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Discussion Starter #1
Wanted to ponder a question across you guys. (My car is at the body shop, so I'm loosing my mind waiting for it to get done)

In the terms of performance from the 289, a good 4b carb and intake is a gimmie.
But what's the 289 biggest weakness? My wild guess would be the heads?

Just curious for the biggest drawback of a 66 289, motor wise.

I'm just pondering on 302, or stroker 8.2, or 351. But if I buy something now, I'd like it to carry over. Like good heads.
 

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I would say heads are the weak link of small block Fords in general. Going to a vintage 302 is not going to yield many gains. A more modern 5.0 will have more power in stock form. That said, with a mild cam, intake, headers and 3.55 gears (before changing heads) my car was quicker than the fox body 5.0s.
 

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Now THERE'S a relative question. For the owner who wants a smooth running, reliable and relatively economical engine the STOCK 289 fits the bill quite nicely. For someone who wants a bit more power than the stock 289 is willing to deliver the options run the gamut of modifications to either increase displacement (stroke), breathing (intake, heads, exhaust, camshaft), ignition timing (curves) or external things to improve mechanical advantage (transmissions, axle ratio's, etc.).

The "weakness" is only a weakness when you want to exceed certain operating parameters. Yes, it is commonly acknowledged that stock 289 cylinder heads, specifically the exhaust port size and shape, is a bottleneck to higher performance, but if you're not going to exceed .400" in valve lift then head work is really not necessary.
 

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The SBF is a good engine but don't confuse that with a performance engine. In stock form even the K code was quite mild.

Heads as stated but putting on better heads won't do much when you are using the stock log exhaust manifolds, cam shaft, valve springs, iron intake, etc.
 

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It is my opinion that other than the weight of the stock 289 heads, once you make them flow by port matching them to your intake and exhaust, and install screw in studs, you have a better head than most aluminum heads mainly because you have a smaller compression chamber which increases the compression ratio which equates to more power.
 

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I'm assuming you're asking about weaknesses regarding performance.

Everyone pretty much nailed it when when they said heads- they're really awful. Poor flow, small ports and press in rocker studs. I would add that 289 cubic inches really isn't that much displacement; big power (outside of forced induction) requires either big cubic inches or high RPM. This brings me to the next weakness of the 289, their ability to split down the middle and crack when you throw high RPM /HP at them :).

Beyond that, they're great!
 

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Whatchya gonna do with it? Cruise it only to shows? Drive it 6 months a year and only on sunny days? Make it a daily driver? Thrash a highway entrance ramp and slip it into overdrive? Or occasionally embarrass someone at the track? My 289 has been reliable after a 1993 rebuild as my ONLY transportation for several years, including to shows, it still gets 22+mpg with no overdrive until I hafta scratch that itch for a little fun, and yeah, back in the day, I did do a little street racing. Don't tell Mom.
You'll get out of it what you put in it. Buy quality reliable parts, let it breathe on the in and the out, and the Mustang is so light you don't need 500 horses to make it a fierce competitor. You can also build a stroker or a GT40P 5.0 to look bone stock for show while having some extra GO.
 

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Discussion Starter #11
Whatchya gonna do with it? Cruise it only to shows? Drive it 6 months a year and only on sunny days? Make it a daily driver? Thrash a highway entrance ramp and slip it into overdrive? Or occasionally embarrass someone at the track? My 289 has been reliable after a 1993 rebuild as my ONLY transportation for several years, including to shows, it still gets 22+mpg with no overdrive until I hafta scratch that itch for a little fun, and yeah, back in the day, I did do a little street racing. Don't tell Mom.
You'll get out of it what you put in it. Buy quality reliable parts, let it breathe on the in and the out, and the Mustang is so light you don't need 500 horses to make it a fierce competitor. You can also build a stroker or a GT40P 5.0 to look bone stock for show while having some extra GO.
Drive it all the time, whenever I feel like it. I've got a brand new F150 that's my daily now. But I don't always need to be driving that. Def highway cruises, and will let into it plenty. Won't see track time. It's a 289 C4 with 2.80 gears right now. My focus now is finishing the body work and then I'm reworking the entire suspension and steering with new/upgraded parts. Along with stiffening the car up with torque boxes and subframes. I've already got the disc brake front conversion, and I've got a 500cfm Edelbrock carb and intake to throw on for now. It's already got stainless long tubes, but needs a better exhaust (it's quiet mufflers on there now). I've updated the points to the pertronix deal, but I'm having the distributor recurved as soon as I get the car back.

