I have a 69 427 and started her up and noticed a bit of a rough idle.
Something else I noticed for the first time while letting it idle.
I have side pipes on the car and the passenger exhaust looked fine but the driver's side was slightly smokey.
It was definitely not black or blue smoke but more of a light white smoke and a very intense gas/exhaust smell.
The car has always had a more exhaust smell than normal, but I always figured it was because of the exhaust exit location.

My first guess, is one of the plug/wires on the driver's side is not firing correctly.
Its been a while since I've done the check on a car but this is my game plan.
If anyone has a better/easier way to this please inform me.

Check to make sure all the plug wires are connected firmly and not damaged from heat for the driver's side.
I'm going to remove all 4 spark plugs on drivers side and look for any obvious problems with the plugs. Discolor/gap etc.
If both these look ok, should I remove the 4 wires and do a resistance test on them?

thanks
jim

 

I recently replaced my wires and I learned something interesting.
A resistance test can show you that they are bad, but does not necessarily prove them good.
I chased a random misfire for quite a while. All the wires tested good on my vom. In desperation, I finally changed my wires because they were 15 yrs old. Problem solved.
But, this is not the first thing I would do.
Yes, start with your plugs.

 

You could also check your wires by looking at them while the engine is running in the dark. See if you see any spark leakage. Jerry

 

I forgot to mention this test also. I will let it idle for a bit and run a IR temp gun on the header tubes. Maybe one will be running cooler if it is miss-firing ?

 

Using an insulated pair of pliers pull one plug wire at a time to see if one of them does NOT cause a drop in idle speed.

 

I always expect the worst case, and hope for the best. Doesn't sound like a wire or plug to me. Smoke that is not blue or black could be steam from a blown head gasket. A quick check of the oil will confirm this. If it turns out to be wires, spend the money and get a good set.

 

Generally yes, but not always. On my '69 BB there is a large difference in exhaust temps at different cylinders. Differences in water routing through the heads, intake manifold and carb differences to different cylinders, etc. make a big difference on the exhaust temps. Some cylinders run richer or leaner than others.
Just the nature of the beast.

 

Last night I took off the spark plug wires on the drivers side and found one big problem.
Number three cylinder had the spark plug boot burned up. I have some of those protective spark plug boot/sleeves.
My guess is it slid off the end by the spark plug allowing the plug boot to get to close to the headers.
You get see the metal inside the wire through the burned up area so I am guessing it may have been arcing onto the header.
I hadn't started the car in a couple days but it also appeared that this spark plug was also damp from I assume fuel.


The second problem I may have with my AC delco r44xl spark plugs. For some reason, I have had the hardest time trying to figure out the gap for these plugs. Seems like it should be an easy thing to find on the internet. The best I could do, is Oreilly web site says they should be .033.
When I checked the 4 I had off, they were all significantly wider than this. Can anyone confirm that .033 is correct? They all looked about the same in gap but I am going to the store today to get a better plug gapper. All I had was the feeler gauge type where you have to combine them to check the gap. I can see one being a bit off but all 4 look to have been set that way. Is there any reason they would have been gapped larger than specs? I do have a petronix flame thrower coil and ignition system conversion but I know I didnt change the gap for that.
The plugs arms also look angled up. Here is an an example of one.


These plugs and wires are probably 5+ years old but probably have less than 100 miles on them. They do look a little black and sooty to me from running rich I believe. Most of these wipes right off.

thanks
for any more input
jim

 

Time for new wires. I recommend Taylor 8 mm spiro pro wires. Set your plug gap at 0.035". Take the car for a good run on the highway and then check plug condition again.

 

On a side note. This seemed to have happened because the protective boots I have for my spark plug wires for the headers just loosely fit on the wires boots.
My guess is over time it just slid off between the header the the boot allowing the boot to get burned up.
I bought the protective boots back in the day. It looks like now they are cheaper and better deigned to stay snug on the spark plug boot.
Does anyone have a suggestion on ones they have used that will stay in place?
I found some on amazon for 15$ that seem, at least in the description, way better than what I currently have

 

I have the same issues with the spark plug boots on my 1968 427 Corvette. The spark plug boots break down and cause a misfire. I have used MSD superconductor wires since I built this engine without issue. The last set is less than a year old and I am loosing my confidence in the MSD products.

Could it be from having a Hot ignition system trying to find an easy ground? I have a MSD 6AL box on my Corvette with the MSD Billet distributor with mechanical tachometer drive along with a MSD coil.

There were no boot burn through's when I used the K66 Factory transistorized ignition for many years. The MSD system makes a hot spark and with my High compression in the 427 it uses a bigger than normal gap.

I would like to try another brand and see if they are more durable than the MSD wires are now. The engine has headers and this makes the boots get exposed to higher than normal temperatures. I even put high temperature covers over the boots and the wires still failed.

I am ready to take the original exhaust manifolds for my 427 and have them ceramic coated and get rid of the headers all together. The factory exhaust manifolds are pretty smooth looking parts. I doubt the headers make a lot more power over the factory parts.

Ideas?

 

Before you start detuning your 427, try the Taylor wires.

 

I NEVER assume that a new plug is gapped correctly; I reset the gap to what I want on every plug I purchase. If you have points ignition, .035" is the proper gap. If you have HEI or another electronic ignition, .045" is appropriate. You might need something different if you have a very high compression engine or an exotic set up, but those are the 'usual' choices and they have worked for any Chevy engine that I've ever had.

Tiip for those trying to diagnose a firing miss: If you have a timing light, just connect it up to any specific plug wire and watch the pulses. You can easily determine which plugs/wires are giving you problems.

 

This!
I just fired an 88' Honda Hurricane that I built the engine and carbs for last Saturday and this is a perfect test.......had three at 400 degrees and one at 190.......took the carbs off and cleaned them again a 400 across the board........
Just be aware that this test works better for fuel related than spark.......

Jebby

 

Why would you bump up the compression and the plug gap? That's a recipe for the coil energy/voltage to look for a different path to ground.

 

The gentleman I spoke with at MSD suggested that with the high compression I should use a .055 gap with a good coil. I removed the K66 from my engine and replaced the whole ignition systems with a MSD 6AL and the Billet distributor. When setting up the distributor is when they started telling me to go to a bigger spark to ensure a long complete burn. My cylinder pressures are high and when I test the compression it is between 235 and 255 psi. They suggest that this situation requires a bigger gap on the spark plugs. I am game to try a smaller gap as long as she runs smoothly.

The result was fine for most spark plugs but when I switched to the Iridium Plugs they started having problems. I normally run plain champion plugs without any fouling issues.
The 427 runs 12.25-1 using a set of L88 pistons with a cast iron Closed Chamber cylinder head. After startup they quickly became oil fouled and started missing. That is when the wires start finding ways to ground.

The MSD super Conductor wires had a great reputation but the latest set are clearly a step away from the old quality. I will see about ordering a set of the Taylor spark plug wires and using something different.

I am now trying to set up the Ignition side of the Holley Sniper Stealth EFI system. I have never created an advance curve for an engine before. Any suggestions on places to learn what would work with my little 427? I will start conservative and get more aggressive as I learn and gain experience. I am hoping to get the fueling and ignition controlled by the EFI system.

 

MSD ignition product user manuals indicate that as compression goes up, plug gaps get reduced. 0.035" is where I would start with the plugs and increase gap only if there is a change in performance.