Hotter spark plug?

[Ray G.]

I have a 427 rebuilt with a 3/4 cam in it, wearing tri power. MSD ignition also. Not sure of the motor internals, because I did not have it rebuilt except it has that hot cam and when I got it the plugs were "AC 4" and fouled pretty bad. Any solution as to the best spark plug that would not foul and run somewhat smoother?
Or is my best bet, replace the cam with a milder one? I am greatful for any help.

[Duke W.]

Re: Hotter spark plug?

Try an AC plug heat range "5" or equivalent, which is the best heat range for most engines, regardless of configuration, that spend most of their time at idle and low load.

A "big cam" requires a very rich idle mixture, which will tend to foul plugs unless they run hot enough to burn off the deposits.

The best cam for a high performance 427 road engine is the OE L-78/72/71 cam, which provides excellent top end power, decent torque bankwidth and because it doesn't have excessive ovelap like most aftermarket cams, a decent idle without excessive plug fouling, and the L-36/68 cam is the next best choice for a slighly milder engine. It's nearly as "big" as the SB L-79 cam.

As is always the case, the biggest improvement in "power" lies in head massaging, not some "magic camshaft".

Duke

[Stuart F.]

Re: Hotter spark plug?

For what it is worth, and there are many that would take issue with me about this, but every Chevy V8 I have had with a "cam", carburation and compression has eaten spark plugs for lunch. They would foul if I got stuck in traffic or for practically any situation of slow and idle driving. They would never self clean and/or if removed and cleaned, would never get you much past 5000 rpm w/o breaking up.

When I got my 63 L-76 Vette new, w/i a few months I had the side plug shields off and stored in the garage because I had to change the plugs that frequently (plugs are still cheap, but it's the knuckles). Then in about 1976, I installed an electronic ignition kit (Prestolite), and that was followed by a Pertronix I (2001) and then a II (2005). Now changing plugs is just part of my annual tune up, and the engine will pull redline all day long without missing a beat. I have been in stop/go traffic, incl. cruise parades where my temp gauge rose and I had to feather the clutch to keep it running, but I can leave from there and blast onto the route 417 on ramp with ease.

Stu Fox

[Ray G.]

Re: Hotter spark plug?

Does anybody think the Tri-power is part of the problem? As in dumping to much fuel? I would think the MSD ignition would be taking care of the excess fuel on start up etc? Tks.......

[Duke W.]

Re: Hotter spark plug?

The carburetion is set up for the OE cam, and is likely not very well calibrated for the "big cam".

In the long run you will have a much more satisfactory driving experience if you install the correct OE camshaft for whatever the original power rating was.

Then you can get rid of the ugly MSD box and go back to the OE ignition.

Duke

[Stuart F.]

Re: Hotter spark plug?

I pine for the days when things were so simple that we only had 3/4 and "Full" race cams to deal with, along with a set or two of points to spend weekends adjusting or changing along with our spark plugs.

Stu Fox