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Discussion Starter · #1 ·
Without starting a melt down
just wondering whether anyone has ever used or had first hand experience with any of the aluminium engine blocks marketed by speed master for any application car or marine
My interest was in aluminium BBC block as was looking at weight savings and whether I could get the weight down close to iron sbc to drop into car older GM holden which came out with iron block/headed 304” /5 litre ( similar to Buick)
Was thinking Aluminiun headed MKIV aluminium block
4.5” bore/3.1” stroke = 394ci (6.5 litre) + GM 6l80e (6-speed) to wake it up
Have most of parts here excluding the alum block although could use bowtie block that is here so figure it was cost of alum engine block vs LS engine (possible needing rebuild)

Go easy with me on the replies we aren’t spoiled for choice down under like you chaps
 

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Good day mate!
Im following. Nice question...
I have a large displacement small block on the stand right now. Most of the reason I didn't go big block was the weight.
If you have parts for big block already, that is a bonus.
Others will jump on this like a dog on a bone, as the sun comes this way today!
 

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After bad experience with pro comp distributor and metering block my take is never again.
Very poor machining to the point of being unusable. Distributor housing was undersized by over .006” and meter block idle mix screw was cocked and off center with non existing seat.
 

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An aluminum block such as an LS or LT was designed to be fabricated of aluminum. All though they made cast iron truck LS‘s too. But the taking of an old BBC design and just changing material to aluminum is not an optimum design under stress situations. One would be in a better situation with an aluminum block that was designed and had extensive testing to verify it’s longevity. Aluminum alloy, lower end webbing, and computer analysis to verify integrity is essential. A fly by nite knock off certainly does not give a warm feeling of providing any of this.
 

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Discussion Starter · #7 ·
You are not the first to ask.


Towards the bottom, there are some valid points made about how OE can spend big bucks on R&D, where smaller companies just cant.
Also something about giving up power vs an Iron Block.
yes, been over this thread the other night from front-back , interesting read
seems SM/PC heads are better and seem few people out there are purchasing them, and some opinions are that the casting are okay if you assemble with valves/springs with good quality parts

However not much noise about the engine blocks
would of thought someone-somewhere would of grabbed one of the aluminium engine blocks and assembled something
there are few things of regretted buying over the years, and still have the picture of the Donovan 500 10.2" block that missed out on a steal of a price
This taught me valuable lesson, thou who hesitates loses out
when you look at the valley webbing its similar to SM block which has been strengthened.
However not sure what actual block the SM alum block was pro-typed on ?
here are few pic's
1. Donovan 500 Alum BBC used
2. Speedmaster Alum BBC new
 

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Discussion Starter · #8 ·
Barry thanks for update on the heads,
Not much noise about the engine blocks
would of thought someone-somewhere would of grabbed one of the aluminium engine blocks and assembled something
There are few things of regretted buying over the years, and still have the picture of the Donovan 500 10.2" block that missed out on a steal of a price
This taught me valuable lesson, thou who hesitates loses out
when you look at the valley webbing its similar to SM block which has been strengthened.
However not sure what actual block the SM alum block was pro-typed on ?
here are few pic's
1. Donovan 500 Alum BBC used
2. Speedmaster Alum BBC new
 

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The amount your going to save running LS heads would tip the scales for me.

But I also have a 68 Cadillac 472 and am always on the lookout for a 500. The high nickel content makes these blpcks lighter. That being said if you can build a 540 for less then 7k your doing something right. That same 7k with a LS can spank a 540.
 

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From what I see a lot more people buy from ProComp than will admit to it. The obvious plum in the pudding is they have been in business a long time. Business that can’t sell don’t stay in business. that’s not to say you won’t get something that doesn’t present problems but it does say in the face of bad press something keeps their boat afloat.

