December 1st, 2019, 07:16 PM

I've had an engine sitting on this test stand for about five years now. The engine is a 400 SB, the Injector is a 3680 unit that I was going to put on my Chevy II. I went through it about 10-12 years ago and the thing ran perfectly. About a year or more ago, I started it up one day and the damn thing was running so rich it fouled the plugs out. Out of the clear blue.

Well, the problem has to be in the fuel meter doesn't it? The axle link that was in it was worn so I stuck a brand new one in it when I went through it. Main control diaphragm was new and nothing wrong there. All the vacuum lines were tight. WTF??????

So, I thought about this for a long time. What could make one suddenly go rich? Last summer, I got the idea that the starting fuel enrichment solenoid just might be sticking open. This would let fuel pressure bypass the normal fuel metering system and load the system up with gasoline.. That is the only thing I could think of that would cause this problem. Keeping in mind, this same fuel solenoid stuck closed a few years ago and wouldn't open to let fuel pass until it finally came unstuck one day. When that happened, I had to shoot a shot of starter fluid in the intake to start it.

Anyway, today, I had a chance to check it out. I unhooked the solenoid line from the float bowl and applied vacuum to the solenoid line. It held vacuum. No problem here.

So I put it back together. Got some fresh gasoline and hooked it up to the fuel pump. The thing fired right up, ran right. Not flooding and seemed to run perfectly.

WTF?????????

Anyway, it's now going on the engine in the Chevy II. Been waiting several years for this to happen.

 

Intermittent problems are enough to **** off the Pope.

Good luck.

 

I'm positive that valve was responsible for the over-rich condition. I've seen that, too.

At very low FI system fuel pressure, like idling, only a spring keeps the valve closed against the pressure of the engine-mounted fuel pump. You know this already.

Maybe the last fuel in the unit gummed up that valve such that the spring couldn't force it shut.

Run plenty of fresh fuel through the starting circuit by driving that Chebby II often and that'll clean the valve and prevent a re-occurrence.

That's my theory and I'm stickin' to it.

Jim

 

When I put vacuum on the line, I might have unstuck it and pulled it shut. As soon as I did that, I thought it might have better to blow through the line first to see if the circuit was open?

 

I'd bet that's what happened.


Had you blown air thru the valve (unpowered) from the fuel meter side, you would have overpowered the spring and the valve would have opened. That might make you think the valve has failed, but that isn't necessarily true.

Apply air pressure from the spider side. Doing so will force the valve closed even more tightly than the spring alone. With the valve not powered, there should be no air flow.

 

Mike;

What is a 3680 unit?

 

It was a very special, low volume unit. Released for owners of 300 hp engines that wanted to stick a FI on their engines along with a 151 cam. When you get your cam installed, let me know and I'll fix you up. Your car will run much better.

 

Whoa, tough room.

 

Definitely.

 

Mike, I am not familiar with these units but know basic mechanics. I think your explanation is probably correct. I also think that when you get it installed on the car and it is driven regularly, the issue will not repeat itself. As we all know, these cars like to be driven and hate being put in mothballs. Good luck, and please post pics when you are done.

 

I have been around these Rochester FI's since 1965. I've owned six of these units. Put kits in two of them, changed a couple of cranking signal valves, a main controls diaphragm and used the Kent-Moore monometer on two of them. Contrary to popular belief, these things don't really need a whole lot of attention and so if you're like me and have a little problem every 10-15 years, it makes you scratch your head just a little.

The guys that mess with them all the time like Jim have a real advantage when it comes to odd ball stuff like this.

This unit will go on this car. Same one I had the first one on back in '65.

 

So does the Chevy 2 also get the 400 or just the FI unit?

Does the Chevy 2 need the special block with the clearances area by the oil filter like the early V8 Nova blocks.

 

The Chevy II has a '66 L79 engine in it with the 30-30 cam so it's same as factory 327/375.

I had this 400 in another '65 Chevy II with a 350 Turbo. Pulled like a freight train. No as fast as today's fast cars but plenty for the day and time.

You can use the short oil filter in a regular pass car block and clear the clutch linkage but the Chevy II uses a unique cross shaft ball location in the block. Easily taken care of with a home made piece.

Since you're reading this, did you know a guy named Gary Wade in Brandon, Fla or Valrico, Fla. that worked for FelPro, Speed Pro and others in the auto parts business?

 

Gary Wade does not ring a bell, my history with Fel Pro did not start till we bought them in 1998.
Our engine guy in Florida was Gaines Matheny back then.
Typical in mergers about 80% of the original Fel Pro guys did not survive the merger. I went though 12 mergers over the years, not one was pretty.