The working theory for the aluminum engine seems to be that for high performance use the cylinders need more support at the top. I've seen block braces for Honda engines, but making such a brace means an awful lot of measuring and machining. An idea presented to me which seems to meet to goal economically is to make a plate to seal the top of the block, invert the block and add enough HardBlok filler to form about a 3/4" thick deck. I am having a hard time coming up with drawbacks to this method so I'm throwing this out for the hive-mind to consider. Cooling is about the only question that comes to my mind. What do you think might go wrong?

Thankfully my block is very nice around the cylinder tops. My concern isn't initial head gasket sealing, but that the cylinders aren't rigid enough to stay put and hold the head gasket at the desired ~220 hp. Has anyone o-ringed the aluminum block and can share their experience?

Thanks!

Edit: The maker of HardBlok says a guy in California has successfully used HardBlok to form a top deck on Cadillac engines. I assume this Cadillac engine is the HT4100/4500/4900 engine family.

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Joshua

This would seem very sensible. The main worry would be thermal expansion differences and cycling, but probably that is OK. Note that I will be testing the new MLS head gasket on my alum slant before long, so hopefully that will do the trick.

I know I've been "almost there" for 2 yrs, but now the old engine is out of the Valiant and the alum engine is sitting next to it with very few parts to put on it (oilpan+pickup) and then run the EFI.

Lou

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Home of Slant6-powered fun machines since 1988

For 220HP I would expect the stock setup to be more than adequate.

If you were running 7000RPM and 20PSI boost, it might be different. It would be different.

But 220HP? Dr. Spock said it best - Live Long and Prosper.

Cool Stuff.

At this point I have never had any interest in the Alloy engine. Although with the proposed mods It seems like you have got some stuff figured out.

I have used Hard block in the Iron Block but I do wonder about it's use in an AL block. Other than that, I say go and make more skookum Alloy slant stuff.

So far you have the AL block→ Bell Housing? →full AL Cased 833 or 5 speed,?→get an AL Drive shaft→AL 3rd Member for the 8 3/4 too.

That would be quite a bit of weight savings.

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http://www.youtube.com/hyperpack

An honest 220 hp is double the stock output. It doesn't take much of a power increase for head gasket problems to surface on the aluminum engine. The 20 psi boost engine will be iron.

If I do the HardBlok I'll make a sheet metal plate with tubes/rods in it for the water passages and oil passage. This would be clamped to the block with a gasket and cylinder head to distort the block as it would be when assembled.

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Joshua

I know Doug was working on a top support at one time. Not sure how it ever turned out.

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Official Cookie and Mater Tormentor.

IIRC, it had aluminum poured into the top of the block and milled to make a closed deck.

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Matt Cramer
1966 Dodge Dart turbo / EFI project

I read all about that. The block Doug attempted to save was badly damaged by corrosion. The casting and subsequent welding of the aluminum deck plate to the block warped the block quite a bit. After all that work the deck plate didn't hold and was pushed down by the cylinder head.

The deck plates popularized by the Honda crowd press into the top deck after machining of the cylinders and upper block cavity. If you're already set up to do that it looks like a reasonable way to go, but this would be an expensive one-off.

I am waiting for a return call from the HardBlok people (person?) before I pull the trigger on their product.

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Joshua

machine it as needed honda style and turn it into a 170 or 210.

Greg

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http://www.youtube.com/hyperpack

I think we lose the head bolt bosses if we shorten the deck that much.

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Joshua

yes you are right.. i forgot about those.

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http://www.youtube.com/hyperpack

There are so called "top hat" sleeves that incorporate a portion of the deck into the sleeve. The fire ring of the head gasket seals upon the collar on the deck surface. I've seen these liners on diesel engines. This would definitely be a custom piece. I believe some open deck Honda engines can use this type of liner. I did a Google search and found several liners of this type. Aftermarket top hat liners are installed on the Buick/Rover alloy V8 that was used in Land Rovers, kind of a cool motor in itself.

Doug made little top hats for the cylinders of the Twiggy engine which ended up throwing a rod through the block.

I spoke with the HardBlok guy. He says that there is a guy in California who drag races with the flimsy aluminum Cadillac HT series engines and casts in a top deck with HardBlok. He allegedly street drives the stuff too. I would like to talk to this guy, but I didn't get contact info.

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Joshua

I am not familiar with the al block, but could the deck be cut to clean everything up and then O-ring the head? I Am thinking the o-ring will allow some compliance for thermal expansion differences and be a lot better than the original head gasket.

Andy; There is no "deck" as is typical on cast iron engines. The cylinders are free-standing, with the only attachment as cast at the bottom of the cooling jacket, and the head bolts and friction offered by the head gasket. Looking at a bare block from the top, one would see the perimeter of the block, with six round cylinders standing in the (relative) middle. Those cylinders have a steel sleeve cast into them, but the overall width of both sleeve and casting is about 1/2" thickness. Doesn't give a whole lot of room for cylinder sealing.
Hence the discussion surrounding cylinder support methods.

Roger