Dieselfumes Posted September 11, 2022 Share Posted September 11, 2022 (edited) Hello. I have a 1949 Pontiac Streamliner with the Straight 8 backed by the hydromatic transmission. When I bought it last year it had a cracked exhaust manifold and was in dire need of a good tune up. So I installed the new exhaust manifold and then went to work on the engine. New plugs - wires - updated the old lume wiring to new wire ( retired electrician) plus I also upgraded the points to the electronic ones. I went through all of the grounds and cleaned up everything that I possibly could find. She fired right up and purred like a kitten. Then I set the timing exactly how the original shop manual directed. Everything works great with the exception that I have a high speed mis / stumble. When I first tuned it. I had a low speed stumble. Then I went over it again and found out that my vacuumed canister had a slight leak. So after installing a new one and tuning it again. The low speed mis went away. Anyone have any ideas on what the culprit could be ? If I feather the throttle it does seem to help. I did check for vacuume leaks but I wasn't able to find any. Thinking maybe it could be possibly fuel related. I put new fuel lines in and completely took the carb apart to clean and inspect it. Only thing I didn't do was to rebuild the carb. Was trying to make a car show and the kit became on back ordered at the last minuet. So I adjusted the float and other stuff to the manual instructions and installed new gaskets. Going to pop the carb off when I put it away for the winter to rebuild it then. Sorry so long winded. Just figure that I would include all the details.. one last think. I was thinking maybe the vacuum pump was bad. I do have a vacuum pump with a gage. however since it's raining here in Wisconsin. I haven't had a chance to get out there to check it out... Edited September 12, 2022 by Dieselfumes Forgot some more information. (see edit history) Link to comment Share on other sites More sharing options...
Oldtech Posted September 12, 2022 Share Posted September 12, 2022 Is it a regular miss or a random hiccup? just reved up or under load? I'm a bit suspecting carb but several possibilities including the "upgrade" on the ignition. Did it do it with the point ignition? Link to comment Share on other sites More sharing options...
Dieselfumes Posted September 12, 2022 Author Share Posted September 12, 2022 Yeah I just upgraded to the electronic points. New cap and cleaned the plates on the distributor along with the new vacuum canister. The miss was while parked and take off before. But now it's just while going over about 45 mph and above. I did try adjusting the gaselector ( spelling ) advancing made it alot worse and retarding it didn't help.. Link to comment Share on other sites More sharing options...
Marty Roth Posted September 12, 2022 Share Posted September 12, 2022 My first choice would be to return to your original used ignition points and condenser- but also check fuel pump pressure and volume. My '49 red Pontiac convertible was my first daily driver after I got my license in 1959 - loved that red car - and yours, too ! Link to comment Share on other sites More sharing options...
Dieselfumes Posted September 12, 2022 Author Share Posted September 12, 2022 Used points where beyond shot. 1 Link to comment Share on other sites More sharing options...
EmTee Posted September 12, 2022 Share Posted September 12, 2022 (edited) Have you verified the condition and operation of the centrifugal advance mechanism in the distributor? If it is dirty or corroded and sticking, it can result in error in the base timing if weights aren't returning properly at idle. Edited September 12, 2022 by EmTee (see edit history) 1 Link to comment Share on other sites More sharing options...
Oldtech Posted September 12, 2022 Share Posted September 12, 2022 Are the plugs gapped correctly? too narrow a gap can cause this. But as EmTee says, verify that all distributor functions are in good order. 1 Link to comment Share on other sites More sharing options...
JACK M Posted September 12, 2022 Share Posted September 12, 2022 Feathering the throttle helps. Possibly starving for fuel? What does it do if you choke it a bit? Link to comment Share on other sites More sharing options...
drhach Posted September 12, 2022 Share Posted September 12, 2022 So it's missing under load or does it miss even when you rev it at a stop? Link to comment Share on other sites More sharing options...
carbking Posted September 12, 2022 Share Posted September 12, 2022 The carburetor uses the same main circuit for high speed as it does for cruise. Guessing NOT the carburetor. First thought is the electronic conversion. Are you running an alternator? Do you have a voltmeter installed to see if the voltage falters when the miss occurs? An ammeter to see if the amperage used at high speed is greater than the source? Second thought is the rest of the ignition system. Third thought is the fuel delivery system (fuel pump, lobe on camshaft, fuel pickup in fuel tank, etc.) Jon. 3 Link to comment Share on other sites More sharing options...
