LL has about 2g of tetraethyl lead per gallon which is more than 60s leaded premium had.

That's provided you can talk the flight station operator into it!

Avgas is "drier" than automotive fuel, is why you need to blend it, say 30% avgas to 70% gasoline.

But it's about as simple to just retard base timing a couple of degrees, or send the distributor off to be recurved to be friendlier to modern gasoline.

You can also go one heat range colder on the spark plugs which will help with detonation.

Not that an AC 43 is any easier to find than the 44 is! You can probably cross-reference an Autolite, NGK or other higher quality brand plug to the 43.

 

I have a '66 Toronado and it runs just fine on "today's 91 or 93" gasoline with stock timing settings. The octane rating system has changed since the old days with Tetrarthyl lead. European compute their octane rating differently than we do. Don't get terrified about octane ratings, you'll be just fine.

Stabilizer might be good, if it sits for long periods of time. "Avgas" (100LL) is blended with more additives to vaporize at higher altitudes (colder temps). This means gasoline in your fuel lines could start to "boil" at hotter temps. Adding some "Race gas" instead of "Avgas" might be a better solution.
.

 

The total advance is the initial advance (that you set by rotating the distributor) plus the amount of mechanical advance (that is build into the distributor by the shape of the centrifugal weights). So the initial advance is simply the total advance minus the mechanical advance. Since the mechanical advance is fixed, it is easy to specify the initial advance (at a particular RPM) so when that is set properly, the total advance is also set properly by default.

 

Ok that's good info. So what about the vacuum advance? How do you ensure that the vacuum advance is working correctly?

 

It's a vacuum canister, so all it does is pull the rod in when vacuum is applied. You can connect a timing light and watch the timing as vacuum is connected and disconnected. The timing should increase with vacuum application and drop back to nominal with no vacuum. I have never checked the operation of one beyond ensuring it pulls in with vacuum application.

 

Really simple. Either use a clean hose, or the hose already attached to the vac. canister. Suck on it w/ your mouth then place your tongue over the hole. A working vac. can. diaphragm (no leaks) will hold a vacuum with your tongue over the hole at the end of the hose.

 

sysmg identified the correct way to tune your engine - spot-on.

I'll add two points to this discussion -
(1) Dwell influences timing - timing DOES NOT influence dwell;
(2) After you've set dwell & adjusted timing, adjust your A/F mixture (ratio) screws on the carburetor for optimal performance.

Engine tune-up (points + condenser) always in this order:
(1) Set Dwell
(2) Adjust timing
(3) Adjust A/F mixture

 

Some top notch advice here folks, thanks so much for your help.

 

100LL generally won’t hurt anything. I used to get drums of it for free and ran a number of old, carbed cars on it, straight, for years, small engines as well, with no noticed wear or ill effects other than making me absolutely detest the smell of pump gas. House and diesel truck ran great on free Jet A as well, fwiw. Good to have buddies working at the FBO that were happy to have me remove their waste fuel.

HOWEVER, as mentioned, I would advocate the mixing of it with pump gas and even better, mix race fuel instead of the Avgas unless there is a large price difference. Downside to either is the inconvenience and expense, I think race gas is $8-10 (last I knew!) and have no idea what 100LL goes for these days. “They” say to add ATF or Marvel to 100LL if running it straight or higher concentration but I never did.

If you can get 93 at the pump, I would time it per original specs and see how it behaves before mixing any fuel. Might be a good idea to go through the carb with components that will better handle alcohol in the fuel and tune the carb, recalibration might be in order as well.

​​​​​​….

 

Its good that you ask questions. I don't think you have anything to worry about. I cruise at 70-75 MPH and no overheating. I do a short "burn out" before I park it each time....just to make sure everything is working well.

 

Just as a follow up to this thread, I was going to go ahead and just replace the points and condenser in my 66' Toronado and was wondering what is the best way to go about this? Maybe someone has some tips?

I now have my dwell meter and can accurately set them to 30 degrees once up and running, however, when you're putting in a new set what is a good starting point? Do you guys just disable the ignition and crank the engine while watching the dwell and adjust accordingly or can you set them with a feeler gauge just to get you in the ballpark?

 

Make sure your vaccum advance is working i.e. it adds 9 Deg for advance. One can check with your timing light.

What one can do is mark your harmonic balancer, going clockwise from the notch(downward) in 5 degree in increments to 60 deg.

they make tape for this as well:

http://store.wpsracing.com/timtapol35wi.html

and use the Top Dead Center 0" on the timing tab as a reference.

Vacuum advances not working are common as the rubber diaphram deteriorrates. You wont get as good a gas mileage and also could cause over heating..

usually not a problem but one could also use the bottom chart to check the mechanical advance as well.

A timing light with a rpm readout makes it easier..

I checked mine by adding inital + Mechanical + vacuum = Total timing

usually about 3K rpm is about maxtotal advance then ithe advance will start to fall off as intake vacuum starts to fall offf at high rpms and the vaccum advance... this helps with reducing pinging at higher rpm..

 

Install the new points and see if the car starts, they usually start and then adjust the dwell with it running. You can check it with a feeler gauge if you wish first. Put a very slight film of grease on the distributor cam to reduce rubbing block wear, too much will sling off onto the point contacts. The block wears quickly early on and then slows so don't be surprised if the dwell changes after a few miles, if it does reset it.

