hp limit on alum bocks

**xirxious** · 11-02-2007, 11:03 PM

I'm working on a winter project and debating getting the parts and rebuilding the alum one, or building an iron one. I'd like to aim for 500hp, maybe add a 100 shot, too. Supercharging is a little more than I want spend as I have a '70 Formula that needs finishing, and that thing is dang thirsty.....

It would be alot easier to build a motor, then just swap it, but no sense buying another alum block for it. Anyone know the weight difference in the 2? based on the density it should be about 1/3 the wieght of the steel one, I wanted a relative amount. I'd like to stay with teh add a pound here, remove one there idea.

I did a search and saw many hp numbers and it looks like over 550-600 needs iron

**silverz28camaro** · 11-02-2007, 11:18 PM

some people out there are running 450 hp on 383 ls1 aluminum block strokers, i would say 500-525 is the limit and as far as weight goes do a search on the millennium motor and it will tel you the entire history of the ls1 motor and how it became how it is today, i do believe the block alone is 60lbs lighter the a regular 350 small block and is also shorter in length and hight dimension wise by 1-2 inches making it alot easier to work on compared to lt1 camaros.

**danziger** · 11-03-2007, 10:12 AM

This topic has come up before if you want to do a "search." I've never heard/read of someone splitting the aluminium block due to excess HP. The iron block may add stability of cylinder shape at ridiculous levels of power and may offer better head clamping strength in high cylinder-pressure applications, but under 800rwhp, I wouldn't sweat it. My factory LS1 short-block survived for a few years of H/C/100shot to the tune of 576rwhp/590rwtq before pushing a head-gasket (my fault). When torn down, it looked beautiful... My current aluminum 383 is well into the 600s on the squeeze...no problems.

**Mr. Luos** · 11-03-2007, 11:21 AM

As mentioned, the aluminum block will take plenty of abuse.

Unless you are building an all out drag car that makes 850-900+, stick with a forged aluminum motor.

**Bouvers** · 11-03-2007, 11:22 AM

I'd like to see more input into this thread, I too am aiming for 500 rwhp someday and I expect that I will redo the bottom end. I have had one friend tell me that I might aswell change out the block too but I have never heard anything to justify that. I've never seen a video of an ls1 engine blowing the block out its always pistons.
I think this thread needs the input of people that have blown their stock ls1 internals or even block, and tell us at what hp and build this occured with.

**danziger** · 11-04-2007, 01:27 AM

Originally Posted by Bouvs

I'd like to see more input into this thread, I too am aiming for 500 rwhp someday and I expect that I will redo the bottom end. I have had one friend tell me that I might aswell change out the block too but I have never heard anything to justify that. I've never seen a video of an ls1 engine blowing the block out its always pistons.
I think this thread needs the input of people that have blown their stock ls1 internals or even block, and tell us at what hp and build this occured with.

The problem with asking for folks that have blown their stock internals, is that it is usually due to user error, not factory limitations. A faulty tune or getting greedy with boost/nitrous will result in failure and most people won't "man up" to their mistakes.

The weak links in the factory LS1 are:
a) pushrods
b) piston ring-lands
c) rod-bolts

500rwhp is a joke for factory aluminum block. If you avoid detonation/pre-ignition, it is no problem for the factory bottom-end as well. The stock crank is seriously tough and folks have gone over 600rwhp with them easy.

**ibanez7** · 11-04-2007, 02:53 PM

Originally Posted by danziger

The problem with asking for folks that have blown their stock internals, is that it is usually due to user error, not factory limitations. A faulty tune or getting greedy with boost/nitrous will result in failure and most people won't "man up" to their mistakes.

The weak links in the factory LS1 are:
a) pushrods
b) piston ring-lands
c) rod-bolts

500rwhp is a joke for factory aluminum block. If you avoid detonation/pre-ignition, it is no problem for the factory bottom-end as well. The stock crank is seriously tough and folks have gone over 600rwhp with them easy.

exactly!!!!!

to add to this, top fuel and funny car engines are aluminum blocks! yes they do get rebuild after each race however it is still an aluminum block holding the 7,xxx + HP together for those 4-8 seconds.

