The inline six runs best with at lease 28* - max of 33* mechanical and static, and total of 12* vacuum... max of 45* timing. The centrifugal advance should be fully engaged at 1,800 to 2,000 RPM on a non computer vehicle. The V8 guys can go higher
I'm not even remotely saying that those figures aren't working for you(although the terminology does confuse me a bit).. but I've never found similar results on maybe 10-12 various sized 6's in Mustangs, Falcon's, and a few others that my brain can't remember right now. And believe me.. I try like hell to get mechanical to come in as fast as possible. Just never could get it all in by 1,800 on just about anything I've ever tuned.. Ford or otherwise. Doesn't seem possible unless the initial is set way too low to begin with at 2 or 4 degrees or something. Could you please break those numbers down for us into the typical "initial setting.. mechanical sweep.. and vacuum assist"? IOW.. initial + mechanical = total.. and then we add vac assist number to that for maximum part throttle ignition lead. Thanks much if you have the time to clarify.
Here is a chart of my setup using a dial-back timing light (click thumbnail). Ideally you want all mechanical advance in at 1800 but the best I could get things running right was a fast ramp up to 1500 and then a small ramp to 3000 starting with 12* base or initial timing. I have my vacuum advance coming in real slow to prevent pinging. I was doing this the old fashion way with no distributor machine. A lot of distributor removing and tab bending and lot more of swinging an allen wrench on the side of the road. I think the last time I messed with the distributor I ended up sliding a plastic sleeve over the tab to make the tab think it was in a smaller slot. I have a 13L / 18L plate but the tab thinks it is a 10L slot. Here is a good read on what I tried to follow. http://www.jeepforum.com/forum/f8/team-rush-ignition-coil-connector-wiring-595104/ and done this too http://www.junkyardgenius.com/ignition/phasing/phasing01.html
Wow, I shouldn't reply to this until I have time to look at the links. I leaned the carb out this afternoon. I turned the mixture screw in until the engine started to run rough(er) and then backed it out a half turn. I bumped the timing up to 14* (initial timing). I drove the car. I would say it runs as good as my 200 was running, which was good in my opinion. I still ahve some work to do and want to learn all I can about recurving my distributor for maximum performance and fuel economy. Rememer, the carb I'm running is for a 200, so ai'm not getting the cfm that I should be getting for that engine. I also feel like the bend from my "over the axel" to the muffler is too sharp and has reduced the exhaust pipe. That will be fixed in the next few weeks. I did a little playing with the timing light and the advance. I disconnected the vacuum from the advance pot and slowly brought the rpms up. I believe this is "mechanical advance" that I was checking. Like Jeff, my mechanical advance doesnt kick in until upwards of 1,800 rpms. Now here is where I'm a little confused and maybe I just don't have the correct equipment. I brought the rpms up to 3,000 to check my max mechanical advance(?). How the heck do you know what it is when the line is way off the gauge? I estimate it to be about another length of the gauge, so about 36*. I connected the vacuum line back up to the advance pot and did it again. That max was real hard to tell because the line almost went out of sight. I do that you guys for the help, I'm going to spend the evening reading the links that you both posted. BTW, the hood won't close with the breather on that carb. Guess I need to replace it sooner than I wanted to. I have some stuff to send classic inlines for some $$$, that will help offset the cost. I let it out for some sun today, the interior was looking a little pale... I know the bumper is crooked, it's straight now.
Whew, been reading all night about tuning and recurving the distributor. I have learned a ton, thanks you guys!
Thanks for the info, Jeff. From what I'm seeing of that curve.. it appears that you have two different springs and it's interrupting the sweep to cause it to look like that. I used to do something similar with a very weak spring on one of the posts.. and another heavier spring that was adjusted to not kick in until the weaker one had stretched a bit. IOW.. the second springs post was bent in such a manner that the spring didn't even make contact and start stretching until the first one had stretched out a bit. Kind of a dual stage centrifugal curve. I'm tired out from the day and hopefully that makes any sense. :16suspect Sorry to keep drilling you with questions here.. but I have another one for you so I can learn what you've done with yours. How did you "have my vacuum advance coming in real slow to prevent pinging"? Manifold vacuum is on full tilt at idle and light throttle and I'm not sure how you could do that. Are you simply saying that you had it running off a timed port rather than full manifold vacuum? In the end.. there's many ways to arrive at a similar curve and a lot of it revolves around the parts and tools you have to work with. Through the years I've arrived at the simpler solution to give the motor(especially low compression/large chambered heads) the maximum initial timing it will allow to give maximum engine vacuum readings and then finish it off with minimal amounts of mechanical sweep to arrive at the total number that gives maximum power @WOT. From there I give it the max vac advance it will tolerate under heavier loads up hills and/or with a loaded car. Very similar to yours at any given rpm.. only that it starts off much higher at idle and plateaus quicker, is all. Oops.. I lied. One last question. What engine vacuum number did you reach on your setup? Did you ever make it to 18" at idle like Don's?
