does your distributor have vacuum advance?

 

You will hopefully get some very detailed answers to your question here. Do a search on this forum and you will probably find hours of reading enjoyment...

With just the small amount of info you have given, my quick and dirty answer is to set your total timing to 34-36 degrees before TDC and let the idle timing fall where it will. There is a LOT more to getting this right than this, but assuming your distributor has the correct mechanical advance in it, this should work pretty well. To do this, run the engine up to around 3500-4000 rpm and read the timing, it is a safe assumption your distributors mechanical advance is "all in" at that rpm. If running a vacuum advance, unhook and plug that when setting your timing.

The worm hole is deep here, timing curves are important. Depending on the distributor you have, it should have a mechanical advance system in it, the springs under the rotor dictate the rate the timing advances mechanically, sometimes these systems are locked out. You may also have a vacuum advance, that advance is in addition to the mechanical. There are a few members here that are highly knowledgeable on this subject, far more than I am.

To get a solid answer here, people will need to know a lot more info, what distributor you have, how it is set up, are you running an ignition box, etc...

 

Thank you both for your answers! I will provide more info once I got home from work.

In short for now:
My distributor has vacuum advance.
No ignition box, just Flamethrower -> distributor

Everything else will follow later and I will be happy to provide any other info needed.

 

Your cold start running rich soot situation sounds to me like a carburetor choke adjustment problem. That's assuming you're not running an EFI setup.

 

while the rich at idle cold can be a carb adjustment, you need to have the timing nailed before making final carb adjustments.

ideal timing at idle is 20-24 degrees WITH VA connected. So at 8 degrees without VA you would want VA to add 12-16 degrees. Depending on which VA canister the distributor has (they are marked with a letter then number), VA decreases as RPM increase with vacuum being zero when wide open throttle as "mechanical" advance takes over VA on top of whatever "base" (no VA) timing is

It is all a balancing act where limiting the amount VA provides and when it starts to go away as mechanical timing comes in. Mechanical timing can come in sooner with lighter springs

At 3k RPM total timing should be 34-36 degrees and at that RPM no VA should be happening. Just base and mechanical advance.

Modified motors with cams make less vacuum than a stock motor so typically need more "base" (10-12) degrees but that all depends on much advance VA provides. You can connect the VA after the 8 base and with a timing light see how much VA is being provided. If to much, that is where the VA stop plate comes into play but that is a separate conversation and how to do that.

Once all that is nailed, including final carb adjustments which, depending on motor, may require different jets, step up springs, metering rods, etc., a carbureted car will perform expellant in all throttle/driving conditions

 

As stated, plenty of good information in previous threads, so do some reading. First, you need to find out your distributor curve mechanical advance and vacuum advance. Once you have that, then you can start dialing it in for your own setup.

Based on what we know the following should get you a pretty close starting point :

The Tickflow heads are fast burn heart chambers. You'll probably find about 32-34* total mechanical (static + centrifugal without vacuum) @3000rpm makes the most power without detonation with those heads. It's easy to put too much timing into modern fast burn heads. Sometimes it doesn't necessarily mean knock, but it can still reduce power.

A Comp Thumpr has an f-ton of overlap. Your soot is misfire due at least in part, to too little initial timing. And if you have a Holley, I bet in order to get enough air to idle, the primaries plates are opened up enough to uncover the transition slot; causing it to dump extra fuel. You can tell if leaning out the mixture screws has no effect.

I'd dial in about 16* static without vacuum. Throw in some fresh spark plugs. Reset the idle speed (it should jump up from previous due to the added timing). Now you can dial in the fuel mixture screws for highest vacuum reading @ idle. If it cranks easily hot, then you could try another 2* but I wouldn't go more than 18* with the static. If it cranks slow when hot, back it off in 2 degree increments until it spins freely.

