Question on upgrading a 289

[Slash]

Larger combustion chambers have lower compression, therefore less performance. You want smaller combustion chambers. For the amount of money/effort that you would be putting in those E5 heads you could do much better. Just my opinion.

If you do end up using the stock heads, don't bother with a cam or intake. All it will do is shift the torque peak higher to a point where the engine isn't capable of breathing enough air to make good power. You will just lose torque and power instead of gaining it.

A stock 289 won't really rev past 5500rpm. Possibly less. With the factory cam and heads, the torque probably comes on at 2,000rpm so you have a nice 3,000rpm window of torque, 2,000-5500rpm. If you put in a high-lift cam, it will shift that torque peak. So instead of that 2,000rpm-5500rpm sweet spot, it will be more like 3,500rpm-6500/7000rpm. Which is great if the rest of your engine can cope with that. But with stock heads, you are still limited to 5,500rpm. So you are just narrowing your torque band in reality, with no increase in power nor torque. I've done this before, it was the worst mod I ever did to my Mustang. Now my friend's car had a full trick flow heads, cam, and intake package. His car came alive at 4,000rpm and didn't stop until 7,000. It was an animal.

You can get certain cams to transfer the power that he does have to different RPM ranges however, which could be beneficial depending on how he drives the car. Since he will be having a low powered engine, a low RPM range cam would be beneficial to really get the car moving quickly so it's not a total dog off the line. And as said, a better rear end would really boost performance as well. With a low rpm range cam though don't epxect it to wind up past 4000-4500 rpm.

 

[Dennisch]

But this Mustang, on the other hand, should hold a Jaguar V12 just fine.

/Crossthreadjump.

 

[Slash]

But this Mustang, on the other hand, should hold a Jaguar V12 just fine.

/Crossthreadjump.

The engine bay isn't much bigger than the Fox Body. It would probably be slightly easier than stuffing one in a fox body though.

 

[Dennisch]

L6 fits, V8 fits, therefore V12 will fit.
4 speed E-type Gearbox, and you will be going 85mph in second gear.

 

[Slash]

L6 fits, V8 fits, therefore V12 will fit.

That logic means nothing unless it's based on specs. Yes, it's possible certain V12's will fit depending on block length, but fitting any block over 27 inches in will NOT happen.

 

[Slash]

I've done a basic "Desktop Dyno" run on a mild build with some decent figures. I ran a 650cfm carb, on a single plane high flow intake with stock 302 sized ports with canted valves with stock figures of what early 302 heads can do on a 289 (mind you I set them for 4v vs 2v). Set up for 10.5:1 compression same as the early 302's and from a stock 289 it will be a decent size bump in compression. I ran the profile of a stock mid 70s 302 cam as well, not a mild street cam or RV cam. Also chose long tube headers with no mufflers (straight piped), and left the block completely stock and no overbore or stroking. Here are results with different exhaust setups. Now, if I remember correctly, the block has already been bored out .030.

Please note, these are flywheel hp and torque figures. Wheel hp will depend on the drivetrain.

Longtube headers, straight pipes
Longtube headers, mufflers (the power output does not vary but 1-2hp MAYBE)



332hp @ 5500rpm
338ft-lb @ 4500rpm






Stock exhaust manifolds with mufflers

300hp @ 6000rpm
295ftlb @ 4500rpm


So with this basic setup you'll be getting probably about 250-275 to the wheels all the time if you run what's posted. Obviously there is plenty other options out there as well. Please remember these figures are just a rough estimate of what to expect.

I did run a .030 overbore again, and as expected, not much of a gain was there so these figures still stand either way. The most noticable bump was torque being boosted to 341ft-lbs with straight pipes.

 

[Eric.]

That logic means nothing unless it's based on specs. Yes, it's possible certain V12's will fit depending on block length, but fitting any block over 27 inches in will NOT happen.

What do you do with all that space in front of the motor then?

 

[Slash]

What do you do with all that space in front of the motor then?

Pulleys and accesories if they havent been deleted. It's still a tight squeeze.

 

[Dennisch]

Looking at that under the hood picture.
Lengthwise it will be a sure and easy fit. But the space between the springmounts will be quite the squeeze for a V12.

 

[Slash]

That is why the Mustang was redesigned in 1967 so the 390 big block would fit.

 

[Buddy rawls]

I know this way after the fact on this thread, but there was a 4v 302 in 1968, and it was not a rare or uncommon motor. It was, however, a single year production motor, though. It used a 53cc combustion chamber, like the 64.5-67 289's. It is the motor that came in the 68 gt350's, as was also available in the mustangs and cougars, etc. it was designated as the 302-4v Premium Fuel. it was essentially a 289-4v (rail rocker version) except in the 302 geometry. The standard 2v 289 that lingered thru that year (its last) and the 2v 302 were awful motors with their 63cc chambers that made higher compression impossible without dome tops.

So anyway, the guy that sold the car/motor may not have been as 'off' as the thread comments indicated. Yes, its not a hipo, no such thing. But it was a special, higher hp version, 302. And it did come in shelby cars for 1968.