HP Performance 426 Hemi Block - any good?

[ChargedNJ]

Hey all. Anyone have experience with the quality of these aluminum blocks? Looking to build a 528 or 572 and want to get off to a good start. I know Keith Black is the bees knees but twice the price. Any help appreciated.

[c00nhunterjoe]

Any particular reason you are going for an aluminum block? I assume race engine? Opens a whole new avenue into the build process.

[ChargedNJ]

Nah, street motor. Just looking for the typical advantages aluminum provides. Weight, heat management.

[c00nhunterjoe]

Heat management may play against you here. In my end of the field (more race oriented) an all aluminum vs all steel engine needs to be minimum 2 pts higher compression when comparing apples to apples. Usually more like 3 pts. So if you were planning on a "9:1 street motor" like most guys get stuck in their heads- and then build one in all aluminum, you will have a really really expensive boat anchor turd. I would wait and see what challenger 340, bsb67, and prh say, but my 1st thoughts on this plan is that you should stick with an iron block.

[1974dodgecharger]

I agree with Coon stick with iron block for the streets leave the aluminum stuff for the drag racer guys even if you do both take the iron block since you will be on the streets. 

[alfaitalia]

Subscribed....interested to hear more on this. My block is Aluminium. Most modern cars are all alloy of course...head and block.....at least over here.

[c00nhunterjoe]

Your charger has an aluminum block in it? The base cost just to buy a bare big block mopar aluminum block is more then most guys on this forum want to pay for the whole engine, not counting the machining after purchase.

[c00nhunterjoe]

If your goal is weight savings off the nose, i would suggest alternate methods such as moving the battery to the trunk, aluminum heads, radiator, possibly even fiberglass hood rather then going to an aluminum block. If you are building a 572 track monster and want indefinate strength and horsepower, then we can keep chatting.

[Mike DC]

        
You cannot build a moderate-weight 426 Hemi with a repro iron block.  The new blocks have extra meat cast into them in the critical areas and they weigh about 310 lbs.   Even with aluminum heads & intake you still end up with a 700-lb motor.

The alloy RB/Hemi blocks are more like 145 lbs.  An all-aluminum (gen-2) Hemi is about 530 lbs.  That's medium weight by American/muscle car standards.  By real sports car standards it is still kind of heavy. 

[alfaitalia]

If your goal is weight savings off the nose, i would suggest alternate methods such as moving the battery to the trunk, aluminum heads, radiator, possibly even fiberglass hood rather then going to an aluminum block. If you are building a 572 track monster and want indefinate strength and horsepower, then we can keep chatting.

Surprised you say that...because generally iron blocks are considered to be stronger than ally ones...even the weight saving are not that huge. Ally is about half the weight of steel...but also about one third less strong...so more metal has to be used. Even then the engine remanufacturing industry, (which annually rebuilds three million failed engines apparently...thank you Google!) finds that aluminum blocks are more susceptible to failure from overheating, warping, and general distortion at big power levels as well as more susceptible to corrosion from dirty oil than cast-iron blocks. Did not stop me going that way due to what I want to achieve.....but ultimately I might have a stronger engine had I gone for steel.....but mine will probably never see a track and certainly won't be under a massive load.....specific output wise at least...thermally however? Well that's a different story!

[Mike DC]

        
I think the specific numbers were 309 lbs for the repro iron RB block and 143 for the alloy - that's 166 lbs difference.  That's the size of the difference between a slant-6 versus a B/RB wedge from the factory.  


It's always engineering compromises.  On a little 4-banger that uses modern thin-wall casting methods, the difference between an alloy or iron block might only be 25 lbs.  That's a strong argument to stick with iron.  But with a big aftermarket muscle car V8 it's another story.  

GM and Ford and many other brands have been using alloy V8 blocks in hi-po applications for decades.  Mopar doesn't do it but that doesn't mean it's untested tech.

