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Discussion Starter · #1 · (Edited)
I know this has been done a fiew times but there were still alot of unanswered questions for me so I started to preform this swap and have figured alot of them out. This is how I did the SOHC to DOHC Swap in my 2000 Mustang GT on a budget.


First things first... You need to purchase a DOHC Engine. I was lucky enough to find one on Craigslist pre-pulled and with relitivly low miles... (74K and mt 2 valve has 202K) It is out of a 1998 Lincoln Mark VIII (This is in my opinion the engine to get... The 97-98 mark VIII is the closest to the 96-98 cobra as far as not having to replace alot of parts to make it work. )



After getting said engine I sugjest replacing all of the gaskets before installing it. (I know it is a little pricey ($50.00 just for valve cover gaskets) but a good way to save some money doing that is to order the parts on Advanced auto parts website and choose pickup in store (You can use online coupon codes... my fav is "VISA" $50.00 off an order of $150 or more)

You will be using a couple of parts off of the origional sohc engine. Mainly the oil pan and motor mounts. I recomend getting new hoses instead of using your origionals.

1)

Well, I have overcome alot of things in the past fiew days doing this swap so here I will start the list of items you will run into.

This is from installing a 97-98 Mark VIII into a 2000 GT Mustang

The fuel lines are different
The oil pan is different
The oil pickup tube needs to be modified
The throttle cable and cruise cbles are different
The radiator hoses are different
Your wiring harness will need to be taken apart and one side of the coil plugs lengthened
You will need to use some of your origional vacume lines and some from the Mark


First things first... Lets modify the fuel rails to work. There are no rails that I have found that will work without being modified. to fdo this you will need to remove the primairy fuel pressure regulator from the fuel rail and cut off the return line. next take the fuel pressure sensor off of the GT fuel rail and insert it into the Mark fuel rail. mark the fuel rail so you can drill a hole in it and remove the sensor. drill the hole in the fuel rail and enlongate the other side hole in the sensor. install the sensor and use a small nut abd bolt for the hole you drilled and the origional bolt in the other side. Now you will want to remove the aux regulator. grind off the plastic nipple flat and re-install it. Fuel lines are done and now are returnless rails.



The wiring harness is the next thing to be taken care of. What you are looking to do is set it on your workbench in the same orientation that it is in the car. Split the looming off of the harness down the sides.. (Where it would be between the intake and cam covers) the coil harness can now be pulled out of the wiring harness. Now you want to remove the wires from the coil plugs. (Pop out the yellow retainer. It just pries out with a small flat screwdriver. ) and reverse the polarity of the coil plugs. (flip the wires in the plug and re-install the yellow retainer) If you do not do this you will ruin the ECM in your car. Now you should extend the coil wires about 5 inches for bolth sets. This will keep the wiring harness centered in the engine bay. you at least must do this for the passenger side coils. they just will not reach. before you tape this all back up you want to relocate the TPS plug, IAC plug and the fuel pressure sensor plugs so they will reach. (This can be done without cutting and splicing. ) tape it all up and there a go... One wiring harness modded for a 4 valve.

Next thing is to mod the oil pan pickup tube to have it sit deeper in the sump. just using it as is will most likly not hurt anythingbut it sits almost 2 inches from the bottom of the sump. You can bend it a little bit and use a longer bolt with a spacer to re-attach it to the main cap bracket. (Sorry... I goofed and have no photos odf this) keep adjusting till the pickup tube is appx 1/2 inch from the bottom of the sump. Install the GT oil pan and new gasket and call this one done!

Next thing to do is head over to your local Ford dealer and get some Cobra parts. you want bolth heater tubes for a 99 and later cobra. They offer them and I will put the part numbers in here later.

Go ahead and install the motor mounts now. (You'll have to gring one of them a little because of the extra ribbing on the aluminum block. )

When removing the old engine you do not have to discharge the A/C or unhook the power steering system. The compressor will sit out of the way and you'll need a 10mm rachet wrench for the power steering. for the power steering remove the 3 bolts you can get to and then use the ratchet wrench to fet to the last bolt under the pressure line. this bolt will not come out and it will be the first one to install with the new engine. Also it is possable to install the engine with the transmission in the car and the K-member fully installed... I just did it.



The alternator wiring is simply change the pluf and match color for color.

For the cruise control you can get a cable from a 99-04 V6 car and use it. Just drill a small hole to slide it over the barb and use an "E" clip to hold it on. You can cut the stock GT bracket and bend it to bolt it to the mark bracket for simplicity.

for the EGR. Just make a delete plate if you don't want it ir mock up and weld up a pipe before installing the engine because bolth engines have different size pipes. I deleted mine so I will not be much help here.

