Made a new post on this. Original post was at:

https://www.ford-trucks.com/forums/8...dified-fe.html

Finally, it runs like it should. But against most timing numbers, and against basic rules on dist adjustment.

Here's my final numbers:

0 rpm (23 Deg BTDC) and it cranks fine.

800 rpm idle (28 Deg BTDC)

Max advance (38 Deg BTDC)

Operation is smooth and powerful. None of that pounding you get when the ignition is too retarded. And as far as I can tell, no knocking under acceleration. At least engine isn't fighting me as the revs rise, which is good. Bog is gone.

At 800 rpm, max vacuum was 20 in Hg at 38 Deg advance. Too much to accelerate and not expect knock.

At 800 rpm, lowest good idle was at 16 deg, which is textbook for the cam I am using. Engine ran hot there, and pounded when acclerating.

Not having a vac dist, I went in-between 16 and 38 and based on old data, I went with 28 as listed above.

Not sure this would work with a heavy truck, but it's interesting none-the-less.

And for those who say vacuum advance is only for economy (like I always thought), you are wrong. It will adjust for the best advance dependant on the load, not just the rpms like a mech adance.

I think I'll get me one of these in the near future:

http://www.shopatron.com/product/par...26688.2096.0.0

 

Congrate, glad to hear you found a balance

 

Something ain't right. 23° initial should fight the starter every time you crank the motor. It is way to much. 28 at idle is also way to much and if it doesn't ping like hell going down the road then either the timing numbers are wrong or you are major league rich or have no compression. You don't list at what rpm you reach that 38° either but from what your 800 RPM number is I would suspect in is before 2000 rpm, which is also very wrong.

Oh and you would be wrong about vacuum advance it was originally designed to improve mileage (there were no emissions when vacuum advance first appeared). When emissions came along they started screwing with vacuum to change emission number (hence the dual diaphragm units). When accelerating there should be so little vacuum as to not effect timing, ever. Properly setup vacuum advance will only effect timing at above idle (that's why ported vacuum is there) and as light engine loads (not much throttle opening). I suspect you are watching these effects with an unloaded engine which is not real world engine operation. Don't believe? Spend some time with a dyno and see for yourself.

 

Well, I double checked the new balancer marks, plus put paint on the pulley next to the TDC mark so if the balancer outer ring slips again, I'll know. I'm using a Snap-On digital timing light which I trust.

Not sure when it all comes in as I seem to be getting breaker-plate bounce around there, but from what I remember, yes, it's not far off 2000 rpm...maybe between 2000 and 2500.

I don't deny that vacuum advanced was first designed for economy. What I am saying is that it seems to me that for part throttle application, the spark advance should be between that required for pedal-to-the-floor and steady cruise.

Total vehicle wieght is 2500 lbs. Single plane manifold, twin vacuum Holleys. Different combination than a truck, and maybe driven differently too. I never put it to the floor. 1/3 throttle is scary enough for me. 1/2 throttle and the front tires barely grip the pavement.

The advance I am using now is still less than what worked for me for years and quite a bit less thna when I experimented and finally broke a piston. I just didn't realize how advanced it was due to the balancer being out. That's how I got into this mess.

I do plan on going to a vacuum dist. It will be interesting to see how it all adds up then. I am hoping it will give me proper timing no matter what I do, from flooring the pedal, to lightly accelerating and everything in between.

I am happy with the performance right now, but it's limited a bit. I think with the addition of a vacuum dist, my choices on how hard I want to accelerate will broaden dramaticaly.

I suspect that I can reduce the basic mech curve to say, 16 intial and 38 max, but with the vacumm addition, I can set it for the 38 Deg at idle where I find the best vacuum and highest rpm (only co-incidence the advance for best idle is the same number as the max full-load advance). With some tinkering, the advance should then move appropriate to the amount of throttle (engine load)I want to use.

Anyway, I agree with everything you've said, and it's the reason I posted. I find the numbers don't add up to what I would expect.

I do wish I had a dyno, and a dist machine, and a vacuum dist, and......oh well.....maybe just the dist.....

On a side note:

Ported vs Manifold Vacuum

From what I understand, these two ports should work in reverse, and therefore vacuum dist's are made for either one or the other. And you shouldn't switch vacuum sources unless you change to the proper dist. But I see in these forums all the time where people do.

My Holley vacuum source gives me nothing at idle, then jumps up as I open the throttle.

On the other hand, manifold vacuum is highest at idle and drops when I open the throttle.

When ever I have aimed a timing light at a vacuum dist equipped engine, it is always very far advanced at idle, and drops as you open the throttle.

I think that's why my timing works well. It's because I don't open my throttle completely (down low), so I need some extra advance, which is normally what a vacuum can would do.

