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Old Fuel Pump vs New One
Posted by: Frog ()
Date: September 09, 2018 05:37PM

I've read "Mechanical Fuel Pump Observations..." by kenzen, Jim Brandberg, Wagon Master, et al., and I've decided to reinstall my original fuel pump given all the bad press new ones received.

If my old pump fails, I have the option of installing the new one I got from Clark's. I have a concern and wouldn't know how to approach it if I need to install the new one. The pump rod in the new one is prominently longer than the original in my '64 95-hp pump. Should I be bothered by that difference in length?

Thank you.

Frog

Rob Lane
Clayton, in the Northeast Georgia Mountains.
1964 500 Coupe
Purchased by me in April of 1964.

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Re: Old Fuel Pump vs New One
Posted by: irfgt ()
Date: September 09, 2018 05:41PM

Depending on how much clearance the factory built in, it could cause undue stress on the diaphragm and rapid failure would result.

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Re: Old Fuel Pump vs New One
Posted by: Frog ()
Date: September 09, 2018 05:56PM

That makes sense to me. I'm wondering if I received a pump for a different year.

I'd forgotten to ask another question while I was on this subject:

I'm getting ready to install a new distributor. Do I need to lube up the gears on the shaft.

Thank you.

Frog

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Re: Old Fuel Pump vs New One
Posted by: MattNall ()
Date: September 09, 2018 06:00PM

Never hurts to pre lube!

I'd cut that shaft down.... it doesn't wear...





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
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..............................110-PG.................................................Webered-Turbo

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Re: Old Fuel Pump vs New One
Posted by: joelsplace ()
Date: September 09, 2018 11:13PM

I wouldn't automatically assume the old one is correct. There is a spec for the amount it sticks out. I think it's in the Clark's catalog.

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Re: Old Fuel Pump vs New One
Posted by: JimBrandberg ()
Date: September 10, 2018 04:07AM

The measurement from the center of the locating hole to the bottom of the pushrod is the critical dimension, the length of the housing bottom is irrelevant.
I thought the the illustration in Clarks catalog was to distinguish a 60-61 pump from a 62-69.
I ground the pushrod down once in an effort to reduce the pressure and it didn't work out for me.
I would think you should just leave it alone but would be glad to read different opinions.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Old Fuel Pump vs New One
Posted by: Frog ()
Date: September 10, 2018 04:12AM

Thanks for the replies.

MattNall, I think you're saying to disassemble the new fuel pump and cut the shaft down to the length of the older one?????

Regarding "joelsplace," this fuel pump is correct because it came with the car when I bought it half a century ago, and it was functioning as designed just before I decided to rebuild the engine.

Frog

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Re: Old Fuel Pump vs New One
Posted by: Bogey72 ()
Date: September 10, 2018 04:41AM

Just a thought... the pictures may be tricking my eyes... From the second picture in your post, it almost looks like the pump shaft length (area from the O-ring down to the rod) is longer on the old one. If so, that would make it just appear like the old rod is shorter. Maybe measure from the hold-down hole to the tip of the rod and compare to confirm the new is definitely longer?

Ed Conto
Saratoga Springs, NY
1965 Monza Convertible, PG
Owner since August 2013

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Re: Old Fuel Pump vs New One
Posted by: GWLee ()
Date: September 10, 2018 06:55AM

Helpfully this will help you.

It seems by your pics you have a 60- 61 pump and a 62-64 pump.

I can't tell what rod your using because of the spring. But read the warning on the pic I sent to make sure you use the correct rod for your pump. HTH

Lee Adkins

A Cave Man car
1960 2dr Coupe with pg
Color Tasco Turq.
With Ermine white top.

Catlettsburg,
In the Beautiful state of
North/East KY!

Not the best pic, but the only I had from then, 1997!

2016!

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Re: Old Fuel Pump vs New One
Posted by: Frog ()
Date: September 10, 2018 01:19PM

May be I can put this to rest.

Using a Husky digital thingy, I measured the protrusion distance of the pump stem for each of the pumps pictured. Clark’s specified protrusion distance for the ’62 to ’69 is 1/8 to 7/32 of an inch. Here’s what I came up with:

My measurement on the old pump is 9/64, which is .016” above minimum distance (within specs; no problem).

My measurement on the new pump is 15/64, which is .016” above maximum distance (outside of specs; problem?).

Iowa Corvair Enthusiasts (ICE), conducted an analysis and measured minimum and maximum distances among original and replacement pumps. ICE’s conclusion is: “The fuel pump stems on all four replacement pumps were too long. The correct length is 1/8 – 7/32” according to Clark’s. The replacements were .046” too long, stretching the lower diaphragm beyond its limits when installed.”

Now, taking ICE’s .046” over spec and comparing it to my .016”, would you learned experts agree—or not—that the .016” outside-of-spec would not be a problem if I installed my new pump?

While I was at it, I decided to measure my pump rod. According to Clark’s, this one should be 3 13/16” long. Mine is right on.

For Ed Conto, I agree that they seem to be slightly different in the images, but I carefully measured them and they're the same length.

Thank you.

Frog

Rob Lane
Clayton, in the Northeast Georgia Mountains.
1964 500 Coupe
Purchased by me in April of 1964.

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Re: Old Fuel Pump vs New One
Posted by: joelsplace ()
Date: September 10, 2018 01:59PM

As Jim pointed out the critical dimension is from tip to center of the locating hole. You could have one that stuck out more but was functionally shorter if the locating hole was in a different location.

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Re: Old Fuel Pump vs New One
Posted by: Frog ()
Date: September 10, 2018 03:57PM

OK, Joel and Jim Brandberg,

I don't understand the term: " . . . measurement from the center of the locating hole to the bottom of the pushrod is the critical dimension."

Please enlighten me.

Thank you.

Frog

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Re: Old Fuel Pump vs New One
Posted by: TerribleTed ()
Date: September 10, 2018 04:11PM

Measure from the center of the hole in the side of the pump base...where the point of the mounting bolt goes. This point is a constant once the pump is installed. The distance from this point to the end of the shaft is the only way to measure the functional difference between the 2 pumps.

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Re: Old Fuel Pump vs New One
Posted by: Frog ()
Date: September 11, 2018 01:02PM

Ted, what you said about the centering hole and the end of the shaft makes sense. I measured them and the result is that the shaft of the new pump is .087" longer. Is that difference any concern?

Thank you.

Frog

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Re: Old Fuel Pump vs New One
Posted by: joelsplace ()
Date: September 11, 2018 01:28PM

This is cool. Another thing to blueprint on pumps!
Someone needs to cut holes in a stock pump cover to make it easy to measure the pump motion and then adjust the rod to get the pump stroke centered when the diaphragm is flat for best life.

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