4.6 detonation issues

[stlcomanche]

I just finished building a 4.6 stroker and I am having issues with detonation. It is an 87 block with a ported and polished 7120 head and 99 intake. It is being run on an 87 renix computer. I am running a 4.2 crank and rods and 677AP 40 over pistons. I had a custom cam cut by comp that I am using. It has .435 intake lift and .448 exhaust lift. The duration is 206 intake and 212 exhaust with a lobe separation of 113. My figured SCR is 9.33 and the DCR is 8.07. I am using 24 lb ford injectors with a adjustable fuel regulator and an adjustable map sensor with 93 octane. I also am using an HO TB bored to 62mm.
The cam broke in just fine and the engine idles very well. The problem is that the motor is detonating when I am letting out the clutch or when the motor is under heavy loads. I tried moving the rail pressure up to 49 psi with no luck. I also tried a cooler plug from autolite. It is the equivalent to a champion rc7yc. That didn't seem to work either. Those plugs or the rc9yc plugs didn't look bad when I pulled them out.
If anyone has any ideas it would be much appreciated. I rather not pull the head and enlarge the combustion chambers if possible.

Thanks

[SilverXJ]

Maybe replace the knock sensor? I'm not up and up on renix so I don't know exactly what it does with timing. I.e. if it might push the timing until it sensed knock. How does your TPS sensor check out?

[stlcomanche]

I just put a brand new tps sensor in so it should be ok. The renix knock sensor is new also. There really is no way of checking it though. I hit the block with a hammer to see if it would retard the timing. I had the timing light on but didn't see any difference.

[shawnxj]

out of curiousity what's your quench?

[stlcomanche]

The quench is .088.

[Cheromaniac]

Your stroker build specs are pretty close to those of my original stroker build when I had the Crane 753905 cam, and I was able to run 91 octane with Champion RC12LYC plugs.
Something isn't quite right with yours. Are you sure you indexed the distributor correctly?

[stlcomanche]

I check the tps and it was a little off and I reset the voltage. It didn't seem to help. I rechecked the dizzy and it seemed like it was in the right spot. I even had a shop check it last week. I did move it slightly a few times but it didn't make a difference in the issue. I guess I will take the knock sensor back because it is under warranty.

[stlcomanche]

I changed the knock sensor and it didn't make any difference. Here is a link to a video of what it sounds like rolling over a block. http://youtu.be/KBLX-sVex2Y

[IH 392]

It's not ignition, it sounds more like the fan hitting the shroud?, letting out the clutch and under heavy load will torque the motor around alot!, how are your motor mounts?

[stlcomanche]

It was the fan hitting the shroud! I feel like such an idiot. Thanks a lot for all of the responses. I am going to lower that fuel pressure switch the plugs back and reindex the distributor. It should really run well then.

[amcinstaller]

good to hear!