Red Hot 71

Has anyone ever heard of General Motors allowing the placement of spark plug wires to rotate one tower on the distributor clockwise to facilitate the tach cable? I am confused as to what to think. When I look @ typical small blocks mine was way out of position. I have not pulled the whole unit yet. And is the MSD pointless distributor w/the box & separate coil considered HEI or just a standard point-style set-up w/o the points? Also, would appreciate opinions on #466624 small block heads. Thanks in advance!

Jims427400

You can rotate distributor clockwise one wire position, then shift your wires one hole and should be fine. 68 had a service bulletin explaining similar problem with ignition shielding hitting vacuum advance.

Alan 71

Hi RH,
As Jim explained…
The original sb distributor was turned for 2 1/2 reasons.
First, it allows the vacuum advance can to be positioned just to the rear of the right side support for the distributor shielding.
Second, it allows the tachometer cable to be connected to the distributor without any stress on the cable.
1/2, it makes setting the dwell easier too.
Regards,
Alan

Jims427400

Great pics Alan..

lars

You can e-mail me for my "How to Install Your Distributor" tech paper. The paper has a copy of the Service Bulletin along with photos and techniques for installing the distributor.

Lars
V8FastCars@msn.com

Red Hot 71

So if I understand correctly, I loosen the distributor hold-down bolt & twist the top of the cap one tower position out of place. Not the whole distributor, right? Then just re-arrange the wires one tower off, but in the same firing order? I think that was how it was originally, because my tach does not work now that I have put it where it normally is. Does that mean I might have ruined the tach cable or is doing what is suggested going to fix that? The reason I moved it was because it would not start in the suggested position. I'm confused!

Alan 71

Hi RH,
No, it's just the opposite.
You loosen the distributor hold down bolt and turn the whole distributor, and then move the position of each spark plug wire back one position in the cap.
Regards,
Alan

From the Assembly Manual.
Note the position of the "forward"arrow, the vacuum can, the little 'door' for the dwell adjustment access and the numbers for the spark plug wires.

SB64

Great question since the same thing is happening to me. The vac line hits just like Alans picture. So you loosen the hold down bolt turn the Dist. past the bracket it hits and then move the wires back one, I think I got it..
RVZIO

Red Hot 71

So @ TDC on my compression stroke the rotor will be @ tower #2 instead of #1? And second question. Does it matter where the dwell adjustment window is on the cap. When I bought mine it was in about the 2 o'clock position instead of 7:00? I do not have anything to adjust since this is a pointless MSD distributor. Just asking? Thanks for you guys being so patient w/me, it has been over 40 years since I played w/these big boy toys!

SB64

I think what Alan is trying to tell us is you don't pull the dist out just turn it so it passes the bracket then move the wires back one. Dist. should still be set to TDC from original install. Hopefully he will answer you.
RVZIO

Jims427400

Exactly
And doesn't change the timing at all.
Distributor could be at any rotation as long as the wires are in correct position.
I took a pc of tape and marked the center position of one of the wires, then rotated dist. one hole to the mark on my tape. Then moved the wires back (counter clockwise) one hole.
Hope this helps..

SB64

I was thinking of putting a piece of tape on the current #1 post. Move the dist. past the bracket, then move the wires back one from the tape making the post before #1 the new #1.

Rescue Rogers

if you have an old cap, cut the center out of it an install it on your distributor, then turn the ignition enough that the rotor lands on a tower. Then when you rotate the cap you can land exactly on the next tower and still be relativley close to your timing. If you just twist it and hope your close, it could turn into a pain in the @$$. This cap can also be used in valve adjustments by firing order. I use Lars' paper on that

DUB

Keep in mind because it had not been stated THAT the MSD distributor is NOT made THE exact same as a factory points distributor.

You can not use the drawing in the assembly manual as a governing standard when installing a MSD distributor. Here is the 'problem'. MSD changed the location of the threaded socket for your tach cable to connect to IN RELATION to the vacuum advance pod. This by itself CHANGES EVERYTHING.

Keep in mind that you MIGHT have to take the distributor back out and remove the roll pin that holds the gear on the bottom of the main drive distributor shaft and spin the gear on the shaft 180 degrees and re-install the roll pin. DO NOT take the gear off...just rotate it on the shaft when doing this.

NOW..I do agree with turning the distributor and moving the spark plug wires....BUT....IF that does not work and allow the ignition shield to be installed. The you either have to completely forget all about what GM wants you to do and pull the distributor and move it ONE tooth and check it again.

