MAGNUM heads on older LA blocks

Since this comes up so often, I am going to post this so hopefully GregZ or one of the other moderators will put it in the "BEST OF" or the tech archives.

Some of the avantages of the magnum heads are: 8mm valve stems (lighter than the LA's 3/8 stem) "swirl port" technology in the intake runner, 63cc closed chamber, great port velocity, improved exhaust runner, stock 1.6 ratio rockers, ability to support 400HP out of the box.

to put magnum heads heads on a pre-magnum small block, here's what you need:

different pushrods
oil through lifters
different head bolts
magnum heads
magnum rocker gear
different intake (potentially)*

people say you can use the LA valve covers, some have had
problems getting them not to leak. I don't have firsthand experience on this....maybe I'll stick some LA covers on my ram and try it out...

now a little discussion about the components in order I listed them:

any prices I mention are from www.mopartsracing.com to get
a rough estimate of total cost, since that's an easy place on line to find part numbers and pricing. any MP dealer should be able to get you these MP parts.

PUSHRODS:
you can custom measure and get custom length ones, or MP offers these:
Special hydraulic pushrods
Designed to allow the use of magnum heads and
standard magnum rockers on standard 1967-91
"A" short block/engines.
MP Part number: 5007477

Magnum head on standard "A" block-set of 16 7.625"
$38.50

if you're running a lot of lift (small base circle on the cam) with standard non-adjustible rockers, or adjustible rockers (dependign on how much lift), you may have to get custom length ones. my guess is you might be able to find some off the shelf ford/chevy parts to work.

LIFTERS:
they need provisions for pushrod oiling. if you have stock lifters (stock cam) they probably don't. if you have an aftermarket cam, you probably do. the way to check: find out your lifter manufacturer (i.e. are they summit lifters? comp? crane? etc) and see if the part number for a mopar is the same part number for an AMC motor. if they are, then you have pushrod oiling capable lifters. most do. I know for sure comp & summit do.

HEAD BOLTS:
the bolts are different length than old LA ones. luckily they're cheap:

MP part number: 4876759 Magnum engine $15.95

HEADS:
any '92-up 318 or '93 up 360 will have them. you might have issues finding cracked heads, or you might not find junkyards to sell you heads, they may want to sell the whole motor. if you get them from a Junkyard, make sure you get the rockers and valvecovers. if you can't fund them in a yard, what are you to do? well, mopar performance sells them
as brand new castings:

MP PN: 4876256 $139.95 each (1.92/1.625 production castings)

or you can purchase R/T heads, which feature stock port locations, and a W2 style bowl, and improved exhaust port. arguably the best iron small block head you can find.
MP PN 5007140 $375/ea 1.92/1.625 valve
MP PN 5007140 $435/ea 2.02/1.625 valve

OR if you want, you can purchase assembled heads. I've heard that the assembled production heads have the crate motor valvesprings. hopefully someone can confirm. these should be good for cams up to .51" lift. CAVEAT: magnum heads start running into seal to retainer clearance at valve lifts much above .525 lift, so if you want to go higher you'll have to machine down the valve guide for clearance.

assembled magnum head:
MP PN 5007086 $310.50 each

assembled R/T heads:
P70005 $595 (1.92/1.625)
P70005 $650 (2.02/1.625)

ROCKER GEAR:
stock magnum rocker arms are actually the same rocker arms as the old AMC 290-401 engine series, and are 1.6 ratio instead of the LA 1.5 ratio. to find out the valve lift, take your cam's valve lift and multiply by 1.067 (1.6/1.5)
aftermarket roller rockers are usually the same pieces as SB chevy pieces, and may require different rocker arm studs. some kits may include them. most aftermarket rockers are available in 1.6 or 1.7 ratio

if you're running a moderate hydraulic cam, stock rockers are fine. if you don't have junkyard ones new ones are available from MP:
MAGNUM V8 ROCKER ARM SET
Consists of 2 rocker arms,2 pivots,2attaching
boltsand 1 guide.for use with hydraulic cams
only,production 1.6 design ratio. NOT for
4.7L V8.
MP PN 4876050 $8.95 (one cyl, need qty 8 )

