Shelby standard block question

[stangbuilder]

Y'all keep talking, just makes me hate 'em more.......LOL

Something doesn't sound right with this whole argument.  If what some of you are claiming is true, no new car manufacturer would build an engine with aluminum block and heads.  I know they are on a weight savings mandate to improve fuel mileage, but the easiest way to improve fuel mileage is compression, and good fuel.  Also, if Lance Smith did R&R the internals from an iron block and install them in an aluminum block, did he blueprint the aluminum block just a carefully as the iron block, did he use new rings, bearings, did he heat the oil, water, engine cycles to the same amount before testing?  Did he do this on the same day? Weather the same, barometer the same?  Etc., etc., I have to say that with all my years of experience, automotive degree, teaching experience, have I ever heard such an argument that cannot be substantiated with back to back dyno testing in a laboratory environment to eliminate all differences but the material used in the block.  A simple gasket mismatch in the intake tract can change the horsepower level on a highly tuned engine, and I have seen 20 hp difference back to back with that situation on the dyno.  I have also seen 20 hp difference with spacers turned around differently, or different timing, fuel pressures, different oil level in oil pan, all make differences in back to back horsepower testing to find the ultimate combination.  A carburetor not opening fully and not caught when installing on the dyno.  I have to call this an argument that I cannot agree with until I see it performed under the same testing environment on the same day with identically prepared engines, and have all the same pulls to break in, all the same temperatures, and same individuals monitoring the testing procedures to verify.  JMO, but skeptical to say the least at 20-40hp level.  Joe-JDC

So what is the fact its well documented that they burn oil??

[Posi67]

"Spend $5k for an aluminum block, pay more for prep, and make 750 hp......or spend $3500 for an iron block and make 800 hp. 

Numbers are theoretical for the sake of argument, but the points are still valid.  LOL"

Well, in my case I didn't spend quite that much on a block and with my setup the 100# off the nose is worth money. I could be wrong but don't expect block prep will be a deal breaker since both the Iron and Aluminum need similar work. I'm not arguing the fact Iron is the material of choice for the serious go fast guys. I have other ways to reduce weight or make a few HP but I prefer to keep my car somewhat "stockish" looking. Results may vary... 

[TJ]

I don't think new car makers using aluminum blocks/heads is contradictory to the notion iron makes more hp than aluminum.  Looks like FE iron vs aluminum makes a difference of 20-40 hp (about 3-6%).  The Craft engine was 482 cubes while the average family car is roughly 220 cubes.  So 3-6% difference in hp for a family car size motor is around 15 hp at most ...not likely noticeable to a consumer.  Add to that all the gizmos and do-dads (like variable cam timing) on modern family cars and the consumer is so pleased by the higher revving/higher hp aluminum block that the iron block of yesterday is not missed.

[JohnN-1BADFE]

Would it be fair to say the Shelby block is superior vs. all other alum blocks?....

Fully redesigned, the Shelby 427 Alloy FE block is 45 percent lighter, yet stronger than the factory cast iron version.

The Shelby block offers these premium performance features:

Deep lifter valley reinforcing webs combined with thick oil pan rails and main webs maximize block strength.
Thick 0.750-inch deck delivers the foundation needed for maximum head gasket sealing and retention.
Priority main oiling system. With the oil gallery raised adjacent to the camshaft bore, oil flow is directed to main bearings first, before going to the cam bearing. Crank life is maximized.
Strong enough to support over 1500 horsepower outputs.
Shelby's FE alloy block delivers superior bottom end stability at high rpm.

This is accomplished by:

Extended skirt design.
2,3,4 main caps are cross bolted with 4 cross bolts. Main caps are billet steel and cap alignment is further enhanced by integral dowel section in the main studs.
Steel caps allow moderate bearing clearances for cold starts.

Centrifugally cast duplicate iron. cylinder sleeves are fitted in the block, with an interference step fit that creates precise, non shift sleeves positioning. Cylinder walls are stained and revised cooling passages make street or race track cooling problems a thing of the past.

The block requires special Shelby head studs, available separately. Unlike a stock block, where the head bolt threads start at the deck surface, the Shelby stud threads are positioned adjacent to the cylinder bore bottom. This configuration delivers maximum gasket seal/retention and minimum cylinder bore distortion when the head is torqued to the block.

[Posi67]

Yes, that is fair to say and they are priced accordingly. I wouldn't trust any of the other brands to take the HP the Shelby does but then they weren't designed to compete in that area. Sorry for joining in the thread hijack which is of course what happens with almost every thread. 

[blykins]

"Spend $5k for an aluminum block, pay more for prep, and make 750 hp......or spend $3500 for an iron block and make 800 hp. 

