Weird Idle Issue.

Redwolff64 · Jun 22, 2012

Having a big problem. I recently pulled my inline 6 from my 66 and dropped in an inline 6 from a 65. I swapped over the fuel pump, carb, pertronix ignition and oil pressure sender. I also added a new flex fan and water pump. We tried starting it, and couldn't. Long story short, we replaced the starter, solenoid, and ignition switch. Still wouldn't. Finally, we ran a hot from the battery to the coil, and jumped the solenoid to activate the starter. We got the engine started, but need to keep the idle above 1000 Rpms to keep it running. As it runs, it revs up and down, sometimes down to the point that the engine dies, as though someone is rotating the distributor back and forth. It is set to 12 for timing (with vacuum advance unhooked) and is hooked to a c4. With the vacuum advance attached, timing is all over the place, but mostly shooting high above the timing block. Any clues what could be going on? I am stumped.

Side notes
All wiring in the engine bay is new
We pulled the tranny with the motor, as the intention had been to swap it for a t5. That didn't pan out, as the guy sold me a 94 t5. We put the original c4 back in with the motor.
The pertronic ignition was originally in the first engine, and worked fine.

MitchGT · Jun 22, 2012

sounds like a vacuum leak, maybe since you changed the carb?

woodsnake · Jun 23, 2012

Any idea of the condition of the timing chain set of the "new" motor?

Redwolff64 · Jun 23, 2012

It may be a vacuum leak, but even without the vacuum advance attached, the motor still revs up and down. As far as the timing chain, the mOtor did take a drop. Bolt broke while it was two feet off the ground. ChIpped a screw housing on the timing chain housing, but the housing itself was intact. Also dented the oil pan, but that was replaced. Could this be the pertronix ignition? I have heard they go weird from time to time, but I didn't think it would be like this.

PoppyMod · Jun 23, 2012

Hi,
Start your diagnosis using an engine vac gauge. Trim the curb idle using the gauge to obtain the highest reading. Of course, you need to have a steady needle with a high reading on the gauge to begin with. If not, report your readings or research the results.
Good luck!

Hack · Jun 23, 2012

It sounds to me like you might have a couple problems:
1. Ignition timing
2.Wiring issue that prevents the car from starting normally
3. Possible vacuum leak or carb problem preventing normal idling.

I would diagnose the wiring first, because you can figure it out without the engine running. Also, poor wiring can start a fire, which can be a disaster.

I would recommend you work on timing second. Did you look at the timing chain before you installed the new engine? If it is tight, then potentially the advance mechanism in the distributor could be the source of variable ignition timing. You can also check the timing chain for slop without pulling the engine apart too much. Pull the distributor cover off and turn the engine to TDC in the normal direction of rotation. Then turn it backwards while looking at the rotor. This will show you how many degrees of slop are in the timing chain. You don't want more than a few degrees..

Falcon79 · Jun 25, 2012

I had a similar problem with a 302 a while back, it would not hold its timing. After all the trouble shooting and searching for vacuum leaks...ended up needing a new timing chain.

Edster · Jul 1, 2012

Check your wires at the plug on the back of the ignition switch. The insulation gets hard and brittle and can break the wire inside if not clean off. Also there may be an issue w/ the ignition switch. I swapped out so much that I have a brand new ignition system when it was the plug, switch, and wire from switch to coil.

bartl · Jul 27, 2012

My guess is something that is plugging the idle circuit in the carb. Was the carb on it when you dropped it? Does your distributor have just vacuum advance or both vacuum and centrifugal. The engine speed changes are why the timing is "all over the place".

rbohm · Jul 28, 2012

first off how do you know your initial timing is 12 degrees? six cylinder balancers, except when new, are notorious for slipping and giving you incorrect timing readings.

did you swap out the load o matic distributor for a later model dual advance distributor? if so did you also change out the card to one that does not have the spark control valve?

have you checked the condition of the adapter to intake gasket? this one is often overlooked when swapping carbs and tend to leak, sometimes badly.

timing chain is also another issue that needs to be addressed. if it is old, replace it. classicinlines.com has a nice double roller chain available.

do you have adjustable rocker arms? if so check that they are all adjusted as equally as possible.

Weird Idle Issue.

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