Interesting information from Stovebolt re: Timing. True?

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Working through my carb issues with tom (which are solved, thankfully), there was some interesting discussion regarding setting engine timing that I would like some opinions on.

For the basis of the discussion, I want to throw out some numbers on my car

Advance at idle 550 rpms (vac disconnected) = 15 deg.
Maximum initial + centrifigal (vac disconnected) = 39 deg
Max initial + centrifigal + vac connected = 57 deg

That tells me, I guess, that I have 24 deg of mechanical, and an 18 deg vac canister.

OK - Tom suggested that the best way to set timing was to adjust the distributor to the best idle. Set your idle speed, and like a mixture screw you can adjust the Dizzy until you get the best idle. At some point more advance doesn't help and you can play it by ear.

Well, I did this and I found that the sweet spot for my Dizzy was about 35deg initial. Givent his, the MAXIMUM advance I can get is 56 deg. total.

That's 1 deg less than my maximum with the vac canister and 15deg initial. Also, an interesting by-product here is MUCH better idle characteristics, and I'm getting another 1-2 HG of vacuum at idle, from about 14hg up to 16hg. So, this 35 initial seems like a pretty good place to be.

Now, here's where Tom's recomendation I need feedback from the group.

Tom says that the Vacuum canister is an absolute must for the car, and that if I have an 18deg can, I should reduce the timing back down to 17deg initial, and hook the Vac advance up to FULL vacuum, so that I get the 35 deg number at idle, but at full WOT I loose that canister. If I don't do this I will get pinging.

My question is -- do I need the Vac advance at all? Can I run 35 intial since the max initial + mechanical is 57 deg?

Hope everyone understands the questions. Feedback appreciated!
 
I've been following your distirbutor saga for some time and frankly, I think if you have one that delivers 57 degrees of total timing, something is wrong.

Most cars will only need 32-36 degrees total at speeds over 2500 rpm. That's initial, plus vacuum, plus centrifugal. The typical distributor only delivers about 20-22 degrees of centrifugal and 5-10 degrees of vacuum.

If you truly were able to crank in 35 degrees of initial advance, the car would have trouble starting. You'd be asking the starter to force it's way against a firing cylinder, a task that it may have difficulty doing.

Is it possible that somehow you've managed to double the numbers or are reading the degree ring wrong? Could you describe the technique and equipment again?
 
Sounds like your timing chain may be loose. I haven't been following 100% though.

Also...maybe a tooth off on the distributor?

Slade
 
Thanks guys -- I appreciate the help.

The timing chain and gears are all new. Also, I just had a cam installed and the installer checked everything. I'm almost 100% positive that the readings are right.

Tom at stovebolt seemed to think that 35 deg. initial was OK given that I have a cam - he actually *expected* that number before I even did the adjustment. The car starts up and idles just fine..

I know this is wierd and I'm equally confused. For whatever reason, the car idles like a DREAM now with that much advance. Perfectly steady vaccum reading at 16hg with no flutter.

I'm more confused about this now than ever.

ALSO -- there are 2 vacuum ports on this Holley and I don't know which one to use. One is down low on the carb, and it gets more vacuum as the engine revs, but very little (like maybe 10hg max), the other is way up at the top of the carb, and it after about 1200 RPM's it jumps way up to the engine vaccum level.

OK regarding the procedure.

I have a Craftsman dial-back light that I'm using for this test. I always use the light so that the mark on the balancer is lined up with the TDC mark on the timing chain cover.

I always disconnect the vac advance to set timing. With the car at 15 deg I set the idle speed screw to about 950 - 1000 RPM's in Park. On my car, that equates to about 650 RPM in drive, which is where the car likes to idle.

Now, I loosened the bolt on the Dizzy and turned counter-clockwise. This *increased* the idle speed. There was a sweet spot where you could advance further but the idle wouldn't incrase. I set the Dizzy at this "sweet" spot. I then turned the idle screw BACK down to 950 RPM's, and checked the timing. I set the dial on the light so that the mark on the balancer was lined up with TDC, and the dial read 35 deg.

That's how I set the timing - this was the procedure explained to me by tom.
 
