450 hp = doom for 302 blocks?

[tds715]

i was told today that when the 302s reach abotu 450 hp they tend to crack down the center is this true?

[DDMTK421DS]

sure any engine can do that if it has no water or oil....lol

[FoxGranadaChuck]

Originally Posted by tds715

i was told today that when the 302s reach abotu 450 hp they tend to crack down the center is this true?

Depends. If the 450hp is achieved via supercharger or nitrous oxide, then yes, block reliability does become an issue.
However, if a stroker kit or something similiar is involved, then an OE-type block is fine.

[GTStang]

A stock 2-bolt 302 500HP is usually the breaking point. Some people have gotten more out of them some have got less not all 302 were created equal. But this tends to be the generally accept point where the main webbing will break. Doesn't matter how you get the power through N/A or FI. IT doesn't mean it will die right away but it is definetly living on borrowed time.

[xviciousx]

depends on the care of the block... every block has a break point (GTStang gave an explination of this block's) but with proper maintenance things will live far beyond any expectations...

[rerun]

if its a 74 or below 302 then there good about 650hp... i think everything above that is around 500..

[boosted331]

Originally Posted by FoxGranadaChuck

Depends. If the 450hp is achieved via supercharger or nitrous oxide, then yes, block reliability does become an issue.
However, if a stroker kit or something similiar is involved, then an OE-type block is fine.

Unless the stroker is zero balanced it will put more stress on the block due to increased harmonics. N/A motors also tend to spin higher than blower/turbo motors, which puts more stress on the block as well.

The level of harshness on the blocks from greatest to least is Stroker-Juice-Blower--Turbo

Turbo stock block 5.0's will last with a lot more RWHP than a blower car because for x amount of RWHP a blower is actually making more crank horsepower but it takes some power away to power the blower, which is why a blower car's BSFC is higher than a turbo. Some people with stock crank/rods/block/pistons have made 600 RWHP with a turbo and had it live for a while, and other people are breaking stock blocks at 450 RWHP. It really is a guessing game though, but if you discover you have very low oil pressure at idle one day, take the intake off and check for cracks around the cam centerline, or if you can afford to drain the oil and pull the pan and you can see if you have any cracks down the mains.

[motor_head_429]

It really depends on the actual block you are using. My buddy runs 400 hp on a stock 5.0 block, and sprays it with a 250 shot, (I got to ride in it, bad ) he's never had a problem with it. The car had a best run of 10.90 (with a 400 pound driver that can't shift) The "recommended" limit for the 5.0 block is 450 horsepower. However, once you start boring out the cylinders, the limit will start to drop. Also, some blocks just have certain casting flaws that will make them give in at a point where another stock block would be just fine. Your best bet would be to get the block sonic tested. Here's an interesting article I read some time ago on sonic testing.

http://www.popularhotrodding.com/tech/0404phr_sonic/

[FoxGranadaChuck]

A blower/turbo motor being less stressful than a stroker motor?! I don't think so! The reason that I say this is heat ;turbos and blowers generate a LOT of heat. Strokers do not generate quite as much heat. Heat kills a block faster than internal harmonics will (although to make it clear, the reciprocating assembly SHOULD be internally balanced for precisely this reason!).
Everyone else is correct when they say that blocks should be judged on a case-by-case basis. If it were me, I would buy a 5.0L Sportsman block.

[boosted331]

Originally Posted by FoxGranadaChuck

A blower/turbo motor being less stressful than a stroker motor?! I don't think so! The reason that I say this is heat ;turbos and blowers generate a LOT of heat. Strokers do not generate quite as much heat. Heat kills a block faster than internal harmonics will (although to make it clear, the reciprocating assembly SHOULD be internally balanced for precisely this reason!).
Everyone else is correct when they say that blocks should be judged on a case-by-case basis. If it were me, I would buy a 5.0L Sportsman block.

Heat kills stock blocks, and go buy a sportsman block?

For starters, the sportsman blocks are POS'es, they're a waste of money. They're a thousand dollars and they're basically an early model thicker wall casting block that's setup for roller lifters, etc. An R302 is 600 bucks more, you have no reason to buy a sportsman.

For the heat, tell me why, please. Heat has absolutely nothing to do with the block splitting down the mains. Why do you think it is that spinning the motor higher causes blocks to split quicker? Increased harmonics. What does adding a bigger,heaver crank and heavier rods do? Increase the harmonics in your motor. A 450 HP stroker motor spinning to 6500 is going to put a ton more stress on your block than a turbo motor that only needs to spin to 5500 to make power.

[stang_racer20]

Well I run a Sportsman 302. I do wish, however, that I would have gotten a R302 but money was an issue then. All the Sportsman is, is a stock cast 302 with reinforced mains. I dont think they did anything to it though to increase the strength around the lifter valley which is the #1 place they tend to crack at. Perhaps down the road I'll upgrade when I get my turbo. It'll handle the power I have now though just fine.

[flex339]

Thats a nice part about engines like the boxster since the opposing pistons cancel the harmonics.

[SkylineUSA]

Originally Posted by boosted331

Heat kills stock blocks, and go buy a sportsman block?

For starters, the sportsman blocks are POS'es, they're a waste of money. They're a thousand dollars and they're basically an early model thicker wall casting block that's setup for roller lifters, etc. An R302 is 600 bucks more, you have no reason to buy a sportsman.

For the heat, tell me why, please. Heat has absolutely nothing to do with the block splitting down the mains. Why do you think it is that spinning the motor higher causes blocks to split quicker? Increased harmonics. What does adding a bigger,heaver crank and heavier rods do? Increase the harmonics in your motor. A 450 HP stroker motor spinning to 6500 is going to put a ton more stress on your block than a turbo motor that only needs to spin to 5500 to make power.

Once again boosted331 has the right mind set, or at least that is the way I look at it as well.

[duplox]

Another thing - the denser A/F mixture from a turbo or super'd motor takes longer to burn than a N/A mixture. This makes peak cyl. pressure for a turbo motor making twice the power of the same motor N/A(ie running around 16psi) will have a peak cyl pressure of only around 20% higher than the N/As. They just produce significantly more power as the piston nears BDC on the power stroke compared to N/A, and since power produced is the area under the curve of cylinder pressure over the power stroke, doubling peak cyl pressure is not neccesary or a reality. Piston speed and rotating assembly weight/imbalance will be more of a danger to the block than 20% higher cyl pressures, and most the turbo crowd don't run 16+psi.