I have a 2056 with raby 9550 cam, and 9:1 compression ratio. I've recently had some problems with pre ignition with a fully warm engine. It usually happens when transitioning from cruise to WOT. I tried retarding the timing to no avail. The engine has been increasingly hard to tune and inconsistent. I could just not get the timing, dwell, and afr to work together at idle.

Whist searching the net for something unrelated, I stumbled on a page at the ngk website. Now, I've always used ngk BP6es plugs with never a problem. the article explained the causes and effects of pre ignition (or detonation). With the info from the article, I deduced that my 6's were too hot, and that my.034 plug gap was too great. This morning I replaced the 6's with 7's and reduced plug gap to 28. The difference upon startup was quite pronounced. The idle smoothed, I was able to obtain 12.7 afr at idle with the ecu knob, and re advance the timing to factory specs. the results were a smoother acceleration with what felt like(butt dyno) increased power in the upper rpms, and no detonation. I'm shocked at the difference a cooler plug made.

Hope this helps if your having a similar problem

that's what so great about this board, sharing of solutions....

Thanks for the info, since I am building essentially the same engine. I will be stopping by with the 911 week after next. Never been to OK before.

What octane fuel are you running?

You could have probably kept everything else the same and run slightly higher octane.

Stu

I've been using 91, real gas.

Well I spent quite a few years at OU.
Just north of Norman & south of OKC on 35 is a huge Pick your part that had dozens of 914s back in ~1990.

South of Norman was an airfield sized VW junkyard as well (My 70 Ghia was laid to rest there before buying my first 914)

I used to coach & Judge Gymnastics all over Oklahoma in 84-90.

Stu

Oklahoma Foreign. (oklahomaforeign.com) Gets picked over fairly regularly now by the OKC 914 guys. Lived in Edmond, OK, till last year, now outside St Louis.