I'm getting a engine rebuilt for my '87 F350 with a 460. I had already put headman headers on it and plugged the EGR valve. It didn't seem to effect economy or negatively effect performace, in fact the headers seemed to help both areas. I'm wondering if the Carb should be re-jetted because of lacking the Exaust gasses? Anyone have any ideas? I'm also thinking of putting a Edelbrock non-egr intake manifold on the motor. The egr valve supposedly lowers combustion temperature, I suppose by leaning out the fuel/air ratio and thus offering less oxegen to burn the fuel. It seems as though this would create more unburned particles and less economy? Any insights on the EGR valve and how it works and any thoughts on performance without one are appreciated.
Tony.

 

You should re-jet the carb, but I don't know how much. One solution would be to put a non-emission aftermarket carb on it. The egr introduces exhaust gases into the combustion chamber, as you know already. The exhaust gas is considered inert, meaning it does nothing but take up space. It doesn't burn or contribute to the firing of the mixture. This means there is less room for the fuel/air mixture in the combustion chamber. So each portion of the air/fuel mix is smaller to keep the correct ratio. When the egr is disconnected, the carb still sends it's smaller calibrated amount of fuel, but with no exhaust gas taking up space, this space is replaced with air. This makes the air/fuel ratio lean, which can cause the engine to run hotter and ping at part throttle.

 

Franklin,
The headers have been on for over 6 months. I noticed no pinging afterwards. I have noticed some pinging since a have remanned heads on the truck. Apparently this has bumped up the compression ratio enough to cause some pinging. It's not severe and I can usually stop it by changing gears and kicking in the 4 barrel. ...... So when the exhaust gasses are included in the combustion chamber, the fuel/air ratio is correct, but when the exhaust gasses are eliminated, the extra air leans out the mixture. I can see how this would happen in a fuel injected motor, but isn't the fuel drawn into the air passing over the jets by suction in a carburator... rather than squirted? Or am I thinking only of motorcycle carbs?... I'll talk to my engine guy. Edelbrock seems to make a nice non egr manifold with electric choke carb combination for the 460. Although it would require going up to a 750 CFM carb rather than the stock 650 CFM carb. Maybe the extra CFM's are to compensate for the air not coming in from the EGR? What do ya think? I wonder what the market is like for a holly/motorcraft 650CFM carb rebuilt with a motorcraft kit 6 months ago.??
Tony

 

Every combination is a little different, and you can get around the problem a little by retarding the timing and disconnecting the dist vacuum advance. But it sounds like now, you do have somewhat of a problem. When you are kicking in the 4 barrels, you are enriching the mixture enough to make it go away. You are right about the air passing by the carb, determining the amount of fuel delivered by the carb, but it must not be dramatic enough for the carb to detect the difference. The original setup is calibrated pretty lean to begin with for emissions, so I guess it doesn't take much to throw it off. If you don't have inspections in your area, the aftermarket carb would be the way to go, especially since you added headers and probably a free flow exhaust too. Better combustion chamber scavenging by the exhaust system will allow more power to be had if you richen the mixture a little with a aftermarket carb.

 

I would think that the EGR valve would not make much of a difference, especially during a pull or hard acceleration. The EGR valve is connected to two vacuum switches...one will shut the EGR down during no/low vacuum situations like acceleration and a hard pull...the other one keeps the EGR closed until the engine reaches operating temp.

Slik

 

Slik,
Thanks for the encouragement. I talked with the engine builder and his thoughts where that I shouldn't have to rejet, but if I did, he'd recommend the 750 Edelbrock. We're going to try the OEM holly/motocraft 650 carb first. I saw the vacuum lines your talking about. The guys who put the heads on might not have got the timeing just right, plus I've since learned that my timing chain has alot more slop than I previously thought. It actually stutters and almost stalls when decelerating and the timing chain load is switched. Otherwise the engine runs pretty good. I don't think I'll have too much of a problem with pinging, and I plan to put a 190 thermostat in for some insurance. Does anyone have any specific experiences where they had to rejet to eliminate pinging? Franklin, I'll keep your ideas in mind.
Tony

 

 

Well, I've got a little story aboout my experience with EGR removal. I, with my superior intellect and infinite wisdom, decided that I was way smarter than any of those dumb Ford engineers and removed the EGR valve and blocked the port on my '84 Bronco. It pinged. Badly. REALLY badly. The only way that I could get it to shut up was to retard the timing so far that the engine ran like crap and was tough to start. Sooooooo, I advanced it back where it ran right and turned the radio up instead. (Let's fast-forward to after I had to build a new engine because the spark knock finally burnt holes in two pistons.) So ANYWAYS, with the new engine in place with a non-EGR Edelbrock Performer intake and an Edelbrock 600 CFM carb, I proceeded to spend a couple weeks monkeying around with the jets and metering rods and a new adjustable vacuum advance. Eventually, I got it to run right and quit pinging. My gas mileage is now noticeably worse than ever because it was necessary to fatten the mixture up enough to help quench the combustion chamber. The power is just a bit better, but you tell me: Was it really worth it? $1500 for a new engine, intake, and carb just to make more frequent fuel stops. But hey! I don't have to look at that ^$#^%$& EGR valve anymore! Yep! I'm waaaaaay smarter than any engineer!

