I would like to know

[rbkt65]

why. I know several guys that put la heads on their magnum engines. They do that to get a better choice of intake manifolds. But why do they also put magnum heads on an la engine? I guess that I don't understand why. If your magnum heads are cracked between the valve seats, new not cracked magnum heads are close, if not more, than aluminum la heads when they are on sale. Help me understand this. TIA.

 

[rumblefish360]

Well, are the Magnum heads cracked? Let’s be sure in this and not just run at the mouth that they all crack. While I’m sure this could be the case. Where are they cracked? I’ll tell you the cracks are at the thin spot between the valves where the metal is solid. The cracks themselves aren’t a nice ending experience nor do they hinder a working engine.

I’ve taken apart a sub 80K 5.9 with cracks. I also seen 300K 5.9’s still motoring on down the Hwy. I’d bet there cracked. While I won’t say “Sure! Use them cracked.”, I have and have zero issues.

The Magnum head is a boost in power via better ports and a smaller chamber. They have a larger intake valve than the typical 1.88 J head & of course the 1.6 rocker over the 1.5 of the LA head. If you get over the non issue of the crack(s) in the head, it’s an inexpensive winner.

But don’t worry, LA heads crack as well. Not as frequently.

 

[rumblefish360]

When it comes to intake manifolds for the Magnum head, there’s really only 4 to choose from unless you find a MP unit. You have the;

Chink knock off RPM style
The Edelbrock RPM
The Indy single plane and the Indy Mod Man with several tops to choose from.

The MP dual and single plane are found used for way to much money.

 

[rumblefish360]

Cylinder head wise, the “MAGNUM” style head has only a few, *I Think* 3 choices for the aftermarket. The iron copies, Edelbrock and the Trick Rlow head that does both LA & Magnum blocks. I do not think Indy has a specific Magnum head. They have there copied-ish W2.

MP had several Magnum & cross over styled heads available.
Key word there, “Had.”
I was looking lucky that a fella here wanted to trade a set of Magnum R/T heads which jumped on.

 

[Dartsun]

Thanks Rumble, and good question.

 

[rumblefish360]

Your welcome. And yea, it is a good honest question.
Like I said above, I’m not going to say “Yea, go run a cracked head.” Though mine don’t have an issue despite the cracks. There small, in between the seats, the valves seal, it’s in an area where there is no coolant. They still work. I’m sure my other 5.9 has cracks. I’ll be running it until further notice with no plans on doing anything about it.

Replacement heads are the iron “Replacement Head” or the two aluminum choice from Trick Flow or Edelbrock. There a crap load more expensive than the iron replacements which really aren’t any better performance wise over the OEM head. I guess you could split hairs there and make some points. I’m not talking about porting ether. Once you start porting the iron replacements, you might as well look into the aluminum heads for a cost vs performance bang for the buck.

I wouldn’t port the OEM heads unless the race rules said you must have an iron head. The aluminum choices are a Edelbrock home run or a Trick Flow grand slam. The only Magnum iron heads worth porting were (key word meaning past tense since there not made anymore) would be the Aussie’s EQ or MoPars R/T head.

Also, a 1.7 aftermarket rocker is available for the Magnum head.
Pop a 1.7 rocker on your LA camshafts watch that lift skyrocket. Do the math! Then use coat on your piston to check! LMAO!

 

[273]

In stock form the Magnum heads vs 1.88 LA360 heads seem to make 20-30 hp over a similar 1.88 LA 360 headed combo. You should be able to get 400 hp with reasonable cam/cr without moding the magnum heads.

 

[rumblefish360]

In stock form the Magnum heads vs 1.88 LA360 heads seem to make 20-30 hp over a similar 1.88 LA 360 headed combo. You should be able to get 400 hp with reasonable cam/cr without moding the magnum heads.

Looking at the MP crate 360/380, I wonder how else
(or more accurately why the factory went the route they did for)
400hp could be made with a different smaller cam and a RPM. I’m not particularly fond of the crate engines single plane, low compression and intake manifold combination choice.