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MG MGB Technical - how to instal distributor

can someone give me a step by step instal on putting in a distributor on my 79 mgb. include how to wire the cap. thanks Doug
dd doug46chief

Look, someone more experienced than myself should really be instructing you, but here goes! When I last took the distrbutor out, I made sure ( took the plugs out.) that I could easily turn the engine over by hand. If there is room a big wrench on the crankshaft bolt. Turn it in the direction the engine would normally rotate, (but might not matter?) get number 1 cylinder to its firing point, ie the cylinder next to the radiator. Do this with the valve cover off, so that you can see the valves moving. Both valves will be closed at No. 1. Now, check the manual for firing order, and if you like, check all the other cylinders in the fully closed position ,ie check your firing order. Now back to No 1, at fully closed. Slacken the pinch bolt at base of distributor,Take the cap off and check that the rotor is pointing at No 1 cylinder, or put it another way will the rotor position fire off the cable or wire leading to N0 1 cylinder, if ok then gently lift Dizzy out. See in what relation the drive dog (for want of better words) is at. When replacing, this needs to be in same position.So now if putting new wires, put them in the order of firing from this point on. then replace the distributor, and re-time with a strobe. Am I close to being right chaps? Mike
J.M. Doust

thanks mike. I did do all that but its firing irratic. Does the distrib fit in the dog 2 different positions or just goes in in one position? What im thinking is i may have it in the oposit position and its firing wrong. Another words the rotation has 2 rotations one for power and one for compression. if the dist is put in at the wrong position in the dog drive then maybe its times to the exhaust stroke. I dont know but i did try to fit it in the other pos but it wont seat.Doug
dd doug46chief

The drive dog is offset, so *should* only fit in one position.
Dave O'Neill2

Doug, Dave is spot on.

Unless you have removed the drive flange from the block and refitted it 180 degrees out, or removed the drive dog from the distributor shaft and refitted it 180 degrees out then by setting the distributor in the correct position and connecting the leads to the correct plugs you should be pretty close to having the timing right.

When the distributor is fitted it should be turned until the vacuum advance mechanism points roughly at #4 spark plug. This picture give a pretty good idea of how the distributor is set up.

http://www.flickr.com/photos/91972735@N00/3270146873/

Cheers
Tony
Tony Oliver

didnt remove from block but can u engage dist 180 in either position or does it fit only one way in dogsl?
dd doug46chief

The distributor will only fit into the block one way. While the cap is off, mark where the rotor is pointing, on the side of the distributor, when the timing marks indicate that the engine is at top dead center and both valves, on #1 cylinder, are in the closed position. Now, install the cap and insert the #1 ignition wire into the cap, in line with the mark you made on the distributor's side. Going counter clockwise, install the rest of the ignition wires. The firing order is 1 3 4 2. RAY
rjm RAY

Ray thanks and thanks to all for the help. I didn't realize the counter rotation of the dist. I had the wires reversed. Now I can time light it tomorrow. thanks again DOUG
dd doug46chief

The distributor will only fit *fully* into position in one orientation, but the offset is so small it can be partially fitted 180 degrees out and the engine will run until it jumps out of engagement. The distributor can also be dismantled and reassembled 180 degrees out, and the drive gear can be inserted in as many different orientations as there are teeth.

The timing mark on the crank pulley is at TDC for both cylinder 1 and cylinder 4, which is why you have to determine when cylinder 1 is at the top of its compression/expansion stroke before looking at where the rotor is pointing. As the plugs would normally be out to allow turning of the engine, rather than disturbing the rocker cover and gasket if it doesn't have to be, I put a thumb over No.1 plug hole while turning the engine and compression will lift it off, so the top of that stroke is the one you want.
PaulH Solihull

This thread was discussed between 09/02/2012 and 11/02/2012

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