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MG MGB Technical - timing chain

I put my chain and gears back on as the book says. Lined the dimples on the timing gears up and put the chain on the gears. Put the keyway on the crank TDC, Cam at 1-o-clock then slide the gears on. My question is this, by keeping the dimples in line, you cant put the gears back on any way but right and still keep the dimples in line, correct? I just want to double check my work. My number one piston was at TDC, then I rotated the camshaft until the keyway lined up, which again was basically 1-0-clock. Does this sound correct? I have assisted in one other engine build, this is my first solo.
Bryan

If the dimples line up you are good to go.
John H

The Workshop Manual is misleading, Haynes is actually incorrect. Both say to fit the chain and gears the dimples must be in-line and adjacent. But that puts No.4 piston at the top of its compression stroke, not No.1. That's fine as far as crank to cam alignment goes, but there is a problem when inserting the distributor drive gear. Haynes says to have the crankshaft in the same position to insert the gear, but that puts it 180 degrees out. The Workshop Manual still says to have the dimples in line, but this time misses out the crucial word 'adjacent', i.e. the crank has to be turned one revolution to put the cam dimple on the far side. If you have already put the front cover on you will need to make sure it is No.1 that it at TDC on its compression stroke before inserting the distributor drive gear, but that needs the push-rods and rocker gear to be installed.
Paul Hunt 2

Earlier Haynes versions of A-series manuals - Minor, Mini, midget, etc - were also incorrect, although this was corrected in later editions.

The first time I rebuilt a Mini engine, I had to swap the plug leads around to get it to run.
Dave O'Neill 2

Paul is correct (...isn't he always?).

In order to install the dist drive gear you first line up
the timing gear dimples directly adjacent to each
other, while the crank is at TDC.

Then you turn the crank one revolution.

The timing gear dimples will no longer be adjacent
to each other - but they will be "in-line".

In other words...the dimple on the camshaft timing
gear will be at 01:00 - but if you place a steel rule
across it - it will be in-line with the dimple on the
crankshaft timing gear (which will also will be at
01:00)

That's when to install the dist gear drive.
Daniel Wong

My number one piston was at TDC, so then I started to put the gears on and basically just turned the camshaft until the key lined up. It sounds like I have it right. The books are very confusing. I read my Haynes and Bentley and still questioned myself.
Bryan

Or you can just leave the dots adjacent to each other and install the dizzy drive with the larger lobe downwards instead of upwards!
Chris at Octarine Services

When I rebuilt my 18G engine three years ago, I managed to get the distributor drive 180 degrees out. It was very late in the evening, so I just swapped the plug leads around as Dave says. Works perfect, so I have never bothered to change it. It doesn´t really matter, does it?

Tore
Tore

Daneil, what you said makes perfect sense now. I read both my manuals several times and deciphered the wording. When putting the drive gear for the dizzy in my dimples were not adjacent but they were in line as you said..also, my timing mark when I held the timing chain cover up and the harmonic balancer, it pointed to the first mark, AND...i beieve the Bentley manual said number 4 cylinder valves should be rocking, (exhaust just closed and intake just opened)...all of these were happening....thanks for all the pointers, I feel it is correct.
Bryan

To follow up on my earlier thread, the timing gears must first be positioned with the timing dimples adjacent to each other at TDC
- then the crank is turned so that the dimples are aligned at approx 01:00 - (take a long straightedge, and line up the dimples with both the turn center of the crank and the turn center of the
camshaft - all four of these points must line up).

To help verify if you have this correct - the # 7 and # 8 valves should be "rocking" - that is, both of the rockers on the #7 and #8 valves should be mid-way down, between open and closed.

That's the position when to install the distributor drive gear.

Failure to do this accounts why many owners live with their
distributors mis-positioned by 180º.
Daniel Wong

This thread was discussed between 30/01/2008 and 02/02/2008

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