Should I chance it?

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YY1 said:
Isn't 8 RWHP about equal to about 22 crank HP?
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Only if you have 65% parasitic losses going through your drivetrain.

So, if you're running a 727, then maybe. LOL! :happy2:

The rocker figure comes from stick shift mustangs, with about 15% drivetrain loss (at that power level). So, 9-10 flywheel horsepower. On a low power car that's worth .1 at the strip on a good day.

Don't forget that the magnum heads need clearance for pushrod angle if you're running them with a flat tappet camshaft.
 
I was using 20% gross to net and then 20% automatic trans factor (and guessing).
Cam lift math should be correct though, eh?

80s stangs would use net HP figures natively, right?

Most 70s Mopar guys I know still use gross ratings.

If you can get a complete 5.2/5.9 for cheap and resolve the induction and balance issues, sure.

My 2000 R/T has 250 NET HP (which calculates to about 315 gross/crank HP), and will BOIL the ($200)tires off my 4200lb truck with 3.91 SG. Piss poor 16 sec 1/4 mile, though.

A 92 5.2 IIRC has 245 net and has 2.5 inch exhaust manifolds (vs 1 7/8 ) and a slightly better cam.
Torque of 5.9 comes on earlier, though.
 
YY1 said:
I was using 20% gross to net and then 20% automatic trans factor (and guessing).
Cam lift math should be correct though, eh?

80s stangs would use net HP figures natively, right?
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Real men go by what it makes at the tires. :) j/k

The typical estimate is you're losing 15% off of net horsepower through the drivetrain with a stick. All the drag race calculators and what not seem to use net horsepower.

Gross to net is not a 20% loss, though that might explain some of the ridiculous horsepower numbers I hear sometimes. LOL!!

Using that method (and assuming I'm only losing 15% through my 904), I could say my car is making 500 gross hp! - nevermind that I'm only running a water pump and alternator - WOOT! who needs a hemi?!

Even using those numbers, I still only come up with best case rocker ratio 8hp at the tires being 12hp, and sled to roller would be accounting for some of that.
(8 (rwhp gain) / .85 (stick to net) = 9.411) / .8 (20% net to gross) = / 11.76

Either way, the metric I care about would be .1 at the track (on a good day).

Yes, cam lift math is correct. Easy formula is current lift/current ratio * new ratio.

I LOVE my magnum. If the OP can pick one up for seriously cheap it might be worth looking into, but be aware that the swap has a tendency to nickel and dime.

But so does the magnum head swap...gaskets, pushrods, rockers, springs, machining, intake, head bolts. If you can figure all the costs beforehand to be acceptable vs, just buying the Iron Rams from hughes, and you can find a set of good heads, I say go for it. I've been very curious forever about what a set of those type heads would get a stock shortblock 318 car, I just haven't been able to justify pulling out the 5.9 to find out!
 
YY1 said:
My 2000 R/T has 250 NET HP (which calculates to about 315 gross/crank HP), and will BOIL the ($200)tires off my 4200lb truck with 3.91 SG. Piss poor 16 sec 1/4 mile, though.
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I want to know what you have done to your R/T. Because they all came with 250 flywheel HP.
 
I don't think that's correct. That would put it in the class with 4 cylinders.

That would also be a horendous ammount of power loss from all the upgrades and engineering advances done to the Mag vs the LA motors.

IIRC, the actual figure is 245, but 250 sounds much better, and is only lying a little.

Why would the industry revert back to gross HP ratings, when they have been using net since 72?

The trend lately, is actually towards "advertized" HP ratings, which seem to be just a little shy of RWHP. That's good news for us, but it's much tougher to be consistant.
Probably why they are understated.

I just have a K&N system and low restriction cat and cat back duals.

It also gets the best average MPG of any in recorded history 14-14.5, and has actually improved since it hit 110K miles (129 right now). It was geting 13.8 when I searched Dakota/Durango.com and Dakotart.com where I found several real world MPG threads.
My ball joints aren't bad, neither my windshield, nor my a/c leak, and the trans has never been repaired or replaced (all common issues with Dakotas of this vintage).
 
