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MG MGA - Timing

I put an MGB font cover on my mga engine with an mga crank-pully, can anybody tell me witch mark (on the top of the cover)i have to bring over on my pully, so that i can later on check the timming.

serge

http://users.pandora.be/mga_world/
serge

Steve Gyles has one of these covers, and so do I (thanks to him). Unfortunately I have a non-standard pulley (special one with a total of three belts but still using the orignal dog nut)for the Judson. I just set the engine to TDC, and marked the pulley against the middle tooth on the timing marks. (I have an adjustable timing light so I don't need any more than a reference point.)

If you are using the original pully, you will have to use a different spark plug lead for your timing light, as otherwise the mark will always be underneath when the strobe fires.

dominic clancy

Serge

On mine, the right hand mark is TDC , when viewed from the front of the engine. The graduations are at 5 degree intervals.

Steve
Steve Gyles

"If you are using the original pully, you will have to use a different spark plug lead for your timing light, as otherwise the mark will always be underneath when the strobe fires. "

That's why i want to put an new mark on my pully,witch is inline with the mgb cover , or is there something im missing here


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serge

I suspct that the marks are 180 degrees out, so using the timing light on plug 4 will bring things into view.
dominic clancy

Serge

I am currently using an 18V engine. It's 6 years since I ran the MGB cover on my 1500 engine. I have just gone out into the garage to look at the 1500 in the corner. I cut a second notch so that I could continue timing on No.1. I presume I did the task methodically, setting the No.1 TDC and cutting the notch in line with the marker.

Steve
Steve Gyles

hi steve

thats what i want to do but do i put the nr1 TDC but witch marker should i use now, i believe there are 3 or 4, i don't have any info on the 1800 engine

serge
serge

Serge

If you are cutting a new notch you can use which ever timing mark suits you with the No.1 piston TDC. However, it would seem sensible to use the right hand one when viewed from the front.

Steve
Steve Gyles

Serge

If you connect your timing light to the lead for cylinder 4, (180 degrees out on the firing order to match the 180 degree change in the cover) the strobe will highlight your original mark on th epulley and you will be able to see which mark on the cover it aligns to. If you have an adjustable timing light, by setting the light to your timing, the timing mark on the pulley should line up with the TDC tooth on the cover.

It's all relative, so it doesn't need to be on No1 cylinder, as long as the marks are all consistent.
dominic clancy

I don't think it is 180 degrees off. As I recall the MGB indicators are around the 9:00/10:00 o'clock position.
John DeWolf

Serge. The 18V cover has five pointers and is located on the left side of the timing chain cover when viewed from the front. The highest, i.e. left hand, pointer is top dead center (TDC) and the four other pointers reflect five degrees of advance before top dead center (BTDC). The engine rotates in a clockwise direction when viewed from the front of the engine. The original MGA, and early MGB timing chain covers had their marks on the bottom of the cover, but in the same order--the left hand pointer is TDC and the pointers to the right represent advance BTDC. Cylinders one and four are moving 180 degrees out of phase with each other and the crankshaft makes two revolutions per firing stroke.

From this common perception, we can make a couple of inferences. One is that either cylinder one or four can be used for timing since they will have the crankshaft pulley in exactly the same place when the plug for that cylinder is being fired. Hence, using the non-traditional number four plug, rather than the traditional number one plug will have no effect on the timing or what you are seeing.

Second, the combination of the 18V timing chain cover and the MGA, or early MGB, crankshaft pulley, will put the timing mark on the pulley and the timing pointers on the new timing chain cover out of phase with each other.

There are two methods of setting the system up correctly. The easiest is to align the timing mark on the crankshaft pulley with the TDC mark on the original timing chain cover, pull the pulley without moving the crankshaft, remove the old timing chain cover, install the new timing chain cover, re-install the crankshaft pulley, and make a new timing mark on the pulley that corresponds to the TDC mark on the 18V timing chain cover.

If the system has been already assembled, the calibration procedure is more complex. You must establish the true TDC position of number 1/4 cylinders, then mark the crankshaft pulley next to the TDC mark on the timing chain cover.

If the cylinder head is off the engine, a dial indicator (clock gauge) is used to determine the actual TDC position. The gauge is dialed in so that it reads zero when the piston is at the top of its travel. Then, the engine is rotated until the piston goes downwards, then comes upwards again. When the dial indicator is reading .001" BEFORE THE ZERO MARK (or something close metric), a temporary mark is made on the crankshaft pulley. The piston is then rotated through the zero reading and continues until the reading is again .001" before the zero mark, a second temporary mark is made on the crankshaft pulley. The actual TDC of the crankshaft is mid way between the two temporary marks and a permanent mark is made at that point and will be used for ignition timing purposes.

If the engine is assembled, some form of piston stop is inserted into the spark plug hole to physically stop the upwards movement of the piston. The engine is, very gently, turned over until the stop hits the piston and a temporary mark made on the crankshaft pulley opposite the TDC pointer. The engine is then gently rotated in the opposite direction until the piston is again stopped and a second temporary mark made on the crankshaft pulley opposite the TDC pointer. The actual TDC is mid-way between the two temporary marks and a permanent mark is made at that point and used for ignition timing purposes.

Les
Les Bengtson

This thread was discussed between 17/05/2007 and 19/05/2007

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