Ignition timing curve

[ArizonaDan]

Good afternnon,

Well this is certainly frustating. I have spent the past three hours searching all over the internet trying to find an answewr to a question that should have taken less than three minutes. What is the amount of TOTAL advance at what RPM should I have for a 1968 FE 360? The engine is bone stock (two-barell) with absolutely zero aftermarket components. I would like to know what Ford recommended to be optimum setting and I will fine tune the timing too my preferences from there.

Thanks,
Dan

[BRUTUS_T_HOG]

i don't remember for sure on TOTAL advance.. 30-40?



i do know that timing specs are 6 degrees at 550 rpm... that all i know at the moment.. but if you're bone stock then thats all you shuold really have to adjust. i adjust mine to 8-10 degrees without any problems.

points are supposed to be .017 and dwell 24-32 or something

[garinger]

Well I don't have a 69 MOTOR manuel but the 70 states: Centrifugal Advance starts at 1/2 deg. @ 350 RPM and maxes out at 19 deg. @ 2550 RPM Vacuum Advance: starts 1 1/4 deg @ 5 in. of merc. and maxes at 9 deg. @ 25 in. of merc.
Hope that helps.

[george worley]

My motors truck manuel gives different advance curves by dist. number. You might need to get the number off the dist. housing and che.ck that way. There where many different applications depending on what model truck it was on and where it was delivered to.

[ArizonaDan]

Thanks for the response and advice George,

Here's why I was hoping to get a more general answer to my question: I will be replacing the points based distributor with a remanufactured Duraspark II unit as soon as I convert my charging system to run a 3G alternator. Therefore, the specific performance characteristics of the original points style distributor will not translate directly to the performance characteristics of the Duraspark unit, which was engineered for later model engines. In my case the specific distributor originally installed is not as important as the timing advance requirements of my engine (1968 360 two-barrel.)

My understanding of timing advance is that the ENGINE itself determines what its timing advance requirements are, and that a variety of different distributors can be utilized to meet this requirement. Hence the enormous popularity of the overpriced performance distributor market (MSD, Mallory, DUI, etc...)

I have spent too many hours already digging through old Chilton's and Motors manuals myself and still have not been able to find a straight-forward answer to what the ENGINES timing requirements are.

As an added note: I was led to even more confusion when reading the distributor specs from a 1967 Chiltons manual that stated clearly that all RPM readings for distributor specs were DISTRIBUTOR speed, not engine speed. Since the distributor spins at half of crankshaft speed the following information is very suspicious to me. This is EXACTLY what the specs said for a 1967 390 two-barrel:"Full Govenor advance, 9 degrees @ 2000 RPM." Now, I'm no math genious but I CAN double 2000, so according to Chiltons I should not have more than 9 degrees centrifugal advance at 4,000 ENGINE RPM! Even taking into account my base timing of 10 degrees + 9 degrees centrifugal I should have only 19 degrees mechanical advance at 4,000 ENGINE RPM? I'm not buying that at all.

This timing advance curve is not even close to any other timing advance curve I have ever seen for any other engine. Most timing curves are in the neighborhood of 30-38 TOTAL degrees advance at around 3,000-3,500 ENGINE RPM.

The more I research this timing question the more confusion I subject myself to. My next option is to find a shop in this town that has a distributor re-curve machine and ask them what my curve should be. I had no idea that this question would be so hard to resolve.

Somebody out there in Fordification land must have access to the correct Ford manuals that can help us ALL with timing advance curve questions, right?

As always, thanks for the responses from all,

Dan

[george worley]

I don't know how to tell you to find what you want to know,but I can tell you what my dist. advance curve is. I had a dist set up by a man who raced and built FE engines. At the time my engine was 100% stock 390 2bbl. auto. He said the dual diaphram 68 dist was not the one to use . He changed it to a 1966 single diaphram single point dist. He told me to set the timing at idle to 10 btdc. and the total timing was 35 btdc at 3000 rpms. I don't know the amount of vacuum advance it has. But I can tell you it really made a big difference in the way it accelerated. I could still run it on regular gas back then. Later on I put a 4bbl, mild cam,dual exhausts and a shift kit in it and it really ran good. I think the best thing to do is find a shop that can recurve your dist. Tell them what how you use your truck and what you intend to do to it and let them set it up. Trying to change springs and weights your self without a dist machine is a big pain in the A#$ and you may never get it the way it should be.

[ArizonaDan]

Thank you George,

That is exactly what I was looking for, 35 degrees @ 3,000 RPM. I will use that as my baseline setting and tweak it from there.