Numbers are theoretical for the sake of argument, but the points are still valid.  LOL"

Well, in my case I didn't spend quite that much on a block and with my setup the 100# off the nose is worth money. I could be wrong but don't expect block prep will be a deal breaker since both the Iron and Aluminum need similar work. I'm not arguing the fact Iron is the material of choice for the serious go fast guys. I have other ways to reduce weight or make a few HP but I prefer to keep my car somewhat "stockish" looking. Results may vary...

There is a little more work with the aluminum blocks.  Sleeves need to be set and provisions need to be made to make sure they don't leak due to porosity issues.  I think Barry sends all of his off to have them coated internally which adds to the cost of the machine work/prep work.   I don't have them coated, but do a pressure test first.  If they don't pass, they go back.  If they do pass, then I include a bottle of ceramic seal with the engine after it's dyno'd and sent out.   I should be talking in past tense as I haven't taken any aluminum block builds in over a year and really don't intend to do any more.

[blykins]

Would it be fair to say the Shelby block is superior vs. all other alum blocks?....

Fully redesigned, the Shelby 427 Alloy FE block is 45 percent lighter, yet stronger than the factory cast iron version.

The Shelby block offers these premium performance features:

Deep lifter valley reinforcing webs combined with thick oil pan rails and main webs maximize block strength.
Thick 0.750-inch deck delivers the foundation needed for maximum head gasket sealing and retention.
Priority main oiling system. With the oil gallery raised adjacent to the camshaft bore, oil flow is directed to main bearings first, before going to the cam bearing. Crank life is maximized.
Strong enough to support over 1500 horsepower outputs.
Shelby's FE alloy block delivers superior bottom end stability at high rpm.

This is accomplished by:

Extended skirt design.
2,3,4 main caps are cross bolted with 4 cross bolts. Main caps are billet steel and cap alignment is further enhanced by integral dowel section in the main studs.
Steel caps allow moderate bearing clearances for cold starts.

Centrifugally cast duplicate iron. cylinder sleeves are fitted in the block, with an interference step fit that creates precise, non shift sleeves positioning. Cylinder walls are stained and revised cooling passages make street or race track cooling problems a thing of the past.

The block requires special Shelby head studs, available separately. Unlike a stock block, where the head bolt threads start at the deck surface, the Shelby stud threads are positioned adjacent to the cylinder bore bottom. This configuration delivers maximum gasket seal/retention and minimum cylinder bore distortion when the head is torqued to the block.

I would agree that the Shelby block is superior, although I have heard of several 1000+ hp Pond aluminum block builds.

The underlying argument here though is not how much hp they will withstand, but if an aluminum block’s pros outweigh the cons.  I would argue that any aftermarket FE block would hold 1000+ hp as they all have provisions for priority oiling, billet steel caps, increased structural support, etc. 

[machoneman]

I wonder what actually causes the excessive oil consumption? Is it oil slipping past the sleeve to cylinder head junction, then getting burned in the chamber? Blowby primarily? Would not the spark plugs get fouled pretty quickly then? Or is it the sleeves flexing against piston/ring movement?

I've oft considered an aluminum block (sorry, a 351W design, stoked to maybe a 408-427) to reduce nose and overall weight for my Mach 1 but the cost is damned high as killer, big-bore 4.125" iron blocks are readily available and the overall cost/prep work is far cheaper. Based on all these great comments, I may stick with the OEM iron block as a 358 CID engine. 

[blykins]

I would assume it’s the cylinder not being able to stay straight and round because the support around it is flexing and moving.  We torque plate hone blocks but I have taken all-aluminum FEs back apart after dynoing to do head work and have seen shadows in the cylinders.

You also raise a good point about oil slipping past the sleeve, as when an aluminum block gets hot, it will grow up around the sleeve. 

[machoneman]

I would assume it’s the cylinder not being able to stay straight and round because the support around it is flexing and moving.  We torque plate hone blocks but I have taken all-aluminum FEs back apart after dynoing to do head work and have seen shadows in the cylinders.

Ah, thanks Brent and also for the fast reply! That makes perfect sense. Have zero exeperience with modern aluminum blocks but crewed on a 417 Donovan alky motored dragster long ago. Those sleeves and modern 426 Hemi-based fuel engines of today have super thick sleeves, now in solid blocks that I guess have near zero flex. The Donovan sleeve's bores always looked good save an engine blow-up or a backsided piston due usually to a too-lean tune-up. 

[Leny Mason]

On Nick Arias Engines they were six hundred inch and bigger and maybe the cubic inch has something to do with it, but it was all better after new sleeves the third time, we are doing a Nissan V eight now it is cool it has an intake port for every valve and a lot of valves anyway the sleeves are cast into the aluminum maybe that is why they work. Leny Mason