Rotor positioning for valve adjustment...

[RyanH]

Hi. I am not familiar with this rotor and I am about to have a go at the valve adjustment backside method on my 1970 911T Targa. Which bit should be pointing at the mark? The photo is with the pulley at TDC but nothing significant is pointing towards the mark. The mark on the housing is under the top little notch on the plastic in the photo. Anybody? Thanks......

[pete3799]

Turn the motor 180* (back to TDC) and the rotor will be lined up with the notch.

[boyt911sc]

Ryan,

Remove the rotor and the black plastic shield off from the distributor. And install the rotor back without the plastic shield/cover. Set the crankshaft pulley @ Z1 (TDC). If the rotor is pointing directly towards the notch mark on the distributor body the engine is at compression state and ready for your valve adjustment. However, if the rotor is pointing the other way, your are at exhaust state and need to rotate more for the next cycle.

Take pictures and post.

Tony

[Bob Kontak]

Believe OP is asking what part of the rotor lines up with the #1 cylinder/TDC mark on distributor.

[ivangene]

the rotor is the "rough alignment" - crank pulley marks are your alignment marks - the rotor merely indicates if you are on the exhaust stroke or the compression stroke (valves closed)

if the rotor is pointing in general area of #1 spark plug wire on the cap - you are on the right spot - which on my car (later) is closer to 1:00 and in your pic you look closer to 11:00 - but my car is not the same as yours - the method is the same though

[ivangene]

on mine looks like this:
there might be a notch in the dist housing as shown

you might be there - remove the dust cover and the mark is under it I bet

[hcoles]

I always double check by looking at the position of the cam lobe, things are open and you are there anyway. If the lobes are pointing approximately 180 away from where the rocker pad contacts the cam, you are good for the adjustment.

[Driver_X]

The part with the white arrow should be pointed at the red arrow. I think you are set @ #4 cylinder not TDC.

[Bob Kontak]

Originally Posted by pete3799

Turn the motor 180* (back to TDC) and the rotor will be lined up with the notch.

+1

Ahhhh - I read the OP's post more closely. Yep.

[ivangene]

180 on dist = 360 on pulley?

[boyt911sc]

Originally Posted by ivangene

180 on dist = 360 on pulley?

Ed,

Yes. The distributor shaft rotates 1 revolution per 2 turns (revolution) of the crankshaft pulley.

Tony

[scarceller]

I have this home made TDC tool in my tool box. It helps find TDC on ANY cylinder.
Porsche, the mother of invention

[frosty2]

Hi guys not trying to steal a thread but looking at the picture posted by ivangene
when I turn my distributor to TDC the center of my rotor is about the same
distance right of the notch as this picture shows to the left.
Car runs fine but would this mean I am in the wrong tooth?

Thanks
Mike

[hcoles]

you might be able to look at the rotor and cap and see where the system is firing, is it on one end or the other or in the center?

[BK911]

Originally Posted by pete3799

Turn the motor 180* (back to TDC) and the rotor will be lined up with the notch.

Or just start the valve adjustment on cyl #4.

[KTL]

The rotor is just a reference. You don't have to be dead on TDC mark for each & every cylinder when adjusting the valve clearance. You just have to ensure that the rocker arm is fully relieved of the cam lobe (valve closed). If you watch the rocker arms as you're turning the engine (easy for me to say, since I often adjust valves on the engine stand) you'll see the rocker/valve stays motionless for quite a while as you approach, get to, and depart TDC.

I do understand that just because the rocker is not being loaded, it doesn't mean being way off TDC is OK when adjusting the valve. Because the rocker could be just ready to move at a point far away from TDC and that could impact your valve adjustment setting. So it is important to be nearby TDC but not dead nuts on it. Key is to look at the cam and make sure the rocker in question is near the base of the cam lobe.

Not sure why people choose to do the backside method. The elephant foot adjuster is where the critical clearance is needed. The rocker's cam pad doesn't care what the clearance is at the cam (I do understand that clearance at the cam and clearance at the valve are directly related). The cam follower pad could ride on the cam all the time and it wouldn't matter to the cam or the pad. It's the valve closure that's most important, to allow for thermal expansion and cooling of the valve (by closing on the valve seat & transferring heat to the head) & I prefer to measure that clearance directly. To each his own I guess.

[ivangene]

Originally Posted by KTL

Not sure why people choose to do the backside method. The elephant foot adjuster is where the critical clearance is needed.

To each his own I guess.

+1

I prefer the foot - it gives a very confident feel - but there are many who like the backside method - I watched someone do it and thought - why would you do that...the foot is right there???

but as you say

as for the comment about the rotor position right/left
what year car? - if electronicaly controlled they can be off way farther then mechanicaly controlled spark

[frosty2]

Ed the car is a 1973T with a 2.4 and Zenith carbs

Thanks
Mike

[frosty2]

Sorry Ed it also has the standard points in the distributor

[RyanH]

Thanks to all who commented on my valve adjustment project. I completed my first valve adjustment, as well as oil change, oil filter, new plugs, air filter and fuel filter, also adjusted the carbs. Started up and sounds great, just waiting for the horrendous downpour we're having here at the moment to leave before I can go for a run. Brakes next!! If I ever do another valve adjustment I'll give the original way a go to compare, I found this a bit awkward but it was my first attempt. Thanks again, the PP forum is a great source of information......

Originally Posted by RyanH

Hi. I am not familiar with this rotor and I am about to have a go at the valve adjustment backside method on my 1970 911T Targa. Which bit should be pointing at the mark? The photo is with the pulley at TDC but nothing significant is pointing towards the mark. The mark on the housing is under the top little notch on the plastic in the photo. Anybody? Thanks......