If I remove the e.g.r. carb plate and hardware,hoses (the whole system) from my 1978 351m/400 engine will it run ok?

 

EGR reduces combustion temperature to allow an excessively lean fuel/air mixture without pinging. At a minimum, you will need to re-jet the carb to enrich the fuel/air mixture to compensate for removing the EGR.

I would suggest keeping the EGR plate, which acts as a regular carb spacer when the EGR valve is disabled. The spacer effectively increases the plenum volume of the intake manifold, improving mid-range power.

If any other systems are interconnected with the EGR control system, you have to carefully isolate those systems to prevent other problems. The easiest way to disable EGR is to disconnect the vacuum hose from the EGR valve diaphragm (just behind the carb) and plug off that vacuum hose so it doesn't become a vacuum leak.

 

I agree you may need to adjust the carb and distributor. I wouldn't keep the plate however. I would replace it with a solid spacer if you want one. The originals tend to burn out internally from the hot exhaust gasses that pass through it Especially the ones made of aluminum. I've seen more problems with the plates than with the valve. Sort of erratic vacuum leak symptoms.

 

If you go without your egr plate put a 1" Phenolic spacer.It's like a plastic it dosen't transmit heat to your carb like an aluminum plate will.

 

After removing e.g.r. system-- I want a holly 650-750.
Will that work?

 

I have a 400 in an '82 F150 with EGR disconnected, and plate still in place. Use a high quality silicone black sealer on the bottom of plate.

My engine will ping under light part throttle, especially on a hill. If I wind the gears out enough before upshifting, it won't ping. If I put it to the boards from a dead stop and go through 2-3-4 gears (it's a 4-speed), it won't ping and runs really good, better than some so-called "musclecars" I've been in

So you will experience a ping at part throttle, no doubt about it. By the end of the 1970's the EGR was kind of designed into the sytem. IMO it's still worth removing it. There is not a WOT lean spot, but rather an off-idle lean spot when lugging the gears a bit, or climbing a steep grade. The fix would be to either drill the jets out, change them, or use a metering rod with a smaller diameter at the off-idle area of the rod. The idle and WOT metering is fine.

hope this helps. FWIW on the modern computer spark controlled cars, the ECU just automatically retards the timing, as it senses the ping with a knock sensor. A retrofit kit would be great- for the older engines like we have.

 

For a street engine daily driver:

Max carb size in CFM = 1.5 X engine displacement in cubic inches.

351 x 1.5 = 525 CFM
400 x 1.5 = 600 CFM

If you are mud bogging at 5-6000 RPM you can go higher. Too big a carb will hurt low end performance and fuel mileage.

 

My truck has the stock Autolite 2-barrel on it. But I have used the Edelbrock 750 and 800 carbs on other V-8's, let me say that it was a big eye opener. THOSE ARE GREAT CARBS for the money, and the mileage and fuel metering are a mighty S. better than an out of box Holley. The E-carb has externally removeable main metering rods and springs, so you can tune it very easily without taking the top off or removing fuel bowls. These parts change out right from the top and lock in with 1 screw. It's a great design. We put an 800 E on a Pontiac 400 with a bigger hyd. cam, it loved it. They also come with electric chokes that work like gangbusters, just hook up one 12v hot wire from the ignition. This is a big plus when using aftermart alum intakes.