Ignition timing on 5.7L

[Reel Poor]

Re: Ignition timing on 5.7L

First thing to do is make sure TDC on the timming pointer is actually crankshaft TDC.

You should check the total timming advance. You will need a timming light with a advance knob built into it. Set the total advanced timming to 32 degrees with engine at a high idle of about 3200/3500 rpms. If it's totaling out over 32/33 degrees it's to high and needs to be backed off. Set the total advance then bring it back to an idle and check the base timming again just to see what it is set at. If it's over about 10 degrees your gonna have problems starting the engine when it's hot.

 

[bruceb58]

Re: Ignition timing on 5.7L

Reel Poor,

32/33 degrees seems too high for total advance. My Volvo manual reccomends between 26 to 31 depending on the fuel octane for a 5.7L.

Did you get that number from the Merc manual?

 

[John_S]

Re: Ignition timing on 5.7L

32 degrees total advance (initial + advance) is common for V8 pre-vortec engines, including Merc. The common Merc combinations I've seen are (10 initial + 22 advance) and (8 initial + 24 advance).

 

[I/O WALDO]

Re: Ignition timing on 5.7L

I have a noise coming from the motor that sounds like an exhaust manifold leak without the ticking noise that accompanies it. I would think this would be a vacuum leak, but the problem is, it seems to be coming from inside the carb. ..... What it is?

 

[95yj]

Re: Ignition timing on 5.7L

Actually solved a piece of this a while ago. The vacuum leak and ticking that sounded like an exhaust manifold leak was the EGR block off plate had an internal leak between the exhaust side and the intake side. That's why it sounded like there was an exhaust manifold leak inside the carb. Once I built a good gasket for the plate, I could set the initial timing to 8 btdc and the motor runs smooth.

One thing that still bugs me is that the revs pick up and run better still if I advance the timing. I'm used to motors idling at their best when the timing is set correctly.

Now I'm wondering if I don't have a Thunderbolt V instead of a IV. When I put the plastic cover back on the flame arestor, I noticed that it did say V, but the connections on the distributor don't look like what my Merc manual says a V should look like. For one thing, there is no knock control module. Upon closer inspection, it's not exactly like an IV either.

I'll get pictures and exact wiring description off the motor later today and maybe someone can identify the ignition for me.