Then add enough vacuum to get about 22-24* @ idle hooked directly to manifold. With a large overlap camshaft, if you set the initial static too low and try to make up for it all with manifold vacuum advance, it can cause it to idle hunt, and have poor part throttle driveability. You want to balance it. Give it as much static it can take and still cranks (hot), then add the rest with manifold vacuum. So get an adjustable vacuum can if it doesn't have one, or find one with low added timing.

Remember, once you make all your final timing adjustments, you'll want to readjust all the carb settings as one affects the other.

Another option is buy me a ticket to Germany and I'll tune it for free. My German is a little rusty, but I'm sure once I start working on your Oldtimer, I'll at least remember a few swear words, lol.

 

Thank you for your answers! You gave me a lot to read about and doing some research to catch up to everything you wrote.

At least, I checked the mechanical advance curve of my distributor. I add the info to the start post, so everything will be there and any additional info will go there, too, to have everything in one place.

 

No ignition box, just Flamethrower -> distributor

Pertronix makes a couple different types of "FlameThrower distributors (HEI, small cap, etc). Can you post the specific model number of the FlameThrower distributor that is installed in your vehicle. By providing this info, it could assist with recommendations on how to adjust your specific distributor.

At least, I checked the mechanical advance curve of my distributor. I add the info to the start post

The above is not your TRUE mechanical advance curve... it appears to be a copy of information from the instructions. The advance curves shown in the instructions are not always accurate (and the chart shown above does not account for your initial timing). You need to check/confirm what numbers your distributor is producing in your engine with a timing light and tachometer.

 

You need to be able to limit the total mechanical advance. 30* will be too much by the time you set your initial where it needs to be. Hopefully your distributor has that option, or there's a kit. You can't do it with springs alone, that will only control the rate. Post up the model so we can see the instructions.

What carburetor are you running?

P.S. You're going to need a timing light, vacuum gage, and tachometer.

 

"set your total timing to 34-36 degrees before TDC and let the idle timing fall where it will"

THE single most wrong thing you can do in any ignition system that still has weights and springs.

For that 383, 10 initial, add 10 on the vacuum advance, and plug it into full manifold vacuum for 20 IDLE degrees (Oh, wait, you ripped the vacuum advance off, or listened to someone that insisted you rip it off the distributor, well, no way to fix it, except to put the vacuum advance back on and set it up correctly)

Timing curve, added by tailoring the mechanical advance start/stop points, 24 degrees, for a "total" of 34 degrees at stop rpms.

BTW. do not use a "dial back" dial on the timing light, the advance curve IS NOT being set electronically in an EFI computer, you do not need to "correct" the curve, it is not being electronically altered.

 

Thanks for your answers, guys.

Pertronix makes a couple different types of "FlameThrower distributors (HEI, small cap, etc). Can you post the specific model number of the FlameThrower distributor that is installed in your vehicle. By providing this info, it could assist with recommendations on how to adjust your specific distributor.


View attachment 327279
The above is not your TRUE mechanical advance curve... it appears to be a copy of information from the instructions. The advance curves shown in the instructions are not always accurate (and the chart shown above does not account for your initial timing). You need to check/confirm what numbers your distributor is producing in your engine with a timing light and tachometer.

The picture is taken from the instructions that came with the distributor advance kit. The highlighted row is the installed spring. I'll add the full instrucitions in the opening post.

You need to be able to limit the total mechanical advance. 30* will be too much by the time you set your initial where it needs to be. Hopefully your distributor has that option, or there's a kit. You can't do it with springs alone, that will only control the rate. Post up the model so we can see the instructions.

What carburetor are you running?

P.S. You're going to need a timing light, vacuum gage, and tachometer.

The distributor model is unknown to me. I don't think that it was changed during the engine rework. The carburator is a Quick Fuel Slayer 600. I already have a timing light, but have to get a vacuum gage. Do I need the tachometer for rpms? I'll have a buddy helping me, so he can check rpms in the car.

