Help with Timing marks

[j.fernie]

My Haynes tells me that the marina had 2 different locations for the timing marks:
One directly underneath (at 6 o'clock) and the other below the alternator (at about 10 o'clock).
My car has the "teeth" at 6 o'clock but the notch on the pulley is for the 10 o'clock position.
Does anyone know where/how I can find out the angle between the two positions?
Does anyone have one of each so I can measure the difference?

[j.fernie]

Re: Help with Timing marks

A little thought and I think I have answered my own question.
If I turn the engine until I have no. 1 cylinder at TDC (on the firing stroke) I can then mark the pulley opposite the first of the timing mark "teeth" as this is meant to equate to 0 degrees BTDC. I recognise I won't be particularly accurate, but it should be sufficient as I don't suppose the timing marks were manufactured to that degree of accuracy either.
Can anyone see any flaws in my masterplan?

[daniels917]

Re: Help with Timing marks

if the marks are 180deg out time it on No2 tdc, then it will be in line

[h_m_cumming]

Re: Help with Timing marks

Since the fireing order is 1342, 180deg out would let you set up on No. 3 cyl.

[h_m_cumming]

Re: Help with Timing marks

Sorry Merv, your right, 2 will also work as 2 and 3 are 180 deg out. It's too early, my brain isn't in gear yet.
If you do a search of the forum Jim , you'll find a method of finding TDC accurately I posted some years ago.

[stevejgreen]

Re: Help with Timing marks

Not easy to set TDC easily without putting a dial test indicator on the piston as there is atleast 5 deg when there is little or no movement of the piston.

As the timing is rather dependant on the fuel, air temperature, wear on the distributor and other variables, rather than set the timing 'by the book' do it by trial and error.
MGB timing covers are generally 10.00 timing and are readily available. Its an ideal time to consider going duplex timing chain.

[j.fernie]

Re: Help with Timing marks

Good thinking guys - If only life were that simple!
The pulley mark is about 120 degrees off when No. 1 is at TDC so I can't use any other cylinder for timing.
I don't want to take the engine out as it always seems to take longer to put everything back together - it took me all of last summer to complete last winter's rebuild!
I'll have a go at locating TDC using Hugh's method (I found it eventually!) and then fine tune from there.

[c.weedon]

Re: Help with Timing marks

Hmmm a problem - although I think that you are on the right track with your original idea.

Set the engine up with TDC on cylinder 1 (on a 4 stroke engine it won't matter whether the crank is at TDC or 360 degrees out, unlike two stroke or if you were timing the cam). A probe/screwdriver down the plug hole will suffice. Steve's is right that the piston may move over a 5 degree range around TDC, so swing the engine to one extreme of TDC and then from underneath the engine scribe/scratch a fine line on the pulley where it lines up with the TDC tooth. Then swing the engine to the other end of TDC and do the same. You'll end up with two marks probably about 5-7mm apart. Split the difference between them and mark the pulley with a fine line of white Tipex or similar. That is now TDC. Then set up with a strobe light. The next time (if ever) that you take the pulley off, take a junior hacksaw and cut a very shallow groove along the Tipex and then apply Tipex into the groove - permanent solution.

Chris