1986 5.7L 260 V-8 - lack of timing marks...how to time it?

[Blueghost924]

Before I drop my boat back in the water (and after getting the stern drive water impeller changed), I'd like to check timing. A couple of folks may remember a posting I made about a month ago about how I couldn't tell what the serial number is on my engine. After a couple of pics, Achris said it's gonna be a 1986 260 with the 4 inch risers. I believe it was also mentioned that it could have been a custom engine build number.

The dilemma I have now is i can't find bonafide timing marks to tweak the timing to (I believe it requires 8 degrees BTDC). Attached is a pic of the timing mark on the harmonic balancer and what I believe is the only resemblence of any timing reference. The pic is taken from the port side right under the power steering pump looking down towards the balancer. I thought about buying a timing mark tab from OReillys Auto and/or AutoZone and attaching it.

Any advice?

 

[alldodge]

I would use timing tape
TO make it more accurate I would also set It up using a stop bolt

 

[CamaroMan]

buy a piston stop tool - about 10 bucks
remove cyl #1 spark plug
Rotate motor till you are at EXHAUST TDC - (no air coming out of plug hole)
Now rotate motor 300 degrees - install plug stop (make sure its locked), turn it till it bottoms out against the head-
Rotate motor SLOWLY/CAREFULLY clockwise till the piston stops against the stop. Now make a mark "A" on the fly wheel on the current timing mark on the engine (if u dont have a mark bend a wire off the block and point it on the block almost touching the damper)
Now remove the tool - rotate engine clockwise about 90 degrees -
Install the piston stop again (make sure it bottoms out same as before)
Now rotate engine BACKWARDS gently till it again contacts the piston stop - make mark "B" on damper.

EXACTLY between these 2 marks is your perfect TDC - take a screw driver / flat chisel and make a straight hammer mark on the damper - OR a point can work, just make it clear. Paint it with white paint or something very visible, white out also works.

You can now buy timing tape (correct length!!) and use the "0" mark from above, remember to put the tape on with the 0 on the zero and the 10 - 20 - 30 numbers going CLOCKWISE.

 

[boatman37]

i don't like timing tapes. tried it once and it flew off as soon as i started it. but oh well. i would get a good timing light with the adjustable advance dial on it to help verify findings. and also what was mentioned above about verifying TDC

 

[bman440440]

i don't like timing tapes. tried it once and it flew off as soon as i started it. but oh well. i would get a good timing light with the adjustable advance dial on it to help verify findings. and also what was mentioned above about verifying TDC

what he said... also I have the same setup on mine as the OP and the timing gun with an advance dial is the only way to go!

 

[Bt Doctur]

If the harmonic balancer`s line is the true TDC then you can paint new white lines every 10 degrees to the right of the balancers line. If I remember right
A nickle is 8 degrees ,so 3 lines to the right would be 32 degrees total advance
So without a dial type light a nickle to the left of the plastic tab at idle is 8 BTDC , and almost to the 3rd line would be 30 Total advance @ 2800 rpm

 

[CamaroMan]

I put a thin layer of clear epoxy over my tape - its still holding up 4 years - even if just on the ends..

I must say tho i have yet to see a factory damper with a key way NOT be perfectly on tdc or near enough to not matter (degree or 2 at most).. unless timing cover production varied and someone put on the wrong one -

That timing cover looks lijke the 90's vortec ones, and the pulley is a v-belt (which they were not). Its possible a vortec style timing cover might have been used - cant say for sure if the vortec marks are/were the same as sbc, even though they used the same blocks..

either way you WANT to verify tdc and use whatever timing method thereafter.

 

[Bondo]

Ayuh,..... I bought an adjustable timin' light, that uses the marks in the picture, just fine,....

 

[jrs_diesel]

Just did this procedure on my friends Bayliner with the 4.3 V6. Has a similar timing nub that you have, That nub is there to mark TDC for the #1 cylinder. In order to set the timing correctly, you need a timing light that you can set the advance on.

For my friends boat, it calls for the base timing set for 10? BTDC. We set the timing light to 10?, we then adjusted the distributor to have the crankshaft mark and timing nub line up. It's that simple.

 

[boatman37]

^ what he said. i have a 1986 sea ray sundancer with a merc 260 and thunderbolt ignition. mine calls for 8* static timing. can't say for sure that is what yours is but thats what mine is. if that mark is accurate for TDC then set the advanced light at 8 and line the mark on the damper with the notch on the tab and that is your 8* but you need to be sure that tab is actually TDC first

 

[Blueghost924]

Thanks for the responses. I'm going to follow the advices...with the first piece ensuring that at the #1 TDC, the harmonic balancer mark lines up with the plastic timing tab. I'm also going to mark the balancer with timing marks along with a backup check using an advance timing light set at 8 BTDC. Offhand, I did see a website in which someone made a comment that 1/16" is about 1 degree, so 8 degrees would be 1.2". This lines up with BT Doctor's advice of a nickel's width.

I do have another quick question. While I'm in the tune up mood, I've already replaced the rotor, cap and plugs and now want to replace the wires. According to the Mercruiser Parts website, original part number for the wires is 84-816761Q4. The local West Marine and another boat show has the "A4" in stock but not the "Q4" suffix part number. Will the A4 wires be sufficient?

 

[alldodge]

The A4 is Mercruiser, the Q4 is Quicksilver, same part

 

[achris]

Thanks for the responses. I'm going to follow the advices...with the first piece ensuring that at the #1 TDC, the harmonic balancer mark lines up with the plastic timing tab. I'm also going to mark the balancer with timing marks along with a backup check using an advance timing light set at 8 BTDC. Offhand, I did see a website in which someone made a comment that 1/16" is about 1 degree, so 8 degrees would be 1.2". This lines up with BT Doctor's advice of a nickel's width.

This ^^^ is quite wrong, and will get your engine advanced too far.

Some very basic high school level math will get you the answers you want.

You want to know the arc length for an 8? angle. All you need to know is the diameter of the pulley. 8? will be the diameter of the pulley divided by 14.32..... (Circumference divided by 360 multipled by 8, which is πD/45, π is 3.142, so it's D/14.32)
So if the pulley is 6" (as most are), then take a ruler and measure 0.42" from the line. That will be 8?. If you use calipers, not a ruler, then you need the chord not the arc. But for such a small angle, they are essentially the same, 0.42". (it only varies at the 4th decimal place ) Personally, I still prefer an advance timing light.

Chris.......

BTW, a nickel is 0.835" diameter.... and a dime is 0.7".... Neither of which are even close to 0.42"