Ignition question from a rookie

[Lenny]

On the X, after running about 3000rpm for about an hour straight and then WOT I lost about 1400 rpm from what I could quickly see. At the dock, idling up to the ramp, it was running REALLY rough and SURGING like mad.

Anyways, I put in fresh plugs (MR-43 AC Delco) and it is still the same. Fuel (with arrestor off) if flowing fine, filters are good (replaced)

So anyways, I was just running it in the driveway and pulling off plug wires from the cap (linemans rubber gloves on) and there are 4 that make no difference to the lousy idle. Two on port and two on starboard. Also, once I disconnect these wires from the cap, the cap arcs across the perimeter to hit the post where the wire would have normally been. When you rev it up to about 1500 you can hear it kick in and out and all sorts of ignition bursts.

Any ideas? 350, HEI distributor. Keep in mind it was "cruising fine" and only got "$hitty" when I slowed down and then the surging started and the WOT disappeared.

?

[DONZI]

Lenny look inside the cap for a possible crack.Also ck. the condition of the rotor.Plug wires are another possibility.It is always good to do a compression ck. on the suspect cyls. to give you a good baseline.

[Pismo]

Its usually ignition. Sounds like no spark in several cylinders. New cap, rotor, wires, you already did the plugs. Maybe just water in the cap if lucky. You don't need the gloves as long as you are on the cap end of the wires, you do at the other end tho.

Good luck

[Sierra]

Lenny follow the track on the intake from each miss firing plug, and you we see that one side of the carb is not working.

Ricardo

[Sierra]

Or possible bad carb gasket. Will cause a vacuum leak and you will have one bank miss fire.

[MOP]

This may be fun as Lenny has stated a few times he is No Mo-hanic! All great tips above take them from the top, when you changed plugs a compression check was in order to see just what you have from there if it was good got to be ignition, vacuum leaks manifold or carb. If the old plugs were clean no sign of rust you can rule out water as a cause. Lenny dive in you will feel good with the knowledge you will gain!

Phil

[RickR]

Lenny
Be VERY carefull pulling wires off the cap to diagnose your problem.
With HEI or CD ignition the coil will discharge and will find a ground even if it has to go through the side of the coil :(

[Lenny]

Plugs were fine, all similar in clour and no oily messes anywhere. I will look into the carb thing. Good advice about the runners. I will buy a fresh coil/wires/cap and rotor for fun anyway. I will remove the plugs again and do a compression test for future reference. Got to fly to Vancouver now and price/draw a couple kitchens. Back on Friday eve and will dive into this this weekend.

Rick, good advice on the coil too. That would explain the arcing coming out of the cap to the post with the wire off I guess.

Thanx

[Pismo]

True the coil will find a ground, but not thru you unless you stuck your finger right in the hole in the cap/coil or pull off the spark plug end of the wire and hold that. There are far easier routes for the current to go than thru you. All good ideas, 90% of the time it is ignition somewhere, so abrupt for wires tho.

[MOP]

Lenny put the wires on and retest it, I have seen many a set go south causing what you are talking about. I have seen bad sets light up shooting spark to the looms and any metal touched when then engine were started in complete darkness. I like plastic retainers like Jacobs ignition supplies, even good wires can find ground with the newer high voltage systems.

Phil

[Rootsy]

True the coil will find a ground, but not thru you unless you stuck your finger right in the hole in the cap/coil or pull off the spark plug end of the wire and hold that. There are far easier routes for the current to go than thru you. All good ideas, 90% of the time it is ignition somewhere, so abrupt for wires tho.

tell that to the scar between my eyes... 40,000 volts between the eyes.. i saw the spark arc and zap me... out of the nick in the coil wire at the cap... it is quite unnerving to be straddling a running motor and wake up from being knocked out with her still running... i heard it arcing.. i saw it when it was tooo late...

J

[Pismo]

Yes the trailing end of any hot wire will bite you, such as your experience with the trailing end of the coil wire, but not the leading end when unhooked. True, you must always be on the lookout when working with high power.

[Formula Jr]

Lenny, given the description of how this started and that you have found two cylinders on each side that don't seem to be firing all the time, Sierra has the best explaination. Follow the intakes of the missing cylinders. If they line up to one barrel of the carb you have found the problem. I'll bet there's a little piece of something wedged in the jet. When you say that it surges, that pretty much eliminates the ignition system. With cross fire you'd get loud knocks and backfires. With a slight miss, you would be shorting one of the plug leads. But you're engine is surging, and it started all at once - as you were backing off the throttle. A failing coil drops the entire firing order momentary or the missing plug would occur randomly in the firing order. Spraying ether or cold start into that barrel should make it purr again if it is a carb failure.

2 cents.

[Lenny]

OK, I didn't have time to work on it tonight (this weekend) ( next weekend etc) BUT, anyways, I have an Edelbrock Peformer on there, and the plugs that have LITTLE effect are the ones for the tall part of the casting in the manifold. Does this make it a carb issue?

Sorry for being so "naive" about all this stuff but it is new to me. When a junker breaks down on a highway I can probably fix it or at least figure out what I need. This is new to me.

I appreciate all your help and in two years I promise to not be so stupid :yes:

...oh, and that pertains ONLY to this stuff :D

[Sierra]

Lenny what are the pistons that are missing on each side ? Oh if you want to know a simple way to check the carb gasket for a leak use WD40 on a hand pump spray bottle NOT A CAN. You start the motor and spray in between the carb and the intake, if the motor has any change then its the gasket under the carb. If no change its the carb.Ricardo

[Lenny]

Thanks