When you found that 18" of vacuum with a specific number of ignition lead.. keep that number in your head for later on too. You may even find more vacuum than that but carb tuning gets much tougher to do with air bleed changes, pump shots intensity/duration and all the rest of the detail related type stuff. That's also the point that you start quickly eating into safety margins and are forced to run premium fuel for added protection. Also, you'll want to be VERY careful with timing lead on that smaller than required carb too. It's surely off from optimum jetting for what that 250 needs at higher rpm. Seems' like you're on your way now. BTW.. the car looks great.. keep up the "tuning 101" study time and all the rest of the good work you're doing here.
Yes, two springs...one light spring and medium spring. The medium spring fits loose on the anchor tap and has to wait for the light spring to stretch. By "vacuum coming in slow", better words would be I turned the screw inside vacuum pot so it needs a strong vacuum to move. I ran both ported and manifold vacuum and I can't tell the difference when the car is rolling down the road. Only difference I see is when the engine is at idle. Once the throttle plate is cracked open the vacuum measures the same at the distributor.
Don, if your YF came off a 75-79 250 engine, it was rated at 195 cfm. The 70-74 RBS was rated at 215. If the YF came off a 200 then it was rated at 187 cfm
The yf on the car is from a 200, but its too tall. The yf that was on the engine when I got it is the correct height so Im guessing correct for a 250, just dont know the year. I have an rbs on a 76 250, but the tag is identifying it as an 80 model (E0 part number). I will do more tuning next week and continud reading. Im curious to see what weights I have as the distributor is from my 200. I will compare that to the old one from the 250. Lesson learned, just because it fits, doesn't mean it's right. I think I will follow Jeff's curve or at least shoot for it. I don't know what total advance I should have, but I know when my intial is at 12* the car is happy. Get the correct weights and start working on the curve. I will get this eventually. Thanks again for all the help. I really do appreciate it.:Handshake
Here's how to eliminate variables form the vac advance pots current calibration being less than ideal. Disconnect it.. advance the initial until the engine vacuum is highest(make sure to readjust the mixture screws after adjusting idle back down to what you prefer).. make note of that number and replicate it later on with part/MOST of that number being initial.. and the other part being supplemented from the vac advance pot running off full manifold vacuum. Also remember that the vac pot likely has internal allen key adjustment too. Don't have much time because I'm leaving town for the weekend but I will also say that NOT using the maximum initial advance and relying too heavily on the vac pot leaves you in a situation that when the car is given hard throttle from standstill?.. the vac advance pots contribution will abruptly fall away and the car will struggle harder to come up into the rpm where the centrifugal kicks in. Which is basically why Jeff was forced to use such a fast advance curve on his setup. Lack of initial will cause that and that's why you want the most you can get from it. Makes the engine feel much larger than it really is and funner to drive. Good luck with it.
Spent the better part of the day tending to things in the yard. Since I was a good boy for doing that, I felt it was ok to play with the car for a bit. I pulled the carb and DSII out of the 76 parts car. The carb tag is something like E0DE, and not an rbs like I thought. Not sure what it is really, but I put it on and fired it up. It ran but not great. Only had an inch of throttle and my breather wouldn't fit it, so I took it back off. I was about to put the 200's yf back and I glanced over at the yf that came off the 250 that I had rebuilt and tried first. I thought, what the heck, let's try it again since I messed with the timing the other day. What do ya know, it ran great! Still vibrates a lot in gear when stopped but this is the first time I noticed a difference from my 200. I still need to play around with the info I learned about recurving the distributor, but heck, great improvement. I thought that since I put the shorter carb back on that I could close the hood with my breather on it....wrong! What the $^$%@^! I had to remove my pretty FORD nut and put a regular bolt in and it closes, but it sure is close. I do have an issue with 2 noises that I'm hearing. One I hear when I start it, the other I hear when I make a U turn at the end of my road and get on the throttle. The noise I hear when I start it sounds like the fan dinging off a belt or something. Only one or two dings and it's gone. It doesn't always do it. The other noise I thought was a tire rub, but that's not it. It's a rapid clicking sound that I want to say is coming from the tranny. It's hard to tell exactly. The exhaust is so close to the body and the drive shaft that it could be related. Will have to wait until that's fixed to be sure. I don't think either noise is anything serious. Here is a pic of the vacuum I'm pulling currently.
Looks like a nice vaccum reading. Ur vibes might be from a carb problem. I thought it cud/might be vac leak, until I saw that vac reading.
It may not as bad as I think. I have the door taken apart, my dash is a little messy, the console is out, the truck is tore apart. Plus that dang exhaust is really bugging me. I think once everything is back together it will be much better. Its running to good and too smooth for there to be an issue....I hope
