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MG MGB Technical - Timing Marks Missing

Greetings..

I am trying to install a new euro-spec dizzy on my 67 MGB. I have read the procdure for finding TDC etc. My problem is, I do not see any timing marks on the timing chain cover, either at the bottom or at the 10 O'clock position as I face the front of the engine. The crank pully has a very small notch on the inside of the V that I assume is the pully mark. It is hardly visible.

Can anyone tell me the rough location of the missing timing marks on the timing chain cover. Is it possible that the pully is not the correct one and is covering them up? Or maybe the timing chain cover is not the correct one?

Is there another way to get it close enough so I can install the dizzy.

This engine has not been run since rebuild by PPO 10 years ago :(

Any help will be appreciated...

Moe
C Eldredge

The timing marks should be on a small metal tab that is tack-welded onto the bottom of the timing cover
at the 06:00 o'clock position. Only the small tips of the timing marks should be visible. It may be
possible that the tab is bent, and the tips are hiding behind the pulley (??).

The pulley should have a thin groove across the circumference of it's outter ring.

In anycase, in order to install the dizzy without the timing marks:

1) Remove the valve cover and the #1 sparkplug.


2) Turn the engine by hand until you can see the top of the #1 piston (at it's greatest travel height)
through the sparkplug hole (use a strong flashlight for this).

...also...

...BOTH the #1 intake and #1 exhaust valves must be closed (both valves NOT depressed by
the rockers). This is very important.

This is (roughly) TDC, and is good enough for your purposes.

You may have to turn the engine over a few times to get it right. Do not turn the engine backwards if
you overpass the top travel of the #1 piston. Just turn it over again a few more times.


3) The dizzy can be now installed.

The drive tabs at the end of the dizzy will meet up only one way, so once the crank (and cam)
are positioned at TDC (as in Step 2) it's basically goof-proof after that.
Daniel Wong

Thanks Daniel, I just checked again and It feels like the timing marks may be jammed up behind the pully as you mentioned.

Does anyone know the size of the socket to fit the crank pully nut on a 67B ?

Moe
Moe

1 5/16"
Jared Snider

Thanks Jared, I'll pick up a socket and see if I can get the pulley off !!!

Moe
Moe

Moe - You may find that you have to have the socket shortened to get it to fit behind the steering rack housing. Any good machinist can do this for you.
Good luck - Dave
David DuBois

Thanks David for the heads-up. It looks like the socket will fit OK but I am not sure there is enough room to get the pully off... I'll give it a shot tomorrow after I get a socket.

Moe
C Eldredge

Moe, You'll still need to know true TDC to be sure your timing is correct. The article below is part of an article I submitted to the North Carolina MG Car Club for their newsletter. Your problem is discussed in detail. With an old spark plug and a 3/8" bolt you can make a positive stop to be used when you need to find true TDC. Done carefully it will be accurate within 1-2 degrees. If you need a photo of the stop I made I can email it or put it on my Yahoo Photos. Clifton

"To be sure the timing is correct you need to know where true TDC is located. The most accurate way to verify true TDC is to remove the cylinder head and locate TDC with a degree wheel and a piston stop or dial indicator. I used an old spark plug and a 3/8” bolt to make a positive stop that can be used to get very close if not on TDC. I removed the center part of the spark plug and cut off the outer electrode. Next I threaded the inside of the spark shell with a 3/8” tap. I added a few drops of blue Loctite on the threads and screwed the bolt into the thread end of the spark plug shell and cut the bolt off about 1 ¼” to 1 ½” from the plug threads. I rounded off the tip of the bolt so it would not damage the top of the pistons.

To find TDC remove all spark plugs and insert the tool in number one cylinder. Disconnect the battery. You will need to make a pointer, an old coat hanger will do. Fasten the pointer so it reaches over the crank pulley. Turn the engine over slowly in a clockwise direction with a wrench on the pulley nut until the piston bumps the stop. Make a thin mark on the pulley under the pointer. Slowly turn the engine anti-clockwise with the wrench until the piston bumps the stop. Make a thin mark on the pulley under the pointer. Measure the distance between the two marks. TDC is at the exact center of the distance between the two marks. Make a mark at the center. Remove the bump stop and turn the engine clockwise to line up the center mark under the pointer. If the crank pulley and timing marks are not aligned with the timing cover TDC pointer make a new TDC center mark on the pulley opposite the timing cover TDC pointer. If you were careful with marking and measuring the new mark will be within one or two degrees of the true TDC. Use the new marks for future ignition timing adjustments."


Clifton Gordon

Clifton, Thanks for that great explanation.... I was going to try and do something like that but I doubt my procedure would have been as accurate as the one you just described. I'am off to get a socket for the pully then try to see if the old marks are there somewhere. If not, I'll try your method. I may try your method anyway just to see how it agrees with the old marks (if I can find them).
Moe

Clifton's explanation covers making new marks on the pulley from those on the cover, you will have to go the other way and use the pulley mark to find where to stick new pointers on the cover.
Paul Hunt

OK Gents, I found TDC (within a degree or two, I think) The crank pully notch was down at about 6 O'clock where the missing timing marks should be but aren't. I then marked the Crank pully and the timing chain cover with two marks lining up with each other at about 10 O'clock position on the pully. The engine still sitting at TDC for #1. with both valves closed. These marks are my new reference points.