I have had to deal with this issue COUNTLESS times...and YES..I have tried many methods that I HOPED would keep me from having to remove the distributor. but...seeing how I have done this numerous times...there is a point when I know that I WILL have to remove the distributor and rotate the gear BECAUSE that changes HOW the distributor goes in by a HALF a TOOTH...which...oddly enough ...is all that it takes to get it right in some scenarios.

My main concern is that the vacuum advance pod on a MSD distributor will be FORWARD of the metal stand that holds the ignition shield box on the right side. I do not care about the 'window' in the cap....and when you have the vacuum advance pod in a good position...you will see that your tach drive cable will be able to be installed and NOT allowing the cable to kink. REPEAT...do not follow factory photos here...or you will pull your hair out...Unless that is what you want to do.

Lastly...when I am done and I have my timing set to where I want it and all is good in regards to engine performance. I have ALSO sometimes realized that I have to go back into it one more time in order to re-set the distributor one more time by moving it a tooth so when the timing is set back to where I NOW knows it needs to be for the best performance. I am making the distributor positioning look a bit better. I like it so the vacuum advance pod is not close to the intake and also close to the stand for your shielding. I like it in the middle or there about....but that is just me being picky about 'visual aspects' that make me feel it is more pleasing to the 'eye' and also has adjustment if needed. However slight it may be.

Then if that is not enough to deal with...you might also have to worry about how the distributor cap twist fasteners that hold the cap down are now possibly able to make contact with the ignition coil mounting bracket.

DUB

Red Hot 71

Man, that was a lot to take in! I did not remove the distributor before all of this happened. All I did was change the plugs & wires & made the mistake of just pulling all the wires off instead of one for one. I thought a small block was a small block when it came to location & firing order. Boy was I wrong. Would anybody suggest that I pull the timing chain cover & check notch alignments after I am @ TDC on my compression stroke. There has to be an easy explanation to all this? I already have the fan assembly off the motor. All I have left to do is remove the harmonic balancer & remove the cover. Does it sound like I could have jumped time? I really do not know what to do next after hearing all this.

Big2Bird

Not to start a fight here on this, but that is not a good thing to do. Your placing the rotor out of phase. It would be fine with an adjustable rotor, but not a very good thing for a novice.
If requested, I would install an adjustable rotor and check the phasing on my Sun Machine if a half tooth correction was desired.
Yes, MSD sells adjustable rotors.

Rescue Rogers

just move the wires one tower, its not a big deal. the distributor doesn't know what is going on on the cap, it just spins a rotor. remember the dots line up twice for one revolution of the distributor. if you remember where number 1 was roughly, pull the cap, see where the rotor was. then line up the timing dots if the rotor is 180 away, just crank the motor over 1 revolution and align again when its pointing towards the front. once you know the rotor is pointing at #1 turn the distributor until it is where you want and that will be the #1 tower

DUB

Here is my point because I KNOW PHOTOS are needed in this scenario. When you see the differences between factory distributor and an MSD...you will hopefully understand ...and THEN...if doing the 'trick' of spinning the cap or spinning the distributor gear or whatever can come into play.


NOTICE how the vacuum advance pods are basically clocked the same ..BUT the tach drive fittings are NOT. Notice how MSD put the tach drive gear area on the OTHER side of the main shaft of the distributor.


Another view from looking down a little bit.


Side view with vacuum advance pods lined up and if you look you can see the tach cable fittings are not the same


Photo of the MSD all by itself to compare if you have one handy.


Maybe this photo makes it clearer of what I had previously mentioned.


DUB

DUB

THANKS!!!!!
Sometimes I need a kick in the head and get 'reset' so my thoughts and fingers link up when I type.

I am NOT going to argue you on this. No argument here. I am not a novice a BUT back in the day I was one. Sometimes I forget to state the REALLY important stuff. MAN....I REALLY dropped the ball on that one. Thanks for commenting on how erroneous my comment was for a novice.

That being said....I will suggest that a person should not do as I had mentioned about spinning the distributor gear due to I failed in my responsibility to completely give CRITICAL information that I knew about...but simply forgot to mention. You can...but as stated...it is a little bit more involved.

But I still stand firm on what I wrote about how different the two designs of distributors are and following the GM assembly manual can get you into trouble...if you are trying to position the MSD like the 'book' shows.

DUB

Big2Bird

Dub,
It's getting really hard to remember all I have learned. Don't feel alone.