4.2L 255 from 81 Mustang

Discussion in 'Fox 5.0 Mustang Tech' started by ³à³, May 3, 2004.


  1. Michael Yount

    Michael Yount Advanced Member

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    The adapator won't do you much good - you'd probably be better off working with a performance 2-bbl than you would using an adapter. There's likely more restriction in the stock intake than there is the 2-bble. Are you using the stock heads? If so, all the induction work/cam isn't gonna make much of a difference anyway.
  2. wythors

    wythors Get off my lawn!!! Founding Member

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    To the best of my knowledge, there are NO 4bbl intakes for that "engine". My dad had a Fairmont with that thing in it back in the day. What a dog.


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  3. hllon4whls

    hllon4whls BANNED Founding Member

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    I agree! I tried the 2bbl adaptor in my young dumb and full of .... days.
    You may have to port the factory 2 bbl intake. You can get a 500 cfm 2bbl that will be better than that 350cfm (or smaller) that came on the car. Jegs has some nice 2bbls for dirt track classes that restrict to a 2bbl. You could also get a 2bbl from a big block truck or something with a 2bbl and a 460.

    The other option is a custom sheet metal intake for it. You would need a cam and gears to match, but if you are set on that motor, you have to accept the handicaps and move on.
  4. ³à³

    ³à³ New Member

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    Guy with truck has a Holley intake on his. We gotta check it out and see what the deal is.
  5. Gearbanger 101

    Gearbanger 101 we love us some gays up here Super Mod

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    Let me get this strait. The guy with the truch gets rubber in 3 gears and he's got a 4-barrel intake??? I've got a feeling that he's not running a 255 like you think he is. I'll bet my left nut that it's a 289 or a 302.
  6. 85 Coupe 5.0

    85 Coupe 5.0 Founding Member

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    A guy here in my hometown had a 255 once, in an early 80's cobra. To make a long story short, he lost to my '87 Oldsmobile Delta 88, it had a 160 HP 3.8L engine.

    He also lost to my buddies slightly moded 2.3L, non-turbocharged, but not by much.

    Like has been said, this is going to be a very expensive lesson.

    I bought my current 302 H.O for $400.00 from a salvageyard.
  7. NKau

    NKau Founding Member

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    No problem here either. Just didn't see the need to rub it in the kid's face; he probably feels bad enough already. As far as the Kud pic goes, I remember someone having the animated version; 4 years ago when mudvayne was popular :p If it was yours, I'll begrudgingly let you have it back if that's the case.
  8. charlesw6954

    charlesw6954 Founding Member

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    my friend had a fairmont with a 255 and said it hauled balls. also he said it could take my mustang. i said you are a dumbass.

    hell i picked up a really great 5.0 engine from mps for $650 SHIPPED!!!
  9. maddog11

    maddog11 New Member

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    I had a 255 in my 80 T-Bird years ago... The thing was great on the highway (even with a C4).... As for your drivetrain, it will hold... 2.25:1 or 2.73:1 will make gas stations almost a memory....The T5 should make it a bit better of a car to drive (performance wise)... As for aftermarket parts, I could never find any but that was pre internet days (all the oldtimers should remember those days)... Also watch the rear main, it is garbage as far as I'm concerned... With all that said and done - Good luck, and don't let all this negative feed back deter you from the task at hand, if you accomplish one thing from all this, it is that you swapped a motor (which is more than some people can say!) BTW here is a link to another site that may help - they are into the 4 eyed stangs and capris, so they may have some experience with the 255.... http://www.foureyedpride.com
  10. ³à³

    ³à³ New Member

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    Thanks for some postive statement!
  11. rd

    rd Founding Member

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    If you can get all the v8 trinkets, ie, brackets, oil pan, ignition, throttle cable, mech fuel pump timing cover, etc, it is one way to go. The C4 and bellhousing are the same for a 302 and will work.

    It is externally identical to the 79 5.0 engine in Mustangs. It will fit in the car and allow you to set everything up for a carbed v8. Most will have the old style York ac compressor set up, but the newer ones fit fine also.

    I am not sure what balance it is, so I used the 255 damper and flexplate, it is the 164 tooth version and fit my C4's just fine.

