The Stovebolt Site Forums The Shop Area Engine Shop 235 Fuel Pump?

I have a '58 235 engine (6 cylinder) in my '49 3100. My '58 Shop Manual shows separate diagrams for a 6-cylinder fuel pump and an 8-cylinder fuel pump. The fuel pump installed on my 6-cylinder engine is clearly the 8-cylinder model.

At the time I purchased the truck, the engine was not running, but the fuel pump was working. I know this because I watched it pump fuel into the glass filter and carburetor. This leaves me with several questions. Is this the original pump for this engine or did somebody replace it? In other words, did Chevrolet start using the 8-cylinder pumps on 6-cylinder engines or did the previous owner install the wrong pump? Are these pumps supposed to be interchangeable? The shop manual says the 8-cylinder pump is a higher capacity pump (which I would expect for a larger engine). Can I use the 8-cylinder pump on my 235, or will it swamp the carburetor and engine with too much fuel? Final question is how do I get this dang pump apart. The shop manual says to compress the main spring slightly and unhook the diaphragm from the rocker shaft. No luck for me.

Norcal49er,

I can't offer anything but a WOW, I had no idea both pumps were so close in design. I looked in the old online shop manuals and other than the actuation arm, they look similar.

I wonder if they are interchangeable without detrimental effects. I'm assuming you are trying to dissemble it to rebuild it. Isn't there a new pump available for your engine at the corner auto parts store.

Stuart

NAPA
Fuel Pump (OE Mechanical Type) w/ Electric Wipers
BSH N68553
$25.99 (new)

About 1/4th the cost of the 8-cylinder mechanical fuel pump (sell your used one on eBay).

A 1954/55 fuel pump will work on that engine and the orientation of the fuel lines would be the same as the original (the 1957 and later 235/261 fuel-pump's fuel lines are in a different orientation). This might not make a difference to you, if your existing fuel lines are already matched up to a 1958 fuel pump.

Thanks. I cleaned and inspected the old one and stuck it back on. If it doesn't work, it's nice to know there's an inexpensive replacement available. Not much to them, though, so I wouldn't be surprised if this one lasts another 60 years.

Norcal -- That's what I thought, too. My '65 GMC still was running the original fuel pump last year when I was in the middle of a 300-mile round trip to a show (in convoy with several other trucks). I thought what the heck, the truck only had (at the time) 8,000 miles on it. Well, after 40-plus years of mostly sitting, the diaphram wasn't able to withstand modern gas and disintegrated causing a series of issues not the least of which was an engine compartment fire. Nothing like seeing a burning fire truck ...

Not trying to scare you. But 25 bucks? Give yourself some cheap insurance and just go ahead and replace it.


John

John is right. This new fuel we get with ethanol & who knows what else in it can eat up an old pump & hoses. Even stalled out a mile from home can be traumatic. I can't imagine a V-8 pump fitting on a 6. Maybe it just looks like it. They have changed the design several times during the years. The replacement doesn't always look like the original. Some had a glass bowl strainer under them.

Yikes! I think I'll buy a new pump. Like Wrenchbender, I got to thinking maybe this IS a new pump and it only looks like the original. My pump has a metal tag on it that is stamped... AC E6 531. Does this mean anything to anybody?