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Topic Review (Newest First)
05-21-2006 04:16 PM
amblessed4life
ignition timing 1987 ford ranger 2.9 v6 4x4

i had to take out my distributor to change my pick up coil. I have never done this before . I forgot to mark my number 1 plug an timing mark on my homonic balancer. So their for i have no marks to go by to set my timing back to normal. by my book it say's i have to set my piston at 10 degree's BTDC ( BEFORE TOP DEAD CENTER ) IM NOT SURE IF I HAVE THE TIMING MARK SET RIGHT. I made sure that i heard a air sound for the compression on the number 1 piston . i set the tdc mark as my timing . being off 10 degree's will it effect the way the truck is running. I put the rotor cap at my number one plug . started the truck ran sluggish , no power, hit the gas died on me. sounds like the way your truck is doing. How do i fix this. Before we go through this when i took the dis . out the guy that was helping me bent the metal piece that run's through my pick up coil . That gives the distibutor spark . Metal piece wables .
02-28-2006 04:18 PM
glen242
Quote:
Originally Posted by KNanthrup
Yeah I get that more initial makes it idle faster, I just don't inow how much is TOO much. I think im going to take your suggestion and bump the timing up little by little and test it by going up hill in high gear and listening for pinging then back it off a bit.


Yeah I swear I checked the timing mark when I had the engine apart but I might engine-stop it to check again (even though its a pain in the ***).

Anyways maybe your point about initial timing doesn't matter is right. I'm thinking that maybe the distributor I'm using has weak springs in it also, because all timing does come in before 3000rpms (probably about 2600 like yours). Plus my initial being 22* and my total being 35* means that there's only about 13* of advance in the springs. The only reason why I'm weirded out by it is because I would think that it should run fine with initial set back to say 16* but it just doesn't.
Stock distributor on my '76 'vette has maximun centrifugal advance @ about 4500 rpm. That is the reason for me changing springs. I want it all by 2600 rpm.

The 13* advance probably means you are getting some mechanical advance @ idle. As stated, I get mechanical advance @ idle so I time it for all in +/- 36* @ 25-2600 rpm and ignore the initial timing.
02-27-2006 04:38 PM
curtis73 Don't worry about how much initial you have. If it takes 36* to make it idle properly, then you need 36*. Actual timing at idle is of minimal importance. You have to take into account several things that happen after idle, but its not a big deal.

Mine for instance is locked at 36* No curve except from the vac advance. Of course, my example is a BBC with 8.6:1 compression. BBCs need a good bit of lead and my low compression needs even more. I could have gotten away with as little as 22* and still idle, but 36 still let me crank it to start and gave me another 2 inches of vacuum and a smoother idle.

I suggest finding how much initial your combo will take. Advance it a couple degrees and try to start it. Keep going until it kicks the starter back. Come back down a couple degrees and that setting is where it will let you start and idle. Make sure you do all that hot so it won't cause trouble later. You can guess that your combo will probably like about 36-38 total, so you can make a curve between what you discovered at idle and the total advance. Lets say for instance you start kicking back at 28* initial. You want 38* total. You then just use a combo of bushings that gives you a total of 5* in the dizzy or 10 on the crank. Then pick your springs to set where it comes in.

Then you can use ported vacuum to bring more timing in under part load. That you can set with an adjustable can and just loading it down under various conditions and backing off the canister to keep detonation away.

There are certain situations with heftier cams, larger chambers, or certain combos where the kickback at startup doesn't occur until well after 38*. Its rare since it often occurs with very low cranking pressures like might be had with a mismatch of low compression and too much cam, but I don't think that will be the case here.

I assume you have an auto tranny. If so, the task is pretty easy. If you have a manual, chances are you'll have to broaden your total curve. If you just set it (like the example above) to your optimal 28-38* curve, 28 might be too much when you floor in third at 1500 rpms. If that's the case, you'll have to back it down (for example) to maybe 24* initial and then broaden your curve to 14* of sweep. You'll have to open up the throttle just a touch to compensate, or drill some holes in the butterflies to keep the ported vacuum hole covered at idle.

In short, the answer to your original question: Best initial timing setting is as much as you need, so long as it doesn't make too much at part throttle or cause annoying starter kickback. In theory, the more initial the better on a non-smog car. The more initial you have, the less throttle opening you need which improves vacuum and throttle response while providing a smoother idle. On a smog car it might make NOx above acceptable for idle tests.

