Hi Everyone,
I bought the "read your spark plugs" guide and noticed that my timing mark on my ground strap is way over at the main body of the plug. In the guide it basically speaks to fixing the known issues first. I picked up myself a fancy timing gun and came out with these numbers:
Vac. advance disconnected:
Idle set to 800RPM
Initial: 8 BTDC
Full mechanical advance at 2500: 24.4 BTDC (this seems low?)
Vac. Advance connected:
Idle set to 800RPM
Initial 23.4
Over 2500 RPM: 44.4
The decision to look at timing is because even with a new thermostat, a rad flush, new rad hoses w/spring, she still climbs in temp, especially on the highway and the plugs say too advanced in the timing dept. Even with the low compression and the 94 she will still ping a touch under full throttle. Taking into account that this motor is in a 1970 Plymouth Duster it only has a 22" Rad. The engine is 10.1:1 compression, 340 based 416 stroker, for fuel I run 94. Rear gear is 3.55 SG. A833 4 speed. Thermostat is a 160 degree unit and opens (had a 180 before).
Should my vacuum advance be pulling that much timing at idle? I thought it was not supposed to be pulling timing at idle? Does the vac advance pull too much timing for cruising on the highway at 44 degrees causing a lean/ hot scenario? I thought ideal was somewhere around 32 degrees. I am running an Edelbrock Thunder AVS carb with the vacuum connected to the port on the front of the bottom plate of the carb, on the drivers side.
Ideas? ideally i'd like to keep the vac advance because the car is pretty much a show car, looks just like she left the factory.
If you are running your vacuum advance off the ported vacuum connection on your carb and your vacuum advance is advancing the timing at idle, it means you have the throttle blades on your carb adjusted too far open. Turn down your idle screw adjustment to close the throttle blades, and then bump up your idle speed by advancing your initial timing (without the vacuum advance connected). If the throttle blades are set correctly, when you reconnect the vacuum advance your timing and idle speed should not change.
Another possibility is that you are running your vacuum advance off the port on the carb that is always under manifold vacuum, which would always engage the vacuum advance. Some folks prefer to tune that way, but I'll try not to start the endless debate of ported vs. manifold vacuum.
Quote from: DeathProofCuda on June 18, 2021, 08:36:20 AM
If your vacuum advance is advancing the timing at idle, it means you have the throttle blades on your carb adjusted too far open. Turn down your idle screw adjustment to close the throttle blades, and then bump up your idle speed by advancing your initial timing (without the vacuum advance connected). If the throttle blades are set correctly, when you reconnect the vacuum advance your timing and idle speed should not change.
This sounds very logical, I will verify this. I'd expect that my initial should be above 10 degrees at least.
Yeah, the port for non-emission controlled vehicles is probably always under full manifold vacuum. The ported vs. manifold vacuum and the vacuum advance vs. no vacuum advance debates are endless. IMHO, neither choice is wrong. You just need to decide which option is best for you and then tune accordingly.
I won't open that can of worms. I am more familiar with the ported way so, I am going to stick with that. I will switch the line and see what happens.
I kind of recall CP mentioned that the vacuum pot can be adjusted with a small allen key or screw driver.
Quote from: 7212Mopar on June 18, 2021, 12:31:58 PM
I kind of recall CP mentioned that the vacuum pot can be adjusted with a small allen key or screw driver.
Correct. If your vacuum advance has the hex shaped end by the vacuum port then you can insert an allen key into the port of the vacuum advance and adjust it. CCW increases vacuum.
Nice write up I had bookmarked on vacuum advance adjustments.
https://www.forabodiesonly.com/mopar/ams/how-to-limit-and-adjust-chrysler-vacuum-advance-cans.183/ (https://www.forabodiesonly.com/mopar/ams/how-to-limit-and-adjust-chrysler-vacuum-advance-cans.183/)
I prefer to set for total first and adjust from there. WITHOUT the vac advance connected and ports plugged rev the motor up till no longer advancing (around 3k). Set the car for 34 to 36 advance. Back off the throttle and see where initial is at. IF its between 15-18 your in pretty good shape. if too low it needs to be recurved. Connect the advance to the ported side and check for total again and see where it is at. if it pings while doing this then you can back out the advance by using a (i think) 5/32" allen wrench through the VA port.