From my understanding the factory heads have been worked (to what extent, I don't know). But in my old weekend warrior 87 Mustang 5.0, I know the heads were always an issue. Figured the same held true with the earlier years, but wanted to ask. (I ran a significant shot of nitrous through that car on the stock block and heads, and it did fine)

Just not sure of my final direction yet. The entire package needs to be figured out harmoniously together before I start making substantial moves.
If I stay C4, I'll keep the gears fairly tall. Might get a little closer to 3.25 or 3.00
If I go AOD, I'll go deeper in the gears near 3.55

Then theres motor options. 306 Roller, 331 Stroker, 347 Stroker, and of course the 351 (which I'm not 100% sold on just yet).

I was just thinking, I could get heads now. And still use them again on the later build (probably would be undersized for the above mentioned builds). Really I'm just playing with ideas in my own head so I can work out what direction to finally go. Really, I just want to drive it now.
 

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It is my opinion that other than the weight of the stock 289 heads, once you make them flow by port matching them to your intake and exhaust, and install screw in studs, you have a better head than most aluminum heads mainly because you have a smaller compression chamber which increases the compression ratio which equates to more power.
For the $ required for a good port job and install of screw in studs one can pretty much buy a set of aluminum heads and have them milled to maintain compression.

A well ported set of vintage heads will not flow as well as modern heads as the valves are smaller.
 

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Now THERE'S a relative question. For the owner who wants a smooth running, reliable and relatively economical engine the STOCK 289 fits the bill quite nicely. For someone who wants a bit more power than the stock 289 is willing to deliver the options run the gamut of modifications to either increase displacement (stroke), breathing (intake, heads, exhaust, camshaft), ignition timing (curves) or external things to improve mechanical advantage (transmissions, axle ratio's, etc.).

The "weakness" is only a weakness when you want to exceed certain operating parameters. Yes, it is commonly acknowledged that stock 289 cylinder heads, specifically the exhaust port size and shape, is a bottleneck to higher performance, but if you're not going to exceed .400" in valve lift then head work is really not necessary.
woodchuck is right.it really depends on what you want from this motor. two areas for reliability are the small rod bolts, and the stock oil pump driveshaft.

the stock heads will limit the upper end power, but fuel economy is generally good overall.

another limiting factor is going to be the stock camshaft as well, it isnt a performance grind to be sure.

the stock bottom end is plenty strong for most things, especially the rods and crank. stock pistons can be a little suspect though, but as long as you are not trying to run too much boost of some form, they will do the job nicely.
 

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For the $ required for a good port job and install of screw in studs one can pretty much buy a set of aluminum heads and have them milled to maintain compression.

A well ported set of vintage heads will not flow as well as modern heads as the valves are smaller.
I did forget to mention that the valves in my C4OE 289 heads are 1.94" intake, 1.6" exhaust, and threaded rocker studs I guess I'm the exception to the rule. It cost me $325 including parts to port match my heads, have the valves replaced, new valve seats, springs and studs. A friend did the machine work. I bought the parts and did some of the labor on the heads with supervision. I reassembled the engine myself.
 

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I know a 289 is relatively small cubic inches, but it is just such an iconic size that screams vintage mustang. And the first Cobras used it.

Not saying I don't love others as well....Boss 429 comes to mind....
 

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Whatchya gonna do with it? Cruise it only to shows? Drive it 6 months a year and only on sunny days? Make it a daily driver? Thrash a highway entrance ramp and slip it into overdrive? Or occasionally embarrass someone at the track? My 289 has been reliable after a 1993 rebuild as my ONLY transportation for several years, including to shows, it still gets 22+mpg with no overdrive until I hafta scratch that itch for a little fun, and yeah, back in the day, I did do a little street racing. Don't tell Mom.
You'll get out of it what you put in it. Buy quality reliable parts, let it breathe on the in and the out, and the Mustang is so light you don't need 500 horses to make it a fierce competitor. You can also build a stroker or a GT40P 5.0 to look bone stock for show while having some extra GO.
How are you getting over 20 MPG? I did some calculating yesterday on mine and I'm getting about 11-12 with a mild build and 3.0 gears.
 

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How are you getting over 20 MPG? I did some calculating yesterday on mine and I'm getting about 11-12 with a mild build and 3.0 gears.
I had a 65 Ford Custom with a 289 w/ C4 transmission, 2V carb. It would get 22+ MPG on the highway consistently.
 
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