[ACUDANUT]

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[alfaitalia]

I think he meant me....and I do!

[c00nhunterjoe]

If your goal is weight savings off the nose, i would suggest alternate methods such as moving the battery to the trunk, aluminum heads, radiator, possibly even fiberglass hood rather then going to an aluminum block. If you are building a 572 track monster and want indefinate strength and horsepower, then we can keep chatting.

Surprised you say that...because generally iron blocks are considered to be stronger than ally ones...even the weight saving are not that huge. Ally is about half the weight of steel...but also about one third less strong...so more metal has to be used. Even then the engine remanufacturing industry, (which annually rebuilds three million failed engines apparently...thank you Google!) finds that aluminum blocks are more susceptible to failure from overheating, warping, and general distortion at big power levels as well as more susceptible to corrosion from dirty oil than cast-iron blocks. Did not stop me going that way due to what I want to achieve.....but ultimately I might have a stronger engine had I gone for steel.....but mine will probably never see a track and certainly won't be under a massive load.....specific output wise at least...thermally however? Well that's a different story!

What brand block did you use? We have an indy maxx block in one of the race cars. Been in it for years, more then 15 at this point. Never had an issue with any of the aforementioned failures. It is rock solid and square on every freshen up and nears the 160 mph point on a throttle stop. Had a rod bolt fail once and punch a hole through the side between two mains. Welded it up, replaced a sleeve, and back to the track and that was several years ago as well. There are advantages to going aluminum,  but in most cases you are only saving 100 to 150 lbs, which on a street car, is not worth the other factors you have to account for in the build process; ESPECIALLY on a street car.

[Mike DC]

              

There are advantages to going aluminum,  but in most cases you are only saving 100 to 150 lbs, which on a street car, is not worth the other factors you have to account for in the build process; ESPECIALLY on a street car.

For the handling/sports car crowd, "only adding 150 lbs to the front end" . . . it's like a drag racer "only removing 150 lbs of ballast from behind the rear axle."  


I wonder how the feedback on alloy blocks would sound if everyone was running top quality blocks + moderate cylinder pressures + correct assembly for what it is.  

The typical alloy block user isn't comparing it to an OEM iron block, but rather an aftermarket iron block with 80 lbs of extra meat in it.  

[c00nhunterjoe]

             

There are advantages to going aluminum,  but in most cases you are only saving 100 to 150 lbs, which on a street car, is not worth the other factors you have to account for in the build process; ESPECIALLY on a street car.

For the handling/sports car crowd, "only adding 150 lbs to the front end" . . . it's like a drag racer "only removing 150 lbs of ballast from behind the rear axle."  


I wonder how the feedback on alloy blocks would sound if everyone was running top quality blocks + moderate cylinder pressures + correct assembly for what it is.  

The typical alloy block user isn't comparing it to an OEM iron block, but rather an aftermarket iron block with 80 lbs of extra meat in it.  

Which is why i said street car. Im not too sure of how many road race chargers we have on this forum? I know of 1. And if you build an all aluminum big block mopar with 9:1 static compression ratio- you will be dissapointed. 98% of the people on this forum are weekend warriors and i dont see them dropping 6 grand on a bare block then add another grand for machine and prep work and most of the blocks dont have the lifters bushed which i would have done if this is not a dedicated drag car so add another 800 or so to the bill. Now you are up to nearing 8,000 dollars on just a block. On a week3nd warrior or even a spirited driver, is 8k worth 150 or even 200 pounds?

[Mike DC]

Which is why i said street car. Im not too sure of how many road race chargers we have on this forum? I know of 1. And if you build an all aluminum big block mopar with 9:1 static compression ratio- you will be dissapointed. 98% of the people on this forum are weekend warriors and i dont see them dropping 6 grand on a bare block then add another grand for machine and prep work and most of the blocks dont have the lifters bushed which i would have done if this is not a dedicated drag car so add another 800 or so to the bill. Now you are up to nearing 8,000 dollars on just a block. On a week3nd warrior or even a spirited driver, is 8k worth 150 or even 200 pounds?

