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Discussion Starter #1
I've got the idea from here to switch to a DOHC motor since my SOHC has the common valve seal thing goin on and i'd rather just change to a bigger motor anyways but I wanted some opinions from you folks.
Basically, if you were gonna swap the DOHC in place of your SOHC, what motor (ex: 95 Mark VIII) and what would be the fastest, easiest way to yank the old and replace with the new, keeping my stock tranny. Any ideas?
 

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Um, the DOHC isn't any bigger in terms of displacement. In terms of MASS, sure, but displacement wise, they are both four point six liters.

a popular alternative is an 02-04 explorer engine. they are cheap, readily available, make more power, and work with most of your existing wiring.

oh, and by the way, try a search.

Since you have a 95 you do have some kind of advantage over 96/97s who want to go DOHC but yeah, it's been done a few times. For smog purposes, I would say 95+ Mark VIII engine because for smog, you can only swap engines from a car of the same year or newer.

there is no QUICK way to go from DOHC to SOHC.

-ghost
 

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Discussion Starter #3
Um, the DOHC isn't any bigger in terms of displacement. In terms of MASS, sure, but displacement wise, they are both four point six liters.

a popular alternative is an 02-04 explorer engine. they are cheap, readily available, make more power, and work with most of your existing wiring.

oh, and by the way, try a search.

Since you have a 95 you do have some kind of advantage over 96/97s who want to go DOHC but yeah, it's been done a few times. For smog purposes, I would say 95+ Mark VIII engine because for smog, you can only swap engines from a car of the same year or newer.

there is no QUICK way to go from DOHC to SOHC.

-ghost
I'm aware they are both 4.6's but the DOHC is better and far more powerful motor IMO. I did a search and just found what people have already done. Since hindsight is everything, figured i'd ask what people WOULD do before doing it. I read someplace that a 96 Mark VIII was the best to hook up to my factory tranny. Something along the lines of the flexplate bolts match right up with no mods needed. (If i'm misquoting, dont kill me- I've been a straight up mustang guy for years now) T-birds have always been a hassle to work on and since everyone seems to have a stang nowerdays, I'm going back to doing something thats not seen alot i.e. thunderbirds.
 

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yeah but you said a bigger motor but the DOHC is not bigger thats all im saying, lol.

ask racecougar as he seems to be the guru on the subject, but anyways there have been like a hundred threads on this, it's a very common topic.

yes, it'll fit in the engine bay and bolt up to the tranny, but that's where the easy part ends-- now you have to figure out how to actuate the IMRC (intake manifold runner controls) which is a secondary set of throttle butterflies inside the intake manifold on the DOHC. I have heard many people use a window switch, but my personal idea was to install a microswitch behind the gas pedal, to be actuated when you press it but closes the IMRCs again when you let off... then there is the issue of a good tune and a number of other issues. In all seriousness do a search, man, there is a LOT of info on the topic.

yeah look at racecougar's gallery to get some ideas

-Ghost
 

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Discussion Starter #5
Yeah, i see how that could be confusing. I'll have to check out racecougars stuff later on. I'm actually not even in the states at the moment, i'm in Iraq looking this stuff up. Reason I'm doing it now is so I can have all the stuff shipped to my pops shop and as soon as I get home, get to swappin motors out. I actually havent even had the T-bird for about 3 years. It's been sitting in my mothers garage for the most part, only the occasional drive here and there. I've had 3 other todays to worry about so had to store the bird, but I'm going to bring it home soon. I miss the ol thing. :D
 

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The Parts Guy
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I have heard many people use a window switch, but my personal idea was to install a microswitch behind the gas pedal, to be actuated when you press it but closes the IMRCs again when you let off...
That wouldn't work well at all. The IMRC's need to be opened/closed based on rpm rather than throttle input.

Beerdog, I'd recommend sticking with any 93-96 Mark 8 engine.

-Rod
 

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Discussion Starter #7
That wouldn't work well at all. The IMRC's need to be opened/closed based on rpm rather than throttle input.

Beerdog, I'd recommend sticking with any 93-96 Mark 8 engine.

-Rod
Thanks brother...can I ask why specifically that particular engine? I saw the shots of your ride...dear god man thats insane! Great piece of work.
 

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numbers for number N/A, a PI motor will put down as much, probably more than a twin cam B head motor stock for stock....and theee DOHC is nicknamed the torqueless wonder for a reason ;)
 

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You will also need to get the torque convertor out of your donor car or get a custom convertor from dirtyd0g, etc. if you want to still use the automatic. The bolt pattern is different on your '95 convertor from the Mark VIII flexplate.
 

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Discussion Starter #10
numbers for number N/A, a PI motor will put down as much, probably more than a twin cam B head motor stock for stock....and theee DOHC is nicknamed the torqueless wonder for a reason ;)
Well, that was the other thought, going with a PI motor out of a Stang (or similar) but if I go with a DOHC, it wont be stock anyways.
 

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The Parts Guy
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Thanks brother...can I ask why specifically that particular engine?
No problem. The short answer to that question would be that it will be much easier to wire up than a 97-98 engine.

And yes, stock for stock, a PI SOHC will run with a "B" head DOHC. But either engine isn't all that much fun in stock form...IMHO.

-Rod
 

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Discussion Starter #12
What does it take to go over to 'C' Heads? Sorry for all the questions but I dont really have the time to search for myself. Thanks for the advice!
 

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The Parts Guy
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Just a head/intake swap. You can keep the coil pack ignition setup by running the early valvecovers, or switch to COP ignition with the later valvecovers.

-Rod
 

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Discussion Starter #14
Just a head/intake swap. You can keep the coil pack ignition setup by running the early valvecovers, or switch to COP ignition with the later valvecovers.

-Rod
Cool. Last stupid question....would all that fit under the factory hood? I've repainted that car 4 friggin times and i'll be dammed if I do it again. :D
 

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The Parts Guy
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That, I'm not too sure about. The Mark 8 intake will definitely fit under your stock hood, but that is a "B" head intake. I'm not sure that you would be able to clear a "C" head or Cobra "B" head intake. I know neither of those would have cleared my stock hood, but you have a little more room under your 95 Tbird hood than I had under my stock 90 XR7 hood.

-Rod
 

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it'll fit under a 96-97 hood for sure, someone will have to chime in about the earlier hoods, but I dont remember reading about any hood issues.

cant he use his old flexplate since its a 6 bolt? I highly suggest doing anything but using your original TC. Since its open already its one of the biggest bangs for the buck to upgrade.
 

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it'll fit under a 96-97 hood for sure, someone will have to chime in about the earlier hoods, but I dont remember reading about any hood issues.

cant he use his old flexplate since its a 6 bolt? I highly suggest doing anything but using your original TC. Since its open already its one of the biggest bangs for the buck to upgrade.
Have a picture of that? I've yet to see a DOHC MN12 with a Cobra or "C" head intake that wasn't running a taller hood.

Yes, he could use his SOHC flexplate, but that would be a step backwards. I'd recommend at least sticking with the Mark 8 flexplate with a Mark 8 TC...at the very least.

-Rod
 

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Do any of the Mark motors have the ''C'' heads?
 
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