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Sat Jan 25, 2025 8:19 pm

esde wrote: Here are two I have that are both zwitter 25hp, not sure why one has the odd adapter fitting.

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I wonder if that adapter fitting is a thread insert. Some inserts have thick shoulders on them. I see lots of these 25/36hp pumps with damaged threads from cross threading the screw in fuel lines.

Fri Feb 28, 2025 11:39 am

gypsydoctor wrote:

Could this "flat top" fuel pump be from a Porsche? I got it from a box of parts from my dad, who had a 1958 Porsche engine. '

That is a 356 fuel pump and adapter, 8mm inlet like the early VW was used on Porsche thruout production.. I believe yours is from an early 3pc case, 1955 thru whenever the newer pump was introduced. The earlier 2pc case used the same pump but the 3pc. case required the adapter you've pictured.

Wed Apr 02, 2025 2:23 pm

Dumb question: what is the purpose of the screw on the lower pump body?

Wed Apr 02, 2025 5:19 pm

thom wrote: Dumb question: what is the purpose of the screw on the lower pump body?

The 25HP pumps and the 1954 36hp pump had the screw/plug that had a stud on it that the rocker spring slid onto. The other side of the spring was held against the rocker. In 1955, the lower casting was the same but not drilled out or threaded, that post or stud was built into the casting that the spring sat against from then on out.

Thu Apr 03, 2025 11:14 am

So is it supposed to be a drain (as I've heard it referred to) or just a way to remove the spring? I was going through my stash of cores to rebuild a pump for my deluxe, and found this one.

wcfvw69 wrote: thom wrote: Dumb question: what is the purpose of the screw on the lower pump body?

The 25HP pumps and the 1954 36hp pump had the screw/plug that had a stud on it that the rocker spring slid onto. The other side of the spring was held against the rocker. In 1955, the lower casting was the same but not drilled out or threaded, that post or stud was built into the casting that the spring sat against from then on out.

Thu Apr 03, 2025 3:26 pm

thom wrote: So is it supposed to be a drain (as I've heard it referred to) or just a way to remove the spring? I was going through my stash of cores to rebuild a pump for my deluxe, and found this one.

Nope, not a drain but a post for one side of the rocker spring to secure to. If you look at the backside of the pump mounting flange, it has an indention at the lower side. So, when the pump is bolted up, there is a small gap between the gaskets where fuel could drain out there if the diaphargms failed and leaked gas to the bottom of the pump.