So, maybe this is an ignition issue? slowly increase rpm, no knock, goose the throttle, and you get a knock? Is the advance working properly? You say you degreed the cam, but is the crank marker correct? Is the advance working smoothly when goosing the throttle? Is this a TB-IV ignition? Module could be doing funny things, or the pickup. Inspect the cap and rotor?
We test ran with 93 and 1/2 pint outboard oil and got the power back BUT developed a hi rpm under load knock from either 6 or 8 .Raise the idle slowly up to 5 k and you dont hear it, raise it quickly no load and it clanks.As little as 4 deg makes it disappear no load.customer said it happened powering up . Will have a update as soon as I get it to take apart AGAIN.
Nope, don't run alky. not even 10%. I only use pure gasoline. Assuming timing is correct, I've found popping through the intake usually indicates a something going on with the valve train. I got here late and it's time for bed. If you want to chat, my cell is 269-277-2404. I'm on central time. Fred
tech ? do you run alcohol fuel .got a 5.7 that I built and have 10 hrs on it. First time cust tried to power up after a few hours of break-in reported popping and backfiring. no carbon on the plugs or in the engine, cylinder walls appear to be washed clean of oil.all 8 plugs show as dried clay color,definitely not carbon color.
Got a cell?