Last time I looked at alloy block prices they were more like $4500 (and the alternative is, what, $2500 for aftermarket iron ones?).  

Are the alloy blocks up to $6k now?  Wow.  For that money I'd like to get the Dremel tool and whittle my own out of a giant 3-foot cube of aluminum.  


Good point on the lifter bushings.  I didn't realize that wasn't being done to the blocks already.  

Wouldn't 9:1 SC be pretty low just because of the material?  I would think more like 10:1 even for pump gas.   10:1 isn't huge compression compared to what a lot of racers hit these blocks with.  

[c00nhunterjoe]

Even 10:1 static on an all aluminum big block is too low imo. Especially considering the grind cams you are most likely going to be running after making a monster stroker. In my experience when going from all steel to all aluminum in a mopar you have to raise 2 points of compression compared to the same build in steel. Im not aware of many people just building a 93 octane 426 or 440 out of all aluminum. Not even sure it can be done with off the shelf parts based on the bores that come in the aluminum blocks?

[Mike DC]

              
Street engine = pump gas.

It needs race gas = you might still drive it on the street but you weren't building a street engine.


Custom pistons don't seem like too much to ask, considering the price bracket of an all-aluminum big block in general.  

[c00nhunterjoe]

Just because it runs on pump gas doesnt mean it is a street engine. As to the off the shelf parts- i was referring to the fact that alot of the blocks come with large bores. My indy block for example, comes with a 4.50 bore... you cant get a 426 out of that with a 3.75 crank no matter what custom pistons you want to order. And to destroke it to get those cubes... well... yeah. Sure, you can resleeve it and build it however you want, but we are back to why? Is 150 pounds at the cost of thousands and headaches worth it?

[Mike DC]

  
Yeah, but who really does that?  

Most guys building a fun streetable engine on this level wouldn't be sticking to 426 or 440 inches.  They would go for 500+ inches and moderate compression.  If they care enough about weight to buy an alloy block, and only wanted 426 or 440 inches, they would be building a small block engine.

[c00nhunterjoe]

 
Yeah, but who really does that?  

Most guys building a fun streetable engine on this level wouldn't be sticking to 426 or 440 inches.  They would go for 500+ inches and moderate compression.  If they care enough about weight to buy an alloy block, and only wanted 426 or 440 inches, they would be building a small block engine.

Which brings us right back to- why are you spending a ton of extra money on an aluminum block for a street car?

[alfaitalia]

I can't talk for him but in my case it actually saved me money.....my car came with no motor. So after much planning and over a year of searching and waiting I came across an alloy block that was sound but had been subjected to a slight and partial cold seizure.  Three of the pistons were near scrap...but since I want about 8.5 : 1 for my application they would need to be replaced anyway. So after the tiniest of skims I had a 618 (was 605)  alloy block (with hemi heads...oh yeah) for under £2000 plus the piston kits....that's just over 10.1 litres for is Euro types! I could not have imported a stock 440 for that and the UK supply of 440s (mainly written off or rotted out Jenson Intercepters) is just about non existent these days. I got it cheap as demand for block like that is next to nothing here.....mainly just funny car drag racers....would be a much more desirable object over there I'm sure! With the price of Chargers in Europe we need to get some lucky deals! The pistons however were custom made......not cheap!
....I doubt mine will ever see the track...we don't have many left! Should be great fun between the traffic lights though.

[Mike DC]

 

Which brings us right back to- why are you spending a ton of extra money on an aluminum block for a street car?

   

[c00nhunterjoe]

An iron block car can hug those turns with a firm feel suspension. Hell, stock suspension can do that with some tweaks. 150 lbs off the nose of a 2 ton sled is not a drastic change on a STREET car.

Alfaitalia, you got a killer deal.