I used manifolds from a Mach 1 and my mid pipe bolted right up.

time to do the swap!!

remove the old engine is streight foreward. installing the new one is just about the reverse... It's not bad at all... I did have to remove the tranny crossmember to push the tailshaft around a little but it is better than removing the tranny.



The mark throttle cable is a direct swap.

The stock (Mark) sensors plugged right into the re-routed GT Harness.



I have the car running (Started) with the 24# injectors that came with it but have to wait till later this week for my tuner to show up.

The car is currently an Automatic. (I will be doing a 5 speed swap in the near future) Just didn't want to deal with the DOHC changes along with the tranny changes. (Getting a nice low mile t45 this weekend)

The next battle is the IMRC Controller...

You'll need a RPM activated switch to use this and I recommend hooking them up. You will loose low end torque without them. They are easy to hook up. out of the wiring harness for it there are 5 wires. You are only concerned with 3 of them.

Red / Black stripe - Switched 12V +

Black Constant ground

Brown Switched Ground (To activate the IMRC)

Hook up the RPM activated switch perinstructions provided and the switched ground goes to the brown wire on the IMRC harness. set the switch to apply a ground signal at 2750 - 3250 RPM (You'l want to play with that a little and get it just right but here is a starting point.)

I'm modifying the stock bracket and will post a photo once I get it how I like it. The box will mount on the pass side valve cover.

I have heard rumors that you don't need a tach driver. I have heard that you can use the tach signal comming out of the computer to run the RPM switch. I will have to try it and let you know.

Got the Tuner in (Sniper) and it made a huge difference! The car idles just about perfect now. Just have a slight rich condition on the #1 Bank to deal with. (Guess it's a little better than lean...) I'll tweak with it and ket you know what happens.

Next thing to happen for the car is to swap out the 4r70w transmisson for a t-45...

Make sure you go to ford and order the correct flyweheel bolts!!! do not skimo put on this...

It's jsut as easy as removing the old transmisson and putting in the t45.... I'll get more in depth with this later...

Something else to ass... The manual pedals from a non hydroboost car WILL NOT work in a hydroboost car...



I will keep updating this post over the week as I have time. I will try to take some photos as well
 

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Discussion Starter · #3 ·
Added more info and Photos....
 

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Nice writeup. There's a big one over at MM on this too.

And you can possibly re-use the GT heater hoses. I re-used them on my 4v swap, but I also did a home made head cooling mod. I just had to flip the heater core inlet hose around, and move the internal restrictor accordingly.
 

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This is an awesome post, Im in the middle of sourcing everything to do the same thing. I have a few questions that you may be able to help me with, I bought and stripped a 98 mk viii lsc, and my 99 gt convertible is overseas so I have no reference, I have to have everything I need shipped:

1- is there plenty of clearance for the oil filter as is? I have read that the filter block is different and needs the GT one used.

2- what did you do for the radiator hoses? I know the top GT hose can be cut and used, but do I really need a Cobra lower to be able to piece it together?

3- are you using the mark air box and maf? If not, how is it put together for the GT setup?

4- will I be able to make the fuel rails work with whats on the GT now? This is very important, It is extremely hard to find those parts where it is now, and if needed I would rather buy whats needed here and adapt it.

5- did you have to replace any of the sensors of the GT onto the MK engine? Have read different things all over these boards about this?

6- I am going to use a SCT tuner, did the car fire up and run on the stock tune, driveable?

7- I have considered long tube headers, but am concerned with the clearance, there are some rough roads and It concerns me. Do you have any experience with headers? Think its worth replacing the manifolds?

8- Pics of the fuel mods would be incredibly useful, and thanks for any help in advance.
 

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Discussion Starter · #7 ·
1- is there plenty of clearance for the oil filter as is? I have read that the filter block is different and needs the GT one used.

******** Yes. There is plenty of clearance to use the mark unit.

2- what did you do for the radiator hoses? I know the top GT hose can be cut and used, but do I really need a Cobra lower to be able to piece it together?

******** I got an upper hose for a 99 cobra, the heater hoses are for a GT, the lower hose was cut from the GT lower hose adn the rest are from the mark. you'll need to get the heater pipes for a 99 cobra (The one on the back of the head and the one from the water pump)


3- are you using the mark air box and maf? If not, how is it put together for the GT setup?

******* I used the mark throttle body tube with a reducer to the mass air meter and an adapter to use a conical filter

4- will I be able to make the fuel rails work with whats on the GT now? This is very important, It is extremely hard to find those parts where it is now, and if needed I would rather buy whats needed here and adapt it.

******* You can modify the mark fuel rails to work. details are in the post

5- did you have to replace any of the sensors of the GT onto the MK engine? Have read different things all over these boards about this?