 

Tach for rpms yes.

The specs on the generic Moroso spring kit are of no use. The weights and centerbar play a roll in how much it opens and how quickly. So your aftermarket distributor with those springs are going to be different.

You're just going to need to map it on the car yourself, and go from there. Don't forget to disconnect the vacuum advance and plug the carb port when checking mechanical advance.

Try to find a part number on the distributor. I have a feeling you're going to need to get some additional parts from Petronix to set it up correctly. According to 1 post on Petronix, the D700D700 kit includes not only springs but also limiters (but it only mentions springs). However I would get the distributor part number in case they ask; then call to verify the kit will work and it includes the limiters. If not, see how you can get the limiters. As I said before, you need to control not only the rate, but the total as well.

The carb is a little small, so along with not enough initial advance, I'm nearly certain you're pulling fuel from the tranisition slot on the primary side because the idle set screw is cranked high to get the idle speed. As I said previously, a quick check would be to continue leaning out the mixture screws. If it doesn't change anything then you're pulling from the slots. The slots will put more fuel in than the mixture screws can take away, so it'll say very rich. Turning them all the way in should cause it to stumble and stall.

On mixture screws, always use light pressure to seat them. The point on the end can easily be damaged. Use 2 fingers to rotate the screw, to avoid over-torquing. And when setting mixture screws for best idle, always have the air filter installed. The base can actually smooth the air transition into the carb, changing the air/fuel ratio. I tested this with a lab-grade (ETAS) stand-alone wide-band @ idle. It actaully varied by ~1 point a/f (e.g. 14:1 down to 13:1) which is a large difference. Since designs of air filters vary, best just to test with it installed and with a decently clearn air filter.

One trick that may help on the carburetor. WIth the large overlap, the engine needs a little more air in addition to more timing. Some drill the primaries, but that's somewhat of a permanent change. Here's an easily reversable fix depending on your starting point:
Just like the primaries, the secondaries should also have fuel transition slots. There's a maximum slot exposure. Too much slot, it'll cause bogging, possible even more fuel. To little means too little metered air (not a problem if the primaries can provide sufficient air), maybe a hesitation. If you take the carb off and flip it over, there should be a screw to adjust the plates. Measure the current position in case you decide to return it back. Ideally .04" to .06" of the slot should be exposed. Try setting the slot height to the .06" depth to get as much air as possible, without over-exposing the transfer slot. (You'll also be able to see at this point if your transfer slots on the primaries are over exposed.)

If, after getting the secondaries set and the timing where it needs to be, still requires the set screw setting to be too high, then you're going to need to drill the primaries. I save this as a last resort, as usually correcting the other 2 (ignition timing and 2ndary plate adjustment) will fix the issue. Looks like the Quick Fuel Slayer 600 has replaceable air bleeds, so next would be getting different sizes to try on the idle side.

Really though, with your camshaft and engine size, you should have a 700-800cfm with annular boosters. The larger primaries will provide the addition air, so the idle speed can adjusted without over-exposing the transfer slots. And the annular boosters will provide a better signal and improved atomization to help idle and torque with the massive overlap camshaft. The 600 will probably start to restrict power above 5500rpm.

 

Motor cubic inch, compression, cam, carb or EFI, fuel type, even density altitude play a part in your timing...not a "set number" since it's not stock anymore.

That cam....not helping you any.

If it was running good once warmed up, I would be looking into setting the choke up properly.
I would not drill holes in the butterfly's

 

Correct. Drilled holes in the butterfly is a signature of a bad tuner.

 

This has gone straight down hill.

Drilling the PRIMARY throttle plates is PREFERRED, but, HOW BIG A HOLE to get the .020 ITS slot opening correct????

