engine Missfiring
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New User
Joined: Jul 2005
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engine Missfiring
I have a 1981 for F-150 i have had it for a while and i have just recently started having problems with it missfiring. I put new distributer, rotor, cap, coil, and wire set on it and it still was missing...well i found out that smallblock ford engines have a bad habit of pounding out the valve seats..so i proceeded to tear into it and i found that it isnt a rumor....i had 4 valve seats pounded out of the heads so i got new heads A cam/lifters and timing set and put it all back together and it still is missfiring so i found another carb(holly street dominator) 600cfm carb...and tried it but no success...does anyone have any idea what my problem is with my engine...if so please reply
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Joined: Oct 2004
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From: Winnipeg, Manitoba
Did you do a compression check before replacing the heads? Have you done one after? Compression should be no more than 5lbs difference between highest and lowest, and should be no less than 100psi, usually more in the 130-150 psi bracket for most engines, depending on year and compression ratio.
Replacing the cam and lifters didn't hurt, but did you also replace the push-rods and tourque everything correctly?
Next option is not so much the wires/cap/rotor/dist, but the spark control module(silver or black box on the inner fenderwell)
It can lead to all kinds of grief if it's crapping out, and it can create all kinds of ghosts. Best off to change it out for a good know working unit. Pay particular attention to the wire colors, as Ford changed this part several times over it's years of service. The order of wires is important.
Replacing the cam and lifters didn't hurt, but did you also replace the push-rods and tourque everything correctly?
Next option is not so much the wires/cap/rotor/dist, but the spark control module(silver or black box on the inner fenderwell)
It can lead to all kinds of grief if it's crapping out, and it can create all kinds of ghosts. Best off to change it out for a good know working unit. Pay particular attention to the wire colors, as Ford changed this part several times over it's years of service. The order of wires is important.
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yes i have done a compression check and it tested good...yes i have replaced the pushrods with some new sealed power pushrods and i have tourqued everything down to the propper specifications. The control modual is the only thing i have not replaced but will do. thanks for the reply
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Enjoy FTE....and
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