The moral of this story is this:

My old man always told me that if it ain't broke, don't fix it. Dad should've been an engineer!

 

Blue Oval,
What motor was this, a 351? and what compression ratio did you build with. My engines history is as follows. I got the truck with 150,000 or so and it had the air pumps disconnected. Interestingly, this was a canadian, not catalytic model, but still had the air pumps from factory. I ran it about 40,000 and when the head gaskets needed replaced, I decided to put headers on it. This meant plugging the EGR valve. The headers provided noticable improvement in power and pulling economy, but I still didn't have any pinging. Timing was set at 8 deg. btdc. per specs. So, with the egr valve disconnected, still no pinging thus far. I then tried to get away with only doing a head job after which I found other parts of the motor where in need of repair. (bearings and cracked cylinder wall) I haven't personally checked my timing, but after the heads where put on, I have some pinging but not severe. Alot of garages want to set timeing at 5 deg or 10 deg (I forget which) because most ford v-8's get set there, but the ford 460 I think is a little different. So maybe, my timing is a little off, but maybe my added compression from the head job is causing some detonation. Either way, the engine needs renewed. I'll probably keep the motorcraft carb and the ford intake (it's cast iron). If I get severe pinging, maybe I'll get some tubes welded into the headers? Thanks for your post, It will keep me on guard that a non-egr intake may not solve all my problems.
Tony

 

TonyG,

Maybe things have changed from '82, but why would you need to remove your EGR when you put on headers? I thought the air tubes on the exhaust went to the air pumps. I didn't have any interconnection between the EGR and headers on mine and I ran the EGR a couple of years after putting on my headers and before I found out the inspectors didn't care if I had EGR or not.

Blue Oval,

I didn't have any pinging whatsoever when removing my EGR. I'm wondering if there was an associated vacuum leak or a vacuum switch that was inadvertantly left in that caused the pinging. I get 12-14 mpg with my 351W.

Slik

 

>TonyG,
>
>Maybe things have changed from '82, but why would you need
>to remove your EGR when you put on headers? I thought the
>air tubes on the exhaust went to the air pumps. I didn't
>have any interconnection between the EGR and headers on mine
>and I ran the EGR a couple of years after putting on my
>headers and before I found out the inspectors didn't care if
>I had EGR or not.
>
Slik, maybe there was a change, or maybe someone had removed the connection before you got the truck, if you bought it used.? From my understanding, the air pumps 'pump air' to the headers to both oxydize any combustion still happening in the mixture after it leaves the cylinder and to increase the % of air particles in the pollutants before it exits the exhaust in order to give a better reading for the EPA. With Catalytic models, the air pumps also supplied air to the converter. The EGR valve stands for 'exhaust gas recycle' valve. Thus the exhaust gas must come from somewhere. On the I-6, a diagram in my haynes manual shows a connection straight to the exhaust manifold and an efi 351 with a eegr valve shows a similar connection. The 460 diagram is unclear but I think I remember a tube crossing over the back of the engine. The whole egr valve situation is a little unclear to me anyhow. A lean mixture burns hot and produces nitrous oxides. So to combat nitrous oxides, they introduce "hot" exhaust into the air mixture because it is "inert" and basically takes up space and maybe reduces the available space in the combustion chamber for the air/fuel mixture which in turn richens the mixture??? Is that how this thing is supposed to work. It seems that the attempts to meet EPA regulations has produced alot of 'bandaid upon bandaid' systems.

 

What you say makes sense and after thinking about it...I didn't put headers on until I swapped from my I-6 to a 351W. I think I must have just plugged the hole on the side that drew the exhaust gases...and the I-6 was such a convoluted plumbing nightmare that I gave up trying to figure out the smog systems. I did a lot of looking on the air pipes and mine had the air pipes going directly to the back of the heads (via a series of regualtors and vacuum switches) instead of the headers...I just plugged them up and got by without the entire smog pump issue. I also agree about the smog laws. The solution was to build more efficient engines instead of adding bandaids to try and recirculate spent gases. Even my old 351W with only the cats and PCV system in place will out perform smogged engines when comparing pollutants allowed for '82. But...I have to keep my engine tuned and run the timing retarded to really get the best sniffer readings. I've never had a problem meeting the sniffer test, though.

Anyway, thanks for the explanation, and I'm going to browse my Chilton's to see how my 351W should have been built.

Slik

 

Most older carbed motors I've seen put the egr on a spacer under the carb. It receives exhaust from the intake manifold heat crossover passage that comes from the heads and is built in to all stock intake manifolds dating back when they started making v-engines. The egr valve then decides when to inject the exhaust gas into the manifold under the carb throat.

 

Thanks Franklin2, I thought I was missing something somewhere and I didn't remember any pipes from anywhere on the exhaust back to the EGR plate. I remember looking at the passages cut into the EGR plate and I thought they looked kind of funky. I was wondering just how it really worked.

Slik