ignition timing some odd readings - sorted

[Charger]

read this post and many others about ignition timing …

http://www.moparuk.com/forums/viewtopic.php?t=46806

It involves restricting the amount of mechanical advance in the distributor so you can run lots of initial timing. This makes the engine run better on modern fuel, starts easier, runs cooler, and runs cleaner so you don't get smelly exhaust.

my Charger runs fine, however with minor issues; stinky exhaust and lumpy idle

got me a FBO limiter kit from Jon at the Nats last year, not fitted yet

so today, before I start to pull the dizzy apart, I took some baseline readings, highlighted the timing mark on the index tab and the balancer with some white paint, marked the position of the dizzy to the block with a white line, got the motor up to temp, checked idle was about 845rpm, disconnected and plugged vac advance and hooked up the timing light

I got some odd readings …

20deg at idle without making any adjustments

I continued and advanced the dizzy as Dave described in another post …

With the engine hot and idling, just turn the dizzy until you find that sweet spot where the rpms level off. Then re-set the idle rpm to normal (800-900rpm) and see what initial you have. The engine is telling you by the rpm where it is working most efficiently.

38deg at idle after bringing idle back down to 850rpm, stopped and started ok, also started ok after ½ hour, then again 2 hours later

seems way too high to me for a standard set up, is it possible for the timing mark / balancer to be in the wrong position??

what else do I need to check??

[Adrian Worman]

It seems as if you're reading something other than TDC on the pointer on the tab attached to the timing chain cover.
In essence tho you got it right, so just recheck your timing marks, maybe reference a couple of diagrams or pics.
When you did advance it, did it run better Si? Was idle quality improved?
If it was it shows you are going in the right direction and just need to be certain how you're reading or interpreting the timing marks.
What sort of timing light are you using?
Ideally I'd expect the timing to give excellent results at 18-20 initial with the FBO plate installed on the 14 degree slot, giving a mech advance of 34 deg at 3000rpm, and the vac can set to give a total of 50-52 deg overall at 3000 rpm.
You may have to connect the vac to constant, from below the throttle blades.

[Charger]

cheers Ade, I’m sure I’m reading the index tab right, I cleaned everything up and highlighted TDC with a white line, there’s also a sight hole in the tab at TDC

yes, when I advanced it, I would say it did run better, it was just as Dave described, idle increased and then levelled off

sure I’m happy with the procedure, just a bit thwarted by the unexpected high numbers

the timing light is a Gunson with advance dial

many thanks, I’ll double check the timing marks during the week

[Dave-R]

I have just been looking at a strong 440 last night with a big solid roller camshaft that was timed 19 degrees initial and 39 total (not in until 3500rpm).

When I tried seeing what advance it liked at idle it actually liked 34 degrees best. But no way will it start with that amount of initial.

So it is a case of backing off and finding how much initial it will take and still start OK. In this case I suspect it will be around 24 initial and a softer spring should bring it in faster to a 34 total at 3000.

I ran out of time to find that ideal initial so I have to go back to it. Trial and error.

[Steve]

Hi Si.....are you happy that the balancer hasnt slipped?? Could be that the TDC mark on the balancer is no longer at TDC. Maybe a rod in no1 hole and a big socket and bar to turn her over will just confirm that you are in the right area with marks.

I messed loads with mine and finally dropped on a sweet spot at 10 deg initial. Would run and start ok (ish) at anything between 12 and 22 but generally starts, runs and pulls better all round without any hi cups etc at 10 deg. I used a dial in gun and took it out with me on a run. Started at 5 deg then went a few miles changing in single deg steps until I found where it was happiest. I tried the method of turning the dizzy till the revs peak and it was something like 22 deg. Ran like a pig, backfiring and not starting so backed off again and found 10 was a good setting for my car.

Good luck Si and please keep us updated with progress. This stuff is very interesting and good to learn from others experience

cheers Steve

[Charger]

I have just been looking at a strong 440 last night with a big solid roller camshaft that was timed 19 degrees initial and 39 total (not in until 3500rpm).

When I tried seeing what advance it liked at idle it actually liked 34 degrees best. But no way will it start with that amount of initial.

So it is a case of backing off and finding how much initial it will take and still start OK. In this case I suspect it will be around 24 initial and a softer spring should bring it in faster to a 34 total at 3000.

I ran out of time to find that ideal initial so I have to go back to it. Trial and error.

cheers Dave, but this a stock’ish 383, 20deg and 38 deg at idle seems way to high to me, which is why I’m confused, I don’t want to fit the FBO limiter until I’m happy with the baseline

what else can be wrong?? balancer / timing mark in the wrong place, what is the best way to confirm this??

when I had it advanced, 38deg at idle after bringing idle back down to 850rpm, stopped and started ok, also started ok after ½ hour, then again 2 hours later

so can’t be a real 38deg reading surely??

could it be something else?? I can’t imagine it could be as I said apart from stinky exhaust at idle and idle a bit lumpy (not bad), the motor runs great

[Charger]

Hi Si.....are you happy that the balancer hasnt slipped?? Could be that the TDC mark on the balancer is no longer at TDC. Maybe a rod in no1 hole and a big socket and bar to turn her over will just confirm that you are in the right area with marks.