IS THERE A POSSIBILITY THAT YOUR HARMONIC BALANCER MAY HAVE SLIPPED MOVING YOUR TIMING MARK A FEW DEGREES? OR COULD YOUR CHAIN BE 1 TOOTH OFF? (NOT LIKELY IF THE CAR IS RUNNING STRONG) IS IT THE ORIGINAL BALANCER? :unsure:
 
When you attach the light to #1, remove the vacuum, and dial the timing light back so that the TDC mark is at zero you have 35 degrees at idle accordng to the light, is that correct?

Just having a cam should not cause that kind of advance requirement unless you have a big cam with so much overlap that you have little cylinder pressure at low rpm. But from the low idle and the 16" vacuum, I'd say the cam was not that big.

Something doesn't sound right, but I can't say what it is. I think you may be measuring wrong, but the bottom line is, if the engine runs ok, it's ok.
 
Yes, that is correct. O deg at TDC reads 35 deg. on my dial.

Now, what about running with the VAC canister hooked up to manifold vacuum vs. not hooked up at all?

If I turn the Dizz back down to 17 deg inital (no vac), and hook the vacuum canister up to manifold vac, I can achieve 35 deg inital (17 mech + 18 vac advance).

Now, at cruising speed (about 2000 RPM's), my advance is about 45 deg.

If I *disconnect* the vac advance, and run 35 deg mechanical, I'm running about 55 deg advanced at 2000 RPM.
 
With the advance hooked up that's not 35 degrees initial . That's 17 degrees initial + 18 degrees vacuum. Your initial advance is the setting without any advance, either vacuum or centrifugal. That's why you have to keep the idle speed down and the vacuum off when setting initial advance.

Still that's more than the vacuum canister should be delivering. It's a PITA to take a distributor apart, but the advance weights are marked with a number. That number corresponds to half the mechanical advance that it will deliver when using that weight at that setting. Usually it's either 10 or 15 (20 or 30 degrees centrifugal). If you run with no vacuum at all, you should ensure you have enough centrifugal.

Here's the other thing: Best advance is not necessarily the most advance. The idea is to start the burn so that it is expended when the piston is just past BDC, no sooner, no later. At higher speeds you have less time to do that, so the centrifugal kicks in to light the fire sooner.

Your engine may tolerate lots of advance, but lighting the fire too soon, even if it doesn't knock, may be costing power and economy. Your piston is now fighting the exploding charge while still on the compression stroke and the burn ends too soon to get full power. That's why I've never been a proponent of the "advance it 'til it pings" school of timing.

Maybe you have a bum distributor with the weights set wrong, poor springs, bad pickup coil on a DSII, or a bad vacuum advance. Maybe a combination of those which conspire to give you those high readings. Maybe you truly have an engine that likes 35 degrees of initial advance. Not sure, as it's difficult to diagnose over the net, but the bottom line is, you'll feel and hear what runs best.
 
HowdyCC:

What an adventure, Huh?

I'd say, if you're going to run that much advance, including initial and vacuum, at an idle do it with vacuum and from a full vacuum source. I think the likelyhood of getting knock under acceleration, at lower rpm is very high if you do it with just initial and no vacuum. With a full vacuum source, you know that the vacuum advance will go away under acceleration and a drop in vacuum, lessening the chances of lug sensitive knock. When the lug (load) goes away vacuum returns and so does vacuum advance.

I'd hate to disagree with Tom Langdon, but Jack raises some very valid questions. Something is not right in timing land! It sure sounds like too much of everything to me.

Please check your timing mark to verify that it is dead on.

Do you happen to have another distributor that your could try for comparison?

What are your plugs saying about this much advance?

Adios, David
 
David, Jack et al thanks again for your help. It has been an adventure for sure!

Well, I know of a local place where I can get a NOS balancer for the I6. It's expensive, but I may just have to pick it up tomorrow.

Is there an easy way for me to check the condition of mine? Can I just move the crank around so that the timing mark is on TDC and check that the dizzy is facing the #1 plug? Will that let me know.

Also, David, the scenario you described above is exactly what Tom described to me. The only disagreement may be on the amount of initial timing.

I've run the car for a few minutes with these settings. Did a couple of WOT blips, and set for some cruising (2000 + RPM revs). I put *new* plugs in and just checked them. They are a tannish brown.
 
