The MSD curve kit actually has 6 bushings to choose from. I do not use vacuum advance. When curving the distributor my plug became fouled with the green bushing installed which gave me 13 initial and 36 total. I installed 1heavy silver and 1 light silver spring which is 1 of there slowest options. Before this change I had the blue bushing with 16 initial and 36 total.

Originally I was asking has anyone experienced fouled plugs when retarding timing too much. It seems the discussions have prompted many questions in an effort to help me. Please continue to ask for more info if necessary, I feel I have good knowledge of the topic and my set-up.

The MSD Blue bushing is 21* so you had 37* total.....FWIW.

As set you're getting full spark advance at 4,500 rpm.

http://www.msdignition.com/uploadedI...mingCurves.jpg

What's your car weigh?

What trans?

What gear ratio?

What tire height?

How much vacuum at idle?

With the blue bushing I get total around 3500 rpms, I think the detonation is a cruising/ off idle situation. I have avoided WOT since I noticed the first sign of detonation. At 55mph I run 3000 rpm.

Car Weighs about 3100, 4.30 gear, 26" tall tire, 14 in. Hg @ 900 rpm

The whole point of tuning a car is to get AS MUCH TIMING AS POSSIBLE in the engine without causing preignition. Never have I tuned to retard timing. So I assume that you want to retard timing to reduce idle rpms??? I know your original question was about fouling plugs.... but you're not giving enough info to get right to the heart of the matter. I would ASSume the fouled plugs are a result of not lighting off the fuel mix or allowing enough time to light and fully burn the mixture. But it could be a couple of issues.

That would be exactly right.


I'd be running 1 light blue and one light silver with a 3100 lb car and that gear. Or even 2 light silvers.... and get all the timing in by 2500 rpms...

Did you READ the plugs and find "salt and pepper" on the nose?? Also do you know how to read the strap -- and see where it changes color? Perfect timing will have it change color right in the apex of the bend.

That compression value is only a "static" compression calculation. What's more important - and can actually be measured - is your CYLINDER PRESSURE. The cam bleeds off "compression" so regardless of what static compression the pistons rating is - and the size of the head gasket - and the size of the chamber in the head... the cam will play a significant roll in the cylinder pressures being generated. With the cam you have and that static compression ratio -- my guess is you're making less cylinder pressure in that BBC than one might think. Aluminum heads are a giant heat sink.

The Edelbrock E-CNC head comes in two chamber sizes -- 110 and 118cc - which one are you running?

With improved combustion chamber - and your distributor set up as stated, would have had a very retarded timing curve and a total of 37* --- it's little wonder you're having "issues".

Excuse my graph reading error! :sieg:

Remember there are a lot of causes for that symtom.
Are you running a power valve? Could be blown out or incorrect for street applications.

Sorry guys I have submitted any replies, but my modem keeps failing causing me to loose internet and home phone. I'm going to clean plugs and return to a previous ignition curve when the plugs looked good in terms of air/ fuel ratio. It may take me a few days to update my progress but I will let you know the outcome.

Before I loose internet again I will quickly answer some of your latest questions:

Yes I'm running 4.5 power valves and realize if they leak it will create a rich condition.

Trying to run 93 octane from the pump.

110 cc heads

Yes I saw some pepper spots on the porcelain. The ground strap looked good at 18 degrees of initial timing, when I retarded the timing I was looking to see how it would affect the detonation and assumed I would go back if the discoloration moved too much towards the tip.