Originally Posted by fast68plymouth
Awesome pic!! up

Is the point where the engine starts to have the misfire issue the highest rpm on track to that point?
And what is the rpm where it starts acting up?

I’m just wondering if it’s possibly a valvetrain issue, and the fluctuating fuel pressure is just a by product of the EFI chasing the fuel curve around after the valvetrain gets unhappy.

What I think/recall you had for springs and RR seemed to me like it might be on the edge for high rpm control considering the weight of the lifters.

To test it, you would see if you could duplicate the misfire in 2nd gear, and if it does....... see if shifting into 3rd made the misfire go away.

Just spitballing....... since the fuel system work has to this point been unsuccessful.


It might have a spring issue also, BUT on the data log the fuel pressure problem starts right away, I can feel it laying down & then pick back up through the intire run, it starts banging in high gear at about 5500 rpm, but it will pull 6300 rpm in 1st & second without banging BUT I can feel it surging as the pressure comes & goes in 1st & second , that said I do think my springs are going away like you said.

Last edited by csk; 01/24/22 12:38 PM.
1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392 Stock 11.79 @ 114.5