340 hp capabilities?

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07raptorgytr

07raptorgytr

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Looking to build a beefy 436" out of a 340 block. Was just curious what hp or around what ball park hp do these blocks split apart? I have a 71 factory production block. Would love to get a R3 block instead but I'll take what I can get.
 
I'd guess it could easily handle 500 - 550 before I'd be too worried.

Jeff
 
Well I was hoping to get approximately 600. I just hope this isn't being too unrealistic with a production block.
 
I've HEARD 600 is the most you wanna do on a stock block. But who's to say? Every block is different. If you do all the usual strengthening then you are going to be that much further ahead.
 
By saying doing the strengthening, what all are you talking about. From what I've seen or heard all you can do is main cap girdle. As for 4 bolt billet main caps I also heard they cannot be used on stock blocks because the webbing is too thin for the additional bolts to be drilled and tapped into the block.
 
Yeah it is for a street car. My machine shop said to absolutely not do any block fill. He says the difference along the cylinder walls from where the hardblok starts and ends causes a big difference in thermal conductivity that the pistons get squeezed in the area where hardblok is used, which creates scuffing.
 
Hopefully he is not the one who gave you the 600 hp number. Can it be done? Sure. Will it grenade before it makes it 8000 miles? That no one can tell you. Play it safe and give up a few HP for longevity. On the street 490 HP is gonna be just as fun as 590. Maybe more so.
 
Short fill, high quality stud girdle, the best crank and rods you can find.......I wouldn't be skeered of 700 HP.
 
07raptorgytr said:
By saying doing the strengthening, what all are you talking about. From what I've seen or heard all you can do is main cap girdle. As for 4 bolt billet main caps I also heard they cannot be used on stock blocks because the webbing is too thin for the additional bolts to be drilled and tapped into the block.
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2 bolt steel main caps with dowels
 
My 408 was approaching 600 hp and showed signs of block flex on the main and cam bearings.
 
fratzog lover said:
Hopefully he is not the one who gave you the 600 hp number. Can it be done? Sure. Will it grenade before it makes it 8000 miles? That no one can tell you. Play it safe and give up a few HP for longevity. On the street 490 HP is gonna be just as fun as 590. Maybe more so.
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600 hp isn't all that unrealistic out of a small block. Especially if it is bored 4.100 and stroked 4.125 and a good set of heads.
 
Steel caps, girdles, good cranks and rods don't stop what kills stock blocks. Block flex kills them.
 
justinp61 said:
Steel caps, girdles, good cranks and rods don't stop what kills stock blocks. Block flex kills them.
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How would one reduce block flex? The only way I have seen was to use motor plates that permanently mounts the block to the frame like in high horsepower drag cars
 
07raptorgytr said:
How would one reduce block flex? The only way I have seen was to use motor plates that permanently mounts the block to the frame like in high horsepower drag cars
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A mid plate in addition to a front plate I'm sure would help. The best solution is a X. R, R1 or R3 block if you can find one. Some guys have got by with stock blocks over 600 HP but I count myself as lucky that mine didn't bust a cylinder. My 434 is a R1 block.
 
justinp61 said:
Steel caps, girdles, good cranks and rods don't stop what kills stock blocks. Block flex kills them.
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billet steel caps and dowels will eliminate cap breaking and cap walk and maintain concentricity of the bearings . to not put steel caps and dowels on a block simply for fear of the block breaking anyway makes no sense to me and a stud girdle wont do 1/10th of what the caps and dowels will . might as well run a cast crank and hypereurectic pistons too if one expects it t blow up anyway.

Also, on a high revving build, it is beneficial to true the lifter bores and install bushings with smaller holes than the huge ones that are standard in the bores.

In my experience, it is the people that buy second rate parts and don't go to the additional expense to do these things on big power builds that are the ones that have engine failures more often than those that do these extra things . I have seen countess cases where some fool wants big power but buys cheap parts to get it then asks why their engine blew up, lol.
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barnett468 said:
billet steel caps and dowels will eliminate cap breaking and cap walk and maintain concentricity of the bearings . to not put steel caps and dowels on a block simply for fear of the block breaking anyway makes no sense to me and a stud girdle wont do 1/10th of what the caps and dowels will . might as well run a cast crank and hypereurectic pistons too if one expects it t blow up anyway.

Also, on a high revving build, it is beneficial to true the lifter bores and install bushings with smaller holes than the huge ones that are standard in the bores.

In my experience, it is the people that buy second rate parts and don't go to the additional expense to do these things on big power builds that are the ones that have engine failures more often than those that do these extra things . I have seen countess cases where some fool wants big power but buys cheap parts to get it then asks why their engine blew up, lol.
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I agree completely. By all means I'm not gonna skimp on parts nor machine work. I'm just trying to get an idea of the approximate hp/tq a stock production block is capable of . I would like 600 hp in a street build. But if ultimately I need a x, or r block I will look into that. I'm not counting Big block out but that would be a last resort
 
There is no set number where a stock block will break. Good machining and a sharp tune come into play, not to mention block to block variance. I'm sure steel caps will help but they don't add much strength to the block IMO. I think my R1 block is around 60 pounds heavier than a stock block, it's easy to see why it's stronger.
 
build with the lightest bob weight you can
stay out of detonation
I have a 446 > airwolf heads > 6.67 et
and a 449 > Indy heads > 6.50 et

They could go faster, but, I short shift and keep the rpms below 6000 @ the line.

I don't need to set a speed record, just out there to have "Fun"
Mid 6's is fun for me

I have slowed to 7.00 for the sportsman class.
run mid 6's for the "Street" class
 
And that's the thing. It isnt like I will be out there power shifting from light to light at or above 6000 rpm. It will occasionally go to the strip on a Friday night for fun.
Now on another note, my dad has a 408 that dyno at 590 hp and get thrashed on all weekend long at the strip, and it hasn't been torn down for 6 years. And he is running a production 360 block.
 
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