    I did it this way, with a rebuilt 1980 255 2v from an 80 Capri into my 82 Mustang. Shorty headers fit fine. With a 79 2v carb, it ran a strong 16.67 at 81 mph with 2.73 gears!

    It is every bit as reliable and durable as a 302. In 1981 Car Craft and Car and Driver built cars with this engine!

    However, it is not really worth a lot of money for performance upgrades, as others have said. Main issues are that smaller bores that may lead to valve/bore interference, and I think smaller intake ports than most 302 performance manifolds. Otherwise, intakes, etc, bolt up ok.

    I still have that motor available and for sale also!
  12. CarlsV6

    CarlsV6 Founding Member

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    Yeah, I'd definately recommend posting about it on foureyedpride.com. Prolly get a little more information there though not many people there run the 255's either.
  13. jwzg

    jwzg Member

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    Interesting Post

    I think this is probably the best post I've seen in a while. Why you ask? Although I think it was a waste of money to pay that much for a 255, I DO think that you will have a fine learning experience as we all have with our Mustangs of various types. Everybody laughed when I bought my first car; a 1966 Chevy BelAir 4 door w/a 283 and Powerslide. What a sled! I had a heck of a lot of fun just learning how a carb worked, and I made that car run low 17's. I've been tooling around in my LX 5.0 for almost 13 yrs now, and I wouldn't know **** about how to build this new engine for it if it weren't for a few "learning experiences" with that first one. I'd personally like to see what you can do to make this combination run as fast as possible. Don't forget tuning, air filter, gears and weight. You may have some regrets, but you will have a lot of fun in the process, and you'll be setting yourself up to know what to do when that 255 bites the dust. Just don't get too cocky that you have a V8 Stang :)

    By the way welcome to Stangnet!
  14. ³à³

    ³à³ New Member

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    Thankx to all.
    Update the 255 sits in the car bolted up.
    The intake the guy has on the truck is made by Offenhauser. He thinks he has another one and is gonna check for us. I know that will make a big difference for sure.

    Ill post back up when more happens.
  15. 85_SS_302_Coupe

    85_SS_302_Coupe it sucks (I know) to be on the receiving end

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    The idea of a stout 255 is actually a cool idea, the problem is you'd have to put in more money than it'll EVER be worth to make the power that you'd have with a 302.

    Hell you can build a 392 stroker with all stock parts for less than 1200 bucks if you're doing the work yourself.
  16. Michael Yount

    Michael Yount Advanced Member

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    Good luck with it - remember, all the intake/carb work in the world won't help much if the flow can't make it through those stock heads.
  17. 85_SS_302_Coupe

    85_SS_302_Coupe it sucks (I know) to be on the receiving end

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    This of it like this.....My Cherokee is a 245, that's .2 liters smaller than your motor, and it puts out more power.

    My Cherokee can't keep up with a bone stock 302 Mustang, so you do the math.
  18. bgjohnson

    bgjohnson Founding Member

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    have you gotten the motor started yet? any test runs to speak of?
  19. Brute

    Brute New Member

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    I have to agree with the conscensious here...sell the 4.2L and start with a 302 or 351. If you read the Mustang Performance handbook, they recommend not touching the 4.2. There are NO performance parts that bolt on to that engine. No heads, no cams, etc. In my area (Detroit), you can get a complete 5.0HO out of a wrecked car for $500, complete with accessories. There is an amazing amount of potiential in the 302 and 351, and parts are dime-a-dozen. Running 13s with a 302 or 351 can be done LOW BUCK, with some simple bolt-ons. To get a 4.2 into that range, you'll need an amazing amount of custom head porting work, a custom ground cam, etc. I'm sure it can be done, but it'll cost WAY more than getting a 302 or 351 built.
  20. ³à³

    ³à³ New Member

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    Well it is cranking over. All wiring is complete and looks sweet I must say. The guy is bringing the 4bbl intake over tonight. It is an Offy intake and limited production from what info I have???? we will see.
    After that we put the carb on and go for a test drive. By mid morning tomorrow I should hear this puppy run :D

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