I was rebuilding my 400 and was noticing that I really don't have a vacuum amplifier or the temp switch. I can source one from a JY and rebuilt/repair, but I was wondering if anyone was running an egr from just manifold vacuum successfully. I would think that it might be doable, but on cold start up it might be a hindrance, so at very least maybe a temp valve.

 

It's difficult to help people, when they fail to list all the pertinent info.

There are THREE possible vacuum amplifiers for 1977/79 F100/350 & 1978/79 Bronco 351M/400 as it depends on the applications.

 

Well, I am not too sure of the application either, since the engine, intake and egr are from I believe a 1976 model, the carburetor is from a 1978 manual 351m and the engine is going into a 1978 f250 4x4 400 with tmeyer kit and a mild cam from crower. I guess since it seems all of the vacuum amplifiers are obsolete and not working properly anymore, if I would anticipate operating the egr without the amplifier, maybe using a vacuum temp switch, a delay valve, and seeing if it might work like that.

 

Does the egr need to function for your state?

 

Those 78-79 emissions systems were a nightmare, making 20 year old technology meet federal standards buy keeping it alive on an iron lung. I have slid them past emissions by trimming a chevy starter shim and sticking it under the egr to block it off.

 

No emissions here. I just want to get it working, these trucks did burn less gas with it working.

 

upgrade the intake to a weiland or a edelbrock and do away with the egr. Edelbrock intake does make a adapter to you can use egr if you must but it's not needed in your case. The factory intake on these are heavy and put a ton of unneeded heat directly under the carb because the egr piping is built into the intake. A upgrade will lighten it up, pick up some power and better flow, and lower under hood temp expecially in summer with towing or Ac

 

Thanks for the advice. I am going for a stock thing. I do not want a 4 bbl, I do not want headers, I just want a regular truck. Now, The egr should help mileage, but that I don't know for sure. I can ebay an amplifier and install a new temp port and that should do it for the whole thing.

 

The aftermarket street intakes generally have a heat crossover too. Without carb heat, cooler weather warm up and drivability suffer. But, I also recommend eliminating the egr on those engines. The egr purpose is to introduce exhaust into the combustion as an inert gas to reduce combustion temperatures in order to reduce NOX which is the main element contributing to photo-chemical haze, or smog. You will need to tune for the change. There are probably a few things you can guess on like the timing curve and jetting but it can best be accomplished using a 4 gas analyzer. But once you get it all dialed in (and the change in valve timing with a straight up timing set) that 400 should run like a charm and provide mileage in the 13 mpg neighborhood with good driving habits.

 

Well, I can add it at the rebuild time, and see how it runs, then if it is terrible, I can disable and go from there and monitor the tuning and changes. I have done this experiment on some small block cars, and the mileage improved with a properly functioning egr, and power was unnoticed, due to the carb sucking less air, being the air was replaced with exhaust, meaning that the effective displacement of the engine was reduced while egr was engaged. Thanks and I will totally agree that the aftermarket intakes are a terrible thing if driving in sub zero conditions, truck does not run god or properly without cardboard covering the radiator and warm up takes, well, until you are frozen. I want mine to be like the 79s I remember from a kid. Quiet, smooth, warm, cool, and classic.