making timing marks

[Howard Sterndrive]

I have no timing tab (chrome timing cover) on this 1983 Mercruiser MR185 (229 chev V6)
I found #1 TDC using a piston stop tool I made. I made a timing tab. So I can now see TDC on my timing light! Got it running.

Now, I need to make another mark for setting the timing... i need 12 deg BTDC per manual

I measured the dampener circumference with the admiral's sewing tape measure - it is 49cm, or 19 3/8" circumference

so, here's the math question....: how far from TDC should I paint my 12 degree line?

the whole 180/360/720 degree 4 stroke thing has me confused right now....waiting for my coffee to kick in

 

[Todd157k]

Re: making timing marks

oops.. missed your measurement.

.646 in.

 

[Kainon]

Re: making timing marks

they sell timing tape, sticks to the damper

 

[John_S]

Re: making timing marks

I have no timing tab (chrome timing cover) on this 1983 Mercruiser MR185 (229 chev V6)
I found #1 TDC using a piston stop tool I made. I made a timing tab. So I can now see TDC on my timing light! Got it running.

Now, I need to make another mark for setting the timing... i need 12 deg BTDC per manual

I measured the dampener circumference with the admiral's sewing tape measure - it is 49cm, or 19 3/8" circumference

so, here's the math question....: how far from TDC should I paint my 12 degree line?

the whole 180/360/720 degree 4 stroke thing has me confused right now....waiting for my coffee to kick in

Someone please check:

Assuming exactly 49cm (better to use mm, if not)

49cm / 360 degrees = 0.13611cm per degree X 12 degrees = 1.6333cm or 16.33mm

 

[Howard Sterndrive]

Re: making timing marks

oops.. missed your measurement.

.646 in.

TY!

 

[stonyloam]

Re: making timing marks

49cm/360 degrees X 12 degrees = 1.633 cm A little slower than John, but at least we agree.

 

[Howard Sterndrive]

Re: making timing marks

Someone please check:

Assuming exactly 49cm (better to use mm, if not)

49cm / 360 degrees = 0.13611cm per degree X 12 degrees = 1.6333cm or 16.33mm

16.33 millimeters = 0.642913386 inches - sweet

so, timing spec of 12 DBTDC is 12 crank rotation degrees?
not distributor button rotation degrees.... that's what had me confuzzled...

 

[Todd157k]

Re: making timing marks

Your number is correct.. if it were a straight surface. You have to include the deflection of the arc. (hence, .646, not .643)

 

[John_S]

Re: making timing marks

Your number is correct.. if it were a straight surface. You have to include the deflection of the arc. (hence, .646, not .643)

I'd mark the balancer, not the new tab, which would not need the correction.

 

[Eric 3.7LX Alpha 1]

Re: making timing marks

Can't you use an advance timing light with a dial on it so you only need one timing mark at TDC?

Turn the dial to 12deg. twist dist so light is on 0' mark or TDC, and your set.

Good way to double check your new mark anyways.

Here's a picture of the dial off a Craftsman advance timing light:

 

[bruceb58]

Re: making timing marks

+1 on the advance timing light. Then your problem is solved.

Its also useful for checking total advance.

 

[Howard Sterndrive]

Re: making timing marks

neat!!!

the 16 and change mm worked like a dream... runs nice

I gotta get me one of those adjustable units though

 

[bruceb58]

Re: making timing marks

I have had an advance timing light for 20 years or so! Wouldn't own any other.