Hi everyone I am here again because I am very confuse with this point, I have a 1974 ford maverick 250ci 6 cyl automatic transmision, and I need to know the ignition timing point for my car . I have the Chilton´s Manual and it said that the Ignition point for my car is 6 degree BTDC and 6 BTDC for manual transmission too, but I have been reviewing some links by internet and they say that the Ignition Point should be 12 degree BTDC for automatic transmission and 6 BTDC for MT Is 6 BTDC or 12 BTDC ? http://www.classicinlines.com/SmallSixSpecs.asp#CR http://mustang-s.com/engines/engine_250.php
if you put 250 timing in search you can find other threads that say 6 degrees fo automatic but as much as 8 or 9 is okay and maybe more.
With the garbage fuel we're stuck with, a bit of an increase in timing helps. I have mine at 8° BTDC and it has helped in starting, running, and fuel mileage! I haven't really played around with it yet. Mine is a 250, automatic with duraspark II ignition. A friend of mine hooked a choke cable to his distributor and loosened the clamp enough to where he could adjust it while driving. He set it to where it ran best and tightened the clamp there. I forget how much different the timing came out, but it was more advanced.
I'm pretty sure 12 degrees is TOTAL TIMING. meaning what it should be at 1000 rpm. Idle timing is 5-8 BTDC I believe and total timing is around 12-14.
No, no, no... Base is generally 6* to 12* & total timing with vac advance disconnected at 3000-3500 RPM should be around 25-30*(referring to stock)... With vac adv added in, it may be as much as 45*... This said, I've never been much of a vacuum guy, I like to loosen up the springs in bottom of dist that determines the advance curve... Usually I shoot for 12-14* base and let the mechanical advance dump the remaining 22*-25* in by 2500 RPM(approx 36*-38* total)... Takes a bit of experimenting to determine what a particular engine likes... BTW you did notice this thread is five years old? I was yet to join in April '12...
I did notice that. I have never seen a 12 degree timing at idle. Maybe it a six cylinder thing? I'm more familiar with the 302 and that's between 4-8 At idle stock. I typoed the total timing. Yes 3000rpm. My bad
Many 6cyl engines have only vacuum advance... One of first things I learned 50+ years ago was 99% of time increasing base timing improves performance(crude without other tuning but works)... The tuning specs for most '70s engines weren't just bad, they were pitiful... From day one we were recurving distributors and increasing jet size in the carbs looking for more performance... This was in addition to plugging/removing EGR valves, tossing hot air pick up to carb, retard systems on dist etc... Unless I was doing a stock tuneup for someone, I've never looked at mfgr specs, just go with tuning procedures I know work...
Couldn't have said it better with a thousand words. My general recommendations for this type of tuning is to learn how to adjust timing based on the level of modifications already installed to the car. IOW, bone stock small cubic inches with factory muffler?.. probably no huge gains to be had for the time investment of gutting/recurving.. not to mention carb tuning also becomes mandatory and adds another layer of variables into the mix. There's no way i would not do it myself on anything it could be done to (imo, one of THE most appealing things about old carbed wasted spark ignitions is the fact you can drastically improve them with only basic handtools).. just saying that the learning curve and added potential for engine damage can be daunting for novices. Otoh, even a smaller cid engine can be greatly improved when the basic building blocks have been added. Bigger carb with free flowing larger element aircleaner and good free flowing aftermarket muffler can easily see 25 ft/lbs of extra peak torque and far better averages on either side of peak. People think i exaggerate that number but I've seen and done it many times and even more on v8's. Add full mandrel bent exhaust and some induction porting and the little motors start running neck and neck with the weaker untuned v8's. One wheel peels become stupid easy. Lol. This is because, and as Tom already mentioned, the factory tunes were designed to create more safety margin before they would warp heads pop gaskets or blowup from general neglect and/or abuse. Then add the fact that OEM's of the time still abided NOx regulations that basically traded lowered combustion pressures(indicated by the lower idle vacuum and weaker throttle response) and more raw unburned fuel going right out the tailpipe. Best thing you could do for any of these old motors is to find a much shorter advance stroke 10L reluctor shaft. Some engines already have them and the owners never have a clue to what there missing out on if they uninstall and flip them around. 10L's give 20 degrees of mechanical advance sweep and allow you to run much higher base timing. Combine that with an adjustable vac advance pot near fully tightened and you could realize a much greater power and efficiency gain. 16-18 base timing plus quicker swept 20 degrees mechanical advance supplemented with vac advance of about 8-10 degrees wakes any old motor up.
Decent info from another old members thread to get you started. Pay particular attention to bmcdaniels posts. He seems to understand the combustion physics involved during light throttle angles. http://mmb.maverick.to/threads/10l-distributor-swap-not-a-carburetor-question.34369/ PS, IIRC that thread starter(Scott) ended up around 22° base timing, 16° mechanical sweep, and about 10° vac advance supplementation. So, 22° initial, 38° total, 32° at idle and around 42-48° during light cruise. A much welcome side affect was ending up with nearly 20" of manifold vacuum(up between 5" - 7" improvement from baseline) and the car ran great, albeit even more traction limited than it already was before the tuning. And all that gained with a moderately sized performance cam. I know most people here rarely see 20" of manifold vacuum even with stock cams.. so that's not too shabby at all. And yes.. he did have to tune the carb to make it all work.
Good info in that link, a good refresher just when I need to start tuning on the points dist now in Comet... I had the Duraspark dist performing fairly well but those won't trigger a TFI module, instead require either a Hall Effect sensor, or believe it or not, points...
I wouldn't go past 45* on a 6 cyl...V8 can take an extra degree or three than a 6 cyl. On a street engine 40*-42* would be more ideal
