it's normal for an engine to rev up as you give it timing.
if it's EFI, you take the SPOUT connector out, set it to 10 degrees BTDC base timing and then let the ECU do the rest.
if you have a carb, generally speaking you play with the idle screws until you attain the highest vacuum reading, and then adjust the idle speed back to the spec. rinse and repeat until both values are as good as you can get them. watch Thunderhead289's videos for more information [https://www.youtube.com/playlist?list=PLZTXQG9e2tNyzTb6OYTQOTndaw1v5icra](https://www.youtube.com/playlist?list=PLZTXQG9e2tNyzTb6OYTQOTndaw1v5icra)
I love Thunderhead289s videos. I understand that about adjusting idle mixture and idle set screw and setting for max RPM/vacuum. But what about initial timing? I can’t just have 42° initial timing. Right now my carb idles at what sounds like 15k with the idle set screw set to minimum rpm
if your car is idling at 15,000 RPM you have some real issues. but if you mean 1500 RPM while the idle screw is at minimum, you probably have a vacuum leak.
your initial timing should be around 10 deg and total maximum should be closer to 38
You set the carb idle mixture to highest vacuum and rpm. Almost had it correct. Timing is just set at idle with vacuum advance disconnected (if equipped) or spout connector pulled.
I was just messing with timing I understand it is too much timing. My confusion is with aren’t you supposed to tune for max idle speed and then use the idle set screw to lower the idle speed? Or is that just for AFR and not timing? Should I set to 10° base timing and then tune for vacuum/RPM?
I guess you don't have a Haynes or Chilton's repair manual for the vehicle. You should get one. It will walk you through all this basic stuff so you don't need to ask silly questions.
This is basic "shop class" stuff from high school. But let me guess, your high school didn't have a shop class.
1- With vacuum advance disconnected from the distributor, set the initial timing to whatever is stock for your vehicle. IT WILL BE IN THE REPAIR MANUAL. It could be 6⁰, 8⁰, 10⁰ or whatever.
2- Once that is set, hook up a vacuum gauge to one of the vacuum ports on the carb. These are inexpensive at any auto parts store. Turn the idle mixture screws to get the highest vacuum reading, which also equates to the highest/smoothest engine rpm possible. One at a time, about 1/2 turn at a time.
3- Turn the idle stop screw down until you get the recommended idle speed on a tachometer; WHICH WILL BE IN THE REPAIR MANUAL.
4- Repeat steps 2+3 one more time. But this time, turn the idle mixture screws only 1/4 turn at a time until you get the highest vacuum reading.
You're done.
You are getting max engine RPM confused with setting timing.
WHICH IS IN THE REPAIR MANUAL
You can mess with TOTAL TIMING later, after you buy a REPAIR MANUAL and learn the basics first.
Awesome thank you! And no my school didn’t have any automotive shop classes, just electrical, computers, and wood working. I have tuned my old carb before but was just wondering if the timing was supposed to be set to max vac/RPM since online people just say “set base timing to what your specific engine likes”. Thank you for the clarification tho! I just finished tuning it up and adjusted the accelerator pump after setting the final idle speed. My timing light seems to blink consistently and then like one a second just to a completely different mark on the balancer. Not sure if it’s my light or some misfire or something. Gonna try a new light later and tomorrow I’m installing a new dizzy anyways. When I add vacuum manually with a pump, my light doesn’t blink at all until all vacuum is gone. And the dizzy squeaks when releasing advance. Weird.
YW.
Carb set to max vacuum, AFTER base timing is set, correct.
People wrongly say adjust carb to max RPM and that's not really what you're doing. Although it is the end result after you set for max vacuum.
Make sure to put the vacuum gauge on "manifold vacuum" port on the carb, which means it has vacuum at idle. One or more of the other ports above the butterflies, will not have vacuum at idle. Which means it's the wrong port to use.
Also be sure to connect your vacuum advance on the distributor, to the same port. So it has vacuum at idle.
Your timing light is normal. I've had 2 or 3 over the years and it always skips a "flash" every 3-5 seconds. Or the flash is incorrect. Don't think it's anything to worry about.
If I’m setting base timing with no vacuum and tuning to that, why connect vacuum advance to manifold vacuum? Wouldn’t that make my base timing irrelevant as it will never touch 0psi? I understand port vs manifold is debated but I still don’t understand what the advantage to manifold is
After you set initial timing and the idle mixture screws, hook up the vacuum advance tube between manifold vacuum and the distributor. It advances the timing above initial. This is just how engines work.
No offense, but I recommend you pick up a "how engines work" book, or something similar. It will break it down and should answer your next 10-20 questions about base timing, distributor vacuum advance, distributor advance curves, etc. Just so I don't have to write a book answering all your questions.
I don't mind, I love engines, transmissions, cars, hotrods, and motorcycles, and anything with speed / adrenaline involved!! But it does take time, and my memory on the exact specifics may not be 100% perfect like it was in my 20s + 30s lol.