From the settings you posted above it looks like your set too low and relying on the vacuum advance hooked to manifold as a crutch for initial. On heavy throttle the VA will not pull timing and the motor will fall off in power. under idle and light throttle it probably runs great!
My 416 has 9.7:1 measured compression with Edelbrock heads and I run 91 octane.
I run 32 degrees total advance without vacuum advance. If forgot my initial and curve setting. It's a MSD E-curve distributor. But IIRC initial is over 10 degrees.
Virtually every engine I tune I leave the vacuum advance off or I stick a ball brg inside the hose so it looks correct but will not function generally the timing curve is too long . I don't use a light at all , I bring the engine up to around 2500-2800 & advance timing just until rpm quits rising & leave the timing on the cusp where it rises , any more advance & the RPM will not rise , if it pings yu either need better fuel or you can back off the timing a little . After setting the timing at 2500 rpm return it to idle if advancing the timing at idle from the same setting increases rpm the curve is too long , if retarding increases idle the curve is too short .
Total timing at RPM is the most critical as that is where the engine spend the majority of the time .
Yes you can adjust the vacuum advance setting with a small allen key as mentioned above , there is about 14 turns available inside going from zero to about 14* advance , CCW reduces the advance available .
Or do EFI with computer controlling the timing. Easy to adjust and make changes.
While I go and frig around with this, here are the specs on my motor.
Anyone want to comment on WTF they would do for settings? Is this a big cam that needs a ton of initial?
I'm extremely frustrated. Part of me says shell out big money for a restoration rad with higher cooling capacity but I'm not sure that's going to solve the issue.
I'm off to go and play with it some more.
Back in a bit. I have always struggled with tuning and spark plugs and air fuel. I never know what setting to touch until I have completely screwed it up.
Are you saying you have high engine temperature issues? You say engine look stock so I assume you are running mechanical fan and cast iron heads. Eight degrees initial seems low but timing should not advance that much at idle with vacuum advance connected and 44 degrees at 2500 seems too much. What is the timing at 3500? I would say your 112 degree cam and lift is not too big for a stroker motor.
My 416 is 9.9 CR but running aluminum heads, Comp Cam CRS XR292-HR-10 and 1.6 rocker. My engine builder set mine at 34 degrees at 3200 ruining a 750 Quickfuel carb. He specifically wrote on the build sheet telling me not to hook up vacuum advance. I since had converted to EFI with computer timing control. It is now set at 12 degree initial and 32 degree total. I am running mechanical fan and a brass OEM replacement radiator. Engine temp will get up to 200F on a hot day in stop and go traffic. Mechanical fan don't move enough air at idle stop and go traffic. I solve this by removing the rallye hood insert to let air out from under the hood.
I think you should at least try what CP suggested and disconnect vacuum advance and plug it to see how the engine runs. Have you try adjusting the vacuum advance pot?
So your pistons say 21.5 cc dish?
Or they they flat tops?
Not sure 70.5 cc heads and 21.5 cc dish gives you 10:1 compression
But flat tops might.
I run the comp 274-S with 236/241 @050 and .502/511" not too far off from the OP
I'm at 32 even 31 total.
Sorry for the slow response. Fathers day, repairs to my daily driver and weather got in the way.
I went with the Chryco method. I set the timing to 32 degrees all in at 2500, That put me at 12.5 degrees initial and I have left the vac. advance disconnected but I will plug the line to make it look correct.
The engine starts nice, etc. I Had to open up the throttle blades to get it to idle at 850 RPM. I believe this is causing my next issue. After I drive the car the idle creeps up, somewhere in the 1100 rpm range. If I reduce the idle the engine shakes and runs poorly when the engine is not 160 degrees or more, but warm enough to not be on the choke. If I leave the idle at 1100 it seems to diesel after I shut it off.