I messed loads with mine and finally dropped on a sweet spot at 10 deg initial. Would run and start ok (ish) at anything between 12 and 22 but generally starts, runs and pulls better all round without any hi cups etc at 10 deg. I used a dial in gun and took it out with me on a run. Started at 5 deg then went a few miles changing in single deg steps until I found where it was happiest. I tried the method of turning the dizzy till the revs peak and it was something like 22 deg. Ran like a pig, backfiring and not starting so backed off again and found 10 was a good setting for my car.

Good luck Si and please keep us updated with progress. This stuff is very interesting and good to learn from others experience

cheers Steve

cheers Steve, that’s my main suspicion, that the balancer has slipped, is this possible?? or is it key’d

I’m happy with the index tab on the timing chain cover, but tonight I will double check all the way round the balancer, just in case I have got the wrong line

[Dave-R]

. I tried the method of turning the dizzy till the revs peak and it was something like 22 deg. Ran like a pig, backfiring and not starting so backed off again and found 10 was a good setting for my car.

If you tried to drive it with that much advance without limiting the total advance it would run bad because with 22 initial you would be charging about with 40-50 degrees at 3000rpm.

The spot to find is not where rpms stop increasing completely but rather where the sharp increase starts to level off.

If there is no clear spot and rpms increase in a linear fashion then I would try to find the spot where you have as much initial as possible but the engine will still start.

BUT Make sure you have adjusted the idle mixture and speed before you switch off and try re-starting. That makes a difference too.

[Dave-R]

We are all still learning which is why I offer to tune cars for free. It is to gain as much real world experience as possible. Hopefully the more I learn, from actual experience of engines in different states of modification, the more I can pass on to you guys.

[Dave-R]

Any engine, even stock, should have at least 18 degrees initial and still start fine.
You know timing and mixture are right as you will have a max amount of vacuum at idle and the exhaust will smell "clean".

[Dave-R]

[cheers Dave, but this a stock’ish 383, 20deg and 38 deg at idle seems way to high to me, which is why I’m confused, I don’t want to fit the FBO limiter until I’m happy with the baseline

You sure you are on #1 plug and not #2? They are 45 degrees apart.

Try #6 and see if you have the same reading. It should be exactly the same.

[Steve]

My dizzy is limited Dave, I had a limiter plate off Turnip but when I stripped the dizzy down, it already had one fitted. My car just doesnt like tons of initial timing...runs lovely all through the rev range at 10 deg initial, I cant remember the figures now as to how much advance the dist has built in etc but she just doesnt like much more than 10 deg initial. You are the guru Dave without a doubt so sure Si will get sorted fine.

I was told that the balancer can slip Si but usually only on hi horsepower engine builds, unusual on standard spec engines. Got to be worth checking though mate as a starter for 10

[Dave999]

is the timeing light advance dial set to 0 for your initial at idle test?

i'ms assuming you have a "NICE" timing light, full of features you don't use...

so this is all assuming you have a gun that allows you to set advance on a car that only has TDC line and has an analogue or digital display of advance that you can adjust with buttons or knob.

don't confuse the advance and dwell displays.... (dwell is only really really usuful for points these days)

get it running

point light

the line will be before TDC

as you wind in advance on the gun the line should approach TDC at idle,
read off the gun what the advance is once you have wound the knob to the point where the line and TDC hole on the cover tab match

thats your initial timing

rev it to 3000

do the same process. i.e wind more advance in on the gun until the lines line up balancer and the hole for TDC

thats your total mechanical timing.

do all of this with the vaccum pipe disconnected from the Dizzy and plugged with a screw (on the bit of pipe from the carb) (not down the metal pipe on the vaccum can on the dizzy, seen somobody do that once, they couldn't explian why they had done it )

when you wind the advance knob, that is you delaying the the light flash by X degrees

hence with X dgrees delay dialed into the gun and the lines linked up. X is the advance you are measuring at that RPM.

sorry if i'm teaching you to suck eggs here...some timing guns are overly feature rich...as it were....

my own regaularly just stays at 14.5......!
i can easily knock the thing into measuering battery voltage

if all is ok

maybe one of your advance weights is sticking....

Dave

[Charger]

Any engine, even stock, should have at least 18 degrees initial and still start fine.
You know timing and mixture are right as you will have a max amount of vacuum at idle and the exhaust will smell "clean".

cheers Dave, I hear you, 18deg is what I was aiming for after reading all your other posts on this subject, so imagine my surprise when before I touched anything I got 20deg, 38deg after advancing and it still started fine, something’s wrong or I am missing something

[Charger]

[cheers Dave, but this a stock’ish 383, 20deg and 38 deg at idle seems way to high to me, which is why I’m confused, I don’t want to fit the FBO limiter until I’m happy with the baseline

You sure you are on #1 plug and not #2? They are 45 degrees apart.

Try #6 and see if you have the same reading. It should be exactly the same.

I was defo on no.1, front drivers side ok?? plug leads are also numbered, also separated the leads so I wasn’t getting any false trigger from other leads

I’ll try no.6, thanks again