AMC Fuel Pump

hudsonguy · December 2006

I've followed the recent thread about replacing your stock Hudson fuel pump with one designed for an AMC. I was interested in raising my fuel pressure level, so I recently bought a fuel pump for an '83 AMC 258-6, and something doesn't seem right when I try to bolt it onto my 262 motor.

Comparing the pump with the stock single action Hudson pump, it looks like the end of the arm, or the point that contacts the camshaft is in the same location and orientation relative to the mounting flange, but the arm itself on the AMC pump is arc'ed considerably more, and it feels like it's hitting the top of the access hole thru the block, and preventing the pump from lining up with the mounting holes. It seems the entire pump needs to move up a good 1/2" for the bolts to line up. Of course, depressing the arm gains a little upward movement, but not nearly enough. It feels like I'd be forcing it to try to wrestle those bolts in there.

I've changed plenty of Hudson (Carter) pumps, both single and dual, and they were never difficult at all to install, so I'm a little perplexed. Anyone have any ideas? Or would anyone have any pictures of this arm on their pump?

My replacement pump is a Carter P/N M6737.

Also, some people reported difficulty in bending an outlet line sharp enough to clear the block, but on my pump, I don't see how that could be a problem. The inlet is a pipe 'nipple' that faces forward, so that's easy to connect with a neoprene hose and a clamp. The outlet is a threaded port that faces down, and appears to have ample clearance from everything around it.

What are the outlet orientations of you guys that have done this swap successfully?

As always thanks for the help, and have a Happy New Year!

Doug

Unknown · December 2006

I have an AMC pump on the last engine I put together. The outlet is pointing down. I bent a 180 in a brake line with double flares and works well. I used two of the stacked gaskets because I thought the pump arm bottomed out with only one stack. Seems to work fine.

464Saloon · December 2006

Doug,

I just recently put an AMC pump on my Hornet and had no problems. I was told to just make sure you use the same gasket stack so the depth stay the same. That was all I did. Mine is an Airtex if that is worth anything. Possibly you could have a wrong pump. It woudn't be the first time I have seen a part mispackaged or a parts book wrong.

Unknown · December 2006

Doug,

The 83 AMC 258-6 fuel pump I purchased from Autozone has the inlet and the outlets on the bottom of the pump. That is why the comments in the threads about the difficulty in making a bend in the metal tubing that would be a sharp enough radius to come out of the bottom of the pump yet clear the lip on the bottom of the block. If your pump has the inlet facing you, then this is not the same pump as I purchased from AutoZone. I would definitely check to be sure they did not give you the wrong pump ( sounds like they did ). Also remember you HAVE to use the gasket stacks. I used the original gasket stack ( only one ), but others have used 2 stacks.

BST RGDS

GARY ( happychris )

Unknown · December 2006

I was just thinking that I might be wrong - the inlet was on the front side of the pump, but the outlet was on the bottom of the pump ( thus requiring the 90 degree tubing bend.

BST RGDS

GARY ( happychris )

7XPacemaker · December 2006

I don't think that you have the correct one. I used the one off of my 1981 AMC Concord W/ the 258 Inline six. It came from Advance auto.

hudsonguy · December 2006

I am indeed using the gasket stack as before (just one stack).

I double-checked with my parts guy at Bumper to Bumper, and he verified that the Carter M6737 is supposed to fit '72-'88 AMC six cylinders. Just to be certain, he's going to order another one that I can compare mine to, just in case there is a difference.

Unknown · December 2006

The pumps I have changed I have had to file or grind the gasket pack so the arm has full travel. All the gaskets may not be this way

Unknown · December 2006

Hudson guy, I think the answer to your actual question is getting the pump to fit on the motor so the bolt holes line up. I found on my car I had to rotate the engine until the cam is all the way back so there is the least amount of pressure on the pump arm as you install it. Make sure you use the gasket stack. The amc pump I use from Napa is for a mid 80's amc matador.

mars55 · December 2006

Don't forget you can use a fuel pump from a 70's Pinto with a 2.3L engine.

Unknown · December 2006

mars55 wrote:

Don't forget you can use a fuel pump from a 70's Pinto with a 2.3L engine.

i had one of these pumps in hand before I went with the AMC pump. Reason? the pinto pump has three lines to figure out on the pump, one is obviously an input, and one is the output, the other is, my guess, a return line, which seems like a lot of extra work to figure out what to do with it.