Pull your plugs so the engine can be turned with the fan. Insert, gently, a wooden dowel or finger into #1 plug hole. GENTLY FEEL FOR #1 reaching top of stroke. If your timng mark reads TDC, you're OK. If not, you've slipped. ;)
 
OK i just checked everything. It all lines up.

Moved the balancer bolt around until the timing mark was lined up with TDC on the timing chain cover. Checked the #1 plug and the piston is at the top of cylinder (I can see it with a flashlight and touch it with my pinkie.

I pulled the dizzy cap at the rotor is pointing almost straight down, facing the number 1 plug.

Still, with all that lined up this car loves to be at 35 deg. I mean, it will RUN fine at 15 deg, but moving it up to 35 the idle is just so smooth and it's pulling good vacuum.

I just can't explain it. HELP! :D
 
Jack one more thing on your post.

You are correct, 17 initial plus 18 vacuum. OR I can run 35 degrees with NO vacuum.

When Tom Langdon told me what to do, as I described above, I removed the vacuum source to test the timing. I was originally at 15deg at about 950 RPM's. Tom told me to adjust the timing up or down until I got the best idle. That would tell me the right spot for my initial timing. I moved the Dizzy counter-clockwise and the idle increased, and there was a point where the idle wouldn't increse any more. I moved the timing back until JUST when the idle speed started to slow, then adjusted the idle speed screw back to 950 RPM. THEN I checked the timing and that's when I say 35 deg.

I called Tom back and he wasn't that surprised that with the cam I might be running 35 deg intital. However, he warned me (just as David did above), that 35 deg initial would be too much at cruise. That's when he said to hook the vacuum up to full manifold vac, and set the timing back down to 35 deg so that my intial advance would have only some mechanical and FULL vac.

Anyway, that's what I have right now. 35 deg at 950 RPM with (17 mech + 18 vac)
 
I ultimatly eliminated my vac advance so as to better control the curve. I did a lot of set and drive testing and used a number of combinations during the process. At one point I set the timing via the best idle speed method and I did get a 35* initial number. The car did idle very nicely and I did not have any stater issues. However, I could not get the car to live with the all-in number this combo created, i.e , WOT ping was unacceptable. What I found over time, however, was that the car liked 15* initial and an in gear idle speed of 650 rpm just as well, and the resulting all-in with mechanical advance only gave me very nice throttle response and elinimated the WOT ping. So, I have 15* initial and 35* all-in, no vac. I find it interesting, given my experience, that you initial of 35* and all-in of 57* are both 20* higher than what I found to be the ultimate settings. Note that most of the other posters are also suggesting 15* and 35* (approx) as the best settings. Is there something to the fact that your cars runs well and you timing light says you are 20* out of the norm at both spots. I would have to suspect the light, the damper, the cam timing, or the dizzy timing. In this regard, if the cam, or the distributor, are off a tooth it is not the end of the world. Just set you car up to run well and make note of the setting for future use. If it works, don't fix it. Having said that, however, this issue may require correction / adjustment upon completion of your next mod, or the next, so be prepared to reconsider these possibilities. Since the light is new, and the cam timing set is new, I would take a hard look at the damper and the dizzy installation.

Personally I think this is great fun. Hope you see it in the same light.

Buy the way, want was the fix for the carb??
 
Steve

Thanks very much for the info. You're right - it's interesting that I'm 20* ahead of your settings, but you did say the car liked 35* initial at one point.

I just did a visual test of the dampner, piston and dizzy, and the whole setup lines up. So, if there is something wrong, it's not showing up externally. What's interesting, is that by setting up the timing this way, with vac advance all in so early, my total advance at cruise is actually less than it was before.

OK the carb -- it was actually VERY confusing and ended up being a combination of three problems. They are all solved now thankfully.

1. The float was set a LITTLE to high.
2. The jets were backwards - the rich jets were in the primary side and the lean jets were in the secondary side.
3. Apparently, the secondary throttle plate is supposed to be open a TINY bit even at idle. Mine was closed completely, which was causing me to have to set my idle speed screw too high, causing the throttle plate to open too wide, creating too much vacuum in my primaries which was sucking gas out of the venturi at idle. All this was complicated by point #1 and #2 above. By adjusting my secondaries to be open JUST a hair, it releaved the vaccum off the primary and smoothed everything out.
 