Two reasons why many people switch to iron over aluminum is because of the misconception that aluminum is not strong and will not hold up. That is just the old way of thinking and being unsure of a new(er) technology. The other reason it because many people believe the only way to increase HP is to increase displacement and they bore the hell out of their blocks. The factory 346 aluminum block can be bored however when it starts pushing over 404 (bore+stroke) the block does lose rigidness.

**xirxious** · 11-05-2007, 07:37 AM

The LS7 I assume is an aluminum block, is it that different from a LS1 block? I know they're getting 505hp on a 427cid.

Thanks for the info, everyone I talked to said 500 is the limit for alum blocks, none of them have ever owned one. Ironic that they thing 400hp is acceptable from an alum 2.5L 4 banger

**Bigjohn366** · 11-05-2007, 08:38 PM

well iv hurd the alum blocks dont like to be bored over so thin , imagine the ls7 a tempered sleeved block

thats why im building a 5.3 project

rod bolts and pushrods an rockers id say that sums it up to have a motor

**Sleeper101** · 11-06-2007, 06:57 AM

Alright guys I personally work on a professional race team, We run Drag Boats instead of cars, But we run the 500 C.I Keith Black Hemi aluminum block we put down over 7000HP. The block is not what holds the power, Its the cylinder sleeve, out of the 6 years on the team we have never busted a block due to too much power, We have bust lots of blocks due to rods coming out of the side, But since its aluminum we just weld in another plate in the side of the block and put in a new set of sleeves.
The Creaters of this disaster!!!! The crew..... Im the youngest in the middle.

Here is a busted Block.

You can see the plates we welded in were previous rods have showed there face.

If you run aluminum you def want a good set of sleeves, but I would go alumium over cast/steel block, The Hp is only limited by what quality of internals you run. But aluminum is very strong, proven over 8000HP worth.

**xirxious** · 11-06-2007, 11:33 AM

I thought ALL alum blocks were sleeved? I'm reading the HP book for LS1's and they state Chevy has a C5R Vette block that the have to a 383 size and get 1200 hp out of. It is a different block, probably the LS7 one, but it was slightly changed for 427 cubes.

**ApexVIII** · 11-06-2007, 11:36 AM

Originally Posted by Sleeper101

Alright guys I personally work on a professional race team, We run Drag Boats instead of cars, But we run the 500 C.I Keith Black Hemi aluminum block we put down over 7000HP. The block is not what holds the power, Its the cylinder sleeve, out of the 6 years on the team we have never busted a block due to too much power, We have bust lots of blocks due to rods coming out of the side, But since its aluminum we just weld in another plate in the side of the block and put in a new set of sleeves.
The Creaters of this disaster!!!! The crew..... Im the youngest in the middle.

Here is a busted Block.

You can see the plates we welded in were previous rods have showed there face.

If you run aluminum you def want a good set of sleeves, but I would go alumium over cast/steel block, The Hp is only limited by what quality of internals you run. But aluminum is very strong, proven over 8000HP worth.

wow thats sick!!

**danziger** · 11-06-2007, 12:01 PM

Originally Posted by xirxious

I thought ALL alum blocks were sleeved? I'm reading the HP book for LS1's and they state Chevy has a C5R Vette block that the have to a 383 size and get 1200 hp out of. It is a different block, probably the LS7 one, but it was slightly changed for 427 cubes.

Yes, all aluminum LSx blocks are sleeved. The C5R block is different from stock LS1 castings and was made stronger with endurance racing in mind.

**2000T/A Guru** · 11-06-2007, 12:06 PM

Well if this helps any, custom alum blocks can handle alot, my girlfriends uncle has a 468 alum block twin turbo setup in his 78 T/A and is moving it to his 98 formula, it holds 1400rwhp at the track most weekends in summer.

