4.2L 255 from 81 Mustang

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.

blk9450 said:

hey no problem there tough guy, by the way, you are using someone else's avatar.

Click to expand...

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 If it was yours, I'll begrudgingly let you have it back if that's the case.

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!!!

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

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!

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.

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 dick 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!

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.

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.

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.

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

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.