I'M NOT GOING TO SAY HELLO!

IF YOU HAVE A STANDARD MOTOR, AND STANDARD CAM IN IT, AND HOT COIL. FIRING AT 57*.... YOU WILL HAVE EXPANDED THE FULL CHARGE 20* DEGREES BEFORE THE PISTON COMES TO THE TOP. THIS WILL DRIVE THE PISTON BACKWARDS..... AND STOP THE MOTOR...WITH THE FIRST TIME IT HAPPENS.

DO YOU HAVE A MILLER MOTOR AND MILLER CAM SET UP? IF THE EXHAUST VALVE IS OPEN ALL THE TIME THEN YOU CAN HAVE THIS SET UP. BUT IF BOTH VALVE ARE CLOSED YOU ARE WRONG... EVRYTHING IS NOT RIGHT ON. A WEAK COIL WILL GIVE A DELAYED IGNITION AND WILL RUN AS YOU SAY,...BUT AT HIGHER RPMS WILL NOT BE HOT ENOUGH TO EVEN FIRE THE LOAD. RIDDLES ARE BEST ANSWERED WITH THE FACT. THE TIMING LIGHT ,WITH THE ADV, SHOULD BE PUT ASIDE AND USE A STANDARD LIGHT. THIS WILL LOOSE ANY MISTAKES BY THE LIGHT AND OPERATER.

TELL US WHAT MOTOR , WHAT DIST. & COIL, WHAT CARB. WHAT VAC. HOOKUPS YOU HAVE. DON'T TELL US WHAT YOU THINK YOU HAVE...OR WHAT SOMEONE TOLD YOU THAT YOU HAVE. MAKE SURE OF EVERYTHING THAT YOU SAY. CHECK EVERYTHING TWICE

SO, CHANGE YOUR MIND. HAVE SOMEONE HELP YOU TO FIND THE PROBLEM.

WHAT I AM SAYING IS.... THERE HAS NOT BEEN ONE PERSON SO FAR WHO HAS BEEN WRONG IN WHAT THEY HAVE TOLD YOU. I THINK YOU BELIEVE YOU ARE TELLING US WHAT IS RIGHT,.... BUT SOMETHING IS WRONG. EACH PERSON HAS GIVEN YOU SOMETHING TO CHECK AND YOU ARE COMING BACK AND SAYING IT'S AS YOU SAID. I SAY IT IS NOT....!!!!

THE ONLY THING THAT MAKES SENSE IS THAT YOU DO NOT HAVE A MECH. ADV. IN YOUR DIST. THEN WHAT YOU ARE SAYING WILL HAPPEN. WITH THIS DIST. AT IDLE YOU WILL GET A VERY HIGH ADV. BUT AS SOON AS YOU OPEN THE THROTLE THE VAC. FALLS AND SO DOES THE ADV. THIS IS CALLED A LOADAMATIC DIST. YOUR MAX. ADV. WITH THIS DIST YOU WILL GET ABOUT FOUR DEGREE MORE THAN WHAT WILL GET AT ADLE. MAYBE 39* AND NO MORE.

I WROTE A POST ON THE PRE.. FAILURE FORUM AND IT WENT INTO HOW THIS WORKS. IT WILL FALL BACK TO WHAT THE LOAD NEEDS. IT RETARDS THE TOTAL ADVANCE BACK TO WHERE THE LOAD ADV. VAC. FALLS!!!

THAT IS MY GUESS!!!!!????!!!!

LIVE IN GRACE

LEROY POLL

THERE SHOULD BE A PRIZE GIVEN FOR THE ANSWER ON THIS ONE.
 
Well, Leroy, I'll say hello to you! Not sure why you're irritated with me :unsure:

All I can tell you is that I have checked, and double-checked before I post.

Here's what I have in my engine. I KNOW this is what I have becasue I did a bunch of the work myself. Apart from the cam and head install, and the actual machine work, I bought all the parts and installed them.

- 252 cam (it was a grind to Comp's specs from a local machine shop). I don't know the specs off hand.
- DSII distributor, and module, from a '79 fairmont. These were all parts-store reconditions. I know it has mech. advance.
- MSD Blaster coil
- Autolite Spark plugs gapped to .050
- Some mild head work (4-angle valve job, hardened seats, etc.), with new ISKY springs matched to the cam.
- Holley 5200 carb from stovebolt.

