Chris's Vapor Lock

["Dave Read"<DSREAD@domain.elided>]

Hi Chris;

I recommend you replace your fuel pump with a new mechanical pump ($45
Napa).  Here's why.

I have a 70 1200 4x4 PU with 30,000 miles.  I got it cheap cause the engine
(304) has a knock.  Previous owner replaced the main bearings, still had a
knock.  Local garage owner tells me "maybe its your fuel pump".  I have a
used IH mechanical pump lying around, so I R&R my fuel pump.  Guess what?
The knock is still there.  Guess what else?  My trunk now dies when hot at
idle.  It won't restart until it cools off (sound familiar).  I go to Napa
and buy a new mechanical fuel pump.  I install the new NAPA pump.  Still
have the engine knock, but no more vapor lock.

I suspect my parts bin pump was marginal and not pressurizing the fuel
enough to keep it from boiling.  Modern EFI cars hardly ever vapor lock,
they pressurize the fuel to 30 pounds or more.  A good mechanical pump is
around 7 pounds.  My parts bin pump might have been less than 2 pounds.

Anyone have any ideas about my engine knock?  My current theory is bad
wrist pin.

Dave Read