Magnum shortblock capability.

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1Fast340

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What can the stock 5.2/5.9 shortblocks handle? Power and RPM?
Also if one was to change just pistons to something lighter and add some better rods what could the oilingsystem and stock cranks handle in these engines?

Just thinking some here, considering that these engines are very affordable and possible to go oldschool on,not a full build just throw cam and compression on the thing add a good intake manifold and a set of headers and let it scream like one would have done to a 340 back in the day.
Edit: if changing rods and pistons a balancing would of course be required,but keep it real basic.
 
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I'll let the experienced chime in, but the numbers quoted were roughly 600 horses with good block prep.
Max rpm depends on stroke... the longer the stroke the higher the stress on the block.
 
Lighter pistons etc will require a balance job. Anything is capable of 2 HP per cubic inch. How well you build it will dictate how long it lasts before it grenades.

A reasonable build can easily get to 4-450 Hp
 
Yeah i should probably have writen the obvious part that a balancejob would have been added,but im more intrested in what the STOCK oilingsystem and cranks can handle in this thread. :)
 
Yeah i should probably have writen the obvious part that a balancejob would have been added,but im more intrested in what the STOCK oilingsystem and cranks can handle in this thread. :)

Well, you did mention changing pistons....
 
Well, you did mention changing pistons....
Yeah i know but i doubt the stock compression is anywhere near enough to support a cam that is capable of killing an ok shortblock.
 
Yeah i know but i doubt the stock compression is anywhere near enough to support a cam that is capable of killing an ok shortblock.

It's not the compression, it's the imbalance. The effective weight increases dramatically at higher rpms. With a lighter piston, the crank weights would be too heavy. probably not as bad as a piston that's too heavy but it will be off, The grenading i was mentioning would be from mechanical rotational stress, not ignition.
 
It's not the compression, it's the imbalance. The effective weight increases dramatically at higher rpms. With a lighter piston, the crank weights would be too heavy. probably not as bad as a piston that's too heavy but it will be off, The grenading i was mentioning would be from mechanical rotational stress, not ignition.

I got a handle on that,no worries. i was just trying to give you the reason for a pistonswap in a very basic build :)
 
What is the goal, or what is the plan for the car, along with weight, transmission, etc.?
The stock crank and rods can live a good long life at 400 horsepower, which is doable with a piston swap for compression, and a good camshaft and intake choice.
If you are thinking of keeping the stock heads, consider the cost involved in rebuilding those heads. Otherwise, you'll be losing a decent amount of power.
If you keep the camshaft hydraulic, you don't really need to worry about the crank and rods too much, unless you add a bunch of nitrous.
Do some google searches for the project sledgehammer 5.9 engine that IMM built up. Plenty of power, but he did use his prepped EQ heads.
 
Are we considering racing the Magnum block?
Or are we just looking for a street rod that does double duty?
 
I'd like to know also.. specifically in regard to forced induction builds.
Maybe if we all start spamming dulcich and frieburger they'll boost a 5.9 magnum to it's destruction for an episode of engine masters?
 
Well, if you REALLY want to test it... throw in some ICON IC743 domed pistons. Very close to stock Magnum 5.9 piston weights..... per my numbers, just grind roughly 1 gram off the small end and 5-6 grams off the big end, and you're right around the stock 5.9 bobweight with the stock rods. No rebalance......but not sure how strong those rods are..... were they the ones that were pressed sintered iron?

With 70 cc heads, you're pushing 12:1 SCR with .039" head gaskets; you now GOTTA cam the crap out of it! But now you need the biiiig heads..... so maybe not really a basic cheapo build.

The only other light 360/5.9 pistons I've run across are Probe 12351's... but they are dishes and not much better CR than stock ones...low 9's SCR.
 
Seems the stock short block can handle about 400 - 450 hp. Above that you would need pistons for more CR as well extra strength and for the price might as well go for better rods. As for block seems like above 600 hp the block becomes questionable. As for the crank Im sure theres people running 600 plus hp on stock one but if I was building the engine if I was looking to build 500 plus hp I'd go aftermarket.
 
I'd like to know also.. specifically in regard to forced induction builds.
Maybe if we all start spamming dulcich and frieburger they'll boost a 5.9 magnum to it's destruction for an episode of engine masters?

There are a couple threads in the forced induction section of this forum where guys ran turbos on basically stock Magnum short blocks. Usually pushes out a head gasket before block, crank, or connecting rod failures.
 
Factory short block 5.9, EQ Heads, AirGap, camswap and good carb (and headers) make for an easy low to mid 12 second Abody. There are a few of us that have done it.
I love my junkyard 5.9 magnum. It is turbo'd now and I've been running it at around 6psi for a couple of years which I believe puts it close to 475HP. I recently turned up the boost to 10-11psi and it's absolutely violent in this little Abody. Probably closer to 550hp at that pressure. Not sure how long it will last but I keep it under 5500rpms and watch my tune carefully.
 
And if I can add a note on the high compression Icon pistons mentioned above..... convert to E85 fuel and those pistons are perfect for a more normal cam.
 
Seems the stock short block can handle about 400 - 450 hp. Above that you would need pistons for more CR as well extra strength and for the price might as well go for better rods. As for block seems like above 600 hp the block becomes questionable. As for the crank Im sure theres people running 600 plus hp on stock one but if I was building the engine if I was looking to build 500 plus hp I'd go aftermarket.
Personally I think you short sell the set up and it could go further. FWIW. OE rods are 4340 forged. Still, I think you have the right idea.
 
This guy is pushing a 360 magnum block to 771 HP. But I don’t know for how long. At the 2018 engine masters challenge he only made 737 HP. Which is still damn empressive to me.

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Ok. Lets try this instead.
Will a bone stock Magnum shortblock with just some forged pistons, a balancejob and an oilpan that fits in a car handle say 7500rpm and 500HP?
If not what would be the point of failure?

If the isue would be rods,pretend that we swap those aswell for someting stronger.


Lets focus on if the cranks and oilingsystems can handle it,pretend its naturaly aspirated engine with a solid roller so we can ignore the valvetrain part of the question for now. No strokers or anything like that. Just stock cranks and oilingsystems.

And im not talking about 7500rpm wide open for hours,more of a street/strip thing
This is partialy out of quriosity but there is some serious thinking behind this.
 
Ok. Lets try this instead.
Will a bone stock Magnum shortblock with just some forged pistons, a balancejob and an oilpan that fits in a car handle say 7500rpm and 500HP?
If not what would be the point of failure?

If the isue would be rods,pretend that we swap those aswell for someting stronger.


Lets focus on if the cranks and oilingsystems can handle it,pretend its naturaly aspirated engine with a solid roller so we can ignore the valvetrain part of the question for now. No strokers or anything like that. Just stock cranks and oilingsystems.

And im not talking about 7500rpm wide open for hours,more of a street/strip thing
This is partialy out of quriosity but there is some serious thinking behind this.
Is say yes. But my concern in your list is rpm & oiling. Specifically at the lifters. The oil holes are still on the large side that lube the lifters. Otherwise I think it’ll be fine
 
Now we are getting somewhere!
Thanks!

BTW damn EU and its global data privacy regulation BS who is screwing with hotrods website,had to use a proxy and google the name of the article to be able to see the pics,but once there that was quite informative!
 
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