Regarding the timing light, it's a brand new Craftsman dial back. I also have a SECOND advance timing light, and I used both for testing to make sure that I wasn't getting bad readings - so BOTH would have to be broken or somehow mis-alligned.

I'm really not trying to prove that I'm right. I'm trying to figure out what is *wrong*.

Externally, I have confirmed that the balancer and dizzy are all alligned. With the piston at TDC on the compression stroke, the balancer is at 'TDC' on the timing chain cover, and the rotor is pointing directly at the #1 terminal on the spark plug cap.

Now, with all that information - here is what I'm saying:

When I rev the car and watch the timing increase until it doesn't increase ANY more, the total timing is between 55* - 57*. I cannot tell you what RPM that total number comes in at. I've looked at this with TWO timing lights, on several occasions, with a variety of vac/mech configurations listed above and in my other posts.

As listed in a previous post, here are the various timing readings I have recorded previously:

Advance at idle 550 rpms (vac disconnected) = 15*
Maximum initial + centrifigal (vac disconnected) = 39*
Max initial + centrifigal + vac connected = 57*

Bottom line -- I'm still not sure what this all means. What I can tell you is that in my '73 stingray, with a re-curved distributor by an ex-GM tech and current hot-rod builder, my max advance on that 350 is 52*. My max mechanical advance is 36* and it comes in at 2800 RPMS. I'm running 25* inital advance at 850 RMS - I've confirmed these number to be optimum for performance by other vette guys. That car runs great.

What I can't comment on are the differences in how timing are affected by V8 vs. an I6. But being in the 50* total doesn't seem to be that unusual. :(
 
Hello CC:
Well... this timing issue sure does get people revved up.
I too was told that the best way to set the timing is by getting the best idle out of it, leave the vacuum advance disconnected and let the mech. do all the work.
If you have a completely stock motor with a stock cam by all means go with the usual settings (10 to 15 deg, initial with vac. hooked up) that's because of the stock cam.
Now, you have a better than stock cam in your motor. You cannot use the stock timing specs. to set it up. Performance cams need more initial timing, thats a given fact.

Also a few guys have been saying that a Duraspark is a complicated dizzy to get into. Not true, they are quite easy to take apart and modify.
I have four or five of them now, One in my 81 Stang with the 250 modified motor and one in my 80 Capri with the stock motor. In both cases I took the stock mech advance springs and changed them with the lighest springs that Ford Motorsport has to offer.

I am not a mechanic by trade but do alot of work on cars (especially my own)
If you are a little nervous on taking a Durasprk apart - can you get one out of a wrecking yard and take it apart first. All you need are basic hand tools (Phillips screwdriver, needle nose pliers)
Just take your time.

Mustang Six is right, when you get down to where the weights are, they are maked with a number (10 or 15)

If you decide to run with no vac. advance I would suggest to put the lightweight springs in (the stock ones are far too heavy and you have to get the rev's up pretty good before they start to move.)

Well in conclusion - I didn't believe on setting the timing by using the best idle method - but now that I have tried it I won't do it any other way.

this is all probably clear as mud for you isn't it? ;)

John
 
This getting interesting. But to clear up a point made, I understood Corillian Corvette to say when he found 35* initial to be the sweet spot he then REDUCED the initial to 17* so that when he added the vac advance he had 35* at idle WITH VAC IN. If this is the case, that would not be all that unusual. The book says 6* initail. Add vac and you woul be at 24* on a stock set up. So, I am not shocked by the idle setting at this point. What I do find interesting is that you are having good luck with the 57* all-in. I can't get past 36* without ping, and at 40 it is BAD. Is it possible that the cam is the answer here? I am running a stock bottom end.

Very interesting.
 
Small point just to be sure we are all on the same page here. Did someone say springs control advance? To be clear - weights control advance (10* - 15*). Distributor * are 1/2 the crank advance (10* in dizzy wt. is 20* at the crank). Springs control rate of advance. I assume we are all talking about dual advance distrbutors at this point.

Sorry, so much here I though it was getting confusing.
 
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