rags
Senior Member
electronic points distributor, so no actual breaker points? if working correctly dwell should be good but could be checked with a dwell meter to verify.
383 cui 2bbl replacement
- Thread starter 69_topless
- Start date
69_topless
Member
After some time, I got to play with the carb some more. The last attempt have this details. Base timming set at 18 degrees BTDC at idle 630RPM and vacuum little nervous at 20 inch. The timming at idle does not change, if vaccuum is connected, or disconnected and plugged. I did not check the increase timming with the higher RPM above 2000. But I set the initial timming with the tube disconnected and plugged.
Lame question, should I adjust the carb with the air filter element on? I removed it for the adjustment for easy access of screws and it seems it will change a little the result.
With lower timming like 13 degrees and idle RPM about 600, the engine hesitate on the take off, almost died before taking a breath and runs up. Thus I set it up higher at 18 degrees where the engine seems to run happy. As I read elsewhere, each engine is unique and require a little different setting. But is not 18 degrees too much? My elevation is just 1000ft, so not big deal due the altitude.
But perhaps the local gas 95 octane (95RON which is comperable with the US 91 PON gas) require more RPM (up to 800) as mentioned by member in the other post? Should I try to adjust the timming back to let say 12 degree and increase the idle RPM? With the vacuum, I can get to similar numbers but more nervous needle as with 18 degrees. I would even say, that higher timming might help to froze the needle, but I was afraid to go higher then 18 for idle.
Or based on your experience, the nervous needle sitting at the 20 inch mark is good enough and its matter of just little final adjustment, which means timming set is OK/correctly? Thanks for your tips, I´m getting hopefully close to final adjustment
Appreciate your help.
Lame question, should I adjust the carb with the air filter element on? I removed it for the adjustment for easy access of screws and it seems it will change a little the result.
With lower timming like 13 degrees and idle RPM about 600, the engine hesitate on the take off, almost died before taking a breath and runs up. Thus I set it up higher at 18 degrees where the engine seems to run happy. As I read elsewhere, each engine is unique and require a little different setting. But is not 18 degrees too much? My elevation is just 1000ft, so not big deal due the altitude.
But perhaps the local gas 95 octane (95RON which is comperable with the US 91 PON gas) require more RPM (up to 800) as mentioned by member in the other post? Should I try to adjust the timming back to let say 12 degree and increase the idle RPM? With the vacuum, I can get to similar numbers but more nervous needle as with 18 degrees. I would even say, that higher timming might help to froze the needle, but I was afraid to go higher then 18 for idle.
Or based on your experience, the nervous needle sitting at the 20 inch mark is good enough and its matter of just little final adjustment, which means timming set is OK/correctly? Thanks for your tips, I´m getting hopefully close to final adjustment
Appreciate your help.
saylor
Senior Member
I would drive that and see how it does. sounds pretty steady.
when I had a stock snorkel I did find that the adjustments needed to be made with the hat on.
when I put an open top breather on it that all went away.
but ya, I found it changed the settings also with a stock intake and a stock breather.
when I had a stock snorkel I did find that the adjustments needed to be made with the hat on.
when I put an open top breather on it that all went away.
but ya, I found it changed the settings also with a stock intake and a stock breather.
cbarge
World Famous Barge in a Budget
Keep her at 18 degrees and use the highest octane available to you that does not contain any ethanol whatsoever.
630 idle RPM is too low,in my opinion.
When put in gear RPM drops too low and engine will gasp for air.
Bring the idle up a bit.Start at 700,put in gear,watch the vacuum,it should be smoother.
If you have to,increase to 750 or 800 RPM. Put in reverse/drive to see of the car is happy.
If it goes into gear too hard,drop her down in small increments and make sure the vacuum gauge remains smooth.
Please blip the throttle after every adjustment to get an accurate idle and vacuum reading,then when settled down,re-read your vacuum gauge and RPM's
18-20 inches is great! Is should either go up or smooth out with idle increased.
You are very very close to a great running engine!
Install the air cleaner and check RPM's blip the gas and adjust the idle speed if needed.
If vacuum gauge still "shaky" you may have to play with the idle mixtures to really smooth her out. It is not uncommon to see one side idle set screw in or out more than the other after getting a smooth vacuum gauge needle
Do quarter turns slowly one at a time and blip the gas after each adjustment--again.
