Interchange questions between LA 360 and the Magnum 5.9

[Kern Dog]

Hello.
Forgive the simple questions that follow. I only ask because I am just not familiar with what interchanges between these two engine series.
A friend has a Mopar Performance crate 360 in a Dart and is looking to build a long stroke 408. He may even change the heads to the Trick Flow Magnum heads.
I have a 1974 360 short block that I pulled from a truck years ago. It ran but did need a rebuild.
Would the entire rotating assembly from the Magnum series fit right in the old LA block? I recall that the balance factor between the 360 and 5.9 were different. Were the crank journal sizes the same? If these parts do interchange, the 360 block could be bored the .20 over to match the piston size and boom....ready to go.
Secondly, if the friend does remove the Magnum heads, what does it take to make them work on an LA block? Is it just a matter of using AMC flat tappet lifters and hollow pushrods to get oil up to the rockers? I recall from years ago that the trick was to use the Magnum heads, AMC lifters, hollow pushrods and a Magnum specific head gasket that would block the oil passage that normally would feed the rocker shafts in the LA series engine.
Am I remembering that correctly?

 

[rumblefish360]

Would the entire rotating assembly from the Magnum series fit right in the old LA block?

Yes. However, the pistons heights vs deck height can be an issue if aftermarket pistons are used. The Magnum has a shorter deck height. Just a little shorter. IIRC, worth checking, the. Agni. Piston will sit in the LA fine but the reverse, should be fine because the low compression engine have a piston down the bore pretty far.

I recall that the balance factor between the 360 and 5.9 were different.

The surface face of the Matnum doesn’t cover the same area of the larger LA head. Some gasket do not even work.

Were the crank journal sizes the same?

Yes

If these parts do interchange, the 360 block could be bored the .20 over to match the piston size and boom....ready to go.

Yes

Secondly, if the friend does remove the Magnum heads, what does it take to make them work on an LA block?

The head oiling issue has to be solved because the. Magnum block lacks the oiling hole in the block.
1: The block can be drilled to oil the heads.
2: An external oil line can be plumbed from the back of the block to the cylinder head e drilling the LA head on the back to a drilled rocker stand meet to oil the heads rocker gear.
3: Pushrod oiling. Requires specific lifters which is now not a problem and they are the normal lifter sold with kits or separate.
Actual MoPar lifters do not send oil up the pushrods.
This also requires the rocker gear to be able to accept pushrod oiling. Comp cams for one example have rockers that can be pushrod oiling feed.

Is it just a matter of using AMC flat tappet lifters and hollow pushrods to get oil up to the rockers?

Ops! Answered above

I recall from years ago that the trick was to use the Magnum heads, AMC lifters, hollow pushrods and a Magnum specific head gasket that would block the oil passage that normally would feed the rocker shafts in the LA series engine.
Am I remembering that correctly?

Yes. However, a standard LA intake will work. The oil coming up through the block on a LA doesn’t need to be blocked via a gasket or anything at all. If your worried about a leak, a set screw in the block counter sink will do.

I’m sure other members will add an item I missed and would appreciate it being done.

 

[Super-Cuda]

Hey Kerndog,

Here's the site I used to build my 408 Stroker to look like an LA engine.

I was going for a "day 2" look so hence the chrome LA Valve covers ,alternator and thermostat housing.

Timing cover is a 70 LA piece.

Great info there!!

Magnum Swap -your source for Mopar engine swap information.

 

[Professor Fate]

Just a rhetorical question here-
If your buddy is completely gutting the engine, and restarting his build from square one, why don't you just trade your LA (and cash) with him? It won't cost him any more to start over with your LA block, and you'll end up with a built, matched, known good engine with no fooling around between the engine families...

