Hot Rod magazine 5.9L magnum Build

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moparspares

moparspares

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I read an article on building a 5.9L Magum engine. Basically they started with a 300HP crate engine which has a bone stock bottom end. They added Comp XFI cam, Edelbrock RPM heads, Mopar M1 single plain intake, and a 750 Speed Demon carb and some headers.

On the Dyno it pulled 448HP at 5800 RPM. This seems pretty incredible for a stock stroke with bolt on out of the box RPM heads. My build is similar but with stroker crank and I was only expecting these sort of numbers as 408 cubes. Am I underestimating my build or is Hot Rod magazine over estimating theirs.

Opinions please

Heres the link

http://www.hotrod.com/techarticles/engine/hrdp_0804_small_block_mopar_engine/viewall.html
 
I hate Hot Rod. They should start with a junkyard motor like 90% of the rest of us, and I think their numbers are skewed. That sounds kind of high to me.
 
Are you building a magnum motor or a flat tappet LA motor?

You probably won't see much difference in HP between a 360 to a 408 at this level.
The main difference will be the 408 will make the HP lower in the rev range and have a flatter torque curve.

But I reckon that dyno is a bit optimistic.
There is a thread here showing 2 engines that ou812 has built and they are going to Australia and they make similar power to the 360 in this article.

I'm in the process of building my 408 using a magnum block, eddy heads, BPE forged crank, forged icon ic983 pistons, forged scat I beam rods, and thumpr cam.

Hopefully will be finished and in the car by the end of the July.
 
Building a Magnum with Hughes roller cam, RPM heads, Harland Sharp rollers, M1 Single plain.

Intake Valve Lift 1.6
Exhaust Valve Lift 1.6.544"
.568"
x.gif
Intake Duration at .050"
Exhaust Duration at .050"228°
236°

MP Cast crank, Eagle Rods, probe 17.5cc forged dish pistons. Aiming for 400 - 450HP. Hot Rods figures seem rather high to me.
 
I think their numbers are a little conservative if anything. COnsidering you can get 400 HP from a 318 with similar parts, I don't see why in the world those numbers are not realistic.
 
Dyno numbers are probably close to right in their shop, but they've got appropriate tools on hand to help them adjust a/f and timing quickly and effectively. I'm inclined to agree with Stroker...you can make 400 out of a 5.2/318 with similar parts, no reason to believe that an engine 40 cubes bigger can't make 40 more hp all things being equal. That cam is no slouch, and with better than stock heads, new roller rockers, long tubes, and dyno trim (i.e. no accessory drives aside from water pump), it's not difficult for me to fathom it could make the numbers they claim.
 
Look at it a different way.Check out LX Guys Dart.Runs 11.70s with a stock Magnum short block RHS Heads,and a similar thread.A out of the box 380/360 crate motor wound occasionally hit 400+ h.p.,with stock Magnum heads.I don't think they are high,just optimised for cam and head sales.
 
I agree the power numbers are quite possible.

The cam they chose is a roller and has a lot of lift, they have a pretty big carb on it and the heads should flow pretty well at 250 cfm on the intake side. Theoretically 250 CFM could support 500 HP.

I disagree with the assertion that moving from 360 CID to 408 CID isn't worth much HP. I would argue that increasing the displacement is worth about 1 HP per cubic inch on a well built engine. This of course assumes that you have the heads to support the additional cubes, as well as an appropriate cam, intake and carb.

Regards,

Joe Dokes
 
dyno numbers are like naked women on the internet ...nice to look at and talk about...but sometimes do not perform to their expectations....

put the engine in a car and run it down the track to see if those results back up the dyno number...
 
Of course it can! It's a mopar....now if it was a chebbie I'd say thier using thier magic cosmic horsepower dream wheel again.
 
Well I figured the stock edelbrock heads would be the bottle neck in this scenario so making more hp would depend on if the heads could flow more to meet the 408's capacity.
 
Two thoughts - The XFI lobes they used are even a faster rate of lift than the XE flat tappet lobes. That intake lobe used is larger and faster than the XS274S solid flat tappet cam. There is significant power in using those modern lobes but most guys don;t want to pay for a custom grind. Second, it is well known Westech dynos can be "happy". In some cases very happy, but I think in this case it's not too far off reality. The cam is the key to that combo.
 
A body bomber; a few guys around here back in the day dyno'd there MP create engines to over 400 HP when equipped as MoPar said they should be.
The E.T. Numbers work for me as well.

Joe, the Stroker should
Make more HP but not a crazy big number more. There really done for torque over HP.

Scrappy Doo; in stock form I think there a bottle neck. But then again, most any stock or should I say, as cast head would be a bottle neck except maybe the W9
@ 290 CFM as cast.

Moped; I slightly disagree in significant power gains in cam lobe rates. Only because of th level of build may not really take advantage. My motto is if your gonna hot it hard, the HIT IT HARD! And really step up and take advantage of the cam. Most do not.
Mental HP is greatest sometimes.
 
70aarcuda said:
dyno numbers are like naked women on the internet ...nice to look at and talk about...but sometimes do not perform to their expectations....

put the engine in a car and run it down the track to see if those results back up the dyno number...
Click to expand...

Absolutely, positively the only way.
 
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