I have a 90 D150 with a 318 I just bought the truck and noticed when I rev it up high there is a puff off smoke white in color and it will seem to have a slight miss if I let come down to idle, when I drive it for awhile without reving it high it seems to idle fine. I seen another guy had a similar problem with a different engine sorry for a repost of the same type of problem I just dont want to get anything mixed up.

Thanks, Dan

 

I assume it's a high mileage mtr. Just how revved is up high? The puff is probably valve stem seals/worn guides. New seals will help.
The miss is most likely due to a weak valve spring letting a lifter pump up,[valve float]which holds the valve off the seat slightly until the lifter bleeds off back to zero lash. Without of pulling the heads,you could kill two birds and replace the springs and seals at the same time. The springs weren't that stout when new,and roller lifters are relatively heavy.
It's also possible a lifter is collapsing,but since you didn't mention any rattlin' rockers
my money's on the springs.

 

no matter what anyone tells you, dont put any kind of "stop leak" powder or additive or watever into your coolant. Yes, if its a coolant leak (white smoke) it will fix the problem. But probably only for half a month, and then itll come back worse. if you wanna fix it for good fix it right the way lugnuts is saying

 

Thanks for your knowledge, it has 77,000 miles on it, I revved it to the limiter just for a second and thats when the smoke came out the pipe. I just got back from a ride I was just taking it real easy driving normal and I couldn't see any smoke and when I would stop the engine would idle fine. So it's only when I really step on it, So how much would this cost at a local garage? If you have a rough Idea. I just dont want to get the short end of the stick.

Thanks I myself would never put that crap, not really a believer in that stuff.

 

That ain't a rev limiter,well not in the true sense anyhow. Your floating the valves,which can lead to bent/dropped valves,busted vavle springs,bent pushrods,busted rocker arms.
The 318 is done making power by 4500 rpm or less, invest in a tach,set it to no more than 4800rpm.
Problem solved.

 

Well I'm a dummy I will not be doing that anymore. I will have to pick up a tach.

Thanks, Dan