Where does the one odd exhaust port cavity go to?

bah, I know everything... I just remember it wrong sometimes...

 

I'll throw this out there. When I was doing research for my exhaust headers I came across this article that said the original idea behind the exhaust cross over was to balance the exhaust pulse.

My original header design was for a 180 exhaust. This article stated the deferance between euro v8's and US v8's. Euro v8's have 180 exhaust sytems they fire left right left right for an even exhaust pulse. But they have to run balancing shafts. US v8's use the firing order for primary balacing this makes the uneven exhaust pulse. It was a very intresting article that I can't seam to find again, it explaned collector sizes, H , and x pipes.

 

Don't know how many of you are old enough to remember the bimetalic spring loaded flap that was on the older v-8's and I-6's exhaust. We used to call them "exhast flapper valves". Anyway that valve kept the exhaust pipe restricted until the bimetalic spring warmed up and lost tension. The restriction on one side of the port caused exhaust gas to flow through that little port between the intakes, to a pocket that was sandwiched at the plenum bottom to heat it up so that as the velocity of the fuel - air charge dropped when it entered the intake manifold it would not separate and leave a big puddle of fuel on the floor of the manifold. On the I-6's the flow of exhaust was routed in an arc under the intake manifold (where the intake sat directly on top of the exhaust manifold) in order to heat the area right under the carb.

this is all old technology from the thirties and fourties that was carried through into the age of EGR and ported injection. The "rodders" of the day would buy special intake gaskets to block off the flow to the intake to keep the charge cooler - and we used to throw away the flapper valves because they used to rust in the closed position and cause problems with power production. None of the reasons for this old stuff is on the modern Multi-port FI engines anymore but the ports are still there for the EGR systems and the old timers like me who still run carbs - the manifolds still come with the mating ports too unless you get one for competition only.
PaulS

 

This whole operation has an evolving history.
It was found early on that heating the intake manifold promoted faster warmup and better low speed operation.
As time went by, gas formulation improved, engine design changed; the heat from exhaust was channeled up thru the intake on V8 engines to the base of the carb.
Along about 1972 emmisions was becoming a hot issue.
A plate was put between the intake carb mounting pad and the carb.
A valve device called and EGR was then used to pass exhaust gas into the intake air stream. This was done to cool combustion temps reducing the oxides of nitrogen emmisions the feds said had to be reduced. The cats/no cats at that time could not handle those emissions.
Today there are smaller displacement engines that produce under the present limits so have no EGR system.
Most all the present day Ford gas v6/v8/v10 engine still use the EGR system in several versions with final cat cleanup using advanced techology.
The newer Powertrain Control has been designed to test these systems for operation as the engine is driven and report with specific codes to id the failure. This is OBDII from 1996 on.
The next control systems are already being use by Ford as of 05 in some models and other mfgers must all use the same by 2007. It's called the CAN system a European software/hardware design.
Like to hear about OBDIII? It's on the shelf so to speak but you the public won't put up with all it's features because it does to much spying on the engine operation by remote means. Road side monitors and drive by testing, satelite testing, notices in the mail etc. All things you like.
Catipillar already has this tech. on there big machines so the service departments can see what is happening from some remote location and call a $100,000 + machine in for service before anything even becomes an operational issue, in most cases.
2000 up cars and trucks also monitor and store your driving/braking habits and can be used in a court of law, if needed to prove an whos's at fault/liablity case. This is seldom done but it is there.

 

Hey Thomas, here's my take on that. It's true that many Euro V8s have had 'flat' cranks, where the pins are all 180 deg offset. Basically, you have two four cylinders that way. It makes for poor balance (hence some having balance shafts) compared to pins 90 deg apart, but it makes for 'perfect' exhaust balance, and no reason to have an H pipe or any kind of crossover. All racing engines, unless banned, have this.

In this case I would seriously doubt that's the cause. For one they are only a couple cylinders, for another it's too short a primary runner for it to work (IMO, havent done the math but I've designed some stuff like this), and also it'd be a real small improvement in power for all the effort. Certainly, if they were doing it for power, they wouldn't have run it under the intake!

Just my opinion though...

 

As a Technician OBD III as intrigued me from day one. I almost like the idea of linking up to a satelite and having somebody else figure it out........Tired of getting out the MODIS scanner. Even then still gotta do some legwork cause fancy 8k boxes don't always tell you the whole story. I have had some really crazy stuff come into the shop and had to deal with oh the fun I have had...... Personally I fix all makes and Models so I can't say I am better at one brand or the other. There all just nuts and bolts to me.........and wires......sensors.....

 

I hate to interrupt...I asked a decent question, and got a WORLD of knowlege in return.

Really interesting stuff.

I found this on accident ("this" being the hole out the back of the exhaust port, remember, the source of this thread?) by doing some mild porting on the exhaust side of these heads. I was using compressed air to clean out the holes after grinding on them. When the air hit this one hole, air whooshed out the back, and I immediately thought I hit a water jacket!!! I cursed a little, just two or three words, then pulled the other head over and hit air in them, and found the same thing. So, I knew I did not mess up the head.

At this point, I became curious as to why just one port had a hole out the back...and the rest is history.

Thanks, all of you, for the insight.

Will there be a quiz on this tomorrow

 

There should have been a port hole in both heads at their back ends.
This is where air injection from the air pump comes in through a tee and a special one way valve.
The rest of the air system from the air pump has control valves that gate engine vacuum to either the heads or the cat converters but not both at the same time.
This all for the original fuel injection application.
Just put short bolts or plugs in to block them off.

 

badmav, it's truly difficult to keep up with all the different makes just like an MD tries to do in all the people he sees daily.
The next step is to specilize in one or two makes but stil it requires you to be on top of the changes year to year and still be knowlegable about each operational function.
That takes a lot of personal time and energy.
Knowing for instance what a code P0401 is all about besides 'insufficient EGR flow' makes things go much better and faster.
This code is an emissions test only, by a DPFE sensor but how it is done is the key to getting the code solved quickly.
For you, there is free info on the Motorcraft website on all the makes from 96 to 04.
But it's like going to school again. The documents are 60+ pages when printed out for each year but most is a repeat of much from year to year except for the running changes.
Wait till you get a throttle by wire problem from 05 on. No physical throttle cable any longer.

 

Hey Charlie

I believe that the article was basiclly saying that with stock manifolds and the exhaust pulse being 90 degree then 180 degree then 90 then 180 the pulses stack up before they get to the exhaust pipe and the cross over releived some of the pressure between the 180 degree pulses. Obvously this would not work with headers.

I wish I could find it again I think you would enjoy it, in a way it made sence. I thought I would toss this thoery out there, I thought it would be funny, what if this was the real reason for it and all the internet experts were wrong