On my 4.6 DOHC engine that came out of a 98 Mark VIII, there is a box on the back side of the left head that has an electrical plug and 2 cables coming out of it. The box is approximately 4” X 4” X 1 1/2 “ deep. The cables run to 2 levers towards the back of each head inboard of the valve covers. Does anyone know what function this performs? I am guessing that it opens the plates that activate the 2nd set of valves on the engine.

 

correct, that is the intake manifold runner control solenoid box which operate plates which are closed below 3000 RPM.

Sam

 

are you going to mod the stock harness or buy an aftermarket one? I am starting on modding the stock harness myself.

Sam

 

the 98 4.6 DOHC modular engine was equipped with electrically operated variable length intake runners. Possibly what you box controls?

Oops, Sam beat me to it.

 

That is what I thought.

On the harness, I have not figured out which route I will take. The cheap side of me says modify the existing harness. The lazy side says buy the aftermarket harness. The aftermarket might look cleaner when it is all complete. Luckily, I have some time before I have to choose which route I will take. I will be very interested in how yours turns out. It would be nice if someone would document what wires need to stay and what can go.
Scott

 

I'll work on documenting the wire changes.. I bought the service manual to get the diagrams. The double harness connectors thru the stock firewall are painful to work thru.
I bought a tuner used, and have it programmed to mod the ECU.. gotta get the engine mounts welded in so I can start it and work thru removing all the extra goo.

Sam

 

Sam
That would be great if you would document the harness modifications! It will give the rest of us something to follow. I am thinking about relocating the runner control solenoid box to the firewall above the valve cover. That will let me position the engine about 1 1/2 “ farther back. I would be interested in seeing what you do for motor mounts. Are you going to utilize the stock mounts
Thanks
Scott

 

watch out for the brake pedal arm if doing under floor master.. very tight

i got motor mounts from WelderSeries. (web catalog currently not working)
plate to bolt to engine, stanchion to weld to chassis.. rubber pivot between

sam

 

Sam
I would not have suspected that it would be tight around the under floor brake set up. That is what I am running. The transmission would be in that area. What causes the interference, the trans cross member? I will have to mount the brake assembly and check it out. Do you have any pictures?
Thanks
Scott

 

don't have any pics, but can get some.. end of week.. about to leave for business trip.
interference is the left side head where I have the engine sitting..

sam

 

Hi guy's I am in the process of putting a 93 markviii motor/tranny/irs in my 50 Merc. I am curious what you will be doing for a fuel system and steering shaft? I have a mustang ii front end as well.

Thank you
Drew

 

Drew
I saved the fuel pump from the Mark VIII. If you are using an aftermarket wiring harness you need to use the stock pump. I cut the access port and pump mounting bracket out of the tank also. I will be figuring out the clearance for the steering shaft in the next few weeks.
Scott

 

I will be using an external rail mounted fuel pump. Walbro GSL-392

As for steering shaft, just the std double D shaft thru borgeson joints

The column shifter is more fun with the floor brake!

Sam

 

A lot of good information. I am also stalling a 96 Mark VIII in my 56. just put my fuel tank. and ran all my fuel and brake lines. I am going with a aftermarket wire harness didn't want the pain. On the pricey side also. Will add pictures later tonight.

 

Sam, you recomend a column shifter over the floor shifter? I had thought about one as well but not sure about connecting it to the 4r70w? I haven't really looked around that much yet though. I am planning on using an under floor mounted booster as well. Great to see there are a few others using the mark viii motors. I'm sure I will be asking lots of questions. I am going to use an aftermarket harness too.

Thanks
Drew