87 2.8 with loud knock

hello all , i have an 87 all original blazer w/2.8 4x4 which has developed a loud knocking at start up, then 10-15 seconds later tones down to a sort of intermiten tapping or clanking. i have searched and read lots of post.but none match as mine doesnt leak oil,burn oil has good oil pressure. 141,000 miles . the only one that came close said the cam shaft was toast, any ideas or sugestions.. i have started her without serp belt and still get the same noise..

Sorry to say that your crank journals are probably toast.
It's the comon problem with 2.8L motors, which are widely known as one of Chevy's worst motors.

There is a plus side to this problem.

A 3.4L from a Comaro is a direct bolt in. You'll need your oil pan, oil pump pckup and you might need your flex plate or fly wheel

Oh, Welcome to Automotive Forums

exact same year camaro?? even with a 4x4??

They're the same engine block, just the updated version. So everything from your motor will fit, including headers if you have them

Here's some links to look into
http://users.spec.net/home/emxjc/
http://www.off-road.com/jeep/cherokee/xjtech/engine/28-34swap.html

I'm thinking of doing the swap this summer even though my 2.8L is still good, just to help turn the 31" tires that I'll be installing soon (along with a 3" body lift to make room for the tires)

From your description of the knock , it could also be a piston pin worn . Either the heat is expanding the metal and queiting it down or the oil is getting to it after the time . Might not be "All original much longer"
By chance , have you tryed octane booster to see if your fuel is too low rated ? Rob
OH , and Welcome aboard !!!:2cents: