i have an 84 datsun pick up 4x4 that i just bought.when i got it the truck was all taken appart because it had a bad head gasket.the head work was done and i put it all together and the truck runs great, but it backfires after it worms up. i was wondering if anybody has suggestions on what it may be. i;m not too familiar with these trucks but i'm really diggin this little truck.

could be a lot of things from exhaust leaks to timing issues... any specific details about the backfiring that might helps us diagnose?

thanks for the reply. i have timed it and messed with the idle a little bit. and the exaust seems to be okay. the truck is missing the catallitic converter but my friend that used to own the truck was driving it like that and it was not back fireing then. the truck blew a head gasket, and he had the head worked on and he put most of the truck together before he sold it me.and i finished puting it together. i made sure all the vacum hoses went on right and the distributor timing, timing chain and i also gaped the valve lash. the truck runs and drives great but when it worms up and you rev it up to about 3000 rpms or more it backfires when you let go the gas. i;m looking for some suggestions before i start working on it again. what else do you think could be causing this problem?

so it only doing it when you let off the gas?

if so, that's not really an issue. that happens a lot with these trucks if you're not running a cat. the reason it does it is because the fuel mixture is a little on the rich side, and when you let go of the gas it 'after fires' the excess fuel

my 84 does the same thing after i put the after market exhaust in it but it does seem to hurt any thing .