Dan

[My427stang]

That advice is good. A 360 doesnt have very good quench, so it needs plenty of timing, unfortunately it cant take too much because of the same reason it needs it.

I use 36 degrees, and go as high as 38 total. Thats initial PLUS mechanical. So if you are setting initial to 12, have 24 in the mechanical. How quick it comes in is more a function of gearing and weight, with a 4000 lb bump, 3000 rpm is pretty good. A Mustang you could drop it to 2500-2600, but Galaxies, bumps, etc, slowing to 3000 makes it more friendly on a hot day / heavy load.

I also use vacuum advance on all FEs, ported vacuum, but I limit it to about 6 degrees on a tight quench / high compression motor (total timing is now in the 40s) and on a 360 I'd allow a little more.

Remember the lower the compression / less turbulent the chamber, the more timing it needs. (Like a 360)

HOWEVER

The greater the quench distance and the less turbulent the chamber, the less timing it can stand (Like a 360)

Thats why so many guys zero deck now, it makes a turbulent chamber that NEEDS less timing but can tolerate MORE

[ArizonaDan]

Thanks to all,

Confirmation from multiple sources is always reassuring. George, your response gave me the solid foundation I needed to start from. My427stang, your response was very clearly written and to-the-point, much appreciation to both of you.

One quick question for My427stang: you state that you allow your vacuum advance to push the TOTAL advance beyond initial + mechanical. My understanding of vacuum advance is that it is only required when low engine speed limits the amount of advance available from centrifugal force, such as under a heavy load. I interpret this to mean that vacuum advance is more of an "auxilary" source rather than a "primary" source. Am I off base with this assumption? I was intending to adjust my vacuum advance with a hand-held vacuum pump so that it reached around 9 degrees @ 2,500 RPM, where I have full confidence that the mechanical advance system will effectively take over from that point up to full advance.

As always, any verifiable insight is greatly appreciated.

Dan

[mouse]

back in the mid 70s when dad added a montgomery wards electronic ignition to his '66 caddy, he advanced max timing and curve. If I remember right he first figure out the curve he wanted, then got a assortment of flyweight springs. he installed them one by one, till he got the curve he wanted by having it run through rpm. he got 3 sets of flyweights and would grind a little off at time and check to see if had reached the advanced he wanted, if he went to far he would through the set in the trash. I have not yet fully examined a duraspark to tell you exactly how but this an example. when I find them I will show you pics, I have 3 dizzy for it. plus for a fe, I got a duel point mallory with out vacuumed advanced that I might put in my truck. my dad had that in a 70s ltd 390ho, 411 rear, headers, 750 holly

[My427stang]

One quick question for My427stang: you state that you allow your vacuum advance to push the TOTAL advance beyond initial + mechanical. My understanding of vacuum advance is that it is only required when low engine speed limits the amount of advance available from centrifugal force, such as under a heavy load. I interpret this to mean that vacuum advance is more of an "auxiliary" source rather than a "primary" source. Am I off base with this assumption? I was intending to adjust my vacuum advance with a hand-held vacuum pump so that it reached around 9 degrees @ 2,500 RPM, where I have full confidence that the mechanical advance system will effectively take over from that point up to full advance.

That is correct. "Total" timing is a poor name, but we all use it. Total=Initial+centrifugal ...... vacuum isn't included in the total

Total timing is limited to high load WOT situations where there is no vacuum to pull any timing in.

However, at times when there is vacuum, additional timing brought in at other throttle positions helps power (but mostly seen as mileage) That's when the "auxiliary" as you put it, adds a little bit of advance.

Your plan for 9 degrees is good, but vacuum is not based on RPM, so the rpm it comes in is a WAG at best.

What I would do is set up the mechanical and centrifugal and then verify it is where you want it with a light. Then say its idling, and at 12 degrees initial, hook your vacuum pump up and bring the advance to full vacuum. If you are at 21, hook up the vacuum line and see how it does.

Some vacuum cans can also be adjusted for rate, some cannot. My Mallory in my Mustang can be adjusted for range but not rate. My truck Duraspark can be adjusted for rate but not range (so I pinned the arm on that one to limit throw)

Clear as mud?

If you remember though that initial + centrifugal is the timing used when your foot is to the boards, and make that equal 36-38 @ 3000, you'll be 90% there.

Then play with vacuum to sneak a little more mileage out of it

[BMJs 67]

This is a very informative thread. It has answered everything I was about to ask about timing on my 390.