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After ya'll read this and finish laughing, please submit me your opinion....I am confident that this is the MOST UNUSUAL performance mod anyone has ever attempted, and possibly a problem!

Myself and a friend built a 347 stroker. Eagle kit, D.S.S. stud girdle & windage tray, AFR Heads, FRPP GT-40 intake, FRPP 30lb. injectors, BBK Cold Air, MSD Pro-Billet Dist., name it. We took our time and did the entire buildup right.
One thing we did that was unique..... we created a "water jacket" between the two ports on the back of the lower intake. These ports are located on the left and right rear sides of the intake and are plugged. One port is used as a provision to plumb coolant to the EGR spacer, and the other is plugged. There are two because on trucks the EGR is plumbed from the opposite side.

Anyway, we used a piece of braided line with fittings on each end and connected these two ports, to allow coolant to flow across the back of the hopes of cooling the block better.
NOW, here's where the problem comes in....ever since the inital run of this motor we have experience the two rear header pipes overheating (turning slightly red). This does not occur at idle, it only occurs when the motor is at opperating temp. and we hold the RPMs at 2000 or higher.

We have checked everything.... we resealed the intake (no vacum leaks), we replaced the injectors (all good), the valve springs are good, timing is at 16 deg. advanced, double checked fuel press. ( was at 41psi...moved to 35psi.)...STILL the two rear
header pipes turn slight red under load!!!!!

We are positive that the "water jacket" we created is causing the problem! It has to have caused a problem in the cooling of the two rear cylinders.

I haven't blocked these ports, like they should be, but plan on it soon. The car was not and will not be driven until the problem is fixed.

WHAT DO YA'LL [email protected]#%

Thanks for any ideas, or advice.

:mad::confused: :confused: :livid:

· Registered
10,466 Posts
I don't think it is because of the ports being connected. If it was, than the rear pass side would do the same on all our cars because it's the return line from the EGR.

One simple way to find out it to just remove the hose and put two plugs in the intake.

But i'm thinking the back two cylinders are running lean for some reason. If header tubes are glowing, i don;t think coolant would be able to cool it off that much. We are talking 1000 degrees vs. 180 degree coolant with a time limit of .5 seconds (not even really) to exchange heat. If anything, the moving coolant takes the heat away better than if it was to remain still if they were not joined

I don't think the hose is a problem but remove it and try anyway before hand. I think something else is causing those 2 cylinders , or maybe all of them, to run a bit lean. How are the 02 sensors? new? Do you get any engine running codes?

Oh yeah, i was also considering looping the back two ports together for a little more coolant flow. I'll just keep this in mind when i do

Discussion Starter · #3 ·
O2 sensors are brand new....Bosch

Have not ran codes on the EEC yet, know where I might get a reader??

Thanks for the input.

· Registered
664 Posts
Aren't the the rear cylinders always more lean than the rest with a typical Ford 5.0 intake? I thought that's pretty well documented. There's definately one cylinder w/problems, maybe two?

· Registered
45 Posts
Just guessing...

I'm sure it's not a water not being there issue. That is telling you that you are running way lean there of course, so I like to think it might be the water temp sensor getting too much flow and leaning your engine out thinking its running too cold. Weird part is that the two last cyls would run lean and not the engine as a whole, but maybe you could chalk that up to the fact that at normal conditions those run lean anyway, just not lean enough to glow and are now noticeable due to an increased lean condition overall. Also check the injector harness, maybe the connectors are not firing them. But like you said this is at operating temp only so maybe...
Just plug it up, and read the codes is the best I could recommend.


Sounds like a beauty of an engine though...

Discussion Starter · #8 ·
Thanks everyone for your input, we'll see.

I checked the injector harness, it is working fine. I don't think it is a feed problem, as the rails are clear and the injectors are new and replaced.
I am going to replace my fuel pump with a 255lph Walbro....I have a used 190lph Walbro, but I lose fuel pressure under load (it's set at 40psi -BBk fuel pressure regulator and gauge-, when throttle is applied it drops to 30psi) the fuel pressure drop is causing a lean condition????

· Premium Member
15,786 Posts
TheShagg said:
check the spark plugs... thats an easy way to see if its lean or not

Most people reading a plug havent got a clue what they are looking for.

Even of those that do use several differnt reads as tunning. Most racers read the porcaline for the tell tale flakes of aluminum signifying detonation. Most Joe Street guys get a read on overall engine performance after several months/years of use, ie genral air fuel mixture, and or oil leaks etc...

For a read on cylinder temp and fuel curve at WOT, you need to cut the engine imeadiatly after a WOT run. And after having installled new plugs you read the strap electrode for length of "high temp" burn. TO know exactly what you want you need a few examples of GOOD engines to know when something isnt right. Basically though you want about an 1/8" or so "burn".

IF the gauge is already telling you your loosing fuel pressure at RPM, we know the problem....

Discussion Starter · #13 ·
Found out that the water jacket is not the problem.
We plugged it and the two rear header pipes (#4 & #8) are still turning slight red under load. We did notice an increase in temp at idle, so the water jacket did assist in cooling the motor!

I pulled all the plugs and everyone is solid black....not oil either. The exhaust smells very rich when it is running, so I am confident there is a rich condition. I can't understand that though with the fuel pressure drop!!
We were using Autolite 3924 plugs, as AFR recomends; however, I switched to the Autolite 3926 (hotter) in an effort to maybe clear up the rich condition. NO DICE!!

Still turning red. I guess I'll see what happens when I change the fuel pump.

Thanks for your input KIM and everyone else.
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