I have a 355 with E-TEC 200 heads, Superram, 219 cam, .045 squish, 31 degress of total timing, 170 degree water temperature, and 12.8 to 1 air fuel ratio, and headers. When I go to WOT I get knock retard of 8 to 10 degrees or more and I am using 93 octane fuel. The knock is real because I can hear it ping for a moment on each gear shift when I am at the strip and if I let the water temperature creap up to over 190 I can hear it all the time if I go to WOT. This problem is sort of baffeling because many people claim to be able to run over 11 to 1 compression with no knock on 93 octane gas.

I am assuming this knock is costing me power because the computer is pulling out timing to eliminate the knock, and I belive the E-TEC 200 heads would like more then 31 degrees of total timing to make max power. I am debating richining up the fuel curve to 12.5 to 1 or 12.0 to 1 and then adding more timing to see if the added fuel will eliminate the knock and allow me to make more power with the additional timing.

What do you guys think, why is the engine knocking and will the additional fuel and more timing allow me to make more power?

The current fuel curve was tested on the dyno and the 12.8 to 1 air fuel ratio made the most power but I never tried more fuel and more timing to see if that would work. The engine kept making more power as I leaned it out until it peaked at the 12.8 to 1 and that was where I stopped tuning.

 

I actually think your timing is too far advanced. People here in cali are running 10.5:1 cr and are not getting knock, and thats with 91 octane gas.
Do you burn youre own chips? If you do, look for where you are getting your knock counts, and retard your timing a deg. at a time untill you dont get anymore knock there.
I think the worse thing you could do is advance the timing further when you know you are getting knock.

 

At what RPM, is the problem?
At what spark advance?
...
Äre you sure your 'mechanical advance'
is what you think it is?

 

You sure your timing is acurate at 31*

I have E-Tec 170s with 10.3:1 and get away with 91 octane.

I run 36* through 4800rpm and 34* after that, this made for the fattest curve on the dyno.

 

I burn my own chips so I have locked my advance to a max of 31 degrees and it starts to detonate at 3500 rpm and higher when it is at WOT. I would like to eliminate the problem without removing timing but that may be my only solution?

Ominous 87 I see your running 36 degrees and 34 degrees, what is your A/F ratio at?

 

Have you went to the Spark Advnace in PE vs RPM table to zero out the values. Then you can reference back to the Main Spark table to set your table a little easier. This way the numbers you see in the main table are the actual numbers and not added with the other table. Maybe try to have all timing into he car before 2800 to 3000 and then start to pull it out and flatten it off. Also check old datalogs to confirm that timing is being held at 31 degrees total when knock comes on.

I run a set of stock heads on 10.5:1 comp with a ZZ4 cam and knock can be no fun to tune out for a newbie like me. I can still run close to 36 degrees total timing on 91 octane and knock is getting a lot better. Before I was getting 13 degrees of knock at certian points and now its down to less than 2 degrees on the 1-2 shift and nothing after that.

 

12.6-12.8

 

What plugs you got in there?


I run an NGK 6.

BRK6E-11, stocked at NAPA, gapped to .050 behind an ACCEL 300+