Mechanical Fuel pump eccentric

[Madgyver]

The outside ring of the fuel pump eccentric on the cam gear has a lot of play when installed on the inner ring. It seems excessive than I can remember in my experience building motors.
How much play is too much?

 

[DJs74]

I can't offer a number as far as acceptable clearance / play, but regardless, if you are at the stage of reassembling, I recommend going with a new one piece eccentric which is what I did last year - not necessarily because of play between the two but more because the outer surface where the pump arm rides looked worn to me on mine.

You'll have to use a dowel pin in the camshaft to drive it but I like a one piece over the 2 piece just in general (one less part to wear/fail/deal with)

If your current 2 piece has been around a while to point of wear / play, the stamped tab could also be weak and suspect. because of where its located and the huge PITA involved to change it after its running - just get a new one piece and never give it another thought

DJs74

 

[gr8scott]

X2^, went 1 piece myself
http://www.summitracing.com/parts/fms-m-6287-b302/overview/

 

[savage]

My 74 302 had a one pc on it, just make sure your timing chain gear will work with the one pc fuel pump eccentric. When my engine builder ordered the timing chain ,he said he ordered the wrong one, it was for a two pc fuel pump eccentric, had to get one for a one pc fuel pump eccentric.

 

[broncnaz]

While there are differances in some timing sets. Its not the timing set that matters its the lenght of the dowel pin in the cam. The one piece type use a longer dowel pin.

 

[DirtDonk]

A lot of play is quite normal. I've had brand new ones in my hand that were very sloppy. So evidently I either had a bad new set, or it's just the nature of the beast.

The one-piece type is nice anyway. Used on cop cars and some heavy duty applications (probably Boss engines and the like) it's pretty solid (no pun intended).
But the two-piece design is for what? More quiet? Better economy? Cheaper to make? Dunno, but they used them on a lot of engines. Curious what their original intent was, as I've forgotten.

Paul

 

[DJs74]

A lot of play is quite normal. I've had brand new ones in my hand that were very sloppy. So evidently I either had a bad new set, or it's just the nature of the beast.

The one-piece type is nice anyway. Used on cop cars and some heavy duty applications (probably Boss engines and the like) it's pretty solid (no pun intended).
But the two-piece design is for what? More quiet? Better economy? Cheaper to make? Dunno, but they used them on a lot of engines. Curious what their original intent was, as I've forgotten.

Paul

The 2 piece was pretty much introduced as a means of cost reduction for the manufacturing process of the eccentrics according to my research I did several years ago.

 

[DirtDonk]

Yeah, sounds about right. Figured as much.

Thanks.

Paul

 

[broncodriver99]

The 2 piece was pretty much introduced as a means of cost reduction for the manufacturing process of the eccentrics according to my research I did several years ago.

I would speculate the opposite. The two piece most likely had a slight advantage hence it being present on the earlier models. Likely, later, a bean counter found a way to save Ford a few cents by making a one piece eccentric. Unless, there was a big leap in manufacturing technology which is unlikely as the two piece is nothing more than a smaller one piece eccentric with a second roller wrapped around it. I would venture to say the two piece eccentric exhibits less wear on the eccentric itself as well as the fuel pump actuating arm. Most likely a Ford engineer found through testing and lack of failures that the eccentric and pump arm would survive at an acceptable rate as a one piece unit without the friction reducing outer roller of the two piece design.

I will say with no speculation that the two piece eccentric is and was more expensive to produce.

 

[DirtDonk]

I could see how the thicker material and tooling needed to stamp it, and the pin to retain it, could be more expensive. But I'm not a production/mechanical engineer (or whatever type it would take) and don't know such things. Just seems like it would be the case.

Two pieces would certainly seem more expensive than one (if you don't count the pin as a piece), on some levels though, so can't argue with either concept.

Paul

 

[DJs74]

I would speculate the opposite. The two piece most likely had a slight advantage hence it being present on the earlier models. Likely, later, a bean counter found a way to save Ford a few cents by making a one piece eccentric. Unless, there was a big leap in manufacturing technology which is unlikely as the two piece is nothing more than a smaller one piece eccentric with a second roller wrapped around it. I would venture to say the two piece eccentric exhibits less wear on the eccentric itself as well as the fuel pump actuating arm. Most likely a Ford engineer found through testing and lack of failures that the eccentric and pump arm would survive at an acceptable rate as a one piece unit without the friction reducing outer roller of the two piece design.

I will say with no speculation that the two piece eccentric is and was more expensive to produce.

Respectively, I'll have to disagree.

The one piece eccentric was produced 1962 - 1972 (by Ford), the 2 piece was introduced in 1973. To my knowledge, I could only find a one piece in the world of aftermarket.

Manufacturing one piece versus 2 piece:

The one piece eccentric due to its thickness cannot be stamped - it can be produced either by casting or machining. If done by casting, it will still require some machining on the OD to achieve the surface finish needed (casting finish is fairly rough) and more than likely both holes would be stamped on machined post casting to achieve the size and positioning needed to match the camshaft. If machined only, they would start with a large slug of material and a large percentage of it would be machined away (scrapped), but even the machined away scrap would have to be included in the part cost and the material being used would have to be of high grade to endure the wear in this type application - so, due to expensive material cost, primary casting, machine / stamp as a secondary operation and then finally plating, the one piece (IMO) would be significantly more expensive to produce.

The two piece eccentric would be manufactured from sheet steel stock and stamped (both the inner and outer pieces) - no secondary machining due to the capability of the stamping dies and the outer ring only could be made from the high quality steel and would probably be plated just as the one piece to increase life due to friction / wear. The inner plate could be made from a lesser quality grade of steel due to no contact / no friction.

In my opinion, the conclusion I come up with: even though the 2 piece design has an extra piece, I believe it would be less expensive to manufacture when compared to the one piece eccentric due to: being able to be more diverse in material selection, less secondary operations, less plating applied, less scrap (machining away expensive material).

I believe the two piece eccentric is a better design concerning friction and wear - on the flip side, I believe the one piece design is a more robust / more reliable design because the dowel pin locks the eccentric to the camshaft versus a small stamped tang used on the two piece eccentric.

And as mentioned, I respectfully post this as my opinion and am no way trying to be argumentative - but I do have about 25 years of experience designing similar parts and have worked with hundreds of casting, stamping, machining shops & raw steel suppliers to produce parts in mass production and have tried just about every process when I was under my own strain of reducing costs.


DJs74

 

[bronconut73]

Been running a 1 piece on my Windsor for 25 years. All is well. I too could only find one piece units in the aftermarket. Even a Ford Motorsport brand name at the Power by Ford store was a 1 piece.