Trippin

Why do you think it is ignition related?
Have you done a compression check?
Even better....A cylinder leak down test.

LAKESIDE RESTORATIONS

I would check for a broken or cracked spark plug, also check to see if your carb is leaning out when it happens.. I have seen this many times.. Jamie / Lakeside

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BadDog

Update:
No Joy yet! Bypassed keyswitch and fed fully charged battery to Crane box as well as main power lead to Crane box. No change.

Replaced fuel water separator, disassembled carb for thorough cleaning no change.

Disconnected Tach to no avail.

Plugs all look fine.

Removed all wires from alternator to eliminate something funky with it.

I am running it up to 3k in a bucket of water to avoid sucking the hose flat. At 3k it still sounds like it is missing. Sort of a burble and stumble. No pops or spits at all.

I have tried swapping all the Crane ignition with stock prior to all the above efforts with no change in symptoms. I also swapped the distributor and pickup with no change. The distributor was from a pile of parts and had a tested coil with it. My current though is both of the pickups (current and one in spare dist.) may be bad.

Going out to run a compression test but the engine only has 75 hours on it.

Next step, try a different ignition module and new pickup.

What am I missing?

Griff

It sounds to me like you might be rich when you get into the secondaries.

Run it up to where its missing and stumbling and then shut it down and check the spark plugs.

Check the float adjustments and replace the powervalves.

The only other thing I can think of is that you've got a bad power wire somewhere on the engine that is grounding out.

MOBILEMERCMAN

BadDog- drag , I once had a similar problem that developed after a charging problem. It end up being the sensor in the merc ign. Seems unlikely you have two bad dist. but you never can tell. Troubleshooting and swapping with used parts sometimes does it to you. Everybody has covered it pretty well. Hope the problem shows its ugly face soon.
Jim

BadDog

The power valve crossed my mind. It would only be the secondaries or when the throttle plate opens. I did inspect them by blowing on them to see if they were sealed. What does a pad PV look like? I doubt it is a wire as I have bypassed by jumping the power straight to the #1 battery while running on the #2 battery but I will check into this deeper.

Compression checked out fine.

Ted G

iTrader: (1)

You may have broken valve springs, might want to pull the valve covers and take a look.

BadDog

PV checks out ok, just pulled it and tested with a vac gauge.

Just visited my local Merc buddy. He gave me a new pickup for the dist. Trying it now and having MGD.

He tells me (Master tech for 20 years but too busy to look at mine now) that burbling is excess fuel or lack of spark which essentially comes down to the same thing. I will look at valve springs but it runs and sounds fine until 3k.

TAZMAN

I assume you have the carbs externally referenced to the intake manifold for vacuum. If not you could be way rich at increased boost. Just a thought.

BadDog

Well nothing has changed in this setup for the last 400 hours other than a full rebuild. After the rebuild it ran like a raped ape and 50 to 79 hours in the miss started to develop. Started out at WOT and has worked its way back to lower RPM. New sensor in dist. did not help. Double checked all PV's and they are good.

WTF? Never been stumped like this.

I suppose the valve cover are coming off for inspection next.