Marty Roth Posted September 12, 2022 Share Posted September 12, 2022 8 hours ago, Dieselfumes said: Used points where beyond shot. Maybe replace electronics with known good quality used condenser and a GOOD set of points? My prior suggestion: 1. Problem with electronic ignition 2. Check fuel delivery for both Pressure, as well as volume 3. When going back to points, A. too small a gap could cause miss at low rpm B, too large a gap could make for easy starting but miss at higher rpm 4. Missing under load (eg - lugging and harder acceleration could indicate wrong plugs or using incorrect or damaged, or poor quality carbon-based plug wires Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted September 13, 2022 Share Posted September 13, 2022 Jon's third thought. Dollar to a donut! Ben Link to comment Share on other sites More sharing options...
Dieselfumes Posted September 13, 2022 Author Share Posted September 13, 2022 If I may ask ? But why go back to the old style points ? All of the research I have done the newer electronic points are the better way to go. I am not questioning to be a smarts a#$. Rather I would like to know why.. thanks for you're imput Link to comment Share on other sites More sharing options...
57j2olds Posted September 13, 2022 Share Posted September 13, 2022 I took my points out and put in what you have and had nothing but issues. I bought a good set of points and new condenser and it was much improved. 1 Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted September 13, 2022 Share Posted September 13, 2022 13 hours ago, Dieselfumes said: If I may ask ? But why go back to the old style points ? All of the research I have done the newer electronic points are the better way to go. I am not questioning to be a smarts a#$. Rather I would like to know why.. thanks for you're imput Some folks are just leery of new stuff. Course, electronic ignition has been around longer than some of them have been alive! Since late 60s -early 70s? His problem is not the ignition parts inside the distributor, unless loose connections. Ben Link to comment Share on other sites More sharing options...
Highlander160 Posted September 13, 2022 Share Posted September 13, 2022 Missing? Wow, where does it go? 🤣🤣🤣🤣🤣🤣🤣🤣 Sorry, sometimes I can't help it.🤭 1 Link to comment Share on other sites More sharing options...
carbking Posted September 13, 2022 Share Posted September 13, 2022 (edited) 13 hours ago, Dieselfumes said: If I may ask ? But why go back to the old style points ? All of the research I have done the newer electronic points are the better way to go. I am not questioning to be a smarts a#$. Rather I would like to know why.. thanks for you're imput IF PROPERLY INSTALLED AND WORKING ON A WORKING ENGINE: the electronics will eliminate points burn, points wear, arm wear, thus eliminating the need for resetting the dwell every 5000 miles UNTIL THE UNIT FAILS. I have yet to see a test from an independent laboratory that shows ANY improvement in performance over a properly working point set-up. Adding the electronics trying to solve an issue simply adds another unknown to the problem: correctly installed, alternator upgrade from generator, voltage regulator working correctly, etc. While I personally wouldn't use it; not trying to talk you out of it; but NEVER add the electronics to solve a problem. Solve the problem FIRST, then if you love electronics, install them AFTER the problem is solved. There are quite a few extremely sharp folks on these forums that are willing to help. All of us have opinions, and sometimes our opinions will actually be correct ; but the key to figuring out the problem is always testing! In order: (1) compression, (2) ignition, (3) fuel delivery system, and (4) carburetor. The order of testing is important. Jon Edited September 13, 2022 by carbking (see edit history) 2 1 Link to comment Share on other sites More sharing options...