******* I used the mark sensors but will be replacing them just to have neew ones

6- I am going to use a SCT tuner, did the car fire up and run on the stock tune, driveable?

****** A tune is only needed if you ue the 24# injectors. If you use teh 19# ones that were in the GT you will not need a tune to drive it.

7- I have considered long tube headers, but am concerned with the clearance, there are some rough roads and It concerns me. Do you have any experience with headers? Think its worth replacing the manifolds?

****** If you buy cheap headers than they will not fit well. If you want ones that fit well be prepaired to spend alot of money.

8- Pics of the fuel mods would be incredibly useful, and thanks for any help in advance.

****** The only pohoto I have of the fuel rail mod is posted. you just cut off the return line. Once you look at it you'll understand why.
 

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Thanks for the help, Its great to have someone like you who knows what he is talking about, too many wrong answers and directions else where.

Few other things I forgot, did you have to replace the coolant crossover tube? I read else where that you need an earlier piece with 2 sensors for it to work on the GT, already went ahead and picked one up from a 93 just in case that was the case.

I was looking at the cheap pacesetter headers but based on what your telling me I will pass and stick to stock manifolds. I wont be running EGR or Cats, can you recommend an off-road pipe? Clearance is the biggest issue, does a x-pipe sit lower than a h-pipe (currently on car).

Have been considering IMRC delete to simplify things, would love to keep them if it would truely make a difference, however if the tune will patch things up Im not too concerned. I do a LOT of mountain driving, lots of turns and sweeps, torque is what I need. Should I just run a RPM switch and be done with it? If so which one? I have been looking at the MSD 8950 switch, its a simple switch, and I think should work without a tach driver.


Thanks again, can't wait to get out there and do the swap the right way, NYC driving is not my idea of fun.
 

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Don't buy cheap headers. Long tubes are great and you can find them cheap if you look around. I bought a set of stainless works for 250. Rob helped with the install a few years ago. And they went on like a glove. I removed them to put hooker pro comps on I bought at NMRA for 275 with the x pipe. Only reason I switch is because of trans removal. Cheap header fit like crap.
Good job on the swap rob. You need a cobra intake now. :)
 

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Discussion Starter · #10 ·
Thanks Richard...

As far as the coolant crossover pipe... The 99 - 04 only has one coolant temp sensor so no, the mark one will work fine. Your stock midpipe will work just fine. for the IMRC... alot of people will tell you to ditch them and alot will tell you to use them. It's up to you. I jsut bought this switch and am waiting for it to show up.

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

Looks simple enough... we will see...
 

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im putting a 99 cobra engine in my 99 gt i have the 99 cobra harness with the motor should i use it or use my 2v harness? thx
 

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That switch looks great, and cheap as well. I will wait for your review before buying one, already picked up a msd 8950 rpm switch and it turns out that I need a msd 8918 tach gmr pickup for it to work on COP ignition systems. Either that or MSD 8969 which is all digital. I looked all over for information and could not find it, called there tech line and just confimed it.

Does anyone know if the MK crossover is the same as the Cobra units? No sense in keeping it if the stock unit will work.
 

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I just got off the phone with Jegs and the tech guy said that switch (555-40822) may not work either, apparently it only reads off the central coil negative or the tach signal of an ignition box. If you went ahead and bought one, please post and let everyone know how it works out for you reading the COP high voltage.
 

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Discussion Starter · #14 ·
I should have it tomorrow night and will install it then. I heard that you can come off of the tach signal from the ECM but not sure. Will see.
 

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Discussion Starter · #15 ·
im putting a 99 cobra engine in my 99 gt i have the 99 cobra harness with the motor should i use it or use my 2v harness? thx
You can only do this if you have all of the 4v harness and the computer...
 

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thx for the reply, so what is easy way get the 4v computer or use the 99 harness and 2v computer?
 

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Discussion Starter · #17 ·
If you can getting the computer is the "better" way to do it. If it is a budget swap than use the 2v stuff.
 

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i hope it isnt to bad doing this swop hope to start it this week
 

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Do you have the oil pan from the '98 Mark VIII?

An82Mustang,
I am reading your great post about installing a '97 Mark VIII engine into your Mustang. I am doing a swap of a '99 Cobra engine into my '96 Thunderbird and I have a bit of a snag right now. I was wondering if you would be willing to sell the Oil Pan from that '97 Mark VIII? The oil pan that I have now is from an older Mark VIII and it will not fit over the larger diameter oil pickup tube that I am using from a '97 Mark VIII (that person doesn't have the oil pan). I could purchase the oil pan outright or I have the oil pan and oil pickup tube from the '99 Cobra for a swap if you have interest in it.
Thanks Much,
Gary
 
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