YY1 said:
I don't think that's correct. That would put it in the class with 4 cylinders.

That would also be a horendous ammount of power loss from all the upgrades and engineering advances done to the Mag vs the LA motors.

IIRC, the actual figure is 245, but 250 sounds much better, and is only lying a little.

Why would the industry revert back to gross HP ratings, when they have been using net since 72?

The trend lately, is actually towards "advertized" HP ratings, which seem to be just a little shy of RWHP. That's good news for us, but it's much tougher to be consistant.
Probably why they are understated.

I just have a K&N system and low restriction cat and cat back duals.

It also gets the best average MPG of any in recorded history 14-14.5, and has actually improved since it hit 110K miles (129 right now). It was geting 13.8 when I searched Dakota/Durango.com and Dakotart.com where I found several real world MPG threads.
My ball joints aren't bad, neither my windshield, nor my a/c leak, and the trans has never been repaired or replaced (all common issues with Dakotas of this vintage).
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I asked this same question on Dak-Dur last week. Every stock R/T will dyno at 190-200 at the rear wheels. I asked because I have a 98 Ram SS/T and the window sticker clearly say 250hp, meaning flywheel HP.
 
I really dont wanna pickup a whole engine because that defeats the purpose of the objective, a cheap somewhat easy way to get unleaded friendly heads. If I end up picking up any engine from my job, it'd be one of the 318 rollercam engines that drove into my work because I'd like to make a good turbocharged engine pushing 10lbs of boost using that as a base with the heavy duty rods and my 340 forged crank. I'm not saying that's the route I wanna go immediately. Right now, I just wanna be able to drive it around without worrying
 
What get's me is the 800 h.p you can pull out of a little 318 with big turbo's!
 
I put Magnums on a 1975 360 LA block for my '70 Duster, I hope to have it fired up the first time this weekend... I'll agree with what has been said, if they check out good with no cracks go ahead and run them as long as you're willing to pay for new pushrods and intake (or have the intake holes re-drilled for LA pattern). Also make sure your current lifters have the hole in the plunger to pump oil through the pushrods, if not you'll need a set of those too. I also agree it'll be mostly the 1.6 rockers that make the difference in power from a set of 360 heads, but I'm assuming you have stock heads on your 318 so the bigger ports and valves will make a bigger increase...

One thing to watch out for, there were two main castings of Magnum heads that had slightly different size ports and chambers. One came on earlier factory 5.9L engines, and the other came on 5.2L Magnums and was also the replacement spec'd for all engines; after a certain year they all switched to the 5.2L castings. The 5.9L ones have slightly bigger ports and chambers than the 5.2's, so for street use on a 318 I'd say the 'smaller' heads are probably better.
 
You better be careful. We're in the planning stages for a twin turbo 323 right now. So far, we've not found a non magnum roller block with any more than .131" on the major thrust side. I think they are all thin, but we're gonna keep lookin. We have a sonic tester and a big pile of blocks, non magnum and magnum.
 
I don't want to start anything, especially with a guy with a gun :)

But...I don't believe "flywheel" HP is an industry standard term.

Gross HP is what most aftermarket engine builders use and what auto manufacturers used intil 1972.
Net HP is what was used after 72 and accounts for all the accesories that sap power.
A very sketchy conversion factor is plus or minus 18%. (I use 20% because the math is easier).
Going to rear wheel HP, you lose another percentage at the trans.
Again, sketchy conversion factors are 15% for a manual and 20% for an automatic.
Taking that +- 245 NET HP figure for the 5.9, and putting back the 20% to calculate an estimated GROSS number (so we can compare it to the figures for crate motors, etc) yields about 310-315.
Subtracting the 20% (from the 245 NET number) for the auto trans will give you that 200 RWHP number.

BTW, I used an accelerometer to measure a backroad 1/8 mile run, and used a whopping 85 RWHP!!
 
Also BTW, I LOVE "Zombie Dart"!

Can cats take 10 zombie bites before they turn?