And honestly, this just might be the pumps in stock now, but every pinto pump I handled from the local autoparts houses here had the same line arrangement.

another thing to consider when deciding upon the pinto pump versus the AMC pump, other than the proper number of inlet and outlet lines, is the pinto pump is for a 2.3L (140 cubes), whereas the AMC pump is for a 4.2L (258 cubes), which is closer to 262 cubes or 308 cubes? (hint... the AMC pump)

Keep it all AMC... :cool:

7XPacemaker · December 2006

My dad runs a pinto pump on his, and has done so for about 12 years with no problems. There is no problem with the flow on them. I have an AMC pump on mine. Reason? price. The last time that I checked(quite awhile ago), they wanted more for the Pinto pump than the AMC pump. Also, some stores did not carry the pinto pump in stock. I made the metal lines for both his car and mine. Was one easier to make than the other? I say "no". The degree of difficulty is about equal.

Unknown · December 2006

7XPacemaker wrote:

My dad runs a pinto pump on his, and has done so for about 12 years with no problems. There is no problem with the flow on them. I have an AMC pump on mine. Reason? price. The last time that I checked(quite awhile ago), they wanted more for the Pinto pump than the AMC pump. Also, some stores did not carry the pinto pump in stock. I made the metal lines for both his car and mine. Was one easier to make than the other? I say "no". The degree of difficulty is about equal.

I forgot about the price factor, and availability.

The pinto pump proves to be a harder to find in stock item, and you're right, the price is higher...

[Deleted User] · December 2006

NAPA M6748 works without extra gaskets. All the others I have tried break when you start the engine. I bought one from a "Hudson" parts supplier that was a different number and it simply did not work even after a modified stack.

mars55 · December 2006

OK here is the deal on Pinto fuel pumps. The '74 - '75 2.3 L Pintos use 6445 pumps which have the three connections. The '76 - '80 2.3 L Pintos use 6748 pumps which have only two connections. The avantage of the 6748 pumps is that the outlet comes out the side which means the the fuel line does not have to be bent as much. The disadvantage is that the 6748 pumps cost about three dollars more then a AMC pump per NAPA web site.

[Deleted User] · December 2006

Pump pressure for both pumps is the same - roughly 4 to 6 psi, give or take. It's not very much, but it doesn't take much to flow through a mechanically-driven pump.

7XPacemaker · January 2007

I just checked prices for the heck of it!

___STORE______ AMC______ FORD

advance auto___$18.48____$28.48

___napa_______$20.59____$30.29

Advance had the AMC one in stock locally, but not the pinto pump

Napa was closed. They are a great store, but their hours suck!

mars55 · January 2007

On the Internet, the prices are much closer.

NAPA: AMC $20.59 and $24.19

_____ Pinto $23.49 and $27.69

Rock Auto: AMC $20.99 (Carter) and $21.79 (AC 41249)

________ Pinto $22.79 (Carter)

7XPacemaker · January 2007

I must be doing something wrong, add another one to my computer ignorance.... this is what I found online.........

http://www.napaonline.com/masterpages/NOLMaster.aspx?PageId=430&CatId=4&SubCatId=2

Unknown · January 2007

Soooo...

I guess what we're getting at is the pinto pump is consistently a bit more in price, and harder to find...

hmmm..

choices. choices....

happy new year guys!

hudsonguy · January 2007

Thanks for all the advice and tips. I haven't gotten back to the fuel pump issue yet. Actually, I spent the weekend (at least my Hudson portion of it) tweaking other adjustments, but I'll revisit the fuel pump this week.

This brings to mind another question. Patrick, you mentioned that the pump pressure on both the AMC and Pinto pumps was about 4-6 PSI. Do you know what the pressure rating of the Hudson pump(s) are?

Mine shows about 3-4 PSI at the carb. inlet.

464Saloon · January 2007

Around 4 is typical for stock Hudson. They say 6 is high for the stock carbs but so far I havent had any problems with the two barrell or the Twin H

mars55 · January 2007

The manual gives 3 - 4 lbs for the AC dual action and 3 1/2 - 4 1/2 lbs for the single action Carter.

hudsonguy · January 2007

Well, I stopped by my local parts jobber last night to compare the AMC pump I bought there last week with another one they ordered to see if there were any differences. To review, the pump I bought last week wouldn't quite fit on my 262 motor, and it appeared that the curvature of the arm might be the problem.

