Static Timing

[Anonymous]

I know, I know, I know...why am I bringing this up, again, for the uptenth time. Well I'm still alittle bit unsure about the whole issue of engine timing. Especially when one person might use different terminology than another person.

The easiest way to find TDC (without measuring devices) is to spin the crank until the #1 piston is fully extended in the cylinder wall on the intake compression stroke, right?

The distributor rotor should be pointing dead center on the #1 spark plug wire (nevermind the numbering on the cap as long as it's all plugged correctly) right?

Once I've done this, I should crank the engine until it lines up with 6* BTDC as indicated on the blocks timing tag. Noting that this will slightly rotate the rotor sightly ahead of the #1 plug location on the distributor.

Now assuming I stated all of this correctly I should then be about to advance the timing with a turn of the distributor as I tune the engine, correct (vacuum plugged, of course)?

Having said all of this, what if 6* BTDC is really not 6* BTDC as indicated on the crank markings?


-Chris

 

[Anonymous]

Chris,
A couple things. Let me start off by saying I'm a little confused as well about the timing so hopefully we'll get a little educated on your post as we go along.

First don't forget that the 4 stroke motor has 2 times the piston gets to TDC in it's rotation. To just feel the piston is at the top isn't good enough, I put my thumb over the opening and bump the motor over untill I feel the pressure then hand turn it over to 0* TDC. That gets me the cam and crank internaly as close to TDC as I can be. Know if the timing mark has slipped on the crank then we're SOL from the get go but assuming it hasn't this is a starting point.

Second you are correct, the rotor will be pointing to #1 spark plug and it doesn't matter which one is #1 as long as the order is correct. In my case the rotor is pointing almost down, away from the block. I've seen several others mention this is the way their dizzy was to.

"Once I've done this, I should crank the engine until it lines up with 6* BTDC as indicated on the blocks timing tag. Noting that this will slightly rotate the rotor sightly ahead of the #1 plug location on the distributor"

This one has me a little confused. You don't crank the motor you leave it set at more or less TDC, the motor should start and run at this enitial setting. If not rotate the dizzy a "FRACTION" counter clockwise and try again. I tighten the retainer nut so I have a snug fit on the Dizzy and that way it doesn't move while I'm experimenting.

"Now assuming I stated all of this correctly I should then be about to advance the timing with a turn of the distributor as I tune the engine, correct (vacuum plugged, of course)?"

Again I'm a little confused, "about to advance the timing" in relation to what? Yes you advance and retard the timing by rotating the Dizzy, advance is counter cockwise, but you haven't mentioned if your looking at a timing light through all this. Without one you have no idea if 6* is where your at or if it's off. Are you using a timing light?? The last part:

"what if 6* BTDC is really not 6* BTDC as indicated on the crank markings?"

You would have installed the dizzy wrong, the timing chain wrong, the cam wrong, or the chain jumped a tooth.

One tooth off on the dizzy install is enough to cause the motor to backfire through the carb or the exaust so check it again and be sure your on the TDC mark forget the 6* BTDC at this point.

NEXT, INITIAL ADVANCE, MECHANICAL ADVANCE, AND VACUMN ADVANCE... WHAT THE @#$@#$ IS THE RELATIONSHIP???

Hope I'm Helping,
Steve

 

[Anonymous]

Thanks Steve.

When I say "crank" I mean in this situation "hand turning the crankshaft". Sorry for the confusion.

I think you cleared alot of things up for me. I was pretty sure that I had too much advance when it started backfiring through the carburator but I just wasn't sure.

I checked and I am set for 6* BTDC now. I removed the fan, radiator, timing cover, etc. to examine the drive chain and sprocket teeth. Everything looked good. Chain slack was within tolerance (1/2" I believe). The two dots on the sprockets lined up at the same time as the tag on the block indicated 0* TDC. I also noticed, like you said, pressure building in #1 cylinder every other time as I approached TDC.

So, it looks like I'm finally getting there. Thanks again.

 

[CobraSix]

If you are backfirign through the carb, is the car running? Make sure you aren't 180* out on the dizzy. THis could happen if you set the TDC on the exhaust stroke instead of the compression stroke. Easiet way to tell is see if the intake valve opens.

Slade

 

[Anonymous]

No the car does not run Slade. It's just shooting fuel up through the carb when I try and crank it over. I think I accidently set the timing on the exhaust stroke instead of the compression stroke as you just stated.

Well, the valve cover is off and maybe tonight I can try it again. Both valves would be closed on the compression stroke, right? My brother is not available to help tonight so it's going to be a little difficult to do the finger compression check myself.


-Chris

 

[Anonymous]

Yes Chris, both closed, the bump and pressure has always worked for me then hand turn it till your timing is at "0" TDC. It sounds to me your a tooth off, to far advanced, your close. Hope you get it then we can move on to the timing questions and advance curves!! )

Steve