Mild 318 pinging

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First plot the factory timing ofthat distributor.
I don't know the idle rpm for '74 but the same distributor was used in '73 on 318s and in the fuel section of the FSM it gives idle rpm of 750.
From the book 550 distributor rpm becomes 1100 engine rpm etc.
upload_2022-5-15_11-30-52.png




1973dust said:
I think I replaced it with a 2nd factory light spring
Click to expand...
A second primary spring will roughly double the spring force from idle rpm on up. (The factory heavy spring has a long loop. That spring slows the advance only after the weights have moved outward. The one in your distributor did nothing until the advance had increased 12 to 17*)
The curve between your two timing measurements (750 and 2000 rpm) will look roughly like this.

upload_2022-5-15_11-43-5.png


The timing will continue to advance at that rate until the wieghts hit the end of the slots.
So the rest of the timing probably looks something like this. Make sense?
upload_2022-5-15_11-52-16.png


Go ahead and get some real timing measurements between 750 and 2000 rpm.
 
Compared with the timing on '67 273 with 4 bbl and 10:1 compression, the mechanical advance you have is in the same ballpark, up to 2000 rpm. Maybe even a little higher in the rpm if the inital was set higher than the 10* at 650 rpm.
upload_2022-5-15_12-6-40.png


My first question when reading your first post was about the 2000 rpm at 55 mph.
I generally use a rule of thumb of 3000 rpm for 60 mph. Now that's with 3.23 or thereabouts and close to stock tire diameters. Have you done the math to be sure its just 2000 rpm at 55 mph?
That would seem to really lug the engine, especially with a stock converter and hot cam.

So differences between your engine and the 67 high performance 273 that will effect timing it needs are compression, fuel octane, and maybe load as well.
Initial of 10 to 14* is perfectly reasonable. 26* a 2000 rpm may be too much, and 32 at 2600 rpm is certainly way too much with vacuum advance. it may be OK without vac advance but with the really load and low octane fuel, I dont know.
 
The timing numbers I already have up to 2000 rpm are as follows - 13* at 1200, 15* at 1400, 18* at 1600, 22* at 1800, and again 25* at 2000 with the initial set at 11* at 750 rpm. I also recorded 48* at 2000 with the vacuum advance connected. Granted, that is no load revving up in the driveway so it could be pulling in slightly less advance on the road. My math on cruise rpm at 55 comes out to 1932 rpm with my 2.76 gears and 26.4" tall rear tires. I could be reading the tach slightly off while driving as I didn't think that 68 rpm of slip sounded like very much. So if I'm reading the charts you provided correctly, I actually slowed down the lower end of the curve with my advance spring magic and really should re-install the long loop spring before going any farther. Thanks again for all of the info and help. It may be several days before I get a chance to plot the rest of the curve I have now and I'll re-verify the lower end as well. I'll also verify the reading of the in-car tach at several points.
 
1973dust said:
So if I'm reading the charts you provided correctly, I actually slowed down the lower end of the curve with my advance spring magic
Click to expand...
Here's the timing you measured overlayed onto the factory and it shows the advance from 750 to 1400 rpm was slower.
upload_2022-5-15_16-5-36.png


1973dust said:
really should re-install the long loop spring before going any farther.
Click to expand...
Yes well Maybe.
Depends on how the governer was modified. There's some adjustment in the spring perches, but not a lot.
If the inside of the slots was welded, then yes that would get it close.
If the outside of the slots were welded, then maybe it will be OK with less initial.

If you have time drive at little with vacuum advance hose plugged and see if its ok under what conditions.

As far as vacuum advance, rig a vacuum gage so you can see what the vac reading is when you are taking the timing measurement.
If you can do that in the garage, then also where you or a passenger can read it when driving steady at 50, and then 60 mph, you'll have pretty complete picture.

I pretty much spill the beans on how each item effects the advance in post 51 and 52
You can follow Rick working through an advance with a points type distributor here.
One difference is that with your combination, need to establish where it doesn't ping under load with the fuel you're using.
 
I'm sure that I welded and re-machined the outside of the slots to limit the total mechanical. My approach was to find an initial setting it idled happy at and then limit the mechanical for a total of 34* I'm now seeing that there really is a lot more to it than that. I hopefully can gather info, as you described in your last post, this week. Thanks again for sharing your knowledge.
 