A vacuum gauge will not tell you how big to make the bypass holes. It won't even help with setting idle primary throttle plate settings to attain the .020 ITS setting, either. Now, some of you brainacs will say that they set to the highest vacuum, WRONG, that does not work. With any engine, the IDLE vacuum is usually lower than vacuum above idle, say 1,200 rpm's, NOT because of anything other than the TIME between intake events lowering mixture reversion, NOT flow rates, air volume, pulse pressure/vacuum, TIME between intake pulse events ONLY. Less time between intake events, less time for the mixture to be forced back up the inlet port before the intake valve closes.... reversion

And, THE SINGLE MOST WORSE recommendation for a vacuum secondary spec, or double pumper carb that DOES NOT ALREADY HAVE 4 CORNER IDLING.... IS TO OPEN THE SECS BUTTERFLY'S. That screw is there to do ONE thing..... TO STOP THE SECS BUTTERFLY'S FROM BINDING IN THEIR BORES IN THE BASE, PERIOD. Literally bind the plates in the secs bore, turn screw to open the plates 1/8th turn to the screw thread, NO MORE, only enough to stop plate binding

Now, I worked in Pro-Stock carbs, factory Holley, and at the races, for 5 years, and not once, did I see any of you here, either with Holley, or other carb companies, not one of you.

But, the net and all sorts of other brainiacs tell you different, and they do not know either.

Consider a head porter, tells you he is porting each port to the highest air flow. Now, air alone is also not how to do it, but.... He guarantees each port will have the best flow, each port, individually. Think for a second, if he is at the best flow, and goes ahead to get better, and the flow diminishes, you do not get the best flow, now, do you. Also, air alone is not what goes down, and back up the port, it has a different specific gravity from a "fog" of combined air and fuel. Adding a flow liquid that has the same SG as the fuel, to the air... IS THE WAY TO DO IT, and not go too far. very hard, except for those head porters that tell you they gave you he best flow for each port.

Like I said, straight down hill.

 

SirPeko:

Here's an article that closely parallel's your situation in tuning challenge. https://www.motortrend.com/how-to/carburetor-tuning-cure-big-cam-sag/

It's 383cid (Mopar, but that doesn't matter), extremely high overlap camshaft (24* versus your 28* @ .050", so you still have even more), very close in size valve events , 10:1 compression ratio (not sure what yours is but if it's lower that'll exasperate the issue slightly), and small (for the displacement) carburetor (650cfm vs. your 600cfm - still on the smaller side). Proper combination of parts working together as a system is key. And if you're mis-matched or on the fringe in some areas, it can make tuning more challenging.

They ran into the same issue where the initial timing was too low for the combination, and insufficient idle bypass air. Too much of the primary transition slots were exposed. They attempted to improve it with more initial timing by putting in 18* initial and re-curving the distributor. Which helped idle stability some, but still wasn't enough to cure the transition slot issue. The only difference, we don't know if they hooked the vacuum can to ported or straight to manifold. From the article, I would guess they tried used ported. Had they tried manifold vacuum, they may have improved the bog as well as solved the transition slot topic when the changed to the larger carb without resorting to drilling the primaries. BTW, although the transition slot exposure is a modular carb issue, the timing and airflow issue would still need to be addressed in the tune for EFI. It'd just be addressed in ignition and idle airflow tables instead of mechanically.

The next step after timing, was going from a 650cfm(w/primary idle circuits only) to 750cfm with 4-corner idle adjustment. This gave them more adjustment range and more idle air. In doing so, it got them most of the way. (Again, hooking the vacuum straight to manifold to add 6-8 degrees on top of the initial 18* might have gotten them 100%.) At any rate, with it hooked to ported even with the the 4-corner larger carburetor, they still needed more idle air. Unfortunately they didn't buy a carb with changeable air bleed metering block, so they resorted to drilling.

So if at the end, all the timing tricks, you still have too much transition slot covered, you need to start making changes to airflow. Also, don't forget to check the power valve rating and verify it's not blown either. You'll probably need a 45 or even a 35 once everything is tuned.

