huge misfire Numbers on cyl 8 . 6.4 based 426 with magnuson 2300

[unicornpower]

I have done a lot of searching on here and found a couple threads and I am still confused.

This is a 2019 Scatpack 6.4 based 426 with a hellcat cam. The car runs great with a couple things needing tightened up, but the misfires are driving me nuts.

Raised the misfire detection to 6200 but all individual cylinder codes are still on. Normal driving is fine, but it racks up 40-50 misfires under a few second WOT pull.

The car goes into limp mode with a P0308

Plugs all look the same, new injectors and its only cylinder 8

anyone?

[Senditnyc]

Compression test?

[edcmat-l1]

Cylinder 8 is one of the first ones to get hurt. Need to do a compression and leakdown test.

[dangrebel]

this is common on Whipple 6.4's, ive got 3 running around like this. throw a new plug in it, make one pull compare to other cylinders.

[Bullet300]

First thing I do with cylinder misfire is change the coil to another location. This is the easiest thing to do and rules out a coil issue.

[unicornpower]

this is common on Whipple 6.4's, ive got 3 running around like this. throw a new plug in it, make one pull compare to other cylinders.

I keep hearing this is common from some guys. I have not had this issue on anything I have touched so far thank god.

[unicornpower]

He has done coils, plugs, injectors all with no difference.

going to comp, leak and scope soon. Thanks so far folks

[veeefour]

Any power adder to 6.4 will pop misfire codes, monitor is not really ready for added 200hp with boost.

Nothing you can really do about it besides disabling the monitor...that is of course IF the engine is healthy.

[dodgeboy]

My 5.7L Stage 2 whipple 2.9L pops a P0308 every spring. Move coil packs, scope, compression test, clear it and then after I get fresh fuel in it it is fine. I added seafoam and octane boost to the tank this year before parking it. I'll see if that makes a difference because the last fill up is usually winter blend.

[vndetta79]

What plug gap are you running? My 6.4 runs 9.7:1 pistons and 16psi with no misfire issues. I run my plugs @ 0.028" gap. Still running the original coils.

[unicornpower]

What plug gap are you running? My 6.4 runs 9.7:1 pistons and 16psi with no misfire issues. I run my plugs @ 0.028" gap. Still running the original coils.

Actually running .028

[veeefour]

What plug gap are you running? My 6.4 runs 9.7:1 pistons and 16psi with no misfire issues. I run my plugs @ 0.028" gap. Still running the original coils.

Well low com pistons with bigger ring gap makes a difference...of a lot. "Stalk seelt" pistons are not really designed for boost.

Stock pistons you might have some mini micro detonations...very minor and that is fine but monitor will be triggered.