Next I installed my new 45D euro tech distributor. I installed it with the vac advance to the left/top since it will not fit into the engine with it down because the starter and oil filter are in the way. This a 67B with a 68 starter due to tranny swap. Don't know if this is the correct orientation for the distributor or not ???

Now, looking at the rotor, with the cap off, the rotor points to roughly the 4 O'clock position. I've been reading the archives and it sounds like it should point to the 2 O'clock position. Does it matter as long as the correct plug wire/distributor post goes to the #1 cylendar?

I realize the timing is not set correctly buy I assume I should be able to get the engine started by rotating the distributor a little one way or the other, then refining it after it is running...

Any help will be appreciated

Am I in the ballpark???
C Eldredge

As long as you are resonably close the engine should start as long as it's not too retarded(ignition timing that is). After fitting my dizzy with electronic ignition I fitted it back in in roughly the same position as was required with the points. Evidently the module tells the coil to fire at a different degree relative to the distributor shaft. When I fired it up it wanted to idle at abot 3000 rpm. I checked the timing and it was about 60 degrees BTDC. After I backed it down it idled fine.

The proper thing to do would be do a static timing, just to make sure it's right before you fire it. I don't remeber the steps but it's in the workshop manuals or in the archives. If you're too far off you could end up with a nasty backfire through the carbs and nobody really needs that.

-Jared
Jared Snider

Doesn't matter which way up the vacuum capsule points, do it for best fit, it should be up anyway, all those in Clausager are. The rotor *should* be pointing at about 1 or 2 o'clock with No.1 at TDC on its firing stroke (remember it is also at TDC on its exhaust stroke i.e. 180 degrees out), if it isn't either the drive gear has been put back incorrectly - it can go back in one of 6 or 8 positions - but if it is 180 degrees out (not here by the sound of it) the distributor could also have been assembled incorrectly. Again it doesn't reeeeally matter, as long as your leads reach and you stick to 1342 anti-clockwise for the firing order. It is more comforting to static time it to about 8 degrees first, then you know it should start and it won't be massively out.
Paul Hunt

It looks like my last post is missing here.

Anyway, I just tried to rotate the distributor shaft to another o'clock position and it will not engage the gear inside the engine except in the 4 O'clock position. I also tried my old 25D distributor with the same indication. Must be inside engine gear is in wrong. Darn that previous previous owner (PPO) !!!

Bottom Line: Engine at TDC on compression stroke, distributor shaft engaged in only way it will fit, rotor points to roughly 4 O'clock as you face the distributor.

I will hook up plug wires with 1 being the 4 O'clock wire and use 1342 as firing order, remembering CCW (anti-clockwise) rotation.

I will try static timing if I can figure it out :-(

It won't blow up will it ???
C Eldredge

The distributor will only engage in one position, the key and slot are very slightly offset. If the position of the drive gear bugs you it can be altered quite easily, see http://www.team.net/www/mg/tech/twist/jt-tech2.html

Static timing is just a matter of connecting a test-lamp or voltmeter (their other side connected to ground) to the points wire on the coil with the ignition on. Turn the engine till the timing mark is at 8 degrees BTDC (doesn't matter which piston is on its firing stroke), then twist the distributor back and fore and watch the light or meter. With the light on or the meter showing 12v the points are open and you are too advanced. Turn the distributor anti-clockwise to retard it until the light goes off/meter shows zero, then slowly advance it again until it just comes on. That should be close enough to get it started ready for dynamic timing, but if you are really pernickety you can lightly clamp the distributor in that position then turn the engine back and fore checking the light comes on/meter shows 12v at 8 degrees BTDC, making small adjustments to the distributor as required. Make sure the distributor is fully seated into the clamp plate before final tightening, and don't overtighten. With a clamp that size and all that surface area it doesn't need to be all that tight to stop the distributor moving, and overtightening will damage the shoulder on the distributor body and destroy it.

The above won't make it blow up, but I can't speak for anything that might be wrong with the engine or how you apply the above.
Paul Hunt

Paul,
Thanks for explaining the static time procedure. The problem I still have is no timing marks and no way to determine the 8 degrees. I made my own marks as mentioned earlier for TDC. Unless I am totally out to lunch, I think I will have to hook up some sort of degree wheel to the pully or just eyeball it to start with to determine 8 degrees BTDC. Haven't figured that part out yet...
C Eldredge

C,
Another alternative for finding x degrees of advance is to invest $70 or so in a timing analyser. It's like a timing light, but it has a knob on it that varies when the light flashes relative to the ignition pulse. The technique is to turn the knob until the mark on the crank lines up with your TDC mark, then read the degrees of advance off the scale on the analyser. Very handy!

Here's one:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=40963
(only $30, not sure about the quality)

HTH!
Rob
Rob Edwards

Paul, I just read a couple of your artles on your web site. Thanks for pointing it out to me. Lots of good info there. I will try to change the orientation of the dizzy drive gear based on the info just read.

Awsome site, good info, I'll be back soon to read more....
C Eldredge

Rob, Thanks for that info. I'll check it out.
Moe (alias C)

FYI: Robert Bentley's book: "The Complete MGB" - features a clear illustration how the distributor
drive dog should be positioned in the engine block.

My additional 2¢.
Daniel Wong

This thread was discussed between 19/07/2003 and 23/07/2003

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