Now, as I said, you do have the changeable idle bleeds (primaries only) in your 600cfm already. But it's going to be more trouble trying to dial in that small carburetor, you'd be better off with something more appropriate for the displacement. Since there's still a probability you'll need more idle bypass, if you're open to replacing the carburetor, look for something with the following:

• 750-850cfm
• Vacuum secondaries (easier for novice to tune, more street-friendly)
• Electric choke (or at least manual - don't get one without a choke)
• 4 corner idle
• Replaceable air bleeds - this is key
• downleg or annular (preferred) boosters

Since you're in Germany, I'd go ahead and buy a idle air bleed tuning kit, so you can try increments. Along with a 35 and 45 powervalve, as many street carbs come with 65s which will be too high for your camshaft.

I only saw one in the Quick Fuel lineup: Part # SS-780-VS.
https://www.holley.com/products/fuel_systems/carburetors/street_strip/parts/SS-780-VS. It's pretty expensive.
Holley has a number of other "brands" (Holley, Demon, etc.) so it's possible there are others with that combination. Or you could buy one with most of the features and covert the metering block.

The other solution, would be to swap the camshaft with something that has less overlap. Similar intake duration (233-236) , but wider lobe separation (112-114) and less exhaust duration (240-245) to get your overlap =<15*. It will provide higher vacuum, require less timing, and less idle air. But that means partially disassembling the motor, and your present carb will still be on the small side.

 

Thank you so much, guys! That's an input I have to sort out first. You mentioned many things I never heard about and I fear that my knowledge is far to little to try adjusting everything myself. However, I want to learn this stuff to be able to work on my own car without blowing it up. 🙃 So, I have to read and learn about much of what you wrote.

The idea behind my setup was to get awesome sound and a good amount of power while keeping it driveable on the street. It should be good for cruising and good to surprise some guys with their "performance cars" at the traffic lights. The cam was described to me as doing exactly that, but adding some shaking to the whole car. That's true and I love it. If I had a bobblehead on my dashboard it would bobble while standing at a traffic light. For that I accept that the engine doesn't run perfectly in idle and low rpms and I don't really want to change that. But I want to change that sooting and little banging while the engine is cold without changing too much of my setup. When warm it runs good and it has enough power to paint some black lines on the street while accelerating. That's sufficient for me.

The engine acutally idles at around 600 rpm.

Btw, I hope that my texts are not too hard to understand or too weird, because English not my native language and I don't want to use a translator software.

 

Thank you so much, guys! That's an input I have to sort out first. You mentioned many things I never heard about and I fear that my knowledge is far to little to try adjusting everything myself. However, I want to learn this stuff to be able to work on my own car without blowing it up. 🙃 So, I have to read and learn about much of what you wrote.

The idea behind my setup was to get awesome sound and a good amount of power while keeping it driveable on the street. It should be good for cruising and good to surprise some guys with their "performance cars" at the traffic lights. The cam was described to me as doing exactly that, but adding some shaking to the whole car. That's true and I love it. If I had a bobblehead on my dashboard it would bobble while standing at a traffic light. For that I accept that the engine doesn't run perfectly in idle and low rpms and I don't really want to change that. But I want to change that sooting and little banging while the engine is cold without changing too much of my setup. When warm it runs good and it has enough power to paint some black lines on the street while accelerating. That's sufficient for me.

Btw, I hope that my texts are not too hard to understand or too weird, because English not my native language and I don't want to use a translator software.

Ich verstehe nur Bahnhof! lol. Doch, ich habe ihnen gut verstehen. Ihren Englisch ist sehr gut (viel besser als mein Deutsch - as you can probably tell).

A cam with less overlap (12-15*) but similar durations would still have a very nasty aggressive idle, but be easier to tune and better driveability, and plant black lines at will. It'll also have a lot less reversion which is another contributor to all the soot. Never the less, sounds like you would like to leave it alone, so I'll respect that. We'll see how close we can get without changing it.

