Onservation about magnum 5.9

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HankRearden

HankRearden

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I like to think I'm pretty familiar with LA 360's and magnum 5.9 performance having put hundreds of thousands of miles on both and daily driving a 5.9 pickup.
But as my dart gets closer to driveable I've taken a few rips with it in front of the garage for fun.
I noticed that this junkyard 5.9 with a cheap air gap style intake 750 edelbrock and old spitfire headers revs much,much quicker than any of the carbed la 360's I ran and far quicker than the injected 5.9s.

I can only surmise the factory kegger intake and cast exhaust manifolds are very restrictive.
I'm really not sure. But I had to try hammering on it a few times to be sure.

I wonder how much better m

y truck would tow and haul with headers and a better induction setup?
 
HankRearden said:
I like to think I'm pretty familiar with LA 360's and magnum 5.9 performance having put hundreds of thousands of miles on both and daily driving a 5.9 pickup.
But as my dart gets closer to driveable I've taken a few rips with it in front of the garage for fun.
I noticed that this junkyard 5.9 with a cheap air gap style intake 750 edelbrock and old spitfire headers revs much,much quicker than any of the carbed la 360's I ran and far quicker than the injected 5.9s.

I can only surmise the factory kegger intake and cast exhaust manifolds are very restrictive.
I'm really not sure. But I had to try hammering on it a few times to be sure.

I wonder how much better m

y truck would tow and haul with headers and a better induction setup?
Click to expand...
My experience as well. Replace the kegger with a carb intake and normal distributor and the Magnums rocket to life.
 
HankRearden said:
I like to think I'm pretty familiar with LA 360's and magnum 5.9 performance having put hundreds of thousands of miles on both and daily driving a 5.9 pickup.
But as my dart gets closer to driveable I've taken a few rips with it in front of the garage for fun.
I noticed that this junkyard 5.9 with a cheap air gap style intake 750 edelbrock and old spitfire headers revs much,much quicker than any of the carbed la 360's I ran and far quicker than the injected 5.9s.

I can only surmise the factory kegger intake and cast exhaust manifolds are very restrictive.
I'm really not sure. But I had to try hammering on it a few times to be sure.

I wonder how much better m

y truck would tow and haul with headers and a better induction setup?
Click to expand...
There's a couple reasons to this...But being that you also compared the engine with a carburetor to itself with injection... let's go there.
The fuel injected 5.9 is managed by a computer with mostly a fixed tune. Has anyone here flowed/determined what the kegger flows? I hear as cast it is around 190's cfm per runner. Now that kegger manifolds runners taper down somewhat drastically at the flange/intake face FWIW. If you gasket match that and open that tapered section ...it will flow a lot more. Side note was it on purpose to speed the air at the injector? I've opened it up and have not felt any negative from it in fact it hauls *** and if I did lose an inkling of torque it was probably about 300 RPMs worth sooner, maybe. Now still staying on the mag vs mag , kegger vs dual plane/4 brl.... the kegger is designed for idle to maybe 5000 rpm, probably 4800 rpm ...but the stock valve springs wont allow more than 4200 rpm or so 'worn and tired @85 seat/ 190lbs open, stock new is 90/200'..

So a factory Magnum kegger designed for 5000 RPM and under, with tiny runner windows... springs designed for Max RPM of around 4500 rpm...
The cam is not the issue as much as the above, believe it or not.
Makes sense that a version with more air/fuel dual plane/4brl, no stock computer tune and some better springs or cam will rev faster alright.

For what it's worth I put some really good heads on my 5.9 Magnum in my truck that has to pass California smog 'has the stock hyd roller cam" I also upgraded the valve springs and Port matched the kegger and put some Summit headers on it + ultra flo muff.
It revs no problem to 4800 and does it quick...though ultimately the computer caps the output.
Imo the intake design and valve springs are 1st, computer second, exhaust 3rd...and cam last as to why it does or doesnt "rev fast".

Screenshot_20230415-152125_Photos.jpg
 
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Based on the below comparison of an EFI 5.9 to an MP 300 HP crate motor, I find it hard to believe that anything without a cam swap would see much difference regardless of the intake or exhaust side changes.



One variable though is that Holdener used an aftermarket EFI pcm, so it could be the stock tune causes some laziness.

I would speculate that a stock 5.9 compared to a basic LA 360 might rev better due to thinner piston rings, a roller cam, lighter rotating assembly and better (stock) flowing heads. But just a guess.
 
DionR said:
Based on the below comparison of an EFI 5.9 to an MP 300 HP crate motor, I find it hard to believe that anything without a cam swap would see much difference regardless of the intake or exhaust side changes.



One variable though is that Holdener used an aftermarket EFI pcm, so it could be the stock tune causes some laziness.

I would speculate that a stock 5.9 compared to a basic LA 360 might rev better due to thinner piston rings, a roller cam, lighter rotating assembly and better (stock) flowing heads. But just a guess.
Click to expand...

dont know but its noticeable.
 
Don't forget too the compression differences since the Magnum blocks have a shorter deck height.
 
I bet my balancd 367 will hit 7200 and back to idle faster than any stock 5.9 with any AG, any carb, any headers, normally aspirated, and maybe, I'll even give you a thousand rpm. Even Thor, cannot hurl thunderbolts faster than this little hummer can free-rev.
I am, of course, exaggerating.
The point is this; it's all about moving air.
If the air cannot get out, fresh air cannot get in.
If the air cannot get in, all the out in China is not gonna help one bit.
 
