need initial timing help

[tpsball]

I just replaced the heads on my 1988 omc 4.3, pre loaded the rockers to spec, got the motor to tdc #1, set distributor facing #1 cylinder and put everything back together and not even close on the timing, started a little but ran rough. what did I do wrong? please help

 

[powderhombre]

Re: need initial timing help

make sure the #1 piston is on the compression stoke, both valves closed, and not on the exhaust stroke. plug wires in right order? are you sure your using the proper #1 cylinder? just some things I would check. also maybe advance the spark a few degrees btdc give the gas a chance to burn.

 

[tpsball]

Re: need initial timing help

that's where i get confused, exhaust or compression at tdc, what position would the rocker arms be on the compression stroke. If this is wrong, than all the pre loaded rocker arms are wrong as well.

 

[Don S]

Re: need initial timing help

Both valves on #1 cylinder will be closed when at #1 TDC on the compression stroke.
If you were on the right stroke when you set the valves, the studs/nuts that hold the rockers should all have about the same number of threads showing.
If you were 180? off, they would be all over the place, some too tight, some too loose.
If they are all over the place back them all off so about 1 or 2 threads show above the nut.
Remove the spark plugs (makes it easier to turn by hand). Now put your finger in #1 spark plug hole, turn the engine by hand till you feel compression starting to build. Now, continue turning till the timing mark on the vibration dampner lines up with the 0 mark on the tab. You are now at #1 TDC on the compression/firing stroke.
Now, you can adjust half of the valves and install the distributor, turn the engine one complete revolution and ajust the rest of the valves.

 

[tpsball]

Re: need initial timing help

I removed the #1 spark plug and rotated the motor until piston is at the top and blows out compression, removed the distributor and it is pointing at the #1 cylinder. I'm not sure how to tell if that is the compression or exhaust stroke though.... and that's how I set the rocker arms. I do believe that both the #1 rockers were pointed down at what I thought was the compression stroke. I am going to take the valve covers off right now and investigate. Thanks.

 

[Bt Doctur]

Re: need initial timing help

You must also have the dist rotor pointing to the plug wire your calling #1

 

[tpsball]

Re: need initial timing help

The rotor was pointed towards #1 at about 11 0'clock, the carb being 12 o'clock. Here is what i did next, I found tdc, lined up the timing marks, and the rotor at 11 o'clock, I rotated the motor by hand one full rotation by hand, lined up the timing marks, and the rotor was 180 out. I removed the distributor and rotated it 180 and set it in. The motor turned over better but was popping out the carb and not firing. I think I have the rockers wrong and too tight on some preventing firing. Could this be true? thanks

 

[Bt Doctur]

Re: need initial timing help

With the valve cover off to see cylinder #1 valves, rotate motor untill the intake valve(2nd one in) opens and closes, slowly rotate motor untill timing marks line up,
find #1 position on the dist cap, align rotor to face this terminal , install dist . install cap.