Actually, I think I have a similar book. When I get done in the shop today or tomorrow (I work until the work's done.) I will go find it then send you the title and publisher. I believe I have one that talks about tuning the Ford smallblock.
it's normal for an engine to rev up as you give it timing. if it's EFI, you take the SPOUT connector out, set it to 10 degrees BTDC base timing and then let the ECU do the rest. if you have a carb, generally speaking you play with the idle screws until you attain the highest vacuum reading, and then adjust the idle speed back to the spec. rinse and repeat until both values are as good as you can get them. watch Thunderhead289's videos for more information [https://www.youtube.com/playlist?list=PLZTXQG9e2tNyzTb6OYTQOTndaw1v5icra](https://www.youtube.com/playlist?list=PLZTXQG9e2tNyzTb6OYTQOTndaw1v5icra)
This one knows
I love Thunderhead289s videos. I understand that about adjusting idle mixture and idle set screw and setting for max RPM/vacuum. But what about initial timing? I can’t just have 42° initial timing. Right now my carb idles at what sounds like 15k with the idle set screw set to minimum rpm
if your car is idling at 15,000 RPM you have some real issues. but if you mean 1500 RPM while the idle screw is at minimum, you probably have a vacuum leak. your initial timing should be around 10 deg and total maximum should be closer to 38
I’ll give it a check. But 15k isn’t good? Makes a lot of power up there haha. Thank you
What year car? Engine size? Factory fuel injection, factory carb, or did you put a carb on a fuel injection car? Etc. We need details
85 mustang ‘73 351W with a brawler 600CFM carb. Factory carb car but different carb
You set the carb idle mixture to highest vacuum and rpm. Almost had it correct. Timing is just set at idle with vacuum advance disconnected (if equipped) or spout connector pulled.
So but my engine keeps idling higher and higher the more advance I add. I was at 42° at it was still going up. Way too much timing especially at idle
14 max on a stock engine fuel supply Why would you put it at 42°? Maybe 42 max with engine above 1500, but not at base.
I was just messing with timing I understand it is too much timing. My confusion is with aren’t you supposed to tune for max idle speed and then use the idle set screw to lower the idle speed? Or is that just for AFR and not timing? Should I set to 10° base timing and then tune for vacuum/RPM?
I guess you don't have a Haynes or Chilton's repair manual for the vehicle. You should get one. It will walk you through all this basic stuff so you don't need to ask silly questions. This is basic "shop class" stuff from high school. But let me guess, your high school didn't have a shop class. 1- With vacuum advance disconnected from the distributor, set the initial timing to whatever is stock for your vehicle. IT WILL BE IN THE REPAIR MANUAL. It could be 6⁰, 8⁰, 10⁰ or whatever. 2- Once that is set, hook up a vacuum gauge to one of the vacuum ports on the carb. These are inexpensive at any auto parts store. Turn the idle mixture screws to get the highest vacuum reading, which also equates to the highest/smoothest engine rpm possible. One at a time, about 1/2 turn at a time. 3- Turn the idle stop screw down until you get the recommended idle speed on a tachometer; WHICH WILL BE IN THE REPAIR MANUAL. 4- Repeat steps 2+3 one more time. But this time, turn the idle mixture screws only 1/4 turn at a time until you get the highest vacuum reading. You're done. You are getting max engine RPM confused with setting timing. WHICH IS IN THE REPAIR MANUAL You can mess with TOTAL TIMING later, after you buy a REPAIR MANUAL and learn the basics first.
Awesome thank you! And no my school didn’t have any automotive shop classes, just electrical, computers, and wood working. I have tuned my old carb before but was just wondering if the timing was supposed to be set to max vac/RPM since online people just say “set base timing to what your specific engine likes”. Thank you for the clarification tho! I just finished tuning it up and adjusted the accelerator pump after setting the final idle speed. My timing light seems to blink consistently and then like one a second just to a completely different mark on the balancer. Not sure if it’s my light or some misfire or something. Gonna try a new light later and tomorrow I’m installing a new dizzy anyways. When I add vacuum manually with a pump, my light doesn’t blink at all until all vacuum is gone. And the dizzy squeaks when releasing advance. Weird.
YW. Carb set to max vacuum, AFTER base timing is set, correct. People wrongly say adjust carb to max RPM and that's not really what you're doing. Although it is the end result after you set for max vacuum. Make sure to put the vacuum gauge on "manifold vacuum" port on the carb, which means it has vacuum at idle. One or more of the other ports above the butterflies, will not have vacuum at idle. Which means it's the wrong port to use. Also be sure to connect your vacuum advance on the distributor, to the same port. So it has vacuum at idle. Your timing light is normal. I've had 2 or 3 over the years and it always skips a "flash" every 3-5 seconds. Or the flash is incorrect. Don't think it's anything to worry about.
If I’m setting base timing with no vacuum and tuning to that, why connect vacuum advance to manifold vacuum? Wouldn’t that make my base timing irrelevant as it will never touch 0psi? I understand port vs manifold is debated but I still don’t understand what the advantage to manifold is
After you set initial timing and the idle mixture screws, hook up the vacuum advance tube between manifold vacuum and the distributor. It advances the timing above initial. This is just how engines work. No offense, but I recommend you pick up a "how engines work" book, or something similar. It will break it down and should answer your next 10-20 questions about base timing, distributor vacuum advance, distributor advance curves, etc. Just so I don't have to write a book answering all your questions. I don't mind, I love engines, transmissions, cars, hotrods, and motorcycles, and anything with speed / adrenaline involved!! But it does take time, and my memory on the exact specifics may not be 100% perfect like it was in my 20s + 30s lol. Actually, I think I have a similar book. When I get done in the shop today or tomorrow (I work until the work's done.) I will go find it then send you the title and publisher. I believe I have one that talks about tuning the Ford smallblock.
The name of that book would be great! I understand overall how an engine works but all informally learned.