Marty Roth Posted September 13, 2022 Share Posted September 13, 2022 (edited) 14 hours ago, Dieselfumes said: If I may ask ? But why go back to the old style points ? All of the research I have done the newer electronic points are the better way to go. I am not questioning to be a smarts a#$. Rather I would like to know why.. thanks for you're imput 37 minutes ago, carbking said: IF PROPERLY INSTALLED AND WORKING ON A WORKING ENGINE: the electronics will eliminate points burn, points wear, arm wear, thus eliminating the need for resetting the dwell every 5000 miles UNTIL THE UNIT FAILS. I have yet to see a test from an independent laboratory that shows ANY improvement in performance over a properly working point set-up. Adding the electronics trying to solve an issue simply adds another unknown to the problem: correctly installed, alternator upgrade from generator, voltage regulator working correctly, etc. While I personally wouldn't use it; not trying to talk you out of it; but NEVER add the electronics to solve a problem. Solve the problem FIRST, then if you love electronics, install them AFTER the problem is solved. There are quite a few extremely sharp folks on these forums that are willing to help. All of us have opinions, and sometimes our opinions will actually be correct ; but the key to figuring out the problem is always testing! In order: (1) compression, (2) ignition, (3) fuel delivery system, and (4) carburetor. The order of testing is important. Jon As is so often the case, Jon has said it very well. Points were not your problem, or the electronics would have made a difference. The testing sequence will ultimately point to the result we all wish you. Just because something is "Old Fashioned" does not make it bad, or bad, and new is not necessarily better in all cases. I've rescued at least three friends whose electronic ignition went out, but in an emergency, I've helped folks adjust points or swap out a condenser on the side of the road. Good luck with your continuing diagnostics, and when you ask for advice from those who've been there, please be prepared to receive multiple, and differing viewpoints - even those conflicting with your desired responses. PS: A possible reason for going back to points is simply to eliminate one of the changes as a potential cause. - Back to Basics, and the way it was originally designed and functional. Edited September 13, 2022 by Marty Roth (see edit history) 1 Link to comment Share on other sites More sharing options...
Bloo Posted September 13, 2022 Share Posted September 13, 2022 (edited) 1 hour ago, carbking said: While I personally wouldn't use it; not trying to talk you out of it; but NEVER add the electronics to solve a problem. Solve the problem FIRST, then if you love electronics, install them AFTER the problem is solved. This^^ 15 hours ago, Dieselfumes said: If I may ask ? But why go back to the old style points ? All of the research I have done the newer electronic points are the better way to go. I am not questioning to be a smarts a#$. Rather I would like to know why.. thanks for you're imput You could be right, but tune up, driveability, and emissions was my job and I am a lot less sure. I do like electronic ignition for the reasons Carbking outlined, but I have points in my flathead Pontiac. 1 hour ago, carbking said: IF PROPERLY INSTALLED AND WORKING ON A WORKING ENGINE: the electronics will eliminate points burn, points wear, arm wear, thus eliminating the need for resetting the dwell every 5000 miles UNTIL THE UNIT FAILS. Threads like this begin to sound like a holy war, but that is really not how it is. Some like conversions, some don't. As for me I am extremely skeptical of electronic ignition running at 6 volts, not that my opinion about that really matters here. It is no holy war, we just want to get it fixed so you can drive the car. Removing as many variables as possible is just good troubleshooting. An electronic ignition just uses a transistor to switch the coil rather than mechanical points. It really makes no difference as long as the electronic system (or the points) are working properly. Still, If I were troubleshooting it I would put a set of points in. The electronic ignition depends on the same weights and springs for mechanical advance, and the same vacuum pod that the points ignition depended on. If this is a module with 2 wires that mounts entirely inside the distributor, it also depends on the same ground wire from the breaker plate to the distributor case that the points used. Nice looking car! Edited September 13, 2022 by Bloo (see edit history) 2 Link to comment Share on other sites More sharing options...
Dieselfumes Posted September 14, 2022 Author Share Posted September 14, 2022 I did a vacuum pressure test on the system last night and it was right in the ball park that the repair manual said . However, once I hooked the windshield wiper line back up I could hear a hissing sound from under the dash.. So I plug off the vacuum line and found that the timing was acouple degrees off. So I set the timing again and also adjusted the carburetor. Took it out just now and it ran much better. Didn't cut out like it was doing before. Still a little hesitation at full throttle. But by far better than it was. I do have a brand new set of points that i bought. So i will throw them in when i get back and see if it makes any difference. Thanks for all of the advice and I really appreciate it... 2 Link to comment Share on other sites More sharing options...
EmTee Posted September 14, 2022 Share Posted September 14, 2022 10 hours ago, Dieselfumes said: However, once I hooked the windshield wiper line back up I could hear a hissing sound from under the dash. Vacuum leak could be the issue. Disconnecting the wiper line and plugging the vacuum port seems to have made a difference. I'd drive the car this way for a couple of days to determine whether the original problem is gone and take corrective action accordingly. 2 Link to comment Share on other sites More sharing options...
Buick35 Posted September 15, 2022 Share Posted September 15, 2022 On 9/13/2022 at 9:56 AM, Highlander160 said: Missing? Wow, where does it go? 🤣🤣🤣🤣🤣🤣🤣🤣 Sorry, sometimes I can't help it.🤭 I think my mind is missing at a higher age. Link to comment Share on other sites More sharing options...
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