OK, I did this mod in my 86 f150 302efi and it has cleared up some roughness in the motor that I was plexing about for a long time. Mine is an automatic and I didn't have the extra port on the vaccum tree. I capped off the PCV intake at the back of the upper intake and ran a 2 ft. 3/8 hose from the PCV around the back up to the vaccum booster about 6in. from the tree and cut the 3/8 line and put in a T fitting. All cost less than $10. My idle seems smoother too and I'm wondering if the motor running better has affected the computer and made the idle more consistent.?

 

Must be a truck thing, I never had those kind of issues with the PCV on my 5L mustangs.

 

The plenum is totally different on cars, so they may not suffer from this.

 

Yeah it doesn't dump directly by a cylinder, just dead centre at the back of the lower intake.

 

Just wondering if any of you who have tried this have had any problems with passing the emmisions tests?

 

It won't affect emissions, other than restoring the function of the PCV system, which isn't tested.

 

What can make the problem worse is that when the little splash guard inside the valve cover at the pcv outlet gets plugged-up (dirt I guess), oil can be pulled directly into the #8 cylinder, causing excessive load for that piston leading to a rod bearing failure. That is why 87-94 trucks and vans with 302s had a large number of engine failures attributed to the #8 cylinder. It happened to mine ('93 F150 SC 4x4, 302) at 68,000 miles. This sounds like a good fix. A new crank-kit and mine ran great, I have 113,000 on it now, but I think I will perform the modification.

 

It was enough of an issue that Ford relocated the pcv hose to the vacuum tree in 95 I think.The air,vapors can lean out the cylinder.That's what happened to mine.The engine got hot due to a hose failure,but funny only #8 piston was wacked due to the lean mixture.You are right if the oil drain in the baffle gets plugged it will suck oil into the cylinder.Funny thing about liquids,they dont like being compressed.The excess force is enough to fry the rod bearings.The best way to make the mod is to plug the hole in the back of the plenum and drill and tap a new hole in the center of the intake and screw in the old fitting.

CB

 

I just did this mod after reading this thread, and my idle quality improved significantly. Cost about $6.

 

After reading this thread, and another here, I also did this mod while swapping out my cam. All I did, was at a T vacuum hose for my brake booster (it's also 3/8" diameter) and it works great. Also ensured the baffle drain hole was free and clean.

Thanks for the great insight on such a simple but effective mod!!!

Luke

 

I just rerouted my PCV to the vacume tree also. It settled down my idle problem right away. Hopefully it will also stop the oil comming from my crankcase vent hose. Thanks for the great advice.

 

Forgive me for being stupid, but I know where the pcv valve is, I am not understanding where you are cenecting to to. Are you running a hose from the PCV valve still in the valve cover to somewhere? I hate not understanding this, because my car seems to ahve the same problem. when i pulled plugs all but the 8th one was really clean, it was lighly gunked up with oil. . as always thanks for helping a newbe ford nut out

 

PCV valve is routed to the back of the upper intake. I routed a piece of 3/8 hose from the PCV valve to a T fitting, connecting the vacuum line to the brake booster and the PCV valve to the vacuum tree on the top of the upper intake. Probably cost me about 3-4 bucks for the T fitting and the extra hose.

 

Once again sorry, I know what you are talking about, what I am confused about is, why are we concting the hose that enters the intake to the brake booster line. I guess I am not very smart when it comes to fords. Sorry. I understand the conecting the pcv valve to the vaccume T though. Would it not make more sence to attach the pcv valve to the brake booster hose and block off the hose that enters the intake?

 

That's exactly what was done. I'm not sure I understand what you're asking. I routed the PCV line to a "Tee" fitting to connect two lines (PCV and brake booster) to one (line attached to the vacuum tree). What is it you're asking?