Idle timing settings are only important as a means of setting a benchmark for the rest of the curve. When Chevy made a 1978 350, they had a curve that was set for X degrees of advance. The way to set it was simply by putting it at 12 BTDC, but that number has very little to do with what it needs at idle, its just a reference. Setting it to 12 BTDC simply means that it will provide the engine with 36 total by 3200 rpms. Since you're building your own curve, initial timing is not a benchmark for you. You can find your own optimum idle setting and build your curve from that.
02-27-2006 03:08 PM
red65mustang turn the idle way down to 3-400rpm to verify your not pulling some centrifugal advance and reading it as base,

light springs and heavy weights will do that, start the curve at 5-600rpm

(and vacuum advance discoonected and plugged)
02-27-2006 02:53 PM
johnsongrass1 it might run at 16 if your reclaibrated the carb and idle speeds.

See your playing with a finely tuned and calibrated set of circuits. Affecting one affect's them all. Getting them all correct means a lot of trial and error with a degree of systematic logic problem solving. You cannot change just one thing and always expect better result's.

IT'S ALL IN THE COMBINATION!!!!!. is never more true


You have to verify timing marks are correct. Otherwise, your chasing your tail and your gonna catch up it eventually. OUCH!!
02-27-2006 02:17 PM
KNanthrup
Quote:
Originally Posted by ap72
It should idle faster with more initial timing when in neutral or park. For this circumstance I would try adding as much as 6 degrees, 2 or so at a time and when it does start to ping back it down by 2 for safe measure. It's not the most scientific approach, but usually the easiest and most understandable.
Yeah I get that more initial makes it idle faster, I just don't inow how much is TOO much. I think im going to take your suggestion and bump the timing up little by little and test it by going up hill in high gear and listening for pinging then back it off a bit.

Quote:
Originally Posted by glen242
First thing to do is verify TDC using a piston stop. See if the numbers on the dampner are correct.

I also have that cam in my 383. With my modified advance curve, I set mechanical timing at 36*, all in by 2600 rpm because I know I am getting some centrifugal advance at idle with the soft springs. I never set or pay attention to initial timing, only use total mechanical timing.

BTW, I use an adjustable vacuum can that gives me 14* @ 12". This gives me 50* at cruise rpm. I have the can hooked up to the manifold vacuum port, not the ported vacuum.
Yeah I swear I checked the timing mark when I had the engine apart but I might engine-stop it to check again (even though its a pain in the ***).

Anyways maybe your point about initial timing doesn't matter is right. I'm thinking that maybe the distributor I'm using has weak springs in it also, because all timing does come in before 3000rpms (probably about 2600 like yours). Plus my initial being 22* and my total being 35* means that there's only about 13* of advance in the springs. The only reason why I'm weirded out by it is because I would think that it should run fine with initial set back to say 16* but it just doesn't.
02-27-2006 01:28 PM
glen242 First thing to do is verify TDC using a piston stop. See if the numbers on the dampner are correct.

I also have that cam in my 383. With my modified advance curve, I set mechanical timing at 36*, all in by 2600 rpm because I know I am getting some centrifugal advance at idle with the soft springs. I never set or pay attention to initial timing, only use total mechanical timing.

BTW, I use an adjustable vacuum can that gives me 14* @ 12". This gives me 50* at cruise rpm. I have the can hooked up to the manifold vacuum port, not the ported vacuum.
02-27-2006 01:12 PM
ap72 It should idle faster with more initial timing when in neutral or park. For this circumstance I would try adding as much as 6 degrees, 2 or so at a time and when it does start to ping back it down by 2 for safe measure. It's not the most scientific approach, but usually the easiest and most understandable.
02-27-2006 11:41 AM
KNanthrup
ignition timing (in relation to rpms)

Ok so long story short, im a little skeptical about how accurate my timing marks are on my SBC 350. I was almost sure that everything was set right when I built the engine but it has some strange attributes (by the way it has a comp XE274 cam). When setting initial timing, it will not run very good under about 20* initial. It will run if I set it back from there, but not great, the idle rpms drop down a lot and it has a bad studder and very laggy/sudden throttle response... definitely does not feel right. So I can set it to around 20 or 22* initial and it runs great, the idle speed picks up a lot, good throttle response, etc. That brings the total timing to about 35* which is good also.

BUT if timing mark is not accurate and say what I think is 22* is really 16* then my total timing is really 29* not 35* which means I have a lot left in it. I have tried playing with the timing back and forth and I have not noticed any pinging when setting it up with more initial so I'm starting to get skeptical.

SO, my main unofficial half-whitted question is, how does the best initial timing typically affect idle speed? For example, is it usually at the point where the idle speed is at it's highest when playing with the timing only, or is it back a little bit from the highest idle speed, or is it a little farther back the fastest idle speed? I don't know if I'm making my question clear? Maybe it would even help to go on a scale of say 1 to 10 with 1 being barely running retarded a lot, 5 being the highest idle and 10 being tons of initial after the peak in idle speed.



p.s. I know I will need to use a more scientific and accurate method to check this but for now I'm pondering it as food for thought. Any insight is appreciated.

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