You can kill 2birds with one stone, by getting rid of that lo-stall convertor.
Here is something for comparison;
I used to run a stock long-block/1973 318/904/in my 68Barracuda in the winter. It cranked 135psi.
I ran a Big TQ/ small-port cast-iron spread-bore intake on it, with TTI headers and a dual 3" exhaust.
And a 2800TC with a manual shift kit. I ran it with every gear from 2.76 to 3.55s, and sometimes with a 904 and other winters with a 4-speed , or a 4od.
She ran just fine on 87E10, with actually a pretty fast curve and 22* of vacuum advance.
I loved the sound of that Thermoquad, and used to run her up to about 15/20mph, with that 2.76, and then stomp on it in Manual-Third gear, and let her moan to hiwayspeed/ rpm, still at 2800ish, lol. That must have been 12/15 seconds at a crack, lol.
No ping on 87E10, at WOT, with that Big Thermoquad.
But I didn't crank the initial timing up either.......
At 2800 the Power-timing was ~26/28 degrees. And the cruise timing was 50*@2800, which was ~77mph.
At 65, the rpm was about 2300, and cruise timing was ~4 degrees less.
Heat is the combustion chamber's enemy; but
heat is power. And heat is economy.
So I would be very stubborn to keep the coolant temp up for as long as I could. I always ran a 195 stat, which ran about 200 at the stat-house, by infra-red gun. Headers are very good at getting rid of heat. I ran projected nose Champion Copper plugs, sorry I forget the heatrange, probably stock.
Yes that 2800TC was fine on the hiway with typically ~5% slip, or less. You gotta get one!
>During my testing; I found no appreciable difference in fuel economy between 2.76s and 2.94s, and only a little loss in 3.23s. This I attributed to the lack of adequate cruise-timing. So I bought a dial-back from the dash, timing box with a working range of 15 degrees, and I found the cruise timing wanted to be 56* at ~2400rpm. which just happens to be 62mph @5% slip. Take a guess what gears stayed in my 318 winter car? Same hiway economy, but Plus 17% first gear, torque Multiplication.
What I discovered was, that I could not give the Smoggerteen enough advance at 2000rpm with the factory advance system, and NOT have detonation under power.
At 2000 rpm, my engine wanted at least 56*. But the MOST V-can timing I could get was 22degrees. That means my mechanical timing at 2000 would have to be
56 less 22=34*.... at 2000.
You cannot run that much timing in that engine at WOT, on any pumpgas. So the fuel-economy suffered. So much so that 2.94s got no better mileage, and 3.23s were only a lil less frugal, now running the correct cruise timing, AND a generous PowerTiming.
And 3.23s with a 2800TC smoked the tires from a standing start ,lol. You gotta get one!, lol.
 
Very quick update as I don't want you guys to think your efforts to help are wasted. I did get to drive the car on a hot day early in the week with vacuum advance unhooked and experienced no pinging at any time. Part-throttle acceleration definitely was not as crisp without the advance added by the vacuum can. I haven't got a chance to touch the car since.
 
Ok, I have more info. I went ahead and re-checked the entire mechanical advance curve as follows. Initial 10* at 700 with 19" vacuum in park. Drops to 600 in gear at 15.5". 10* at 900, 11* at 1000, 12* at 1200, 15* at 1400, 17* at 1600, 21* at 1800, 23* at 2000, 25* at 2200, 30* at 2400, 32* at 2600 which is full mechanical advance. The vacuum can I am using adds 2* at 7", 8* at 10", 16* at 12", and 20* at anything over 14" and it is hooked to ported vacuum. At 55 mph 2100 rpm I am pulling 16-17" vacuum going up the hill in question and it will start rattling if you don't start letting off the throttle until you crest the hill. Obviously, I am pulling the full 20* of vacuum advance under those conditions so it makes sense that unhooking it got rid of the ping. At 40-50 mph on level road it is pulling 20" and 55-60 on level road it is pulling 17.5". Under what I consider normal acceleration thru the gears, it is pulling 12 - 14" of vacuum which is adding 16 to 20* of timing to the mechanical. I see several options if I am understanding things better now as I think I am, in no particular order.

1. Go back to the factory long loop spring on one of the weights to slow down the higher end of the curve and leave the initial setting and vacuum advance alone. From the info that has been posted, it appears to me that the upper end of my advance curve is too hot for 87 octane and 2.76 gears.

2. Back the initial timing off to about 6* instead of 10* and see if the idle in gear is livable. Leave the vacuum advance as is.

3. Leave the initial at 10* and try to back the vacuum advance can off about 4*. Does the adjustment on the can adjust the total amount of advance or does it just change the point that the advance starts? I'm thinking that it changes the start point.

4. I'm thinking that I probably have too much vacuum to run manifold vacuum on the advance without backing the initial setting off to about 0 and redoing the advance plate to allow 28-30 mechanical.
 
Nice job. I agree with your conclusions
upload_2022-5-24_23-9-13.png


If you can put the long loop spring back in, that will probably get it done.
When the distributor is open, move the weights and see roughly how far into the advance before it contacts.
For example you measured 22* advance on the engine. If the weights moves about half way up the slot with the long loop spring, then it will add its spring force approximately 10* into the advance.
You can turn the spring perch to adjust that a few degrees.

