Engine is 2056 with Raby 9550 Cam and D-jet

I have the stock Bosch plugs with factory gap
Running Pertronix with flamethrower coil
Engine timing is dead on the nuts
Valves adjusted 0 lash (chromoly with swivel feet)
AFR is 12-13 on the freeway

Fuel pressure is 30psi

Car runs great and has a lot of power all the way up to the redline. Engine runs very cool, seems to be happy. I have noticed that on a longer drive pushing higher rpms for extended runs there is a tiny bit of pinging unless i push down or let off the throttle, it goes away. I know that any ping even a teeny tiny ping is bad. SO...

I put Ultra Premium fuel instead of the midgrade and its still there. Keep in mind I might not hear it for a few days, but if I want to drive like I stole it for over an hour it can be heard.

I would rather not retard the timing from spec, and I dont want octane booster. So I was reasearching plugs and found that some new plugs might do the trick.

Question is do I want colder or hotter to cure my preignition. Is changing the plug my next step? A colder plug will help the preignition?



Joseph

12-13 at highway is pretty darn rich... thats WOT mixture.
I'm not sure that heat range in the plug will help with ping
but maybe I don't know any better...

when you say timing is dead on, what number is that for you?
also I have found timing can very if a cheap or different timing light is used.
I have one light that is crap and measure a different timing than another.
so perhaps verifying timing with another light is not a bad idea too...

your compression and temp. effect pre-ignition, so maybe lowering the combustion temp will help..

each different brand of spark plug uses a different system to designate hotter/colder.

for example a bigger number means hotter in one brand and colder in another.

I am driving 1 hour each way pretty much straight, with a lot of up and down hills. I am often @ WOT but when I am not it is closer to 14
27 Degrees BTDC @3500

Will try another light to make sure, but my light is nice
I didnt install the number gauge yet but My temps are AWESOME, even 1 hour of 80mph+ and flying past the other Porsches My gauge will stay on or just before the T in TEMP. Cht gauge will go in next week.
So, if temps are cool and I still get pre ignition, AFR looks good, and running Premium gas, I need to retard the timing 1-2 Degrees. Or try a different plug while keeping the timing right on the nuts

Pinging= Timing issue.