Again it's 94 octane, new gas. So I am now looking at my options.
1. I still think my stock rad is too small for the car and I will be looking at Glen Ray to see what he can do for a radiator resto. Just don;t think the 340 rad was designed to cool a 416 stroker.
2. Colder spark plugs
3. adjusting the carburetor air/ fuel. I also need to check but the carb is a 650, perhaps I could even look at a 750.
4. Colder plugs. I am currently running the Champion 12YC.
any ideas on direction?
Shouldn't timing all in be more like 34 to 36 degrees?
Also, are you running a thermal or electric choke? My electric choke is set up for a nice fast start, but it typically comes off before the car is fully warmed up. Part of this is due to the fact that I have my heat crossover passage in the intake blocked off. I just live with the fact that it takes a bit longer to warm up. Tuning should be done when the engine is fully warmed up.
I am about to fire up my 416 and am doing a bunch of research. I was JUST looking at some timing vids and the guy's video was talking about tuning total timing especially for performance cars. He was saying that once you get that right you might find you have issues in other areas. He was saying you may need to adjust your fuel mixture. I would double check that as well as look at the heat range of the plugs. What plugs are you using? My understanding is as compression goes up you may want to run cooler plugs to prevent early detonation.
Quote from: tparker on June 28, 2021, 10:37:37 AM
I am about to fire up my 416 and am doing a bunch of research. I was JUST looking at some timing vids and the guy's video was talking about tuning total timing especially for performance cars. He was saying that once you get that right you might find you have issues in other areas. He was saying you may need to adjust your fuel mixture. I would double check that as well as look at the heat range of the plugs. What plugs are you using? My understanding is as compression goes up you may want to run cooler plugs to prevent early detonation.
My compression is still 10:1, it's not a high compression motor. I also thought my plugs were too warm but the more internet reading I do I am thinking that is not the case. I am going to play with the fuel mixtures again. I am using Champion 12YC's. The same spark plug I have run since I have been working on Mopars. It was recommended to me on that other "forum" we all came from lol.
Quote from: DeathProofCuda on June 28, 2021, 08:58:25 AM
Shouldn't timing all in be more like 34 to 36 degrees?
Also, are you running a thermal or electric choke? My electric choke is set up for a nice fast start, but it typically comes off before the car is fully warmed up. Part of this is due to the fact that I have my heat crossover passage in the intake blocked off. I just live with the fact that it takes a bit longer to warm up. Tuning should be done when the engine is fully warmed up.
I am running an electric choke on an Edelbrock 1806- 650 vac secondary carb. The choke is set one marking towards rich. My heat crossover is also blocked.
As for the timing, If I advance the timing anymore at full advance, I end up with an initial advance that is up in the 14's. She does not like to start as easily especially when she is warm.
How long does your car take to warm up? I generally start mine up and idle it for 3 or 4 minutes before taking it out. The choke remains on for the majority of that. I can also see that when the car is warm, the choke cam and the high idle screw are not in contact with the throttle.
Not sure, but I'd guess almost double that time on the warm up. If I don't give it some time to warm up it will fall on its face when I try to pull out into traffic at the end of my street.
I'd still say to make any tuning adjustments when the car is completely warmed up. If your settings are changing after taking the car out for a drive, then go back and reset them. Dieseling is typically a symptom of having your throttle blades being open too far.
I usually set the choke so it barely works at all as most of these cars are only driven in warm weather anyway .
I vote for tuning to prevent run on , you can try a cooler plug but it may foul .
From what you are describing I would still lean towards more initial. I have had good results running around 18 initial and 34-36 total.
12 to me sounds a bit low. I suggest a test of bumping it up a bit and checking to see how it starts and idles. 1100 also is a bit high and I would concur that your throttle blades may be a bit too open. The initial should help with this and you should be able to idle her down.
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