TDC - once more with feeling..... Options

[Tdskip]

If your flywheel marks are missing / impossible to see then;

#1 both valves closed with rockers slack?
Pull # sparkplug and make sure piston at top of travel
Distributor rotor pointing at notch
Vacuum assembly on distributor over the hold down nut

Not my car, but like this, yes?

Look like the right check list?

Thanks!

[Superhawk996]

Last thing in the world I'd rely on is the distributor postion. Too many variables affect it.

The time proven method is pull spark plug, measure piston travel, and note when it is dwelling at the top of travel & then verify the intake and exhaust valve positions are both closed.

There are a number of handy TDC tools availabe too ranging from whistles, to machined piston stops that can thread into the spak plug hole, to dial indicators, or just a good old piece of soft aluminum or copper wire.

Once you know you're on TDC of compression stroke, the distributor variances can be chased down. They can go as far as having the camshaft mis-timed to the crankshaft. Can extend up to the intermediate shaft to the crank gear being mis positioned. And finally, the distributor to the intermediate shaft. Heck, I've even seen a rotor misinstalled and not seated properly on a friends Bug and he couldn't figure out why it didn't run.

[Gint]

Last thing in the world I'd rely on is the distributor postion.

The time proven method is pull spark plug, measure piston travel, and note when it is dwelling at the top of travel & then verify the intake and exhaust valve positions are both closed.

There are a number of TDC tools availabe too ranging from whistles, to machined piston stops that can thread into the spak plug hole, to dial indicators, or just a good old piece of soft aluminum or copper wire.

(IMG:style_emoticons/default/agree.gif) A 914 4 will run will run with the distributor 180 degrees out. If you know your distributor is not 180 out, no problem using the rotor position as a guide. BTDT

And again, don't use chopsticks down #1 spark plug hole.

Chopstick method Sammy had a great idea in post #64

[Superhawk996]

And again, don't use chopsticks down #1 spark plug hole.

Chopstick method

(IMG:style_emoticons/default/av-943.gif)

That is a hilarious old thread full of peril and bad advice!

[Gint]

I know, right?

[Tdskip]

Will not use chopsticks! How about a metal barbecue skewer? That would be better, right?
(Kidding).

The car is going to be dynamically time anyway so why wouldn’t the position of the distributor and rotor be useful as a sanity check?

Thanks for the responses.

[Gint]

The car is going to be dynamically time anyway so why wouldn’t the position of the distributor and rotor be useful as a sanity check?

A 914 4 will run will run with the distributor 180 degrees out. If you know your distributor is not 180 out, no problem using the rotor position as a guide. BTDT

If in that position, when #1 is at TDC, the rotor points to #3 spark plug tower on the distributor cap. Car still runs fine if the spark plug wires are in the correct firing order relative to that position. A better way to explain it would be to say the rotor, instead of pointing at around 11:00, would be pointing around 5:00. I had a different carbed 914 10 years or more ago that was like this. Ran great. I never changed it. And expecting the rotor to be at an exact clock position is kind of a crap shoot anyway, because timing advance or retard will change the position of the dizzy.

[IronHillRestorations]

This is where a cheap USB endoscope is handy, you can put it in the spark plug hole to confirm piston location. When in doubt, and no scope, I'd probably pull the left side upper tin and sparkplug to confirm the piston was at the top of it's stroke.

Like Superhawk said, rotor location is relative, as you can change it by moving the distributor drive. I ran into this recently, on a bus block engine in my shop. Unknown build with an upgrade to a 1.8 distributor. The way the distributor was indexed, I couldn't get the timing set properly, so I had to pull it, move the drive a tooth, and go on. Not "anatomically correct" but no choice.

[Gint]

I have to get a newer one. The old one I have is crap. Additionally, even with an endoscope, you still have to verify if #1 is at the top of the compression or the exhaust stroke. I like to check that both valves are closed. If you absolutely must know, then it's worth the effort.

I'll also point out, that once you've been through this entire process on your own car, you will then have a baseline. You will know if your dizzy is positioned properly, you'll verify your TDC mark on the fan, or made one if it wasn't there, etc... Afterward it's much more straight forward.

[Tdskip]

Excellent, as usual, discussion gentlemen.

I'm installing a brand new Pertronix distributor so hopefully the drive is properly installed.

[Tdskip]

This is where a cheap USB endoscope is handy, you can put it in the spark plug hole to confirm piston location. When in doubt, and no scope, I'd probably pull the left side upper tin and sparkplug to confirm the piston was at the top of it's stroke.

Well that seems obvious now that you said it!

[Gint]

Excellent, as usual, discussion gentlemen.

I'm installing a brand new Pertronix distributor so hopefully the drive is properly installed.

make sure #1 is at TDC first and you should be golden. (IMG:style_emoticons/default/beer.gif)

[Superhawk996]

Excellent, as usual, discussion gentlemen.

I'm installing a brand new Pertronix distributor so hopefully the drive is properly installed.

make sure #1 is at TDC first and you should be golden. (IMG:style_emoticons/default/beer.gif)

(IMG:style_emoticons/default/agree.gif)

No hopefully. Check and validate TDC, then intermediate driveshaft position if you question it's position. It's not guesswork. (IMG:style_emoticons/default/biggrin.gif)

[rgalla9146]

Not sure I'd trust a grey rotor that has the back broken (why ?) ...... that also doesn't seem to confirm much.
Just sayin'

[Tdskip]

Not sure I'd trust a grey rotor that has the back broken (why ?) ...... that also doesn't seem to confirm much.
Just sayin'

Hi, not my car as I indicated above, but good eyes. Thanks.

Found this here from a prior post, useful to help visualize.

[Tdskip]

Vroom, vroom another one making noise now....

Thanks for the thoughts on the thread gentlemen.

[ndfrigi]

Vroom, vroom another one making noise now....

Thanks for the thoughts on the thread gentlemen.

Congrats Tom!

[Tdskip]

It's really a 914world community accomplishment. Thank you.