This whole timing thing?

-
Blind Squirrel

Blind Squirrel

Well-Known Member
Joined
Oct 1, 2015
Messages
1,167
Reaction score
861
Location
Pacific NW
Exactly how much does it take to make a difference? All things being equal how precise are we talking here. Can you be off by 1 degree, a half, or is there just a magic window, say a three degree arc.

It seems setting initial, finding the magic total and getting the advance curve down should be paid a lot more attention to than doing a little twistie action on the dizzy. That I may or may not admit to being guil guilt gault wron rong wong - mistaken about.

Are there any standard based rules/theory that apply?

Just for thought. A junior dragster is a single cylinder briggs and stratton style motor that can see 9000rpm (and not grenade). That's firing over 37 times a second. We set the timing "in the hole" .340thou btdc and could see a difference in about a .010 swing either side.
 
It's hard to tell the difference between 1°, rule of thumb is to go in 2° increments...
 
I have my timing locked down at 31 degrees on my blown 340. I had it at 28 degrees and then stepped it up to 31degrees as I am getting used to my first blower engine. the difference between 28 and 31 is dramatic.

My previous 360 N/A engine really liked 16 initial and 34 total. If I tried that on the blower engine it would be hard to start and then grenade when I stepped on it.

Every engine is different, the junior dragster, my 360 and my new blown 340 all require different settings to work properly. It's up to us to figure it out.

Jack
 
Blind Squirrel said:
Exactly how much does it take to make a difference? All things being equal how precise are we talking here. Can you be off by 1 degree, a half, or is there just a magic window, say a three degree arc.

It seems setting initial, finding the magic total and getting the advance curve down should be paid a lot more attention to than doing a little twistie action on the dizzy. That I may or may not admit to being guil guilt gault wron rong wong - mistaken about.

Are there any standard based rules/theory that apply?

Just for thought. A junior dragster is a single cylinder briggs and stratton style motor that can see 9000rpm (and not grenade). That's firing over 37 times a second. We set the timing "in the hole" .340thou btdc and could see a difference in about a .010 swing either side.
Click to expand...

Well there IS more to it than "twisting the DISTRIBUTOR" But there are so many variables "in builds."...........

Compression ratio, type of fuel, combustion chamber design, and cam design "to name a few." And........as mentioned above so many are playing with blowers /turbos that THIS comes into play.

"The fact" is that without close monitoring of engine dynamics, you can hurt stuff. "Back in the day" when compression ratios above 10-11 were common, it was "easy" to eat a plug and crack a piston land / top ring or worse.

This is a good read:

http://www.forabodiesonly.com/mopar/showthread.php?t=158842

The "simplified basics" are

1..Determine initial. Time for highest vacuum at idle or a tiny bit less, and determine if starter wants to kick back or engine pings "out of the chute" at heavy throttle / low RPM

2..Determine top end total, again, time for performance, power, acceleration, monitor engine functions, and look for damage. "Work up" to it

3...Tailor the dist advance curve to meet 1 and 2, then play with advance springs to get centrifugal where you want

4...Play with vacuum, which, normally, is "light throttle" med--to high RPM cruise

See? Easy. One summer, down the drain.
 
Well........the distributor spins in a circle so it gets "dizzy"!!
Not to be confused with a "quicky"!!

treblig
 
Im just starting to figure out this frickin timing stuff and I gotta put the car away...by the time next spring rolls around I will have to re-learn this damned stuff all over again...learn...forget...repeat...now Im dizzy
 
4spdragtop said:
Im just starting to figure out this frickin timing stuff and I gotta put the car away...by the time next spring rolls around I will have to re-learn this damned stuff all over again...learn...forget...repeat...now Im dizzy
Click to expand...


So you're saying that this is a "bad time" to ask this question...
 
krazykuda said:
So you're saying that this is a "bad time" to ask this question...
Click to expand...

Now is the best time to ask the question, some people are at the top of their game right now. Problem is, when you really need the answer is when everybody is dumbed down again after a long winter. LMAO

Jack
 
Regarding the op,
the amount of variance that makes a difference is generally related to your setup.

A high mileage, low compression, stock cam motor isn't nearly as picky about three degrees (for example) as your average high compression, highly modified engine.

For the lo-po (or just plain worn out) engine, the timing being off might cost a few horse power, and its doubtful you'd even feel it. For the high compression or forced induction engine, it can mean death.

If you added computer control, even the computer has variance. The engine can see the exact same data when accelerating as decellerating. Mechanical wear can affect sensor outputs (ahem, magnum engines), etc and yes, the faster it spins, the more precise it needs to be.

That said, generally, the faster it spins, the better the mechanical setup tends to be, so they march in step. As far as general rules, I've had great results with the timing and tuning articles by mopar action's Rick Ehrenberg.
 
getting the timing and curves all set right for your setup is crucial as coyote jack said all engines are different . off idle stumbles hard starting poor gas mileage among many other things are usually timing related. 2 degrees will make a noticeable difference ,
 
krazykuda said:
So you're saying that this is a "bad time" to ask this question...
Click to expand...

Coyote Jack said:
Now is the best time to ask the question, some people are at the top of their game right now. Problem is, when you really need the answer is when everybody is dumbed down again after a long winter. LMAO

Jack
Click to expand...

Lol I actually got it set pretty good Karl. I treated myself to a vac gauge this summer. Tweaking the Eddy is being tackled come spring.
Im eager as heck come spring but takes a while to shake the winter hibernation off.
Shovelling snow don't make me any smarter Lol
 

if the rube goldburg timing system on a small block can keep 1 degree, that is pretty amazing. Smog here will fail you if you are 2 degrees off factory under the gun. I dont think 2 is going to be the margin of error. You got your chain driving your timing through a cam and a 90 degree helix gear through a sloppy slot on the oil pump drive...
 
Timing is very important. In some cases critically so.
There are some basic setups that are great starting points and for most people "close enough". You ask if one degree can make a difference... A friend races NHRA Super Stock. He has a log book. Every run is entered with carb jetting and bleeds, timing, fuel type and source, weather data, engine water and oil temps at the line and stripe, tire pressure, and ballast weight and location. He will adjust any of those to make a difference racing track to track, and run to run. Weather is the first variable - then he bases the setup on the recorded history. One degee can make a difference when you are that dialed in.
But for those if us with a lot less time and enthusiasm... initial of 12-20°, centrifugal of 16-30 to yield a total of 36-42°, and all in from anywhere between 2500-3500 will work in most packages with factory heads. I run a vacuum advance in everything, some don't.
 
Too much advance will make the tops of your pistons soft as they near melting temperature, an 8-71 topped 440 taught me that !!!
 
drawson said:
Too much advance will make the tops of your pistons soft as they near melting temperature, an 8-71 topped 440 taught me that !!!
Click to expand...
Actually the blower setup, timing among them, more then likely caused you issue. More then likely running too lean.
 
Taking one conditions at a time and lets say for example the fuel curve is close. Is it safe to assume that to advanced will = internals (pistons) carry more of the heat. To retarded will = exhaust (headers) carry more?
 
You must log in or register to reply here.
-
Back
Top Bottom