Jeremy38058

Have a well built 408. 12.1 624 lift cam patriot 62cc stage 3 heads. Have had a couple tuners look at it and at 5100 to 5100 and 5900 it falls hard and sputters. Have changed most everything. Tuned speed density and maf and can't iron out. 49lb injectors and racetek 255 pump. Wide band shows 12.0 to 12.6 when it does it. Br7ef plugs. New coils. Help if you can please. I'll try whatever

BLK02WS6

iTrader: (2)

Have you checked the valve springs? Has it done it since it was put together, or did it run right at any point?

Jeremy38058

They put the "extreme" springs in it. Ya it has done it the whole time. Once it gets past the sputter it gets in the power and pulls super hard. It's almost like a rev limiter feel but that is set at 7000.

BLK02WS6

iTrader: (2)

Would really need to see some logs to determine if it is in the tuning...

Jeremy38058

Checked valve springs and rockers. They look good. Same compression on all cylinders. He has posted tune and the logs on hp tune forum I think.