Vote 428 or aluminum 427FE??

[Excaliber]

The new blocks have significant improvements over the original blocks.

They are "improved", but I wouldn't qualify that as a significant improvement. For 99% of those running one, the improvement's are meaningless. What can you do with a modern 427 block that you can't with an original block, that is "significant" to the average Cobra owner?

The cool factor and bragging rights are highly subjective depending on one's point of view. Some may well see an original side oiler as exceeding the "cool factor" and "bragging rights" of a Shelby. Other's see great value in the Shelby name. There is no right or wrong position on that issue, it is what it is.

If I may suggest some things you could with a modern block over an old one.
1. Save time and frustration looking for a nice original block. Buying new takes less energy and generally speaking is a better gaurentee of getting a good block the first time.
2. Build a stronger, higher horse power motor. To realize the benefit, new vs old, I think you would need to be approaching 900 to 1,000 horse power.
3. Run it at a higher rpm than an original block and expect it to live longer while doing so? #3 is kind of iffy, most folks are going to stroke the motor, often to the max, and a big strock and high rpm are not generally two compatible goals. More stroke, less rpm is the rule, a nice fit for a hydraulic roller cam.
4. Bigger bore, in some cases than is possible with an original block, within safe paramenters. Now THAT appeals to me! My prefered recipe is more bore, less stroke, higher rpm. High rpm rules out the hydraulic roller, due mostly to additional expense and ultimately just the limited rpm range of a hydraulic cam in general. A solid roller would not be my first choice for a "street" engine, so your left with a flat tappet as the most logical reasonably priced, street friendly cam choice. And it's pretty clear most folks have moved away from flat tappet (not me, I think they are an excellent choice for many reasons). The benefits of a flat tappet out weigh the negative aspects. So, that which remains is a low rpm, hydraulic roller cam, stroker motor. A recipe I'm not real excited about, new or old block, same same, no significant advantage...

[RodKnock]

Originally Posted by Excaliber

For 99% of those running one, the improvement's are meaningless. What can you do with a modern 427 block that you can't with an original block, that is "significant" to the average Cobra owner?

I personally don't consider these improvements to be meaningless to 99% of us.

Priority main oiling.

Thicker decks.

Billet steel main caps.

The Shelby head stud configuration delivers maximum gasket seal/retention and minimum cylinder bore distortion when the head is torqued to the block.

Extended skirts.

Thick oil pan rails.

Up to 527ci and saves 75 lbs.

There are reasons why the original blocks need sleeves and welding on pan rails.

[1ntCobra]

Originally Posted by Excaliber

They are "improved", but I wouldn't qualify that as a significant improvement. For 99% of those running one, the improvement's are meaningless. What can you do with a modern 427 block that you can't with an original block, that is "significant" to the average Cobra owner?

The cool factor and bragging rights are highly subjective depending on one's point of view. Some may well see an original side oiler as exceeding the "cool factor" and "bragging rights" of a Shelby. Other's see great value in the Shelby name. There is no right or wrong position on that issue, it is what it is.

If I may suggest some things you could with a modern block over an old one.
1. Save time and frustration looking for a nice original block. Buying new takes less energy and generally speaking is a better gaurentee of getting a good block the first time.
2. Build a stronger, higher horse power motor. To realize the benefit, new vs old, I think you would need to be approaching 900 to 1,000 horse power.
3. Run it at a higher rpm than an original block and expect it to live longer while doing so? #3 is kind of iffy, most folks are going to stroke the motor, often to the max, and a big strock and high rpm are not generally two compatible goals. More stroke, less rpm is the rule, a nice fit for a hydraulic roller cam.
4. Bigger bore, in some cases than is possible with an original block, within safe paramenters. Now THAT appeals to me! My prefered recipe is more bore, less stroke, higher rpm. High rpm rules out the hydraulic roller, due mostly to additional expense and ultimately just the limited rpm range of a hydraulic cam in general. A solid roller would not be my first choice for a "street" engine, so your left with a flat tappet as the most logical reasonably priced, street friendly cam choice. And it's pretty clear most folks have moved away from flat tappet (not me, I think they are an excellent choice for many reasons). The benefits of a flat tappet out weigh the negative aspects. So, that which remains is a low rpm, hydraulic roller cam, stroker motor. A recipe I'm not real excited about, new or old block, same same, no significant advantage...

One of the cool things about the Kirkham is that it can be a light weight car with the billet suspension and such. It will certainly be lighter with an aluminum block motor.

Another cool thing about the Kirkham is that it can be very authentic with the expensive and heavier original style suspension.

When you are going for authenticity in a Kirkham, an original 60s side oiler makes perfect sense to me.

When you are going for the high tech light weight billet suspension the modern aluminum block side oiler makes sense to me. In that case who cares if you are not building to block to it 1000hp potential, that is irreverent. It is the light weight block fits into the light weight replica equation.

[Ronbo]

Since we're talking about "period corectness"...

Let's take example from the "period".

The small block cars won all the races, because they handled better. The big block cars were in essence an "attempt" to get the car past the 160MPH "air wall" on long runs, at the sacrifice of handling. (IE: "the turd")

Drop the weight and keep the power of the BB? = Priceless.

And to address the comments that 100lbs on a 2300lb car makes no difference, B.S. that's 100lbs off the front end weight of ~1150lbs. Handling is just as important on the street as the track.

And to think in the "period" they shifted the motor off-center, mounted the batteries opposite the driver. The old man himself only sells aluminum block 427's and now 351's. Wonder what he'd have wished for back then.

As far as over-kill for the 600hp build, well yes, but it's relative: in the "period" production 427's were 450hp (max), the Shelby engines 480hp. A 1500hp rated block is not very stressed which means (hopefully) it's that much longer before stuff starts cracking. A vintage block in the same scenario is definitely "stressed".

From what I've heard the side oiler did little if anything to effect main bearing failure rates except in the most severe racing applications. (quite possibly a fix for a non-existant problem)

Ernie, I think the OP made up his mind about eight pages ago...

"And God looked down from the heavens and saw the Iron man Cobra sporting a nice new CSX alloy block and said "It is good".