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Should I use 1 piece or 2 piece fuel pump eccentric?

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Hi Stangfix, first post from a newb. I'm building a carbureted 5.0 to put in my '65 Mustang. I will use the front cover off the '66 289 that's in the car now. A kit that I bought of engine rebuild "stuff" -- freeze plugs, oil gallery plugs, etc. -- included a two piece eccentric for the fuel pump. I was going to use this, but when I took the front cover off the '66 engine I found a one piece eccentric. I'm thinking, if it's worked for 45 years, why change it now? What do the experts think?
 
The eccentric has to match up the cam gear, there are 2 different center thickness cam gears, you need to use the right eccentric with the right cam gear. I had an engine builder show me both 1pc. eccentric and gear that went with it and 2pc. plus gear that went with it. If you use the wrong ones together you can have contact between the eccentric and the backside of the timing cover. I have seen swirl marks and metal filings in oil and holes grond through the TC. If you use a '66 style 1pc. eccentric match it to a '66 cam gear, etc. Many aftermarket cam gears use 1pc., manuf. usually states it in their instructions.

I think the 2pc. came out >'72? The 2pc. uses a short locating dowel and the 1pc. uses a long one, know which one you're going to use before installing since the dowel can be near impossible to remove (tight fit, smooth surface) once installed which can require you to remove the cam to get it out (ask me how I know...)
Jon
 
FWIW I used a one piece with a two piece gear, but had to mill a small amount off the face.

It sounds like in your situation I would run with the two piece. Make sure you use the correct timing set for the year engine that you have as well.
 
Thanks for the replies. The timing set that's on the engine was the one that the rebuilder installed many years ago. Ford sold this longblock assembly under the tradename, RHO 5.0, which I believe stands for Remanufactured H.O. It has a roller cam. I feel safe to assume that the timing set is correct for an 80's vintage 5.0 H.O. As I recall, I ordered the box of freeze plugs, etc., from Summit Racing, and Summit specified the kit as correct for an 80's 5.0. I will measure the clearance to my '66 front cover first, but it looks like I will go with the two piece.
 
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