Ok, so I figured I would get some advice from you guys on this one. We have a 65 Ford Mustang Coupe, 289 2bbl with long tube headers, automatic, and there is one problem with it.

When going down the road, it smokes a lil bit blue and then when you let off the gas like coming up to a stop sign or slowing down, it smokes really bad. My question is this:

"Is the problem in the heads( like valve seats, bad valves, etc...) or in the cylinder(bad rings, something like that)?" If it is something else, let me know, I am not very experience in motors YET, but I'm getting there.

Also, if faced with the same problem, would you replace the motor(I have a fresh built one on the stand) or rebuild the 289. I am looking for some guidance since I am torn, I like th 289 mustangs, but I like 5.0 motors(out of an 88-93 mustang F.I.)

 

Could be any one or all of those things that you listed. Does it burn much oil? If it was me, I'd put the 5.0 in as you can easily do that in a day and then rebuild the 289 at your leisure.
My first guess would be the valve guides, but if you go so far as pulling the heads to rebuild them it will finish off the bottom end when you put the fresh heads back on top.

 

Stock valve seals are junk. They are neoprene umbrellas inside the valve spring and they crack as soon as you fire it up. When you let off the throttle, the vacuum goes up and you suck more oil past these seals or what's left of them.

Now you might have ring issues as well, as this is an old motor.

Do a compression test. If you have even compression all the way around the motor, a head rebuild with Perfect Circle or other fine brand valve seals would be a safe bet. Check the cylinder walls before you do that, make sure you don't have a gap big enough to check the mains from the top of the motor, a crack, or a gouge in the cylinder wall. (Any of which would probably cause your compression test to be be fubar anyway....)

I had a 65, 2v, 3 speed. Bigger 2v, then rebuilt a motor with 4v, higher compression and a 4 speed. My car wasn't straight (multiple wrecks) and I couldn't afford to redo it right. Sold it for $1100 in '81, just short of 10 years owning it. I like 289s too, but once you get "a motor where the pistons actually move up and down", as one guy in HR mag put it, it's hard to go back.

 

85e150six4mtod is right on about those seals. I think that's most likely your problem. Another thing to watch out for is that those seals can not only crack but can fall apart and the pieces wind up in the oil pan where they can get sucked up by the oil pump. This can lock the pump up and shear the oil pump driveshaft, and suddenly you have no oil pressure! I've had it happen.

Whether you rebuild the 289 or drop in the 5.0 mostly depends on original you want to keep your 'Stang. Me, I can't leave anything alone and I'm always on the quest for more power, so of course I'd go with the 5.0. But I'd rebuild the 289 and keep it wrapped up on a stand so that it could be swapped back in some day.

 

Thanks guys, I kinda figured it was the valve seals, since the compression test checked out even all the way around, which suprised me. It doesn't burn much oil, and the oil looks pretty clean, no discoloration to speak of. It is starting to smoke more and more as the days go by though. I don't care about originalilty of this Mustang, now if it were the 64 1/2 we had a while back, the 260 would've been rebuilt in it. I will probably end up dropping the 5.0 in it for something I can drive instead of my 54 F100 or my Contour SVT, and that will start easy and be reliable(plus to make a good showing to the hot shots around the area with their civics and other imports, which don't bother me untill they try to race me at a stoplight, then I have to prove that my gas will whoop their rice. Even though everybody tells me my Contour SVT is ricer b/c of the exhaust)

Another question for you guys, What was the highest horsepower and torque rated for a 289? I have heard different stories from 250-300+ from the factory. I thought it was 271 from the K Codes in the Mustangs but I could be wrong(stranger things have happened, lol).

 

Shelby got 305 out of the 271 K motor with a few mods.

 

Keep in mind these were gross HP ratings. Now a Mustang might not have much in the way of accessories--mine had the fan, water pump and alternator--one belt. But, I read back in the '80s that they figured the hi-po K motor was probably about 230 hp net. Not sure if that's right.

My favorite 289 story was the guy racing one and running it to 10,000 rpm. Not sure how you do that..... Shelby insisted on 7000 rpm redlines. But valve springs and rods have improved, so maybe you could build one to rev to the moon.....

 

I seem to recall claims of close to 500hp in the 289-powered GT-40, but that was surely not a stock production version...