I have a 88 351 that has what's called a fuel pump eccentric on the upper timing chain sprocket. What is does this thing do?

 

The fuel pump eccentric pushes the arm up and down on a mechanical fuel pump . Some engines were built for use with mechanical fuel pumps but never used with them thus having this eccentric in them and not needed.
If yours has EFI you don't need an eccentric but if you remove it you you have to replace it with a thick washer .

 

Thanks for the info. Does the wash need to be exact? or close to the same thickness will do?

 

So long as the amount of end play allowed by specifications is not exceeded you can use whatever will fit.

 

I don't see how that would effect end play, please correct me if I'm wrong, but based off the Chilton. if its out of spec for end play to replace the thrust plate. The end play spec in my Chilton states 0.0010 - 0.0070, is this correct for an 88 351W?

 

If it won't then disregard my post. I honestly, haven't dealt with this issue. My thought was simply that if you were replacing something of a given thickness with something OTHER than that exact part that the question of end play could be an issue.

 

Its all good, it actully made me read the manual. Looking at things from all angels is always a good thing. I wouldn't have thought of checking the end play and had just replaced the timing chain. I plan on checking the end play and replace whats needed.

 

Something needs to keep the camshaft from moving out of position. It might be that the fuel pump eccentric prevents it from moving out of position by rubbing on the timing chain cover.

Yes, read the directions (Service Manual is best direction), from beginning to end, understand the directions, then follow the directions.

Or do what I do, do it twice, sometimes thrice.

 

That's what the thrust plate is for.It Holds the cam it place

If the eccentic touched the timing chain cover, it would chew right through it and metal shaving would get into the oil.

 

Right, because any metal to metal contact in a motor results in metal shavings.