ive got a 420a motor i just upgraded internals put it all together started hard because the plugs had fouled finally starts runs for 5 mins so i rev it to she what she's got get to 4g's and she dies timings on the money, got spark,fuel, im thinking a sensor might be throwing the timing off a hair any ideas?

can you be err, more specificerererer?
(crank -> cam sensors--> ecm --->coolant temp sensor--->IAC sensor-->all controls the engine)

What do the spark plugs look like now after the 4K rev?

they look wet its like i lost spark all of a sudden i dunno wtf happened just died i checked the sensors they seem fine now the spark timing is off not the timing belt the pulley marks are perfect

If they are wet they may not fire.

Are they wet with fuel or oil?

piston rings were gone compression was to low 90,60,100,70 thanx for the help though so im rebuilding the bottom how much hp am i looking to gain with 10.5:1 pistons

Originally posted by 420aman
piston rings were gone compression was to low 90,60,100,70 thanx for the help though so im rebuilding the bottom how much hp am i looking to gain with 10.5:1 pistons

Until you get away from the stock ECU, very little.

Wait... You upgraded the internals, but lost the rings right away? That doesn't sound right. 10.5:1 should net you about 4%, but it's not going to make much difference at all like Mark said. For the NA cars, power is made in the head. I'd go back to a stock bottom end before I'd give up my race head.