This where you have to let the engine talk to you and you must listen. As you turn the screws watch the vacuum gauge carefully. if the vaccum drops,she don't like that screw being turned in or out. She will respond happily and vacuum will increase and maybe the idle too,for example.
test and tune,drive,test tune,drive,and so on and so on..
Hope this helps
630 idle RPM is too low,in my opinion.
When put in gear RPM drops too low and engine will gasp for air.
Bring the idle up a bit.Start at 700,put in gear,watch the vacuum,it should be smoother.
If you have to,increase to 750 or 800 RPM. Put in reverse/drive to see of the car is happy.
If it goes into gear too hard,drop her down in small increments and make sure the vacuum gauge remains smooth.
Please blip the throttle after every adjustment to get an accurate idle and vacuum reading,then when settled down,re-read your vacuum gauge and RPM's
18-20 inches is great! Is should either go up or smooth out with idle increased.
You are very very close to a great running engine!
Install the air cleaner and check RPM's blip the gas and adjust the idle speed if needed.
If vacuum gauge still "shaky" you may have to play with the idle mixtures to really smooth her out. It is not uncommon to see one side idle set screw in or out more than the other after getting a smooth vacuum gauge needle
Do quarter turns slowly one at a time and blip the gas after each adjustment--again.
This where you have to let the engine talk to you and you must listen. As you turn the screws watch the vacuum gauge carefully. if the vaccum drops,she don't like that screw being turned in or out. She will respond happily and vacuum will increase and maybe the idle too,for example.
test and tune,drive,test tune,drive,and so on and so on..
Hope this helps
69_topless
Member
I will follow up on this thread I started a few years back I recently made some carb-tuning with some new knowledge and have a couple of questions I hope you might clarify.
1. Should be the idle speed and all the play with the mixture screws, done while the transmission is on Neutral? I noticed a small RPM drop while going from P to N, as the transmission pump engage. Right now having circa 730 RPM idle on P, 680 RPM on N with air filter ON and circa 590RPM while in Drive. These values might be a little bit lowered some RPM down but so far it seems engine like it.
I´m using the best premium gas with most octanes available, not regular 95 octane gas (EU measurements).
2. I connected vacuum gauge directly to hose disconnected from vacuum choke pull off this time, not the brake booster and got almost steady needle at 19 to 20 inch while on P. When switched to N, it went down to 18ish and needle become bit nervous. So I guess there is some space to play with the mixture limiter screws (2) on the front side. But I never touched the main rear mixture screw (1). According to my original factory manual, this if ever needed, should be screw all in and back 3/4 turn. Just from the look, looks like its more out then just 3/4 of turns but that's just my estimation. Somewhere else I read this screw can be also used for the getting biggest vacuum, as it controls rich/lean mixture. I tried 1/4 turn each side but seems it does not have any effect on vacuum value so left it as it was.
I know each engine is unique and like something different. But in general, what values I should be targeting? 18 inch at Neutral and get the needle as smooth as possible with the mixture limiter screws? Or should I try to reach 20 inch?
Video with transmission at P
Video with transmission at N
Keeping in mind I still have timing at 18 degrees BTDC, despite the engine seems runs overall great, I get on take off slight hesitation if floor it too much. So must be gentle until the engine takes a breath until circa 5 MPH and then can push it.
Since all the setting is reversible, I can play trying all the possibilities, but still would like to clarify the correct procedure.
1. vacuum timing advance blocked just for the timing, or also for the idle RPM and mixture setting? This requires to plug vacuum canister itself or another end of hose pulled off the carb. That open input on carb can be left not plugged keep sucking the air?
2. any adjusting should be made on Neutral or park position of the transmission?
3. first, adjust the timing, usually at 12-15 BTDC range (I live at 1000ft elevation only)
4. second, chase the highest vacuum on the gauge with the main mixture screw? or the mixture screw limiters?
Initial setting mixture screw limiters all in and then 3 turn out, equal position for both. And main rear mixture screw as per the manual, all in and 3/4 out. Then play with the main mixture screw to get the highest vacuum, and just to stabilize needle with screw limiters? Or really does not mess up with the main mixture screw? I have no way how to measure if the exhaust fumes are too rich or lean.
Timing affects the vacuum amount, right now maybe I´m on the edge being too advanced with the 18 BTCD initial timing and getting 19-20 inches. So if I reduce the timing to i.e. 12 BTDC, I need to chase the higher vacuum with the mixture screws. Correct?
