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Posted by: The Cabinetmaker Apr 12 2013, 10:18 AM

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

Posted by: type47 Apr 12 2013, 11:42 AM

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

Posted by: worn Apr 12 2013, 11:45 AM

QUOTE(The Cabinetmaker @ Apr 12 2013, 08:18 AM)

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

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.

Posted by: stugray Apr 12 2013, 12:13 PM

What octane fuel are you running?

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

Stu

Posted by: The Cabinetmaker Apr 12 2013, 01:42 PM

I've been using 91, real gas.

Posted by: stugray Apr 12 2013, 04:15 PM

QUOTE

Never been to OK before.

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

Posted by: snakemain Apr 12 2013, 06:57 PM

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.

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