Timing Mystery... any ideas??????

I recently had my 331 stoker partially disassembled to make some modifications (intake, pushrods, rockers, heads, and distributor removed).

When I reassembled the engine, it was hard starting, had a hell of a time idling, lacked any power, and the EGT gauge was going off scale. I rechecked everything, tested for vacuum leaks, checked initial timing (14 BTDC), checked fuel pressure, and could not find anything wrong. Though the timing was set correctly, it acted as if it was way wrong and I tried tuning the timing by ear. I continued advancing the timing until everything started working perfectly.

So cool right? No, not cool at all. When I checked, the timing is was set at

30 BTDC! Now this is impossible and I know it so I started looking for the source of the error. The damper timing scale is correct.. zero really is TDC. Plug wires are wired to the distributor in the correct order and plug 1 goes to the number 1 spot on the distributor cap.

The engine is NOT detonating or pinging. It's running smooth as silk and not complaining one bit. Idle is good (for my cam) and power is prodigious. I'm driving it hard and all is well.. except I have no idea what my timing really is (it can't be 30 BTDC).

I have checked all this stuff several times and in a couple different ways and I can't find a way to account for the ~15 degrees of error. Any Ideas????

LJH

95GT
Reply to
Larry Hepinstall
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Computer advance malfunction? Did you leave the SPOUT connector unplugged?

Setting the timing only sets base timing, and then the computer pumps another few degrees of advance in depending on engine operating conditions. If you're not allowing the computer to set the timing by leaving the SPOUT unplugged, or if there's a malfunction in the advance system, it'll cause the symptoms you describe.

I've also heard of people running these cars with the advance disabled (spout unplugged) and running 30+ degrees of static advance. I'm not sure why you'd do such a thing, but it's been done before.

That's all I have off the top of my head..

JS

Reply to
JS

Sorry, should have made myself more clear. I am talking about INITIAL timing. Computer advance works as usual adding even MORE advance to my initial 30 BTDC.

LJH

95GT

conditions.

Reply to
Larry Hepinstall

Wow... so you're talking, with the SPOUT in and the computer advancing the timing, you're ending up somewhere in the upper 50 degrees BTDC area?

I'm as amazed as you are that the thing runs... let alone runs well.

JS

Reply to
JS

Reply to
Michael Johnson, PE

Well I thought of that but one tooth is 1/15 of a revolution or 1/15 of 720 degrees and that equals 48 degrees. Way more than I am off. Unless I am all wet in my thinking?

LJH

95GT

Reply to
Larry Hepinstall

Yes, EXACTLY. I know it is not really that much, that something is off, but I don't know where.

LJH

95GT
Reply to
Larry Hepinstall

No I did not mark it. I just retimed it. And checked it multiple times.

Reply to
Larry Hepinstall

I would suggest rotating the shaft one gear tooth and see what it does to the timing. Is the distributor top turned radically different than normal?

Although I doubt this is it, did you disc> No I did not mark it. I just retimed it. And checked it multiple times. >

Reply to
Michael Johnson, PE

Ignition timing is the result of measuring when the spark occurs... the spark being triggered by the hall effect switch in the distributor. As long as the balancer hasn't spun, and the timing marks on cam and crank have been aligned properly, there should be no problem..... 10° will be 10°.

How did you determine that the 0° mark on the damper is correctly positioned? The only truly accurate way is to use a degree wheel and a piston stop This sounds much like a possible spun balancer. If it's a stock type balancer, check the rubber packing carefully for displacement or other signs of wear/damage.

The signature tells the PCM when number one is at TDC....... the PCM uses this information to determine when to fire what injector(s).

Additionally, the signature PIP needs to be positioned so that it is number one - both on bank fired installations and SEFI installations (look at the trigger wheel in the distributor - one vane will be a different size and it is this vane that needs to be passing through the hall effect switch when the rotor is pointing at number one).

Bear in mind, that those timing sets (I assume one of your mods included a new timing set) featuring three keyways/marks can sometimes be a little confusing though I wouldn't expect a mistimed camshaft to create your symptoms.

HTH

-- Jim Warman snipped-for-privacy@telusplanet.net

Reply to
Jim Warman

It's a new SFI balancer and the 0 mark was determined using a piston stop. I rechecked this when I noticed this problem. Balancer is ok.

The rotor only goes on one way and the cap only goes on one way so I dont's see how this could be wrong (wired correctly). Especially since the engine runs so strong (right injector must be firing). Am I missing something here???

I degreed the cam and checked several cylinders and all were right on. So I know the cam timing is right on.

Thanks for your suggestions. LJH

95GT
Reply to
Larry Hepinstall

I can see having it _run_ with 30* base advance... But how the hell do you _start_ the thing? I'd imagine it would kick back like hell and crank very slowly. Maybe he lives on a steep hill and has a manual transmission? Wait till the engine gets moving then turn the ignition on? But seriously, how do you start an engine with so much base timing?

Reply to
Cory Dunkle

Very well indeed. No such problems.

LJH

95GT

Reply to
Larry Hepinstall

is it possible that you've been connecting the timing light to the wrong plug wire?(number one is the first(front) cylinder on the passenger side). Your timing light could be malfunctioning also,especially if it's the dial type.

Reply to
winze

You missed the point..... there is a definite #1 position regarding the distributor pick up. I can't recount how many times that I've seen a distributor installed one or more teeth out from the original factory position. Instead of re-installing the distributor correctly, the wires get moved on the cap - this makes the signature PIP something other than #1.

After 30some years of doing this stuff, I can assure you that I have noticed that caps and rotors are "keyed"...... Sudden thought.... has the timing cover been replaced or the timing pointer changed or removed through all of this???

-- Jim Warman snipped-for-privacy@telusplanet.net

Reply to
Jim Warman

I wasnt impugning your knowledge. Just cant understand how it can be wrong if the plug wires are in the correct position on the cap.

...... Sudden thought.... has the timing

No. And I retested the pointer position with a piston stop.

Thanks for your input. LJH

95GT
Reply to
Larry Hepinstall

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