New Engine Spark knock any ideas why?

[stanley514]

I have a new stroker 331cu in a LX 5.0 Mustang. Its running rich and spark knocks if the base timing is set over 5 degrees. (With the pill out)
This is the engine.
E7 block Zero decked
AFR heads 60cc
CompCams X HR270
Cobra intake
19# injectors
Mass air meter stock 1992
Stock TB and I have now installed a 75MM
Probe ultra pistons dish ? = CR 8.7 ~ 8.5.
I replaced all the sensors when the engine was installed.

How can it spark knocking with this low CR ??
Is the ECM just flipping out over the extra air from the stroker?
Is my only option a custom chip?? I have a blower to install next spring. I just want it to run better now. I have larger injectors and a Mass air meter for the SC.

Any ideas?

 

[BlownFiveLiter]

I'm thinking it may be the injectors, but while you're still NA, you should be able to compensate for it by increasing the fuel pressure. What's it set at currently?

 

[stanley514]

Spark knock

I haven't checked the fuel pressure. I will check it next week. The fuel pressure could make it run rich. I think most of the problem with the rich mixture is the late timming. I'm lost with the spark knock?

 

[BlownFiveLiter]

It more than likely seems rich because of the late timing like you said. It's getting an incomplete burn, but at the same time is detonating from being lean. If you haven't gotten one yet, toss an adjustable fuel pressure regulator on and bump the pressure up. I'd hate to see you detonate and damage your brand new engine. You could always put your 42's on now, and pull out fuel pressure until you install the SC.

 

[stanley514]

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