If you cannot take off the head try this method
Destroy a champion spark plug by smashing the ceramic post. Remove the
ceramic and you end up with a spark plug with a hole in it. I believe that I
used a 3/8 by 3" bolt but use whatever fits. Put the plug in a vice and
screw the bolt through the spark plug. Now screw the spark plug back into #1
cyl and continue to screw in the bolt until it prevents the piston from
reaching top dead center by about 15 deg. You need to pick up a degree disk.
This gets bolted onto the crank and shows degrees of rotation. It is VERY
important that once you install the degree disk, that it does not rotate
relative to the crank.
Pick a point to measure degrees from . This will most likely be one of the
timing marks on the timing cover (pick the 10 or 15 to keep things neat),
you can also use a magnet. With the crank rotated till it hits the bolt, Set
the degree disk at about 15 deg before top dead center BTDC and set it so
that it wont move relative top the crank. Now rotate the crank backwards
until the piston hits the bolt and measure the degrees on the timing mark.
Say you get 23 deg ATDC. Now add 15 and 23 and you get... uh 38 deg divide
by 2 and you get 19. Meaning, the bolt stops the piston from reaching top
dead center TDC 19 deg BTDC and 19 deg ATDC. Now without moving the crank,
loosen the degree disk and rotate it so 19 deg is pointing at your timing
mark. Tighten it down. Now when you rotate the crank in either direction it
should stop on 19 deg BTDC or 19 ATDC depending which way you turn the
crank. You have just found the top dead center mark on your pulley (not the
flywheel, that's the big thing on the tranny side). It is located where the
degree disk shows TDC or 0 deg.
Why this is the way to do it... You will never be able to judge top dead
center by trying to decide when the piston reaches the end of it's travel.
As it gets closer to the top it moves less for each deg of rotation. At the
very top you can twist the crank back and forth and see virtually no
movement in the piston. The method of finding top dead center by checking
valve clearances only works if you know the particular timing specs for the
cam your engine has in it (open and close times vary depending on the year
of the cam and if it is stock), the cam/ valve train are not worn, and your
not too concerned about being off by a deg or two.
The bolt must be tight in the spark plug as to not move when the piston hits
it. Gently rotate the engine, we're not trying to poke a hole in your
piston. And make sure the degree disk doesn't move when you don't want it
too. Be careful not t move it if you are rotating the engine with a wrench
on the crank bolt.
Chris Reichle
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From: mgs-owner
To: mgs
Subject: MGB Timing
Date: Monday,November 04,1996 8:20PM
My 1970 MGB has no timing marks on the flywheel. I have tried several times
to align at the engine at TDC, but I cannot accurately line it up. I am
therefore unable to set the timing. Can anyone suggest a way to line
the engine up to TDC without taking the head/oilpan off?. My current
method is to stick a straw in the sparkplug hole, rotate the crankshaft,
and wait until the piston reaches the top of its travel. This method
does not provide enough accuracy. Suggestions are greately appreciated.
Thomas James Pokrefke, III
pokrefke@ocean.st.usm.edu
1970 MGB
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