With only one primary spring, the advance will begin at a lower rpm. Turn the perch to add more initial tension if possible.

You could also try delaying the vacuum advance, or doing so in combination with using the longer looped secondary spring.
If cruise 20" and moderate load is 16"Hg, then turning the adjuster ccw may be possible to have it only partially contributing at 16"Hg.
Shown in section 1. b.
How To Limit and Adjust Chrysler Vacuum Advance Cans
 
You have good idle vacuum, so less vac adv at IDLE is needed [ MVA ],
but some is still desirable. Once you are cruising, the engine sees no difference between PVA & MVA.
So I would use about 10* init & add about 18* [ not critical ] of MVA so that the engine idles with ~28*. You achieve this my making a stop for the VA unit to limit plunger travel to provide the 18*. Adjust the Allen Key fully CW. Check with a timing light & make sure you have 28* at idle with VA connected. Do this, idling, in gear if auto. Turn AK 2 turns CCW & recheck timing; do this procedure until timing falters or drops. Go back 3 turns CW. Job done. If you get pinging, it is better to limit the centri curve with a lighter weight &/or heavier spring, than touch the VA.
 
When i bought my 69 barracuda coupe the dist. was set at 5 degrees retarded, pinged a lot when advanced, turned out the heat riser valve was stuck on CLOSED. Engine temp.gauge showed normal, but the intake must have been very hot.
 
plyman said:
When i bought my 69 barracuda coupe the dist. was set at 5 degrees retarded, pinged a lot when advanced, turned out the heat riser valve was stuck on CLOSED. Engine temp.gauge showed normal, but the intake must have been very hot.
Click to expand...
Good point. My heat riser is actually already removed but definitely something for others with similar problems to check.
 
AJ/FormS said:
You can kill 2birds with one stone, by getting rid of that lo-stall convertor.
Here is something for comparison;
I used to run a stock long-block/1973 318/904/in my 68Barracuda in the winter. It cranked 135psi.
I ran a Big TQ/ small-port cast-iron spread-bore intake on it, with TTI headers and a dual 3" exhaust.
And a 2800TC with a manual shift kit. I ran it with every gear from 2.76 to 3.55s, and sometimes with a 904 and other winters with a 4-speed , or a 4od.
She ran just fine on 87E10, with actually a pretty fast curve and 22* of vacuum advance.
I loved the sound of that Thermoquad, and used to run her up to about 15/20mph, with that 2.76, and then stomp on it in Manual-Third gear, and let her moan to hiwayspeed/ rpm, still at 2800ish, lol. That must have been 12/15 seconds at a crack, lol.
No ping on 87E10, at WOT, with that Big Thermoquad.
But I didn't crank the initial timing up either.......
At 2800 the Power-timing was ~26/28 degrees. And the cruise timing was 50*@2800, which was ~77mph.
At 65, the rpm was about 2300, and cruise timing was ~4 degrees less.
Heat is the combustion chamber's enemy; but
heat is power. And heat is economy.
So I would be very stubborn to keep the coolant temp up for as long as I could. I always ran a 195 stat, which ran about 200 at the stat-house, by infra-red gun. Headers are very good at getting rid of heat. I ran projected nose Champion Copper plugs, sorry I forget the heatrange, probably stock.
Yes that 2800TC was fine on the hiway with typically ~5% slip, or less. You gotta get one!
>During my testing; I found no appreciable difference in fuel economy between 2.76s and 2.94s, and only a little loss in 3.23s. This I attributed to the lack of adequate cruise-timing. So I bought a dial-back from the dash, timing box with a working range of 15 degrees, and I found the cruise timing wanted to be 56* at ~2400rpm. which just happens to be 62mph @5% slip. Take a guess what gears stayed in my 318 winter car? Same hiway economy, but Plus 17% first gear, torque Multiplication.
What I discovered was, that I could not give the Smoggerteen enough advance at 2000rpm with the factory advance system, and NOT have detonation under power.
At 2000 rpm, my engine wanted at least 56*. But the MOST V-can timing I could get was 22degrees. That means my mechanical timing at 2000 would have to be
56 less 22=34*.... at 2000.
You cannot run that much timing in that engine at WOT, on any pumpgas. So the fuel-economy suffered. So much so that 2.94s got no better mileage, and 3.23s were only a lil less frugal, now running the correct cruise timing, AND a generous PowerTiming.
And 3.23s with a 2800TC smoked the tires from a standing start ,lol. You gotta get one!, lol.
Click to expand...
2800TC any brand? 9.5" diameter?
 
mine is an ancient Trac-Action dubbed "Dirt-Jerker" It was new in about 1978. I worked at the place that built it for me. It was just a stock 10incher they cut open, replaced the stator, reconfigured the impeller, and put some Torrington thrust bearings into, then lathe-welded it back up..
She has been behind every performance 318 that I have had, ever since, and I suspect has at least a half a million miles on her.
Hang around for a bit, someone will give a recommendation based on experience.
 
