Mapping Timing Events

cr_bobcat

Famous Member
Supporter 2018
Supporter 2021
So I've finally gotten around to mapping the timing events of this new HEI style distributor. This morning I just measured with the vacuum can connected. Tomorrow morning I will measure with it disconnected and the hose plugged. I started at about 700 RPM as this was about as low as I could drop it and keep the engine running reliably.

RPM Timing
----------------
700 16
800 16
900 16
1000 16
1250 20
1500 25
1750 34
2000 39
2250 42
2500 45
2750 47
3000 50

I have an timing light with a built in tach and advance adjustment. Obviously all measurements here are approximate.

This seems a bit aggressive to me but obviously I don't know for sure what this profile should look like otherwise I wouldn't be here. I'm pretty sure my curve is off but that's based off of a gut feeling that I feel like there's more power to be had with my current setup. She just feels a little mushy. Am I right in my assumption here or are things looking ok? Do I need to take some more measurments with vacuum connected?

Pertinent info: idle currently set at 1000, Holley 1940 carb, stock exhaust, unknown cam (let's assume stock), C4, unknown rear-end (again, let's just assume stock)

I still plan to measure how much vacuum I have but haven't gotten that far yet. I've got a guage but I just haven't taken the time to do it. I should just do that tomorrow when I plan to disconnect the can and check to see how much mechanical advance I'm actually looking at.
 
that actually looks pretty normal to me, in fact i think pretty close to stock. when you go to check your mechanical curve, use the vacuum gauge to plug the vacuum hose to the distributor that way you kill two birds with one stone.
 
I am betting it has 24 degrees all in at 3000 ( the same supposed Custom Curve all that I have tested have ) completely wrong for a small Falcon Six , But I digress ,
 
Your DUI just has the generic specs as sold.
Each combination requires a different curve.
Agree completely with FSD.
 
It's not actually a DUI but an ebay special from some speed shop in cincy or kentucky. Anyway, i hope to map the mechanical advance tomorrow. My sluggishness could be the result of multiple things. Vacuum reading will help there too i reckon. It's a learning process but I'm having a lot of fun doing the work. Helps me unwind a bit....
 
Alright, the results for timing events with vacuum disconnected are in:

RPM Timing Vacuum
-------------------------
1000 17 0
1250 19 DNM
1500 25 DNM
1750 31 5"
2000 33 7"
2250 33 8"
2500 33 9"

I forgot to look at my vacuum gauge for a couple of measurements. I didn't have time this morning to shut it down and tee into a manifold vacuum source, but do these ported values look healthy or not?

It looks like I have about 16/17* of mechanical advance and then about the same 16/17* of vacuum advance. Appears that vacuum starts to kick in at around 1600-1700. Looks like I'm all in, mechanically, at 2000 RPM. I'm wondering if my numbers are a tad off because I've typically heard mechanical to be in the 20-24* range and vacuum to be 12-16*. Do I need to slow down and retake these measurements?

Obviously, there is some variability in the measurements since this is me eyeballing something and I can very much see how a Sun machine would help out in tuning these things down to the gnats arse. That being said, I think I will definitely go forward with doing the mods myself until such time as I build up the new engine. With that I think I'll want to eeck every last ounce out of her and will only want to incur the cost of the recurve once. The local guy here doesn't even have his machine at the shop anymore because of lack of use so I may have to be talking to one of you guys to help me out when that time comes.
 
FalconSedanDelivery":23xw2amy said:
I am betting it has 24 degrees all in at 3000 ( the same supposed Custom Curve all that I have tested have ) completely wrong for a small Falcon Six , But I digress ,
What does the correct mechanical curve look like-without vacuum
Myway
 
Without knowing the static compression ratio, cranking compression, & camshaft specs would sure help.
Is the converter stock?? Might be able to help you if you give us the above information. Bill
 
As far as I know, everything is stock. The engine was rebuilt before I bought the car but that would have been quite awhile ago. I bought the car in '92 and have pretty much just done maintenance work on it since then. The only thing that has potentially changed would be the rearend ratio. My speedometer is off by maybe 17%. Part of that is due to the slightly larger tires (when compared to stock). But I doubt that accounts for the whole offset. I don't have a compression tester. Last I had the plugs out I could see the dish on the pistons so I assume the stock 6.5 cc dish. I highly doubt this head was shaved when it was rebuilt. The previous owner didn't strike me as someone who would spend the extra money for machine work. My assumption was that it was a stock rebuild. Not sure how available the 25 thou gasket was back then but I grew up 30 miles south of the lima engine plant so parts were probably a little easier to acquire.
 
