car is an 84 z28 with the 5.0. h.o. motor , when i turn it off the car desiels for a couple seconds ,, what causes this to happen? amd what would be the fix?

 

Plugs too hot is all I can really think of. Did you get the recommended plugs for the HO engine?

I guess poor cooling system performance in the heads could help contribute as well.

Other than that, I dunno.

 

There's a few things that will cause that;

-plugs too hot (rare)
-carbon deposits on piston crown/chambers (run top end cleaner/water through engine)
- too much timing (common)
- throttle open too far (very very common)

If your choke is still hanging open, secondaries hanging open, idle is too fast, vacuum leak, etc. Those will all cause it. If you have a 1300RPM idle and you shut it off, that's why...

 

1. run some seaform through engine.
2. double or tripple check your timing.
3. check your plugs (see what they look like) good for diagnosis.