Another aside:

Here's a story....a few years ago some guy on a green crotch rocket (my son says a Kawasaki Ninja 1000 or some such thing) with his matching green biker clothes and green helmet, started following me around town. I was heading up to the highway to take a short cruise and then get back to town via the next exit. The motocycle guy was behind me as I started genbtly up the on-ramp. I could see him looking over his left shoulder chekcing for traffic, as he was itching to pass and leave me in the dust. So I let him pass. Just as he got by, I gave the car about 1/2 throttle in 2nd gear. And I caught up, and in fact, had to back off the gas a bit. Meanwhile this guy is going up through the gears winding it to red-line with every shift. So he finally relaxes and looks in his side mirror expecting to see me 1/2 mile back. Instead, I was right on his tail. He did this amazing double-take in the mirror. Too funny to see his helmeted head check the mirror, than snap back to check again......

Anyway, not too shabby considering the power to weight ratio advantage a motorbike typically has.

 

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23 degrees, it should be fighting the starter.

 

I don't know what to tell you. Maybe you can set your timing (vacumm disconnected) to 23 at idle, then shut down engine and try and see if it kicks back when you try to re-start. Mine doesn't, and it didn't back when it was advanced even more than that.

Timing marks and everything check out. Only way I can double-check now....oops, that would be a triple or quadruple check by this point, would be to take the valve cover off and check against the cam timing.

Maybe my timing light is out. I can check it statically and see if there's a difference, but I think I've already done this during my tinkering, and it's more or less the same, maybe 1 degree out on account of all the moving parts taking up slack differently on an idling engine vs one turned over by a wrench on the crank snout.

oh well...........

 

You are not listening. If the timing is actually at 23° initial and it doesn't kick back, either you are NOT at 23° or something is real wrong with your engine or you timing technique is screwed up. Either way the numbers you give are not possible with a properly set up engine.

 

C'mon bear - you know better than that. I have lots of builds that fire up nicely with around 20 degrees at idle and 36-38 total. Not at all unusual. You have to consider that the idle timing might well not be the true initial value - fast/light springs will already be advancing at 700 RPM or so.

 

Yeah, with massive amounts of cam to drop the compression on cranking. This is a mild build and I don't buy it, especially when I claims it crank with no problem with even more timing into it.

 

That's exactly how mine is set up. Just enough spring to return it to initial(like 14*), but as soon as it gets any kind of rpm at idle it pulls it up to mid 20's and that really helps the low end power. Unless I would try to lug it in 4th gear at 2000 rpm, it doesn't have a chance to knock. With the camshaft, it doesn't like anything that low anyway. Been this way for years.

 

I'm not looking for a argument, but discussion is useful. I have admitted the numbers look wrong. That's why I made the original post. I didn't get much help, so I tinkered around. Now I posted my results and some of you are telling me my numbers are wrong. Golly Gee...really? I can listen to you tell me I am wrong until the cows come home, but it's not helpful advice.

I am absolutely certain my timing marks are correct. The only possibility is my timing light is in error. I don't have another one, but I can try to borrow one. In the meantime, all I can do is rotate the crank by hand and see when the plug fires and then read the advance on the balancer. I'll try that today and report back.

Now, as far as cranking goes, it would only take 10 mintues tops to do the test I suggested earlier, and see if your own engine will start there. I certainly realize that advanced timing may cause cranking trouble, but nowhere have I seen a "not-to-exceed" timing number. So what is it?

I did a Google Search and didnt' find any quantitative info, but this came up:

http://www.clubcobra.com/forums/arch...p?t-17348.html

Seems like the guy in the link has the same problem I do. He's getting unusual numbers which he can't explain. And they uncannily match up with what I am finding.

So.....any thoughts on how I can find out more about what's going on with my engine?

And for all of you, I appreciate the fact you are trying to help. Even telling me I'm wrong keeps me uncertain enough I will continue to try to figure out why I am getting such weird numbers and why it cranks and starts easily.

 

Ah Freightrain....you must have been typing as I was. Hope your Sunday morning is going well. A little rain here...again.....sigh.

Thank-you for your contribution. It's a bit disconcerting thinking you are alone with a unique engine situation. I feel better now....chuckle.

 

OK ...back again. I turned the engine over slowly with a wrench and and the plug fired exactly at 23 Deg BTDC.

Note: To do this safely, I remove the coil to dist cap ignition wire and using an old plug wire, connect a plug directly to the coil...i.e. no spark to dist, and no chance of the engine firing)

Next, I removed the #1 spark plug and put the engine to 10 Deg BTDC. I put a steel rod into the cylinder through the spark plug hole and marked it in relation to part of the engine. Next I removed the rod, put the engine at 10 Deg ATDC and put the rod back in. Mark lined up perfectly, so I think it is safe to say my balancer is indicating TDC correctly.

 

Why not just bring the piston to the top of it's travel and check if the damper says TDC?

 

a more proper test, to know if the timing ring has slipped.

Stop 1: remove all plugs.
2: with a rod or wooden dowl, ( perfor these so no scaring can happen ) insert it in the 1 one piston, slowly rotate till you fell the rod stop comming up,
3 mark rod. and rotate 360* more and and you feel it tdc once more chak the rod to the timing ring, BUT should be within 1* of true TDC. if not, your timing ring has slipped and need replacing.

While you at this, rotate once more till you feel BDC, mark the rod once more. pull out and measure the marks, if it reads 3 1/2 inches, you have a 360, of 3 and 3/4 you have a 390 or larger