What does the Right Curve / Map look like , hmm , well it aint 24 @ 3000, As every combo , and engine family has its own particulars , what is the Falcon 6 sweet spot ?( Log Head ) , well I am NOT giving that away for free , when the Falcon performance book ( that is sold here ) is made downloadable for free , I too will as well until then I offer My recurve service :nono: :nod:
 
Confuse is more correct , that thread on ( a recurve ) is very misleading , but again its as accurate as DUI's having custom curves , then they show up with 24degrees @3000 at least 5 I have worked have , adding 925D springs does NOT a recurve make , it may help , it may not lots more to it , I am Not The Police , LOL , but I call them as I see them and Ive seen them since 1976, try this Forum as a question about me on Dists, and recurving www.FordFE.com , Ive been averaging a Dist recurve a week this year Done for customers as far away as Australia and Finland, to name a few , on Engines that make more power at Idle than 99% of anything on here, am i blowing my own horn , sure , just tired of seeing guys waste money on non needed parts and ignore things that really help , it gets frustrating , I go away for a while , :arg: and then come back , and see the same things , the same advise ,I may probably get blocked or deleted for this one :nono:
 
JackFish":3h3q0e2g said:
Researching this thread may help
http://fordsix.com/forum/viewtopic.php?t=30894
Or it may just further confuse the issue. :p

I'd offer an opinion but the recurve police are out in force. :(
Just more confusing. The HEI-DUI distributor has spring posts that are fixed & cannot be bent.
It all has to be done with weights,springs & advance stops.
 
Well, like I said, this is an interim solution until i get the new engine built. When i drop in the new engine it will most definitely have to be recurved. That is when I'm going to be ready to have it professionally done. For now i just want to get it running strong.

That being said, what kind of gains am i leaving on the table by not getting it curved precisely? If we're talking 20 hp it's an entirely different story than if I'm only looking at picking up 5. It's a $/hp kind of thing. Again, completely intend to go the full monty later but right now my budget is better spent aquiring parts for the new power plant.

Cheers! :beer:
 
If it idles OK, does not hesitate & accelerates OK then save your money for later when you have your new engine ready & know all the internal specs on the engine.
 
Wow!! "more power at idle than 99% of anything here" :p
Actually Picking up some knowledge here along with some reading, think I will be able to get past Idle ;) My long past experience was circle track where all mechanical advance was used for allowing an initial advance the starter could handle and getting to optimal advance before 3000 rpm.
Keep the info coming :thanks:
Myway
 
Alright. I've done some digging. And for the interim I am going to try to get my setup to here:

37-38* of total advance
20* of mechanical starting ~1100, all in ~2500
17-18* static advance, which is basically where I am today, but slightly more aggressive
I am going to try to limit my vacuum advance to 12* since I don't have an EGR
Cam: unknown, assume stock
CR: unknown, assume stock but slightly worse

Granted, this probably isn't perfect but I think it will give me just a touch more uuumph. For those watching from home, I'm following the guidelines here:

www.firstfives.org/faq/timing/timing_fo ... ngines.PDF
http://www.fordmuscle.com/archives/2000/03/timing/
http://www.73-87.com/7387garage/drivetrain/hei.htm

The numbers I'm going with are coming from a number of other locations but I thought these links above were pretty decent for a part-time weekend grease monkey. Not knowing what my internals are is leading me to extrapolate data from others, but basically all in my head right now. Maybe this week I'll spend some quality time with matlab and try to truly narrow things down with some fancyarse plots.

I'm down with wsa111 and FSD doing their thing. And will be hitting them up for a proper curve when the heavy work needs to get done. If I can get about 1 sigma of what they bring to the table I'll call it a win for now. Reading ain't doing, you can't replace real experience.

:beer:
 
Add More initial , reduce the total to 32-34 , slow it down to all in by 2800 , limit vac adv to 8-10 crank degrees , dont let it start till a min of 10- 12 inches , This assumes a pump gas combo with no more than 9.5-1 and 93 octane
 
Back
Top