318 engine strength

[MOPAR-or-NoCar73]

Hi everyone

    I was just wondering. What hp levels can a stock bottom end 1973 318 engine make without blowing it up. I thinking about supercharging it.

Thanks

Anthony

[MOPAR-or-NoCar73]

Thanks

Yes, I have no doubt that a 318 can make that kind of power. I was just wondering what the  hp limit would be for a 318 with the STOCK bottom end internals. I was just curious to know at what hp level it would be good to go to a forged crankshaft, etc. I read somewhere that they were good for 500 hp with stock components. Just looking for others opinions, experiences.

[HP2]

For continued, long term, reliable horsepower, 500 is about it with stock parts. Sure, you could push that to 700+, but durability then suffers. Metal has finite fatigue limits and when your power output is that high with conventional parts, then you are putting stresses into the parts beyond their design parameters, which means you can probably last a little while at extreme levels before everything lets go, or plan on a regularly scheduled tear down and magnaflux routine. This goes beyond that actual material of the rods and crank and also includes support within the block itself in the main cap area, lifter valley, and the cylinder walls.

[LAA66]

 Youre dreaming about supercharging. The stock small block rods are the Achilles heel.  6000 rpms max, then it's up to fate. Please don't ask me how I know.( Bad memories )

[Jacksboys]

Since it is a cast crank, I would not push it past 500.  Also you will need to make sure it has the larger 360 rods or as LAA66 mentioned, it will not last.  I am not sure what your current setup makes, but I would not push stock cast pistons past 8 psi or you might get a burnt piston.

On the comment about the Jap cars, unless the engine is a factory built turbo, almost all of the internal parts are replaced before making up to 400 hp.  I have done a bunch of reading on people putting turbos on their honda motors, and most of the motors cannot handle much over 200-250 hp in stock form.  There are a few exceptions to this, but most of these motors have high compression (11:1) from the factory, so adding additional psi would be risky in stock form and without racing fuel.

[Chryco Psycho]

truck 318 cranks are generally Steel not cast & are easy to get

[Jacksboys]

truck 318 cranks are generally Steel not cast & are easy to get

I am not trying to high-jack the post, but what are the best years to look for the Steel crank?

[moper]

Um.. 600hp from a 318 stock end? No way in heck. Jap cars do it because they have parts (cranks, rods, and pistons) that are works of art, much better oiling and oil control, ring seal/bore stability, heads that flow more than typical V8s we deal with...lol. Nothing similar. Even if the pistons, rods, and crank held, the block would probably just split after a short time at that level usign a blower.....lol. Tha cast parts will limit things to a safe 400-440 or so. Beyiond that, you will break pistons first, then rods, then the crank...lol. Steel cranks are found in manual trans vehicles from what i understand. Trucks are the easiest to find them in, but if you find early ones (68-70) there's a good chance it will have a forged crank in it. I've found about 50% do, regardless of use from that vintage. You can also just order a stock crank kit (crank, machined, with bearings) with the forged crank... Then just have it balanced with your stuff.

[ViperMan]

They're also doing it with overhead-cam designs, variable-valve timing, direct-port fuel injection, highly advanced spark and fuel control, much higher compression ratios, and aluminum parts.

By the time you spend the money to get your 318 to put that kind of power down, you could purchase and upgrade a 340, 383, or otherwise.  That's what I'm aiming to do.

Jeff

[FJ5_440]

I agreee with LAA66.  Unless you do something with the rod bolts and rods, you aren't very likely to see anywhere near the horsepower a supercharger can make.  If you plan on supercharging a 318 with the stock bottom end, please don't use your original engine.  When the rod bolts give up, they usually do bad things to the sides of the block.  Repeatedly adding a 200 shot of nitrous to a warmed up 318 made the little duster into quite a screamer, but it didn't last long enough for me to call it reliable.  I think a good set of rod bolts would have made a big difference.

[LAA66]

 One of my motors (340) doubled up a rod bearing. The clearances were good when rebuilt and nothing actually broke. I figured the rod bolts stretched due to high RPM operation.

 On another engine the rod actually broke just above the crank journal. The piston bounced up off the head and the remaining section of rod was hammered by the crank into the side of the block then down to the windage tray and oil pan. That one was a complete scraper. Crank, block, rod, piston..... These were the direct connection stock forgings that were double shot peen-ed, magnafluxed, ground and "polished". Not sure whether the bolts were upgrades but they were still 3/8" diameter.

[MOPAR-or-NoCar73]

Thanks for the responses. I figured that stock parts would need to be replaced and the block strengthened. I was just wondering what the strength of a stock block was. Thanks for the help.