i own a 1980 bronco. I get 10mpg around town. i really need to boost this number up some since im not rich. i know that you can block off your egr vavle and somehow block the smog pump. i know where my egr vavle is and i would like to block these off since it will be a free way of getting better mpg. however, i need to be able to hook it all back up when smog testing come around (not for another year and a half could somebody tell me how to preform this. im bout to just start monkeyin with it but i decided to wait to try that. lol.
thank you for your time.
jason

 

Some people might tell you not to do this, but it just hurts the performace of the engine, and you get better mpg when you do so. You can take off the line and stop it up with a screw or just point it straight down, and plug it all back up when you need too.
Trust me take it easy in low gears and you'll see a difference, and when you need to go 1/2 or so and your not in a rush, don't go 60 mpg just to go the 1/2 mile accelerate slow and don't go faster than you need to.

 

removing or blocking that stuff wont gain you any mpg. the best thing you can do is keep the motor running in tip top shape with a good tune up, fuel filter change, keeping your tires inflated properly and going easy on the skinny pedal. you might look into a carb rebuild as well if its been awhile.

 

I'm yanking and plugging all the smog crap on a '83 bronco with a smogged 351w and will keep you up to date if you pm me. I will also be putting a properly built 400 in it this winter sometime as that will increase mpg and performance- alot.

 

a 351w properly tuned will get better mpg then any 351m/400 ever will. thats the wrong motor to try and squeeze mpg out of.

good luck though

 

wrong answer Kemical...folks doing it often...with the right build.

 

its ok, spend your money. get it done and let us know how it goes. if that was true everyone would be doing it.

 

I'm with Kem all the way on this one. If its so cost effective to build a non-smog engine and drop it into the vehicle, the engine rebuilding industry would be BOOMING with the soaring cost of fuel. The "emissions" devices on the vehicle do absoultely NOTHING to reduce the power output of the engine. The average smog pump pulls less than .02 HP from the engine and its the ONLY "emissions" device that puts ANY drag on the engine. The rest is merely plumbing and the redirection of the same air, gasoline and fumes that every engine already breathes anyway. Check the very first thread in the exhaust forum (I thinks its still there). The moderators and admin. thought enough of it to move it from here (Big Bronco Forum) and put a Read First: in front of it. The belief that smog devices ruin performance or reduce it stems from not understanding how they function. Just try to get decent fuel mileage from an EEC-driven engine that is getting incorrect information from just the O2 sensor. It WILL NOT happen. Plugging/removing the Thermactor fresh air (smog) pump will do this immediately. Ok, no more soapbox, I'm done but do check out the Exhaust forum on this topic.

 

I'm with kem and greystreak. Not trying too start a fight but thank about this. A 351/400m is heavy and we all know that more weight means it takes more gas too move. A 351w weighs less and can put out about the same amount of power, do that math.

 

I can tell you from experience in the past 3 weeks since I put headers on and disabled the thermactor and EGR My gas mileage has dropped considerably. I did gain some power but at the result of 2-4 MPG loss! Unfortunatly When I put the Plug in the hole of the EGR I didn't put antisieze on and I cannot get it off at this time. But I do plan on hooking everything back up to regain the 4 MPG. I have heard of poeple having no problems and actually improvements but I'm not one of them. So to each his own- Good Luck!-Bob

 

Just wondering, because I'm not sure what roger dowty, said. Did he say he has a rebuilt 400 and wanted to swap that for a 351W, b/c if that's the cast he would not have to use money to rebuild the 351W and just have more power and better MPGs with a rebuilt 400 ready to go,than a none built 351W.

But if he said the 400 gets better mpgs than a 351W, this isn't true, my 400 doesn't get much better than a 460. And he wants to rebuild either one to get the power and MPG the 351W is a better choice.

 

Hey Roger Dowty,
this site wont let me pm you because I havent posted 15 times yet. but I was going to ask you if you would take some different angled pictures of your trucks engine for me if its not too much trouble... the prior owner of my 83 bronco did this and I would like to know if it was done corectly. and/or if it is missing something or if there is something that I can get rid of.
my engine bay is a night mare and I am trying to clean it all up ( wiring and hosing)... thank you so much... VR: Barrin.

 

no prob Barrin.

To the rest of you... Most do not build the 400 the way it was meant to be built. If I was to build a stock motor I'd lose the bet. I have owned both motors to include several windsors and think that they are a fine motor- the best mpg I got was out of a 87 Bronco and that was 13 ave-auto. I was getting 16-18 out of a '69 Montego-auto.

I know I can build a 400 the proper way and get the same or better mileage PLUS have 450 ftlbs and 300+hp. Folks are doing it all the time. If you want to try to match a stroked CLEVELAND with a windsor for power you need to regain your memory and think again. The weight difference isn't that dramatic and comes from having more metal in the right places.

THe power issue really has me confused- you have to do a bunch of work on your W to get close to a stock cleveland 4v. Now give it the longest stroke ford ever made and the 50 ci and wala you would have a monster. But you have to remember that the stock 400 was detuned, decompressed and ruined by the need for a smogged motor to run on the new mid 70's gas. Most rebuilders use stock dished pistons and don't even know that flattops are available (like in the original motor in '70) I always thought that the 351M/400 were boat anchors until i took the time to research the motors. Now I want to free the stock 400's, add some flattops, decent timing, a dual energy cam for low end torque, intake and 4b carb and a few simple extras and i have a motor that should get me 15-17 in the same bronco and all the ftlbs and hp I'd ever need.

It's being done over and over..I'm just following along. Folks won't be rushing to do it as it is not smog compliant-though could be if put in a 70's unit- and because of it's ruined reputation...but it is being done a lot and more and more are seeing the light and saving these motors.

BTW...what would it take to get 450ft lbs out of a windsor?

 

No one is arguing the capabilities of ANY Ford big block V8. Drop a smog compliant 460 into a 96 and you'll have a screamer. The point being made here is that removing the smog equipment from an engine that was designed to have the stuff in place is detrimental to the performance and fuel mileage that is acheivable by the engine. Of course you can CUSTOM build a non-smog enigne to accomplish just about anything you want it to do (within reason). It still doesn't make the notion of arbitrarily removing emissions equipment from an engine that is supposed to have it a good one nor does it make the idea any more legal.

BTW, "wrong answers" on topics like this are referred to as "different opinions". So far, the argument could easily be made that in terms of right and wrong, removing federally mandated equipment has a greater potetial to be considered "wrong" than complying with the law. Not wanting to sound like I'm jumping down any throats here but in my several years here I cant' recall ever having seen a post that began with "Wrong answer".

 

I just want to mention there are differences between various "smog equipments". Engines with EEC have many sensors and a sophisticated engine control, and any change to the engine control/sernsors/smog equipment is likely to be detrimental. However, earlier incarnations that come without EEC are very different, and there may actually be a net gain by disabling/modifying some of it.