5.7L timing question

[grewvin1]

1987, 5.7L mercrusier thunderbolt IV ignition, checked timing found it to be
12deg. ATDC, put it back to 8deg BTDC rpm went up, turned down the idle and the timing went to 2 deg. ATDC moved it back to 8 deg. BTDC idle went up and settled. Question this seem right? set the timing and idle climbs and timing moves?
Port engine was okay.

 

[Don S]

Re: 5.7L timing question

Adjust both until you get 8? BTDC at idle rpm. If the timing is 8 and the idle is 1000, drop the idle and reset the timing. Repeat as necessary.

 

[grewvin1]

Re: 5.7L timing question

Thank for the fast response, must have been way advanced on the timing, some have told me with electronic ign. timing never changes. I would say it sure does. had to reset three times.

 

[Don S]

Re: 5.7L timing question

Timing shouldn't change, unless something is wrong.
I have no clue what has been done with the distributor or when, or why you was adjusting it to begin with.

 

[greg82255]

Re: 5.7L timing question

Was it running fine before you reset it? If so, why touch it?

 

[grewvin1]

Re: 5.7L timing question

I put the timing light on to check it is an 1987 eng. timing light showed 12 deg. ATDC seem right? other eng. check showed 8 deg. BTDC seem logical to make the adjustment back to 8 deg. on the one. yes it did run but could it run more efficient when set to spec.? Now i'm a little concered I've chaged something I should not have.

 

[Silvertip]

Re: 5.7L timing question

At 12 degrees "AFTER" TDC it is a miracle the engine had enough power to run itself much less push the boat. Of course correcting the timing would increase idle speed. Whoever set the timing at 12 ATDC had to set idle speed up to keep the engine running.

 

[grewvin1]

Re: 5.7L timing question

Yes the idle was high as i adjusted the timing the idle went up and then I brought it down and the timing moved again to TDC 0 deg moved timing to 8 BTDC and idle went up brought idle down and engine ran smooth with the idle adj screw backed right off. Just to mention when i first adjusted the timing I turned the disb. the wrong way just a fraction and the engine began to quit.

 

[series60]

Re: 5.7L timing question

Yes the idle was high as i adjusted the timing the idle went up and then I brought it down and the timing moved again to TDC 0 deg moved timing to 8 BTDC and idle went up brought idle down and engine ran smooth with the idle adj screw backed right off. Just to mention when i first adjusted the timing I turned the disb. the wrong way just a fraction and the engine began to quit.

Make sure the 9/16th nut is TIGHT and the distributor clamp is snug up against the distributor shaft! Use the PROPER distributor wrench. Vibration and centrifugal force will change the distributor's position if not done properly.

 

[Eric 3.7LX Alpha 1]

Re: 5.7L timing question

Sounds like someone tried to adjust the timing by ear before.

Not too far off