Good luck!!!

 

I only had a feeler guage back in the day i n high school. 1st place to start..

Dwell meter is way more accuate! you're doing it right!!! good job..!!!!

 

Yes, I could use a feeler gauge but there's no spec on that, just the dwell setting. The manual tells you to get the points up on one of the lobes, screw in until your test light comes on, and the back it off a half turn. Then use dwell meter to get it right on the money.

Which direction does the crank turn on the Olds 425 anyway? Clockwise right?

 

The crank turns CW (when viewed facing the front of the engine) or CCW (when viewed sitting in the driver's seat). The distributor turns CCW (when viewed looking downwards from the top of the distributor).

 

Yeah, that makes sense now that I look at the degree markings on the pointer. Duhh, I'll get there soon!

 

New points .019", used .016". Getting an accurate gap is difficult on used points because the pitting on the contacts cannot be accurately measured. A dwell meter is a lot better.

Good luck!!!

 

Alright cool, I'll set the new ones to .019" and throw em in. Then use the dwell meter from there, thanks for your help!

 

You can't set the points until they are installed. They might be close enough to get the engine started.

#1 Hook up your dwell meter. Try to place it so you can read it while cranking the engine.
#2 Hook up your timing light to #1 plug wire and plug the vacuum line. You'll want to check timing after installing the points.
#3 Install the points and see if it will start. You can watch the dwell reading on your dwell meter as you crank the engine. You might only need to tweak the dwell a little.

 

I've never had a GM point set that wasn't close enough to run. I always put in the points as they come out of the box. Start the car and set the dwell. Then you disconnect and plug the vacuum advance. Then i use the Tach to set the RPM to spec (850rpm). Then clip on the (induction) timing light and set the timing (loosen the distributor retaining bolt between 1/4-1/2 turn and adjust and tighten the retaining bolt and recheck timing). Then drop the RPM and reconnect the vacuum advance. Then reset the idle as per spec (my 1966 425 was 500rpm in drive). Then you are done.

If you are doing a full tune up (plugs, wires, rotor, cap, air filter, gas filter, PCV) I do all of them before replacing the points. You might start it just to make sure there weren't any problems with these parts. Then I'd replace the points.

 

Uggh,

Well I got something screwed up! Changed the points, condenser, and the rotor......now it won't start. My dwell meter seems to be stuck on 45 degrees no matter what I do to the points. Uggh, I gotta start over or something.

 

Put the old points back in, leave everything else new. Then you can make sure it's just the points.

 

Are you absolutely, positively, beyond doubt sure you installed the rotor? Not that I know anything about that...😊

Curious if you tested the new-to-you dwell tach to be sure it worked, before connecting it after the tuneup.

 

...all good questions/suggestions. Additionally, the fact it is stuck @ 45° would (apparently) kinda indicates/suggests the electrical field is completely "collapsed" (closed) w/ a 100% duty cycle. A GM V8 (cylinder) engine should have dwell set to 30° which yields/provides a 60% duty cycle (30° closed & 15° open [30°/45°=60% duty cycle]). A 100% duty cycle would yield 45°/45° (100% duty cycle=completely collapsed electrical field). If the dwell meter is "stuck" at 45° I would assume/guess there is no opening of the points and the field (points) is entirely collapsed; albeit, there is no headroom. IMO (if this logic is reasonable) you'd never have any firing of the electrical field since it never opens and the coil will never discharge (it's entirely collapsed). You sure you have the dwell meter hooked up correctly? One wire (lead) to the negative coil wire and the other wire to ground.

 

Funny, you are right on the money. The points were indeed opening and closing but I took them out and tested them with the continuity tester on my Fluke......no continuity even when the points were closed. There was corrosion on the contacts completely preventing them from working. A bit of sandpaper, working once again.

These were "new old stock" points, Remy-Delco made in the USA. I can't believe they could have corrosion on them despite never being used. Is this unusual?

 

Need to consider what you're purchasing when it comes to NOS. Electrical components sitting in a box for 50+ years is a crap shoot. Glad you found the issue.

 

Corrosion on point contacts is very common, often just cleaning the points with a light pass of a file would get you started. Age shouldn't hurt a point contact set, I'd be more concerned about the condenser if anything at all.

 

As was suggested in Post #29, you would have arrived at this conclusion, as well.

 

Yeah, my Dad hoarded all the parts years ago. All these components came with the car when he gave the car to me.......I have a pretty large stockpile.

 

I'd have a tendency to disagree w/ you on this one. You'd be lucky to find any metal left on a set of points left laying around in my garage/man-cave after a couple years. Constant near 90% salt water humidity in the air 365 days/year. Every several years I literally grease my hand tools.

 

Sorry, I had to chuckle at your statement (I'm bad). There better be no continuity when the points were open. Good luck moving forward.

 

Norm, Sounds like your paying the price of living in coastal paradise!

 

X 2
I keep a few strips of Crocus cloth in my toolbox.....just for cleaning points. By pulling it through the closed points a couple times on each side does the trick. Anything that is not vacuum sealed can corrode in the atmosphere.