Vid in post 5 verifies 300 GROSS HP with headers from stock 5.9 (rated 245 NET HP from factory).

Did they say what headers they were for 20 HP gain over the Mag manifolds?

EDIT- 288 HP with manifolds. Headers only gained 12 HP. Interesting.
Seems to verify those manifolds are pretty good. I wonder if they were the 1992 only "big pipe" version.

EDIT 2- small manifolds.That supports the theory that those big pipe versions are "just as good" as headers.
291 HP on the "crate" version with a dual plane and a 750 carb. IMO 3 HP difference is negligible.
 
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@YY1 , in the MP catalog, I think they suggested a 1-3/4 header for both create engines.
 
YY1 said:
Vid in post 5 verifies 300 GROSS HP with headers from stock 5.9 (rated 245 NET HP from factory).

Did they say what headers they were for 20 HP gain over the Mag manifolds?

EDIT- 288 HP with manifolds. Headers only gained 12 HP. Interesting.
Seems to verify those manifolds are pretty good. I wonder if they were the 1992 only "big pipe" version.

EDIT 2- small manifolds.That supports the theory that those big pipe versions are "just as good" as headers.
291 HP on the "crate" version with a dual plane and a 750 carb. IMO 3 HP difference is negligible.
Click to expand...

I wish Holdener had done a test with the exhaust manifolds as well as the headers after the cam swap. I think the cam is the real bottle neck on a stock 5.9 and until that is changed I can’t see any of it being a reasonable test.

I mean if it makes the same HP at about the same RPM with that long runner beer bear intake as it does with the MP dual plane, there has to be something else holding it back.
 
rumblefish360 said:
@YY1 , in the MP catalog, I think they suggested a 1-3/4 header for both create engines.
Click to expand...

I don't think the MP folks RE crate engines ever suspected people might use those factory truck and Jeep manifolds in "cars".

Of course they really only work in cars that have manual steering.

I'd be interested to know if that Borgeson steering box clears Magnum manifolds.
 
Electric water pump on the $5500 mag vs the stock mag w/mech water pump.
The power diff can be huge. 30hp
DionR said:
Based on the below comparison of an EFI 5.9 to an MP 300 HP crate motor, I find it hard to believe that anything without a cam swap would see much difference regardless of the intake or exhaust side changes.



One variable though is that Holdener used an aftermarket EFI pcm, so it could be the stock tune causes some laziness.

I would speculate that a stock 5.9 compared to a basic LA 360 might rev better due to thinner piston rings, a roller cam, lighter rotating assembly and better (stock) flowing heads. But just a guess.
Click to expand...
 
MOPAROFFICIAL said:
Electric water pump on the $5500 mag vs the stock mag w/mech water pump.
The power diff can be huge. 30hp
Click to expand...

Doesn't look like they ran a belt on the stock 5.9 in the test. So apples to apples?

Assuming you mean that there could still be a difference in power between the 2 motors since one had an electric pump and the other didn't.
 
barbee6043 said:
Has Dull Chic and Fried Burger even done any dyno tests on the magnums?? Just curious.
Click to expand...

Yes. No idea if it is on YT, but on Engine Masters they compared a stock BB intake to a modified BB intake, added an oval port TB from some place, then swapped an MP dual plane and then an AG and played with spacers. I think they started with the same crate motor Holdener used above and it had the Comp cam in it for all the test (I think).
 
I did it! Magnum 380 crate in a 74 Road Runner 4 speed with power steering. I used the early truck manifolds and an Edelbrock Performer 750. The driver manifold "kisses" the power steering box, but does fit in a 73/74 b-body. Yes, I realize that I am not getting optimum performance from the engine with both the carb and manifold choices. Believe it or not, I did correspond with Mopar Performance about my intentions at the time and they were supportive but stated their determinations from my plans and their advertising at the time did define the optimal set-up. 25 years later, I am still happy with the engine, it does have more power than my 340 powered Satellite but not more power than my 440 Road Runner.

As an aside, there were blurbs in Mopar Performance News at the time about the use of truck manifolds in cars and somewhere I have a letter response from MP stating the manifolds would fit my application.
YY1 said:
I don't think the MP folks RE crate engines ever suspected people might use those factory truck and Jeep manifolds in "cars".

Of course they really only work in cars that have manual steering.

I'd be interested to know if that Borgeson steering box clears Magnum manifolds.
Click to expand...
 
YY1 said:
I don't think the MP folks RE crate engines ever suspected people might use those factory truck and Jeep manifolds in "cars".
Click to expand...
Agreed. I used Hooker Super Comp headers @ 1-3/4 in my ‘79 Magnum. The current 5.9 project is going in a ‘74 Duster with the standard style 1-5/8 header. I’ve read some headers have an issue with the Magnum motor mount boss. IDK about my case just yet. It’s easily taken care of.
YY1 said:
Of course they really only work in cars that have manual steering.

I'd be interested to know if that Borgeson steering box clears Magnum manifolds.
Click to expand...
This, I have no idea of. It would take a good search of pictures here to see who did what.
 
DionR said:
Doesn't look like they ran a belt on the stock 5.9 in the test. So apples to apples?

Assuming you mean that there could still be a difference in power between the 2 motors since one had an electric pump and the other didn't.
Click to expand...
Lol yeah I was going off the thumbnails for the videos...I didn't actually watch this videos this time. I did already though, just a long time ago. In the pictures one has an electric water pump the other one doesn't , so naturally...
 
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