Technical 327 with miss under load

Hope the gurus here can help with some advice. I have a 327 with triple 4G Rochestors but only using the middle one at the moment. The other 2 are correctly blanked off for both fuel and butterflys.
When the car starts it idles OK and revs freely in Park. Under load it develops a miss and there in lies my problem. Any trouble shooting suggestions.

 

I'd start with the ignition system. Are the spark plug wires new? Running a points and condenser? If so, condenser might be crapping out. Even if new..offshore ignition parts aren't the best.

 

Three 4G’s?

 

I think electrical also. Have done timing and pulled plugs and refitted. just got back from a test and tune and waiting or it to cool down to check plugs again.

 

Yes but had lots of problems with fuel leaking from front and rears so blanked off. I am using the proper base plates without idle screws.

 

Get a mobile O2 meter on the tail pipe. That will at least rule in or out one of the two major variables.

 

Two Gees x three

 

Oh yes 2 G's. I was having a moment there like someone else I know.

 

Check the simple things first.
It will probably take a scope to properly check the condenser but check an make sure that it is tight in it's holder. I had One do the same thing with a loose condenser.

Plug wires especially with ram horns or headers can get burned is a place you might not see right off.

Worn out older distributor causing the shaft to wobble a bit when you romp on it.

Carbon tracked cap or cracked cap.

Points with a weak spring bouncing.

Coil breaking down.

I'd bet on wires or condenser though.

 

I would start with a new coil wire and go from there. Plug wires next. Common in points and condensor engines.

 

Just yesterday I had a 50 Chevy Fleet line In the shop with the similar problem .at a idle and Revving it up, it seemed to run great but once I drove down the street and got into the RPm's it's stuttered and missed. I put one of those inline spark testers on it so you can see the spark and revved it up Pretty high sitting still and I could see the spark missing. I looked at the points and condenser a few times even swapped the condenser and looked back at the points, and I could see that the Spring to hold tension was on the outside of the points not on the inside holding tension. Put it in the right way and The Thing ran great. Just my experiences thought maybe it would help.

 

The car has an electronic set up in the distributor and then no condensor. It has a small electronics box inside on the firewall.. The distributor is an original style with releases on each side.
The coil sits in one of the ribbed style cases and I did wonder if that has caused heat buildup and reduced the efficiency of the coil. New spark plugs fitted yesterday and no change. I then checked the route of all the spark plug wires to the distributor and compared to diagram I found showing where each one should be. Looking at the image shown here I think No 1 wire should be the first wire AFTER the tie down on the RHS. My No1 is where No 2 is on the diagram and that means all wires are one spot out? However if that was the case the engine would not run Ok at idle and would have misses and backfires I would think. Maybe TDC was set on No1 in that position but not what this diagram shows and therefore all wires one position around but still correct firing order.

 

Basic diagnostics.
The internal combustion gasoline engine requires a lot of things to run right. To properly diagnose a misfire requires knowledge, tools and time.
The basics are compression, fuel, and spark. However, there are many other things that can cause issues that also need to be checked. If the engine has developed an issue recently, consider what has been changed in roughly the same amount of time. Once that has been done, check the easiest, cheapest things first. Does it have even, expected compression in all cylinders? Does the ignition system provide strong consistent spark? Is the fuel system delivering a good supply of fresh gas?
To answer the spark plug location question, the cap distributes the spark at the proper time. The wire location could be anywhere on the cap and still be properly 'timed'. The diagrams show the factory stock position, which most use, but it can easily be moved anywhere if timed right. A timing light is used to check this on a running engine.You have a running engine. 360' divided by 8 equals 45 degrees off. the engine would barely run, if at all 45 degrees off, so that is not the issue.
Please list out all the specs of the engine and supply systems rather than have us guess then provide another piece of the puzzle.

 

I ahve traced all plug wires are they are correct.I pulled the coil out of the finned cover it sits in and it was super hot.
Then drove for awhile with coil out in fresh air and when I came back it was too hot to hold. Maybe look at coil replacement now.

 

Coil brand? (I have couple of useless coils on the shelf of shame)

 

I f the coil is that hot and your electronics don’t require a ballast in the power feed; I’d look for a ground short in the distributor

 

If that was the case why does it run fine when in Park and revs freely without apparent miss. As soon as it goes into gear than it starts to stumble and after a short drive and stopping in gear to take off again it misses. Once revs are up on open road it seems to run fine.
I haven't ruled out fuel issues either at this stage. I have fitted new spark plugs and coil(just a normal coil) and problems still persist.
I think I need to find a mechanic and we start with resetting TDC and make sure rotor is correctly positioned on No1.

 

Could be worn cam lobe. It acts that way,when that starts to happen

 

The spark is going to take the path of least resistance. When the engine is under load, cylinder pressure increases and it's "harder" for the spark to jump the gap at the plug so it seeks a path with less resistance, usually a leaky spark plug wire. At least that is how I remember it from way back.

Gary

 

A miss under load is frequently misunderstood, but you are correct in your memory.

The plug wires should shoe evidence of burn through, or there may be cracked porcelain on the plugs.

The go-juice is getting out.

 

I haven't seen a bad wire in years, but way back when it was really common. Testing for continuity and resistance is a good thing, but, be sure to move the wires around while the meter is on them. Used to find a lot that would read OK until flexed. Apparently the core was making contact until it was moved by vibration or something.

Bottom line the miss under load is almost always ignition, wires, condenser, point gap or condition, coil (rarely IME), or plugs. I have suspicion every time I encounter an aftermarket electronic setup. Simply because the normal troubleshooting steps have to be altered because of it's presence. Is it working as designed, dwell etc? Can't really tell.

 

If possible, find a shop with an ignition oscilloscope and a mechanic who knows how to run it.Put the engine under load in gear and you'll know in short order if the ignition system is up to snuff. If it pops rapidly in the carb under load suspect a flat exhaust lobe on the cam.

Terry