fuel pump eccentric - Pontiac GTO Forum
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post #1 of 12 (permalink) Old 01-29-2006, 06:22 PM Thread Starter
 
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fuel pump eccentric

How loose/free should the fuel pump eccentric have? It seems to have a lot of slop.
Just put in a new cam, didn't notice the play before, it could have been there.
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post #2 of 12 (permalink) Old 02-03-2006, 08:12 AM
 
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They're pretty sloppy... they have nice slip fit over the inner ring, but there's a lot of end play in them, to the point that they seem to rattle around on the inner sleeve.
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post #3 of 12 (permalink) Old 10-13-2013, 06:58 PM
 
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They're pretty sloppy... they have nice slip fit over the inner ring, but there's a lot of end play in them, to the point that they seem to rattle around on the inner sleeve.
Can anyone verify this? I seem to have alot of play in mine as well

You outta see her on a road course, or a quarter mile
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post #4 of 12 (permalink) Old 10-13-2013, 08:52 PM
 
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Also with the thrust plate installed and torqued down the cam gear pushes against it all the way right? I kno the cam is in right as it spins freely and is perfectly lined up with the cam bearings. But why all that slop in the essentric?

You outta see her on a road course, or a quarter mile
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post #5 of 12 (permalink) Old 10-13-2013, 09:39 PM
 
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There's a fair amount of play in the eccentric. It's hard to know what is too much. I replaced mine a year or so ago because it was noisy. When I put the new one on, it didn't feel perceptibly different than the one I replaced, but my noise went away.

When the only tool in your toolbox is a hammer, you tend to see every problem as a nail.
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post #6 of 12 (permalink) Old 10-14-2013, 08:28 AM
 
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There's a fair amount of play in the eccentric. It's hard to know what is too much. I replaced mine a year or so ago because it was noisy. When I put the new one on, it didn't feel perceptibly different than the one I replaced, but my noise went away.
Thanks for the reply Chuck. The one i have was not noisy before with the old cam. Should I just run it? Id say it moves about an 3/8 of an inch back and forth, maybe a lil more. Were you running a mech pump on it or no? My fear is if it is that loose, will it create metal shavings in time? From what im reading and seeing online the slop is sort of common.

You outta see her on a road course, or a quarter mile
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post #7 of 12 (permalink) Old 10-14-2013, 09:26 AM
 
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That's a tough one. If you really have 3/8" of end play that sounds like an awful lot. Check to make sure everything is installed correctly.

Mine was pretty loose end to end AND it made an odd rattling sound at idle, so I replaced it. As I said, the new one didn't seem much different, but I figure that once everything is installed, the pump arm tends to make it run where it should.

Now, the new one from Ame's Performance was something like $40, so if it's peace of mind you're after, I'd say replace it. You may not notice much difference in end play, but you'll know it's new and that it's right. Plus if you try to use the old one and you end up with a problem, it's a pain in the ass to go back after it. The downside now is that you're ready to go back together and you'll have to wait for your part unless it's available locally (which it probably is and maybe cheaper).

If you can get it locally, get it from Napa or some other reputable retailer, not Autozone, O'Reilley's, etc.

When the only tool in your toolbox is a hammer, you tend to see every problem as a nail.
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post #8 of 12 (permalink) Old 10-14-2013, 12:06 PM
 
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A new one is probably the way to go but im afraid its going to look exactly the same and do the same thing. I used a brand new thrust plate on this motor. If the cam was out of the block more it would be fine but thats not the issue as my cam is lined up in the bearings about perfectly. My movement is block to timing cover not side to side.

You outta see her on a road course, or a quarter mile
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post #9 of 12 (permalink) Old 10-14-2013, 02:50 PM
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When the cam gear is installed correctly, the end of the cam will actually stick OUT of the gear face a little bit. The inner race of the pump eccesntric uses that part of the cam to center itself. There are two versions of the pump eccentric assembly. They differ from each other by the deal of the tang that keys it to the cam. One version has a larger tang that fits into a hole on the cam gear, the other has a 'nub' on the inner shoulder that fits into the keyway on the gear. I like the one with the larger tang better, myself. If you look at the back side of the inner race you'll see it has a shoulder on it. This shoulder seats against the cam gear. When you tighten the bolt that holds it on, that shoulder holds the cam gear while tightening the bolt pulls the cam through the center of the eccentric until it's stopped by the washer under the bolt.

Also, there's a bronze bushing that goes between the cam gear and the retainer plate. If that's not there, there'll be too much end play as well.

If not installed properly, it results in both too much cam end-play and allows the lifters to ride on the edges of the cam lobes - and "bad things" often ensue.

In Jim Hand's book, there's an explanation and a photo of how it's supposed to look.

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post #10 of 12 (permalink) Old 10-15-2013, 08:27 AM
 
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It was my own paranoia at fault. After speaking to Butler and KRE they both said about .050-.080 play is fine for the eccentric. I had .064 last night so I bolted it together. The bronze bushing you speak of between the cam gear and thrust plate, this is news to me sadly.. Where can I locate one or see a pic? Oddly enough every thing lines up perfectly with a new GM thrust plate and Comp timing gear. Is it built into the cam timing gear?

You outta see her on a road course, or a quarter mile
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