 

[Kern Dog]

I thought that all of the crate engines were all remanufactured roller cam blocks. If I were him, I wouldn't change back to a flat tappet setup.
To repeat,
I was wondering about what is required to change my LA 360 block to use the Magnum 360 heads. I know that the AMC lifters and hollow pushrods would get oil to the rocker arms but was not sure if the traditional LA oil path to the rocker shafts was blocked off by the Magnum head or the Magnum head gasket.
I forgot about the different intake manifold and the weird bolt hole arrangement in the ends of the Magnum heads for alternator mounting.
I never heard anyone state that the deck heights were different between the LA and Magnum series.

 

[junkyardhero]

I thought that all of the crate engines were all remanufactured roller cam blocks. If I were him, I wouldn't change back to a flat tappet setup.
To repeat,
I was wondering about what is required to change my LA 360 block to use the Magnum 360 heads. I know that the AMC lifters and hollow pushrods would get oil to the rocker arms but was not sure if the traditional LA oil path to the rocker shafts was blocked off by the Magnum head or the Magnum head gasket.
I forgot about the different intake manifold and the weird bolt hole arrangement in the ends of the Magnum heads for alternator mounting.
I never heard anyone state that the deck heights were different between the LA and Magnum series.

5.9's are shorter than LA 360's 9.580 vs 9.599 deck heights

some of the early magnum blocks are drilled for head oiling, but not all. the magnum head doesn't have provisions for oiling in that manner so it's blocked there and by the head gasket as well. even if you use a LA head gaskets (which you can) and even if the block is drilled, the oil has nowhere to go.

anyway, to your question at hand: to knock magnum heads on you'll need: heads, head bolts (they're different), rocker gear, lifters that have a provision for push rod oiling (dem AMC jobbers), custom pushrods, and headgaskets-- preferably magnum but not 100% necessary.

then you just need whatever intake you want to run.

 

[4mulas]

Kern you just need aftermarket mopar lifters or amc lifters which I think are now the same. Before, amc lifters were the ticket but I think the aftermarket has covered both with one now. Also will need shorter oil through pushrods and whatever rockers you want to use. Not sure about the old oiling system. Likely just blocked off…

 

[Kern Dog]

I may just skip the Magnum heads.
The LA deck being .019 taller would barely affect compression enough to matter to the pistons. The decks could be resurfaced to match a Magmum anyway.
Thanks guys!

 

[junkyardhero]

I may just skip the Magnum heads.
The LA deck being .019 taller would barely affect compression enough to matter to the pistons. The decks could be resurfaced to match a Magmum anyway.
Thanks guys!

the benefits of the magnum head: closed chamber, good squish characteristics, fairly decent flow for what it is if you keep the cam reasonable enough to take advantage of that aspect. 1.6 rockers, updated valves & hardware over the 360 stuff.

if the 360 heads needed any work and the mag heads were more ready to run or needed less $$ to get them on there i would say they would be the better choice-- depending on the nature of the build.

(edit: because evidently i forget what rocker ratio magnums are)

 

[Kern Dog]

the benefits of the magnum head: closed chamber, good squish characteristics, fairly decent flow for what it is if you keep the cam reasonable enough to take advantage of that aspect. 1.7 rockers, updated valves & hardware over the 360 stuff.

if the 360 heads needed any work and the mag heads were more ready to run or needed less $$ to get them on there i would say they would be the better choice-- depending on the nature of the build.

I think that you meant 1.6 rocker arms.

 

[junkyardhero]

I think that you meant 1.6 rocker arms.

yes. correct 1.6 thank you.

i think i probably hit my head one too many times on the lift today...

 

[Kern Dog]

Here is another one.
If one has a Magnum block but wants to use LA pattern heads, how do you get oil to the rocker shafts? I thought that the Magnum didn't have that oil hole/passage that the LAs had.

 

[TT5.9mag]

Here is another one.
If one has a Magnum block but wants to use LA pattern heads, how do you get oil to the rocker shafts? I thought that the Magnum didn't have that oil hole/passage that the LAs had.

Option 1. You can have the block drilled, cam bearings installed with the oiling hole, and a cam that is drilled for timed oiling.