EDIT---9, I mean 9, that's what I get for rounding my figures !!
 
YY1 said:
I don't want to start anything, especially with a guy with a gun :)

But...I don't believe "flywheel" HP is an industry standard term.

Gross HP is what most aftermarket engine builders use and what auto manufacturers used intil 1972.
Net HP is what was used after 72 and accounts for all the accesories that sap power.
A very sketchy conversion factor is plus or minus 18%. (I use 20% because the math is easier).
Going to rear wheel HP, you lose another percentage at the trans.
Again, sketchy conversion factors are 15% for a manual and 20% for an automatic.
Taking that +- 245 NET HP figure for the 5.9, and putting back the 20% to calculate an estimated GROSS number (so we can compare it to the figures for crate motors, etc) yields about 310-315.
Subtracting the 20% (from the 245 NET number) for the auto trans will give you that 200 RWHP number.

BTW, I used an accelerometer to measure a backroad 1/8 mile run, and used a whopping 85 RWHP!!
Click to expand...


Whatever terms you want to use I really don't care. The fact is that ALL R/T Dakotas came with 250hp at the flywheel. And if you look around you will read that pretty much everywhere. Here is a thread I started Feb 9 2012 on dakota-durango.com. 190-200 stock. Reverse your math and you get 250hp at the flywheel. Period. This info pertains to the 5.9 Dakotas, Durangos, and Rams.

http://www.dakota-durango.com/forum/showthread.php?t=153932
 
The difference in Net and Gross is the accessories on and functioning and the exhaust system. The drivetrain loss is not taken into account. So a Gross rated 318, in 1970, had 230 gross flywheel hp. That was the engine, driving the water pump and fuel pump, through manifolds. A 5.2L Magnum 318, was also rated at 230 flywheel hp. But it was rated with the water pump, power steering pump, and AC compressor w/clutch engaged, thru factory manifolds and exh including the cat. At least that's how I understand it.

Having driven and almost bought a 5.2L V8 Magnum 2wd Dakota with a stick and 3.91s in the early 90s, and then driving the 5.9 RT auto... I'll take the 93 with a stick every time.
 
moper said:
The difference in Net and Gross is the accessories on and functioning and the exhaust system. The drivetrain loss is not taken into account. So a Gross rated 318, in 1970, had 230 gross flywheel hp. That was the engine, driving the water pump and fuel pump, through manifolds. A 5.2L Magnum 318, was also rated at 230 flywheel hp. But it was rated with the water pump, power steering pump, and AC compressor w/clutch engaged, thru factory manifolds and exh including the cat. At least that's how I understand it.
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Agree- that's another way of explaining it.

"At the crank" doesn't give enough information.

...Especially if you are trying to compare crate motors or magzine build dyno numbers to factory figures for motors that came installed in vehicles.
 
Its easy, magazine numbers are all high.

Crate motor numbers are pretty accurate give or take 20-30 horsepower. LOL

When someone posts "at the crank" figures, estimating it from the numbers got from a chassis dyno, "crank" numbers = "net" because you usually have to run exhaust and accessories on a chassis dyno (though they may or may not be running all factory accessories).

Irregardless, 8 rwhp is not equal to 22 or 23 horsepower gross/net whatever.
 
You are correct- very subjective calculations of gross minus 20%, minus another 20%, indicates that 12.5 Gross HP equals 8 RWHP for an automatic trans.

What was the OP's question again?
 
YY1 said:
Also BTW, I LOVE "Zombie Dart"!

Can cats take 10 zombie bites before they turn?

EDIT---9, I mean 9, that's what I get for rounding my figures !!
Click to expand...

Ha, I love it too, I really need to get on posting some updates. It's my undead project

YY1 said:
You are correct- very subjective calculations of gross minus 20%, minus another 20%, indicates that 12.5 Gross HP equals 8 RWHP for an automatic trans.

What was the OP's question again?
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I hardly remember either :toothy10:




And Rob, I'm guessing they must get really thin on the thrust side. I really just wanna go 30 over, but this kind of makes me hesitant
 
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