Anyway, the new pump they ordered (also Carter M6737) was indeed different than the one I got there a couple of weeks ago. The arm as it exits the body was in a different location (by about 1/4"). The casting itself was much bigger and beefier (although it was the same basic shape) all around. Of course the port locations were identical. But the force required to move the arm on the first pump must have been at least twice the amount required to move it on the new pump. The first pump arm also didn't appear to travel as far.

I haven't put it on the car yet, but I'm pretty confident it will work.

So after all of this, I can certainly conclude that not all AMC fuel pumps are created equal. This leads me to the question of why use it in the first place, when Hudson rebuilt pumps are still readily available (thru the mail, anyway)? Is cost the only motivation people have had to replace their Hudson pump with an AMC pump?

I guess the reason I was considering this was to raise my fuel pressure by a couple of pounds.

7XPacemaker · January 2007

I did it for two reasons. Number one, I was having trouble with the rebuilt Hudson pumps lasting only 2 years before I had to purchase another one. The diaphram gets hairline cracks and fails. The Second reason was availability. I can get an AMC fuel pump from just about ANY parts store chains anywhere, and it will be in stock. Price was not even a consideration to me- It was dependability.

Unknown · January 2007

yup, got to love the dependability, if it stops working, take it back to autozone, get a new one, lifetime warranty. The people that rebuild the hudson pumps don't offer a lifetime warranty.

Price is another factor, heck <$20 for a lifetime pump, versus what is it now $70 for a single, $90 for a dual? and a core?

Drive it far away from home, you can get an AMC pump at any auto parts store, or even carry a spare at that price.

Sell the car? the next owner can easily swap the original back.

Is there one single downside to using the AMC pump?

hudsonguy · January 2007

It turns out my problem fitting this pump was indeed the gasket stack. The center slot for the arm clearance was way small at the top.

While I'm at this stage I was thinking about machining a spacer out of 304 SS to replace the gasket stack. It seems to me I read that this spacer thickness is supposed to be .275". Does anyone know if this is right?

The stack I have that came with the latest gasket set I bought is around .250" thick, but it missing a layer of material. I was planning on making the SS spacer .225" thick, with a .025" gasket on either side of it to bring the total thickness up to .275". Any ideas why this shouldn't work?

Thanks,

Doug

[Deleted User] · January 2007

hudsonguy wrote:

It turns out my problem fitting this pump was indeed the gasket stack. The center slot for the arm clearance was way small at the top.

While I'm at this stage I was thinking about machining a spacer out of 304 SS to replace the gasket stack. It seems to me I read that this spacer thickness is supposed to be .275". Does anyone know if this is right?

The stack I have that came with the latest gasket set I bought is around .250" thick, but it missing a layer of material. I was planning on making the SS spacer .225" thick, with a .025" gasket on either side of it to bring the total thickness up to .275". Any ideas why this shouldn't work?

Thanks,

Doug

Doug This may have no bearing for what you are proceeding to do , but part of the reason for the thick stack of gaskets was to act as an insulation for the fuel pump to help prevent vapor lock. If you use a stainless spacer the heat will have an easy route to travel to create more percolation problems. If you're going to make a spacer block,make it out of something that dosen't conduct heat too well.

hudsonguy · January 2007

Hudzilla wrote:

Doug This may have no bearing for what you are proceeding to do , but part of the reason for the thick stack of gaskets was to act as an insulation for the fuel pump to help prevent vapor lock. If you use a stainless spacer the heat will have an easy route to travel to create more percolation problems. If you're going to make a spacer block,make it out of something that dosen't conduct heat too well.

Hudzilla,

I never even thought of that. Thanks for the advice! I'll have to use some industrial grade plastic like Delrin, or something. It's a simple flat part that can be CNC'd in no time, so maybe I'll try several different materials. Cheers, Doug

7XPacemaker · January 2007

Doug- If you make them, let me know. I'll buy three of them.......

SuperDave · January 2007

I like your idea because it may keep the stack compression from causing loose bolts and subsiquent leaks. If you can find some phenolic material. It works great. We have used it to raise carbs off manifolds for years on stock cars and it takes the heat without distorting or transfere. Some racers call it a "wood" spacer. but then again some aren't too bright LOL.. One source of phenolic blocks might be a used electronic outlet.. one of those surplus places.

Good luck, Davew

AMC Fuel Pump

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