I just removed the upper intake manifold on my '89 5.0 truck. I noticed that it is divided into two plenums. Each plenum feeds four unique cylinders and is fed by one of the two valves in the throttle body. The lower plenum and TB valve is connected to #1, 4, 6, and 7, the upper #2, 3, 5, and 8. (that is from memory, I might be off). The EGR and the PCV connections each feed both plenums equally.

Several people here and a page at the ford fuel injection site recommend moving the PCV from the back of the upper manifold to the middle. Some have said that it is a Ford TSB (I have not found it so far). The PCV at the back currently feeds both plenums and cylinders #4 and 8. The Ford fuel injection sample looks like it is in the lower plenum.

If I am to relocate the PCV port, which plenum should I relocate it to? The upper would redirect the gases to #3 and 5. #5 has already been getting some gases already! The lower would send the PCV gases to #4 and 6.

I could build a manifold out of pipe that connects to both the upper and lower plenums (a manifold to the manifold?), but that would be difficult and ugly. I could put a port in each cylinder's runner and move the PCV connection every week!

Ideas? Thoughts?

 

When I've looked at the FFI page what has always bothered me is why do they show what appears to be an edelbrock upper in the first pic? And a std ford in the lower?

http://www.fordfuelinjection.com/files/Reroute_PVC.pdf

The lower illustration seems to feed the "common" or what I would guess is an open area of the upper. (I haven't had my 5.8s upper off, so I can't say) Seems the best place would be closer to the TB where flow would disperse the fumes across all cyls in the same manner as the EGR gasses.

Just spit-ballinhere.

8 ports & a rotataing? Well... if yah wanna, I guess.

 

There are only two "common" areas connecting the plenums, each the size of a nickle. One is at the EGR. the other is at the PCV.

It is a good idea to put the "new" PVC as close to the TB as possible. Perhaps I could install TWO new ports. One in the upper, the other in the lower and "Y" them together to the PCV. I would put this double PCV as close to the TB and EGR as possible. But, I don't know if that would work either. Any input on the passenger side of the plenum would be directed to the furthest cylinder from the TB (8 or 4). Likewise any input on the driver side would be directed to the closest cylinder to the TB (1 or 5). The spot immediately behind the the TB is the best. I would hit all the cylinders. It is already taken by the EGR.

The drawing I did below is a simplified sketch of the upper or lower plenum. I have shown only three cylinders for clarity. The red arrow is where the PCV is now. Its input cannot cross a black airflow line. It can only go to the last cylinder. The blue arrow is the FFI method. Likewise its input can only go to the last cylinder no matter where it is placed on the passenger side. Anything put on the driver side, by the distributor, will only go to the first cylinder.

Scndsin, I did not think of this until after I wrote the first post. Sorry.




I agree with your analysis of the FFI picture. The top shot is of the Edelbrock. It has one plenum for all the cylinders. The bottom shot is the Ford. The placement of the "new" PCV in the Ford is located in the lower plenum, feeding only cylinder 4. All that is done in this example is moving the problem from #4 and 8 to 4! If the new PCV port was put in the top plenum, all the input would still be directed to 8! Furthermore, if it is done in this manner to a MAF motor (5.0 non HO) the two banks would have a different A/F ratio, connected a single shared HEGO, resulting in one rich bank and one lean bank!

 

updated drawing



The drawing I did below is a simplified sketch of the upper or lower plenum. I have shown only three cylinders for clarity. The red arrow is where the PCV is now. Its input cannot cross a black airflow line. It can only go to the last cylinder. The blue arrow is the FFI method. Likewise its input can only go to the last cylinder no matter where it is placed on the passenger side. Anything put on the driver side, by the distributor, will only go to the first cylinder.

Any work-arounds? Any ideas?

Thanks

 

You're assuming constant airflow. It's not. When the intake valve is closed (most of the time), there is no airflow to that cylinder. Whichever cylinder has its intake valve open, that is the direction the air heads. The farther you have the vapor dump from the head side of the runner, the better chance of it being dispersed to other cylinders.

Jason

 

Granted, there is no flow.

From what I've been taught about air flow in a runner, particularly a long runner efi design, is that there is a "bounce" effect. Where the air charge, literally a chunk of air, reverses its direction momentarilly while the intake valve is closed. Then goes back when its opened. Think of a line of boxcars going forward & then back as they carry whatever they contain (either air fuel/ EGR fumes/crankcase blow-by from the pvc) to their destination. The uniformity of that "chunk" is dependant on the "tuned" design of the common area in the upper plenum.

Thats just my take on everything I've assimilated over the years since the introduction of efi.

 

I think if you drilled an oversize hole at the blue location right on the divider, and went about 3/4 - 1 inch into the divider you would provide access to all runners. You could also drill a pair of holes, 1 above and 1 below the divider, and connect them with a Y.