After doing alot of backbreaking work, I finally replaced the intake manifold on my 94' 351W (broken stud on corner was drilled out and repaired), fired up the motor and IMMEDIATELY there was a knock/loud tap. No delay, it was there as soon as it fired up. The truck purred like a kitten when it was parked last. I pulled the upper/lower intakes and valve covers, but was meticulously clean about it so I'm not sure what could have happened here.

The truck has been sitting for over a month while I've been working on it, and part of my thought that it was a stuck lifter but once it warmed up it still did not go away. I pulled off the drivebelt to ensure that it was not a function of one of the accessories.

Do you have any way of helping isolate the noise without opening the motor back up? I rotated the crank manually and can't feel anything out of the ordinary. Right now all I can think of is to run a compression test to see if anything is out of whack (stuck valve, etc.).

Oh, and I'm not missing any tools. :-)

 

hook up a mechanical oil pressure gauge to see how much oil pressure you have. the stock gauges suck and are not accurate at all.

 

I had to follow up on this....mainly b/c I'm an idiot. One of the problems I encountered while fixing the truck was that the starter cable was in bad shape. Rather than do the smart thing and fix one problem at a time, I decided to do this as well. I broke off the copper stud trying to get the cable off the starter, then noticed the starter was missing a bolt.

The missing bolt was actually broken, and I had to cut the flexplate in order to get in there with a drill to drill and tap it. What I failed to realize was the relationship of the starter to the flywheel and how critical it is. The starter was reattached but misaligned since the flexplate wasn't doing it's job anymore some part of the flywheel was hitting the nose cone of the starter once every revolution.

Realigning the starter appears to have put an end to this saga...but even if your tempted in the future, don't cut the flexplate!

 

WHOA! Cutting the flexplate will throw the rotating assembly out of balance.