I recently made some carb-tuning with some new knowledge and have a couple of questions I hope you might clarify.1. Should be the idle speed and all the play with the mixture screws, done while the transmission is on Neutral? I noticed a small RPM drop while going from P to N, as the transmission pump engage. Right now having circa 730 RPM idle on P, 680 RPM on N with air filter ON and circa 590RPM while in Drive. These values might be a little bit lowered some RPM down but so far it seems engine like it.
I´m using the best premium gas with most octanes available, not regular 95 octane gas (EU measurements).
2. I connected vacuum gauge directly to hose disconnected from vacuum choke pull off this time, not the brake booster and got almost steady needle at 19 to 20 inch while on P. When switched to N, it went down to 18ish and needle become bit nervous. So I guess there is some space to play with the mixture limiter screws (2) on the front side. But I never touched the main rear mixture screw (1). According to my original factory manual, this if ever needed, should be screw all in and back 3/4 turn. Just from the look, looks like its more out then just 3/4 of turns but that's just my estimation. Somewhere else I read this screw can be also used for the getting biggest vacuum, as it controls rich/lean mixture. I tried 1/4 turn each side but seems it does not have any effect on vacuum value so left it as it was.
I know each engine is unique and like something different. But in general, what values I should be targeting? 18 inch at Neutral and get the needle as smooth as possible with the mixture limiter screws? Or should I try to reach 20 inch?
Video with transmission at P
Video with transmission at N
Keeping in mind I still have timing at 18 degrees BTDC, despite the engine seems runs overall great, I get on take off slight hesitation if floor it too much. So must be gentle until the engine takes a breath until circa 5 MPH and then can push it.
Since all the setting is reversible, I can play trying all the possibilities, but still would like to clarify the correct procedure.
1. vacuum timing advance blocked just for the timing, or also for the idle RPM and mixture setting? This requires to plug vacuum canister itself or another end of hose pulled off the carb. That open input on carb can be left not plugged keep sucking the air?
2. any adjusting should be made on Neutral or park position of the transmission?
3. first, adjust the timing, usually at 12-15 BTDC range (I live at 1000ft elevation only)
4. second, chase the highest vacuum on the gauge with the main mixture screw? or the mixture screw limiters?
Initial setting mixture screw limiters all in and then 3 turn out, equal position for both. And main rear mixture screw as per the manual, all in and 3/4 out. Then play with the main mixture screw to get the highest vacuum, and just to stabilize needle with screw limiters? Or really does not mess up with the main mixture screw? I have no way how to measure if the exhaust fumes are too rich or lean.
Timing affects the vacuum amount, right now maybe I´m on the edge being too advanced with the 18 BTCD initial timing and getting 19-20 inches. So if I reduce the timing to i.e. 12 BTDC, I need to chase the higher vacuum with the mixture screws. Correct?
69_topless
Member
The second part of my questions is related to the vacuum choke setting. I should test its functionality by sucking the air from the hose, to see if it makes anything, well next time I will try.
But I´m more concerned about the play on the end of its tracks. The metal rod going from the manifold does not allow to close the butterflies of carb completely until the stop position is reached on the other side of the carb. The rod is too short, for the test I removed the safety metal clip. Shall I bend it to make it a little longer? Next, vacuum canister controls another rod, but in its track have dead ends on both open/close positions. Again, shall I try to adjust the position of choke vacuum canister or that rod to eliminate dead endplay?
I did try to make a short video of the choke control play, to better explain the current setting.
Few pictures
But I´m more concerned about the play on the end of its tracks. The metal rod going from the manifold does not allow to close the butterflies of carb completely until the stop position is reached on the other side of the carb. The rod is too short, for the test I removed the safety metal clip. Shall I bend it to make it a little longer? Next, vacuum canister controls another rod, but in its track have dead ends on both open/close positions. Again, shall I try to adjust the position of choke vacuum canister or that rod to eliminate dead endplay?
I did try to make a short video of the choke control play, to better explain the current setting.
Few pictures
The settings should be done in neutral.
The 383 2bbl will not pull as much vacuum as a 4bbl. 18 degrees advance is too much for 2bbl unless your mechanical advance is starting to advance around 600 Rpm, which is way to low to start mechanical advance.
You are correct in plugging your vacuum advance for initial tune. I usually use a spring clamp with a flat head to crimp it off.
On my fresh ‘68 383 2bbl I don’t get much more than 17 or 18 vacuum It runs like crap if I try to push it higher.
If you have a dual timing light check your mechanical advance. You should not see much additional advance movement until the rpm is is up to 925-1400 and then should. I don’t have a ‘69 manual, but for ‘68 my starting point is 7.5 degrees TDC for initial timing at 600 RPM. Not sure if they bumped it up for ‘69 emissions or not. At 950 rpm the allowed range is 7.5- 15 degrees. At 1500 rpm should be around 21-1/2 - 25-1/2 degrees and then maxed out at 36-38 at 4500 rpm.
Before I replaced my advance springs I could not get idle to set at 600. As soon as I would get down to about 630. It would instantly drop to 450-500. It turns out my mechanical advance was kicking in too low at 620 rpm.
I run 91 octane non ethanol gas and have good success at 600 idle 7-1/2 degrees initial advance and with the springs changed in the distributor to give the proper advance.
The 383 2bbl will not pull as much vacuum as a 4bbl. 18 degrees advance is too much for 2bbl unless your mechanical advance is starting to advance around 600 Rpm, which is way to low to start mechanical advance.
You are correct in plugging your vacuum advance for initial tune. I usually use a spring clamp with a flat head to crimp it off.
On my fresh ‘68 383 2bbl I don’t get much more than 17 or 18 vacuum It runs like crap if I try to push it higher.
If you have a dual timing light check your mechanical advance. You should not see much additional advance movement until the rpm is is up to 925-1400 and then should. I don’t have a ‘69 manual, but for ‘68 my starting point is 7.5 degrees TDC for initial timing at 600 RPM. Not sure if they bumped it up for ‘69 emissions or not. At 950 rpm the allowed range is 7.5- 15 degrees. At 1500 rpm should be around 21-1/2 - 25-1/2 degrees and then maxed out at 36-38 at 4500 rpm.
Before I replaced my advance springs I could not get idle to set at 600. As soon as I would get down to about 630. It would instantly drop to 450-500. It turns out my mechanical advance was kicking in too low at 620 rpm.
I run 91 octane non ethanol gas and have good success at 600 idle 7-1/2 degrees initial advance and with the springs changed in the distributor to give the proper advance.
Here is a video of mine with narrative. I hope you understand my North Dakota accent. My Czech Colleagues in Dobris can.
If you have any more questions let me know. I have found that some of the advice for 4bbl or HP engines is not always accurate for 2bbl
If you have any more questions let me know. I have found that some of the advice for 4bbl or HP engines is not always accurate for 2bbl
The choke setup is described pretty well in the service manual if you have one. If not this link should help you.
[URL="http://www.mymopar.com/index.php?pid=109"]MyMopar - Mopar Forums & Information - Service Manuals
I[/URL] don’t see a Polara one, but the ‘69 Plymouth one should be good enough for your mechanical questions and carburetor choke specs and set up.
[URL="http://www.mymopar.com/index.php?pid=109"]MyMopar - Mopar Forums & Information - Service Manuals
I[/URL] don’t see a Polara one, but the ‘69 Plymouth one should be good enough for your mechanical questions and carburetor choke specs and set up.
James Romano
Well-Known Member
I noticed you have a fairly thick thermal gasket under your carb, which will definitely change the length and contact points of your choke thermostat linkage.
If I recall correctly I the tried to use one in my rebuild kit and my linkages lost clearance and of course screwed up the choke linkage. I think this could very well be the original gasket, at least been on there since I took it over in 1984. It has metal bushings in the holes to keep from over tightening or squishing down to far. There are no bend marks on the original thermo actuator Rod.
69_topless
Member
Here is a video of mine with narrative. I hope you understand my North Dakota accent. My Czech Colleagues in Dobris can.
If you have any more questions let me know. I have found that some of the advice for 4bbl or HP engines is not always accurate for 2bbl
Thanks for the advice and video description. No problem to understand your accent, I spent a couple of summers in USA as a student and later on attending some exhibitions. In Dobris is good local airfield.
However, I was pretty busy travelling as better covid situation allows me to travel abroad visiting my customers, so had limited time to play with Polara. Just yesterday, I took her out with kids for a short spin and felt running strong. August will be quieter after vacation, so will dig into timing setting again and post the results. Summer weather is getting short here, two more months and it's over - I should better to burn some fuel yet
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