**danziger** · 11-06-2007, 12:11 PM

Originally Posted by Sleeper101

The block is not what holds the power, Its the cylinder sleeve, We have bust lots of blocks due to rods coming out of the side,

If you run aluminum you def want a good set of sleeves, but I would go alumium over cast/steel block, The Hp is only limited by what quality of internals you run. But aluminum is very strong, proven over 8000HP worth.

Well, yes and no. The block holds the sleeves, so ultimately holds the power. The design of the block, webbing, water-passages and such will come into narrow focus at higher power levels. I'm sure you guys have filled engine blocks with cement at some point in your racing career to increase rigidity...
Having a rod ventilate a block is a whole different scenario...
Iron blocks have their place in the LSx world due to cost and clamping pressure. Unless you want to spend big dollars for a LSX block with extra head studs, there is something to be said for the security of the threads in iron vs. aluminum. FI and big nitrous hit guys will often opt for iron.
Having said all that (pshew!), I would still go with aluminum.

**Sleeper101** · 11-06-2007, 12:40 PM

Well We also run a pro mod which is a 550 C.I motor all aluminum, 2500HP,alcohal, The only maintanence we ever do is check the valves per round and change plugs every 10 rounds, also change the oil every 10 rounds, We never have a problem with head studs backing out on that engine.

So I have not seen a problem with the head studs backing out, on our smaller engine, Might not be the case in the Lsx world, I have never been able to experiment with one.

Although on our Top fuel motor the head studs will back out about 5 turns per pass, But were cranking so much boost its hard not too, I have never seen a stud stripped, nor the block. Its really weird that it don't but in 6 years it hasnt. plus each head bolt is locked down with 160 ftlbs of torque.

The difference in the LSx aluminum and ours is we dont run water jackets or any type of coolant, Both engines are cooled by the fuel, and is only ran for a short time period, So I have no experince when it comes to that, But I do know the aluminum structure will be fine for any amount of HP you can throw at it.

TFX, Keith Black, Billet, B/A are the most top name brand blocks used in the racing we do. One of these might make a Lsx block.

**99Ls1fever** · 11-13-2007, 06:41 PM

Originally Posted by Sleeper101

Alright guys I personally work on a professional race team, We run Drag Boats instead of cars, But we run the 500 C.I Keith Black Hemi aluminum block we put down over 7000HP. The block is not what holds the power, Its the cylinder sleeve, out of the 6 years on the team we have never busted a block due to too much power, We have bust lots of blocks due to rods coming out of the side, But since its aluminum we just weld in another plate in the side of the block and put in a new set of sleeves.
The Creaters of this disaster!!!! The crew..... Im the youngest in the middle.

Here is a busted Block.

You can see the plates we welded in were previous rods have showed there face.

If you run aluminum you def want a good set of sleeves, but I would go alumium over cast/steel block, The Hp is only limited by what quality of internals you run. But aluminum is very strong, proven over 8000HP worth.

Good call case dismissed amen people have seen the light. for some reason people always have this idea the block will blow, personal I dont think there is but a few people that even have the money to try to accomplish this task lol...

**Chris Arnold** · 11-22-2007, 09:53 AM

Blocks certainly do hold the power and must be strong enough to handle it. Iron or aluminum material can both be used in high hp blocks. The design of the specific block matters more than the material used. Case in point: the 302 windsors will typically split down the middle at somewhere between 500rwhp and 650 rwhp. Put the strongest billet internals, and the most conservative "safe" tune and when you get to that power levelt, the block still splits right down the lifter valley.

This isn't the case with the LS1s, though. With good strong internals, I wouldn't be afraid to run 700 rwhp. North of that, I'd have to start doing some research.

Chris

**davered00ss** · 11-24-2007, 09:16 AM

Stock shortblock is good for 500rwhp. Forged are good well into the 800-900rwhp area. As stated above the rods & pistons are the weak point. The stock crank is even good for 900rwhp.

**xirxious** · 11-26-2007, 08:37 AM

I'm kind of torn between buying a 427 set up or just building the stock to ~500hp. I'm debating buying a new Z28 next year and this would be more of a toy car. I'm just not sure if I want to put the kind of $$ into a 427. If I get a new Z, it will need upgrades