The Stovebolt Site Forums The Shop Area Engine Shop fuel pump boss 235 vs 283/350

Can anyone confirm that the fuel pump boss on a 235 matches that on a 283, or a 350 (ie., same gasket would seal on both the L6 and V8 engines)? If they are the same then I can buy a cover plate listed as fitting a V8 and not have to make one for my L6 if I go electric fuel pump. Also, a machined cover will probably fit nice and flat onto the boss giving a good seal. Thanks.

Yes, the chrome block off plate for the 283/350 fuel pump should fit the 235.

Thanks.

It fits a 216! I had one on my old one before it broke a hip. Why are you changing from mechanical? I did, huge mistake! I went back to original with newer engine.

Chris

The change is under consideration to prime the carb and avoid dethanol issues. What problems did you experience? What fuel pump did you use? What was the gph and psi rating? What lift capability did the pump provide on the inlet side? Where did you mount the pump? Did you include a filter on the inlet side? What micron rating was the filter? Was there lots of debris/rust in your fuel tank? Was it wired to engage for >3 seconds when the ignition switch was set to ON, and then stay on when set to START? Was it wired to shut off if either rpm or oil pressure drops out? These are all the things I am evaluating. Apparently, others have done this modification and really like it.

James,

Here is what I did. I went to car quest and picked up a fuel pump that was 3-7psi since that was the closest I could find to the original. I mounted it about 2 feet behind the battery on the inside of the frame rail with an inline fuel filter (actually 2 of them). One was connected to the pump and the other was a normal inline filter. This kept the pump within the 18 inches of the tank (ensure you have a clean tank or it really sucks!). I actually tried 2 different options

1. First attempt was to run the negative side through a switch on the backside of the oil guage. This allowed the fuel pump to run whenever the engine was cranking. PRO: if engine died, fuel pump stopped pumping. CON: Since I had a 216 (low pressure), once the engine warmed up the oil pressure dropped below the switch I had in place. This took 3 month of breakdowns and being towed home to figure it out!

2. Second attempt was to run the positive through the ignition switch so that the pump only ran when the switch was in the "ON" position. PRO: very simple and worked well. CON: if you forget to turn the key off or the engine stalls, you keep pumping fuel until you turn physically turn it off. I know that other guys have ran it this way also.

My final plan was that since I blew my engine up and replaced it with another 216, I went back to the stock fuel pump and simplified the system. This eliminated all the issues that I had with both of the 2 options above. My opinion is that if it ain't broke don't fix it! Or as HOTRODLINCOLN would say (paraphrasing), GM invested millions of dollars to design it, why change something that has been working for years.

All in all, I went back to stock and I plan on keeping it that way as long as the lobe on the cam allows me to do so. I learned the hard way with a few things, listen to the other guys or more experienced guys on here, they are smarter than me.

Just my 2 cents, good luck!

Chris

Chris, thanks for the info. I appreciate it. Sorry about your troubles. Glad things are working again. If ever you decide to try again, a circuit is available that works off the tach signal instead of oil pressure to control operation of the electric fuel pump; http://revolutionelectronics.com/Fuel_Pump.html

I use a carter 4070 back by the gas tank. The 4070 is a rotary vane type, so fuel will flow past the pump if it is not operating, runs 4-6 pounds, and does not need a regulator. The carter is used to prime the mechanical pump and the multi carbs. I still run the mechanical pump. When priming, the electric runs right through the mechanical pump. I run the carter through a oil pressure switch and a toggle so that I can use it for starting, then turn it off. Every once in a while, lately it’s been even less, lol, I run the 261 down the strip so I turn it on for the racing. The thing with the carter 4070 is that you want to mount it with their rubber mounting isolators, and you must run a fuel filter before the pump. The carter uses the fuel to cool the pump internally so if it injests a lot of junk from the tank, jams the pump up.

If anyone is so interested, My mechanical pump is modified. I had about twenty old pumps in my parts box. Found one with a top that used 3/4 valves as opposed to the more common 1/2 valves and had a very thick casting. I put it on a Bridgeport and drilled the in and out fittings to accommodate 3/8 fuel lines. You can’t just drill it out though. You need a thick casting, and you drill using the top of the threads for the 5/16 lines as the top for the 3/8 lines. In other words you are lowering the hole slightly in the casting so you don’t break through the top part where the casting is thinner.

I am keeping my truck as simple as possible. It will never break any land speed records with it, so I am just going to enjoy it. If I ever change to a bigger engine then I might go back. No need to change what I have.