As for aluminum blocks made after the pattern of those of cast iron, the weak points of the design are apparent and the numerous failures by the Big 3 to successfully bring an aluminum copy of a cast iron block goes back a long way. The Chrysler slant 6 was one of the first, originally to be aluminum but configured as if iron it didn’t get through its first year before being recast in iron. Since Chrysler as a money saving effort simply used the aluminum patterns for the iron castings which proved to make one mighty tough engine. Everybody tried aluminum versions of iron V8’s while some held together to finish a race, none were ever considered sufficiently good for regular production. The aluminum Buick V8’s went to Rover who‘s much slower production rate and some redesign ended up with a fairly decent engine, especially by British standards. The Vega engine was a disaster. It being designed like an iron engine but without any upper cylinder support to the cooling jacket. Somehow GM thought that an iron head through a head gasket would stabilize the upper bores, it didn’t. While the popular press loved to blame the high silicon aluminum the pistons rode on and that was a contributor, but the root of the problem was the floating upper cylinders that were free to wobble and wave around as temperature and pressure may dictate.

On the bottom end the concept of free floating main caps secured with vertical bolts as in an iron block just doesn’t hold up. Here you need to look to the high power V type aircraft engines that reached their design pinnicle in WW2. Here you would see the bottom end is a Y block with cross bolted mains with the Mercedes Benz and Rolls-Royce engines and with a bolt on girdle that is one piece with the main caps on the Allison. Lacking these approaches to the bottom end aluminum simply lacks the rigidity and strength to simply use a mid crankshaft parting line block with free standing main caps.

It should be noted that the Gen III and on SBC with aluminum blocks use the Allison style one piece girdle with mains on the bottom and at the valley has extended the head deck inboard past the pushrods as was done in post war OHV automotive V8’s starting with the Cadillac and Oldsmobile engines and common to Chrysler and Ford. The SBC was the first breakaway from this design which was quickly emulated in the second V8’s design wave of the mid-late 1950’s by everybody.

So it is reasonable to expect aluminum copies of cast iron blocks do not have real long life spans even with cast in reinforcement bars across the valley, having worked on many a Donovan aluminum copy of the Chrysler Hemi that cracked along the valley walls even with this reinforcement. It just isn’t the right thing in the right place.

Bogie
 

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I've started to run across a few instances of guys using the Iron SBC performance block from SpeedMaster.....2 of those guys are making north of 1300 HP at 406" and 421" and haven't had any problems with it. (twin turbo on E85 or Methanol).
One runs 5.80's @ 140 mph in the 1/8 mile on a 28" x 10.5" slick at about 2900 lbs. Been together for a season and a half.
What I don't know was how much of a machining "tune-up" did they need at their local machine shop....whether it is similar to prepping a Dart block or if it was more involved.
 

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Discussion Starter · #12 ·
like i said i have the parts to put together a few bbc however restriction being as they are here in Australia was thinking to utilise 3.1" billet crank I have here and drop into alloy block, to make 4.5/3.1" = 394"
try and keep weight down for stout smallish BBC
its for local run around, no track use
was thinking to bolt in 6 speed auto to get it moving
 

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like i said i have the parts to put together a few bbc however restriction being as they are here in Australia was thinking to utilise 3.1" billet crank I have here and drop into alloy block, to make 4.5/3.1" = 394"
try and keep weight down for stout smallish BBC
its for local run around, no track use
was thinking to bolt in 6 speed auto to get it moving
Use your Iron block. (If it was me...)
Cheers!
 

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If you’re not going to press it for big power numbers that then get used a lot at that level I’d be OK with the PC/Speedmaster as lightweight street block in a hot rod street cruiser.

If any of these guys whether Dart or ProComp or whomever would take a lesson seen in the Gen III and up blocks and either put a deep skirt i on the block that uses 4 bolt mains in all positions with a cross bolt then they’ed have something. The upper bores need to be tied to the coolant jackets and since the heads already overhang the valley a bit put some structure under them as well as the ribs side to side over the center bearing bulkheads. Now you're talking a real race ready block. It I ever hit the Mega Lotto the first investment I’ll make is an SBC and SBF aluminum block like that.

Bogie
 

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Discussion Starter · #15 ·
bogie
i think you may have something there,
I can see where the advantages of the LS design block in main cap area with long skirting and 6 bolt mains
if you were looking for 600 Hp in daily driver, with 6L80E transmission, just to give it a blip now and then to shake the tyres, have 3.1", 3.76", 4" stroke crank however was trying to keep the ci down, as not sure what I can get away with legally registering car here
Not looking to put 1500-2000hp with block
 
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