Start with getting the timing sorted, and we'll go from there.

• By the way, what is your static compression ratio? I was assuming somewhere around 10:1 but I don't see it listed.
• What header primary size and exhaust size? Do you have a x-pipe or h-pipe crossover?
• Which intake manifold?

If you can, please upload a video with the cold start so we can hear the banging noise.

 

I said this in an earlier post. Check the choke operation. Your video's sound to me like the choke is not adjusted properly. Also 600 idle rpms is too low for an automatic transmission in park. It should be 700-750 or so especially with a non stock cam. When the choke and fast idle cam is adjusted correctly and the car is cold started the idle should be about 1200-1500 rpm's. Check the choke before you start changing the timing. Once the choke is correct then go the timing and then go to carburetor adjustments. On cold start press the accelerator pedal to the floor and let it up. Then hold the pedal at about half throttle and start the car. Multiple pumps should not be needed unless the car has been sitting for a while allowing fuel to evaporate from the carb.

 

Thanks again! I havn't done anything so far, because I am waiting for the vacuum gauge to be delivered. That has been delayed and will arrive in about a week.

Thus I should have the time to check the choke operation. One issue more to read about. I learned more over the last couple of days than the time before, thanks to you. I will report back the results of my choke adjustment.

 

Thanks again! I havn't done anything so far, because I am waiting for the vacuum gauge to be delivered.

Get some additional meters of vacuum hose. Long enough that you can temporarily route it though the firewall, so you can tape it somewhere to watch it while you're driving.

Also make sure you have a notebook and pen to write down values and changes that you're making. A marker would be good too. Then you can mark the starting position of the distributor body relative to the intake manifold, before you start making adjustments.

 

google whatever carb you have and download a owner's manual for it. Will have all the 411 on adjusting and choke settings

 

Yes, already did that. Do you have a secret expert advice to get the adjustment right quickly? For adjusting the cold start will be difficult once the engine got too warm. ;-) So maybe there's a trick I do not think of to avoid the "adjusting, waiting until cold again, adjusting" chain.

 

Really no point in adjusting the choke setting until the carb is adjusted properly @ idle when warmed up. No point in adjusting the carb until the timing is dialed in. Cold start is last thing in tuning.

For now, just confirm the choke is even working, which is easy and requires no tools. Since it's electric, just take the air cleaner off so you can see the choke plate, key the engine to on position, and wait several seconds. You could see it start to move to the open position. The electric choke adjust is simply a bi-metal spring that expands when it's powered causing the choke plate shaft to rotate.

 

So, to be clear:
1. Air cleaner off, to see the choke plate
2. Start the engine
3. Wait for the plate to open

The thing is that I have to rev the engine to avoid it to stall. Does that disturb the process? It should not, right? I just can't start it and let it run without any throttle.

 

You shouldn't need to start it. Just key it to accessory mode without starting, and it should activate if it's wired correctly. It will take a minute before it starts to move to the open position, and even longer to fully open. It'll be very slow and move in steps.

 

You shouldn't need to start it. Just key it to accessory mode without starting, and it should activate if it's wired correctly.

Ah, ok, thanks, I'll check that.

 

1. Air cleaner off, to see the choke plate
2. Verify choke plate is closed
3. Turn the ignition to accessory position (but do not start), leave it in that position
4. Go to the Kuehlschrank
5. Pour a 0,3L of Pils
6. Go back to the garage and enjoy a Pils while watching the choke open
7. Turn ignition off after it's open.
   

 

Oh, no, too bad... I got the order wrong and started with no. 4 after no. 7... But now I have a beer and the confirmation that the choke is correctly wired. It did exactly what you described and opened fully slowly after a while.

 

I find beer is a very beneficial tool....

 

I think your 600 RPM idle isn't helping

Try 850-ish

 

That's one of the things that will be improved.