Option 2. Run external oiling, plumbed from the oil gauge port to the back of the heads. Involves drilling heads and rocker shaft bolts. Restrictors need to be made/installed because you’ll have full time oil and lots of it. I have a magnum bottom end with W2 heads and I use .040 per side.

Either way, if you’re using magnum lifters you can also use purshrod oiling for the adjusters.

 

[volaredon]

I've put magnum heads on a couple of LA engines. Wasn't a big deal at all. Mopar and AMC lifters are identical except for that hole, they sell the same ones for either or now a days. 7.650 pushrods and the magnum rocker gear and your pretty much there. The MP conversion pushrods they used to sell (may still?) were 7.625.
This is with hyd flat tappet cam.

 

[NC Engine Builder]

You can put LA heads on magnum blocks, and oil through the pushrods if you use the PRW steel rockers

 

[volaredon]

I just used stock magnum rockers

 

[TT5.9mag]

You can put LA heads on magnum blocks, and oil through the pushrods if you use the PRW steel rockers

I forgot about that thanks. That can be option number 3. The prw rockers are drilled so they will oil the shafts.

 

[TT5.9mag]

@volaredon he asked about going the other way. LA heads on magnum blocks, which is quite a bit more work than magnum heads on LA blocks.

 

[volaredon]

I've seen threads on that.... but I don't remember asking about LA heads on magnum block....(just the intake) and I asked about LA accessories, timing cover out front.

 

[Kern Dog]

I asked about LA type heads on a Magnum block because a friend is looking to build a stroked MP crate 360 and he wants to use Trick Flow heads.

 

[NC Engine Builder]

I asked about LA type heads on a Magnum block because a friend is looking to build a stroked MP crate 360 and he wants to use Trick Flow heads.

Most of us understood your question. Just use oil through pushrods and PRW rockers and it's a bolt together simple deal. He will need to be cautious of deck height however.

 

[Bobzilla]

I asked about LA type heads on a Magnum block because a friend is looking to build a stroked MP crate 360 and he wants to use Trick Flow heads.

Check his block after the heads are removed. Some of the Mopar crate engines and short blocks were built with early blocks that had the LA oil passages.

 

[Kern Dog]

Here is a question that has me curious...
Say a man has a Magnum 5.9/360 and swaps to a set of Trick Flow heads with rocker shafts that are used to being oiled through that passage in the block....
How do you get oil to the rocker shafts now?
I've read that you can try drilling the block to open up that oil supply passage. Is that still in place in ALL of the 5.9 engines?
What if one didn't feel comfortable drilling into their block...can you use hollow pushrods and use traditional pushrod oiling? If so, how does that provide adequate oil to the rocker shafts and the rockers themselves?

 

[Bobzilla]

If you have a Magnum block with no head oiling holes and you successfully drilled the two holes, you then install LA style camshaft bearings and LA style camshaft drilled for LA oiling as well. That is it. Then you can run any LA head and treat the top end as an LA with rocker shaft oiling.

Trick flow heads can be used on Magnum blocks without the oiling holes but you have to use pushrod oiling. That means lifters, pushrods, and rocker arms that have pushrod oiling provisions built in. Trick has a Harland Sharp rocker arm kit part number they recommend for this.

You can actually run any LA head on a Magnum block as long as the correct pushrod oiling setup is used. Comp Cams Ultra Pro Magnum rocker arms, and the copies like PRW, have the pushrod oiling provisions too.

 

[Desoto291hemi]

Option 1. You can have the block drilled, cam bearings installed with the oiling hole, and a cam that is drilled for timed oiling.

Option 2. Run external oiling, plumbed from the oil gauge port to the back of the heads. Involves drilling heads and rocker shaft bolts. Restrictors need to be made/installed because you’ll have full time oil and lots of it. I have a magnum bottom end with W2 heads and I use .040 per side.

Either way, if you’re using magnum lifters you can also use purshrod oiling for the adjusters.

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Excellent work on your plumbing,,,,,looks great,,,,,,good looking engine too !

Tommy