RustyRatRod said:
Just for kicks, get a compression tester on it and see what the cylinder pressure is.
Click to expand...
Finally got around to doing a compression test. Engine was warmed up with throttle blocked open and all results are dry. The first 4 or 5 cylinders reached max pressure at 5 strokes. The last few took 6 or 7 strokes as I think the starter was slowing a little even though I had a charger on the battery. I did check #3 a second time with oil and saw no difference. I'm pretty happy with the results considering a stock 74 smogger shortblock with a little cam. I wasn't sure how many strokes to max is normal. Plugs all look good, also.

1-150
2-145
3-145
4-143
5-145
6-145
7-153
8-150
 
Ping update. I tore into the distributor and put the factory long spring back in place and also added a little tension with the perch. Once I got in there, I discovered that I had actually replaced the long loop spring with one of unknown origin that was lighter tension than the factory primary spring. Therefore, the curve from idle up to 2200 rpm ended up basically the same. I think I see now why it's recommended to weld the inside of the slots rather than the outside so the springs start out with a little more tension. The curve now has a linear increase from 25* at 2200 rpm up to max advance of 30* at 3000 rpm. Max advance was occurring at 2600 rpm before. I ended up having to live with 8 initial timing for now as I still was having some slight pinging at wot. I've made several wot runs from about 25mph up to 65mph in 2nd gear with no audible ping. I also adjusted the vacuum advance to pull in 2 degrees less timing at 16" vacuum which ended up being 1 1/4 turn ccw. I figure I could probably bump the initial timing at least a couple degrees if I ever get a 3.23 rear. Hopefully, this saga will help someone else in the future. Thanks again for all of the suggestions and help.
 
Sounds like you’re on a good path to gettin it figured out.
 
Does the engine have an EGR valve?
 
:thumbsup:

1973dust said:
I wasn't sure how many strokes to max is normal.
Click to expand...
Pick a number between 3 and 5, or as you observed if the cranbking rpm is dropping, then it may take another compression stroke or two to get max out. As long as you have notes and its repeatable test method, that's fine.
1973dust said:
I ended up having to live with 8 initial timing for now as I still was having some slight pinging at wot. I've made several wot runs from about 25mph up to 65mph in 2nd gear with no audible ping. I also adjusted the vacuum advance to pull in 2 degrees less timing at 16" vacuum which ended up being 1 1/4 turn ccw. I figure I could probably bump the initial timing at least a couple degrees if I ever get a 3.23 rear.
Click to expand...
If that engine likes a little more initial then this
I think I see now why it's recommended to weld the inside of the slots rather than the outside so the springs start out with a little more tension.
Click to expand...
would be the way to accomplish that using the same springs.

Roughly sketching out the new timing set at 8* initial, its not too surprising it was pinging a little with more initial.
upload_2022-6-7_8-15-20.png


If you're satisfied where its at now, great.
If at some point you want to or find you have to get back in the distributor, welding up the inside is one adjustment, and engaging the long loop spring earlier is another. (Or try to find a slightly shorter, heavier long loop spring). I think you see that they do different things.
 
Frank Mopar said:
If you haven’t dropped plug heat range thats next the next step
https://www.autolite.com/docs/defau...ing-spark-plugs/autolite_heat-range-facts.pdf
Click to expand...
I actually was wondering about that. I just looked at an NGK chart and a GR4 is equivalent to a 14 or 16 Champion heat range, so obviously a pretty hot plug. I got the plugs from Rock Auto when I did the cam and intake and ordered plugs for a 340 4 barrel. However, I just looked on their site again and noticed that they list the same plugs for a 318. I just assumed that the 340 plugs would be a little colder. I probably will try dropping one range and see how it does.
 
Mattax said:
If that engine likes a little more initial then this
Click to expand...
It definitely seems to like more initial. Idle was noticeably dirtier when I backed it off to 6* initial from 10* and off-idle tip-in wasn't as crisp. I think it would actually be happy at 12* if I wanted to try to limit the curve and the max some more. 2* initial seems to be worth about 1" of idle vacuum on that engine. I'm going to leave well enough alone for a while before I make any more changes.
 
1973dust said:
I actually was wondering about that. I just looked at an NGK chart and a GR4 is equivalent to a 14 or 16 Champion heat range, so obviously a pretty hot plug. I got the plugs from Rock Auto when I did the cam and intake and ordered plugs for a 340 4 barrel. However, I just looked on their site again and noticed that they list the same plugs for a 318. I just assumed that the 340 plugs would be a little colder. I probably will try dropping one range and see how it does.
Click to expand...

Go down two heat ranges.
 
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