I use NGK BCPR5EY they have a .034 gap.
The engine came with Delco-4 and they have a bigger gap.
But found the engine was runnig better with the NGK´s and they are easy to get in Europe, the Delcos must be ordered overseas.

Something elese came to my mind, the first time the problem occured was directly after harder deceleration with the engine. I just let the gear in after a wot acceleration and let it slow down with the throttle closed.
All I know is that this is making a big vacuum. But has this influence on the plugs as well? I could imagine the high vacuum is sucking more fuel and so richen the AFR, causing the plugs to get carbonized. What do you think?

 

Update:
Engine runs great now with new plugs. Missfire at WOT completly gone, revs good above 5000rpm.
After 20mins I recognized the slightly missfires when cruising with 1200rpm again.
Then played with the idle AFR, found out that it absolutly does not like to be adjusted lean. It likes more rich, but you can´t solve the issue with just the idle screws.

Ok, then drove home, checked vacuum with the gauge, seems to be ok.
Then the timing, found out that I had mixed up the two hoses for full and ported vacuum yesterday when I reassembled the carb. So I was running full vacuum to the distributor, and I know the engine does not like this in low rpms. It easily starts to jerk then.
Switched that back, and put another TI-coil into the car. Had tested the coils on the bench, but they seem to make the same spark.
Then drove it again, the problem is nearly gone. But I am still not 100% happy.
Seems I am running there close to boarder where it depends on many values that have to be set to work good together.
Next thing I will try is the new TI-module from Lectric Limited that I have lent from a friend. They write it will double the voltage at the coil with the result of 10% stronger spark. We will see...

 

FYI, We have been having problems with two different TI Coils on our 65' from K&B...both brand new. They will run fine for about 20-30 mins, then all of the sudden the car will start missing, idle fluctuates and occasionally dies and just generally running like crap. We can swap the TI coil from our 66' that is also a repro coil from one of the other vette vendors and it runs perfect all the time..

So if your coil is from K&B, definitely swap it. The guy from K&B denies there is any problems with the coils and says they test great and there is something else wrong with our car, yet another coil from another brand runs perfect so.....

 

Well I doubt the coils I have have a failure. I do not have the problems you mentioned.
I have the old original coil from Delco and a new one, but don´t know who made it.
Idle and other running conditions of the engine are fine. It never died or run like crap.
Have only some slightly missfires when cruising at ~1200rpm with throttle close to idle.
If I would drive an automatic tranny I would not recognize it i guess. You can hear it a bit,
but what disturbs most is slightly jerking. It´s just not 100% smooth.

I think it has something to do with the cam duration, the vacuum, the AFR and the engine load (Without load I did not recognize a miss fire so far). And the plugs reading tells me that the AFR distribution is not equal at all cylinders. It´s basically the same it was with my previous 454 engine with the same intake. Think this comes from the intake design of this 3x2 setup.

Assumed the AFR conditions in the combustion chamber are not very good, will a stronger spark help to ignite? I have no experience here. I only know that MSD wrote about their company history that their system was invented because the lean running engines needed a stronger spark to iginte the lean AFR.
So I assume a 6AL box could help here.

 

Ok, I bought this:



hided here:



Result is: missfires are gone, but little jerking sometimes still present. I even can´t tell if it comes from the engine or bumps on the road.

Besides that, the increase of low end torque was dramatically
This time the advertisement was not a lie, the engine performes much better now, exhaust sounds stronger also Other than that peak power seems to be the same as before.

I had to rise the idle a bit, it seems the MSD triggers some degrees later then the TI does. So i wanted to adjust the timing, but my nice and expensive timing light



does not work with the MSD. Nothing new, they write it in the manual.
Is there one available that works with the MSD and has a retard function, so I don´t need speciel markings on the balancer?

 

On some of the MSD units you can temporarily disable the multi spark function while setting the timing.

 

Not with this one, and it isn´t the low-end model.
Thats really stupid, it would only need a small switch at the box to realize this.

 

Now, after I think I found the reasons for my problem I found this page

http://dtec.net.au/Multi%20Spark%20Ignition.htm

that confirms my suggestions:

Instability comes about when mixtures are leaner than that for smoothest operation, there is poor mixture formation (rich and lean 'pockets' as not fully homogenous) or low ignition energy. At higher rpm it’s not needed due to cylinder turbulence creating better mixture formation and COV isn't an issue as engine loads get higher.

 

Have you tried your light yet? Or just read in the manual its not compatible?

I have two "dial back" timing lights. One is new Sears Professional digital light similar to yours, my other is a 20 year old SunPro dial back with the ****, both work on my car with the MSD-6AL and read within 1 degree of each other... Everyone told me they wouldn't work but they do.


I believe Flaming River makes a traditional style timing light that works well with MSD... Or you can get raped and buy the MSD timing light that is compatible for about twice the cost of other lights.

Glad to hear your problems are resolved.

 

Thank you.
Not so easy for me to get your timing lights in germany, I would have to import them. But a friend told me of a dial back light (with the ****) he uses and it works with his MSD box. I ordered it and let´s see what happens.

The light I have is really nice to handle, you can hold it with one hand and set the retard with the thumb, while you are at the throttle with the other hand. And it shows you the rpm all the time. So it´s quite nice working with it.

When I started the engine the first time with the MSD box I noticed a lower idle, so I think it´s triggering the timing a bit retard compared to the TI-system. Then I wanted to measure, but did not work.
Found an article on the net about this timing light, stating the same.
There is a low-end version of this timing light available, without retard function and display, and this one is known for working with MSD.

Well, I could put some markings onto the balancer, but what I really want to know is the engine rpm when I set timing. So all the cheap lights are out.

 

I'm with you. I love the dial back style timing lights. That's the only way I set timing is by total degrees... I could care less what the timing is at idle..

I used to hate fooling with timing tapes on the balancer.

I have read that some digital/dial back lights will work with the MSD boxes but can be in accurate as much as 1* per 1000 rpms but...

I have been tuning my 650hp engine with the same two timing lights for 5 years/14k miles and it's still alive so... I assume they are accurate enough.

Good luck on your tuning process. I am doing the same on our 65' 396 problem child.. Had issues with the new TI system, so I thru an MSD HEI in it and it runs fine.. Rebuilt the TI distributor and I am about to try it again... Needless to say, I am not impressed at all with repro TI systems...

 

Well I still run the old TI-Distributor, it works fine.

Today the new gun arrived, its a Gunson Supastrobe, and it works with the MSD box.




But despite that, this thing is a dinosaur. Big, heavy, you need 2 hands for adjusting the advance and the display shows only one value a time. Just no joy using it. With the other light i was able to track the advance at any engine speed while raising the rpm with the other hand.
This time I was just happy to see the timing advance stop at 36°, no clue what rpm it was. But i know it´s around 2500.
Luckily I will not need this timing light very often.

Oh btw: the timing was set correct, but idle speed still slower than with the TI unit. Idle timing was also equal. I have no explaination for this, but was an easy fix.

 

MSD Superconductor in ss-braid looks a bit fat. But thats the way it is...
Btw: mechanically the wire is really good, the best wire I ever had.