OhioTed

I am rebuilding a 289 & would like to stroke it. I visited a local, well-recommended machine shop to discuss having them do the relief work.
However, the shop told me that "they don't like opening up 289's any more than necessary".

Could I get you all to provide your experience/input regarding the practicality of building a 331 or 347 stroker out of the 289? I'm running a T-5, and just want a healthy, torquey street car, with the old standby formula of 1 hp p/ci. I may go out to the drags now and then, but in general am not looking to build a grenade.

67mustang302

Well, depending on how you drive you may end up killing a T-5 with a 347. But, if all you want is 1hp/cid then a 289/302 is fine. Hell, I'm prolly pushing 300+rwhp out of my 302, and it's relatively mild. If you're set on replacing the bottom end, then stroke it to a 347.

THUMPIN455

You only need to bore it enough to clean up the cylinders, usually .030 over is enough. If you tried to bore a 289 to 331 you would find these open spots in the iron block where water is supposed to go. You can stuff a crank, rods, and pistons in it easy with more stroke and that is where you get the bigger engine from.

The biggest drawback to a 331 or 347 crank is shredding tires and getting exhibition of acceleration citations, provided you dont break the T5. The other drawbacks are:
1. cost, if you have a good crank you could always resize the rods and put new pistons on it. That would be cheaper but make a little less power and considerably less torque.
2. increased fuel consumption unless you have an overdrive, light foot, and you cam it to make lots of torque in the cruise rpm range.
3. some crank kits arent balanced and or require special parts to make them work. Balancing can get expensive if you need to add metal to the crank.

Other than that, its fun having a bigger engine. Thats why I drive 455s and larger.

Starfury

My Scat 331 rotating assembly still only cost the quoted $175 to balance. The builder said that some of the really cheap cranks can sometimes require a lot of mallory to get them balanced properly, but that he never had a problem with any of the Scat setups. I can't imagine any of the more expensive setups would be any worse.

THUMPIN455

Nah its the super cheap stuff that is a pain to balance from what I hear. I like to get them already balanced so I can drop them in a freshly machined block.

109jb

If it were me I would just go with a 351W. It is already stroked to more cubic inches than a 331 or 347. It will fit in any of the early mustangs with some work and header selection. And there are lots of aftermarket go-fast goodies for it.You could pick up a 351W engine to start from for less than the cost of clearancing the 289. Don't get me wrong, there isn't anything wrong with a stroked 289/302, its just my personal preference. In either case, 289,302, or 351W, I don't like to see the bore opened up more than 0.030" over stock.

Jonk67

I like having the orignal 289 in my '67 but wanted more power for 1/8, 1/4mi., autocross, open track, etc. and still be able to daily drive it so I had it stroked to 331 (actually 333 with .040" bore). I looked at the 347 kits but decided that it was too close to 9/10ths of what the engine could stand for a long period, I want to get another 100K out of my motor. The 331 kit did not require my lower skirts to be notched even, the 347 turns at a greater thrust angle and requires notching and put more pressure on the cylinder wall because of the rod angle.

Don't get me wrong, there are plenty of guys running 347's but to me the 331 is closer to 7/10ths which translates to lower cylinder pressures and rod angle = less stress. I haven't installed/started mine yet but expect to be pleasantly surprised over the stock hp/tq. I also installed AFR165's and a few other add ons to make sure it breathes well.
Just my .02,
Jon

67mustang302

A 347 will outperform a 351, simply because the internal components are lighter so the engine will rev faster and lose less power from rotating inertia. If you put a 351 in it then you might as well build a 408 and get the major power out of it.

It also depends on the goals. If you plan to road race for instance then the smaller 302 block with a 347 setup(or 363 on an aftermarket block) will keep the front end lighter so it will handle better, plus the shorter 3.4" stroke produces less inertia so it's not as much of an issue running at sustained high rpm. A 351 will handle the rpm fine as well, but then you end up with less performance and more weight over the front, so again you might as well build a 408 to benefit from the extra power. But then a long 4 or 4.1" stroke engine like that in a road race setup that runs sustained high rpm can be expensive to build and maintain, in a type of racing where having a bunch of power is only 1 part of a MUCH larger equation.

If you want to drag race and drive it as well, then at least a 347, or a 351 stroked to a 408/427. Or if you just want to build a bunch of street power on a budget, keep the block you have, get it bored to .020 over if it cleans up there, if not .030 and slap a 347 kit in it. If all you want is 300-350hp at the flywheel, you can do that in a 289/302 easily.

There's a bazillion 347's running around out there and the only problems they have are like Thumpin mentioned, burning tires, tickets etc

OhioTed

Thank you all for the informed input, guys. I've done a little research and gotten myself a bit ejikated on the benefits and shortcomings of stroking the 289.

Seems that in order to pull off 347 c.i. with a max overbore of .040, the rod length is such that piston wristpin location intrudes on the oil ring. Manufacturers have attempted to overcome this by developing pistons with offset wristpins. Regardless, a reasonable option appears to be to go instead with a 331 kit which, if I have read the data correctly, does not require machining rod-clearance grooves into the bottom of the cylinder bores. Also, info on 331 kits indicates they generate less side-load on the rotating assembly.

Does this all sound about right?

JMD

Well, say "for the sake of argument" that a 347 will only last 80% as long as a stock 289, then perhaps the engine will only last to about 80,000 or so miles.

OK, apart from Carlos, how long will it take most any classic Mustang owner to drive their car 80,000 miles?

For most of us it is so long that we will grow tired of the 347 long before it wears out...

So my opinion,,,,,, stroke the freaking engine... all the way to a 347...

>>Edit>> also, the issue of the oil ring intersecting the wrist pin has been largely marginalized by continued improvement of the kits, this has thus far proved to be a non issue on my sons 408.

Clearancing can be reduced by running H beam rods over I beams.