INTAKE:

currently only MP makes intakes
MP PN 5007380 dual plane $239.95
MP PN 5007381 single plane $239.95
MP PN 5007398AB 2BBL MPI W/EGR $335 (92-96 truck replacement)
MP PN 5007852 2BBL MPI W/O EGR $335 (97-02 truck replacement)

Edelbrock is coming out with a magnum Air Gap this year, and Professional Products is coming out with the Crosswind, a copy of the eddie airgap that will bolt to both an LA or a magnum head. (http://www.professional-products.com/sbchrysler8.htm#)

*Also, fellow board member 349magnumRT has come up with a simple yet ingenious jig to redrill your magnum heads for an LA bolt pattern, so any LA intake can be used. PM him for details. He's loaning it out for the cost of shipping to board members.

That's basically the gist of adding Magnum heads to an LA motor. for a 318, the 1.92 valve is about the perfect size. any larger (to say 2.02's) will physically fit, but the shrouding caused by the smaller bore on the larger valve will negate any flow increase. besides, ported, the stock valve will flow over 260 CFM, enough to support 500+ HP. look in the Best Of section for some of ryan J's flow results from magnum heads.

I'd like to thank the board members who have over the years contributed information, and to Mopar Muscle, car craft, and Steve Dulcich for the articles they've written/published on the matter who I have gained some of the info from. This is a great forum with a lot of knowledgable guys, hopefully I've been able to contribute a little to help others out.


Steve D also had a great article in building a non-ported head 318 using magnums here:
The Little Mopar that Could

which is a great reference article.

Moderators, please make sure this makes it's way into the best of section so I don't have to type this again

Good job Patrick. Now how 'bout doing the same thing for:

-what cars had #302 heads?
-what's the best SB head?
-what's better MSD or MP?
-why do I have no oil pressure?
-will this trans fit my 360?
-what's the biggest tire to fit an A body?
-what do I need to put a 360 in a /6 car?
-how much can I bore my block?
-max compression on pump gas?
-how do I get my timing tape to stick?

-what cars had #302 heads? -85-89 2bbl M bodies, and 318 2bbl/efi trucks with roller cams until '91
-what's the best SB head? -production, IMHO, magnums depends on your application (race? street? how much ya wanna spend???!!!
-what's better MSD or MP? performance should be the same, MSD might give better idle quality for large cams
-why do I have no oil pressure? where do I begin
-will this trans fit my 360? maybe
-what's the biggest tire to fit an A body? how much sheetmetal do you want to cut?
-what do I need to put a 360 in a /6 car? I'm getting bored I'll let someone else take this
-how much can I bore my block? bore till you hit water, back off .150.....
-max compression on pump gas? depends on quench, cam duration, timing, head material, any thermal coatings on components, and elevation.
-how do I get my timing tape to stick? superglue. worked for me. too bad I didn't realize till after I had the motor in the car you're supposed to put the timing take on backwards/upside down on a small block. I like I think it was unlawful or streetwise's suggestion. take and measure the circumference of the damper. divide by 10. put a line with a permanent marker or paint on the damper that amount away from the 0 line. there's your 36 degrees to time it all in to!

Thanks, Patrick. We're not worthy, we're not worthy!

Good info Patrick.

I think the Magnum Air-Gap is out now. The latest Edelbrock ad on pg 17 of the June '04 Mopar Muscle has it listed as RPM Air-Gap Magnum #7577 with a big "NEW!" sign next to it.

I also read that when putting Magnum heads on LA factory roller engines you can use the Magnum lifters and pushrods.

All we need now is for someone to make some decent exhaust haeaders that will match up with the magnum exhaust ports.....Hmmmm (Hint, Hint TTI)

I thought I saw where the regular small block headers bolt right up to the magnum heads.

'bout time Patrick. LOL

Headers....normal headers fit. Magnum R/T heads have a little different exhaust port shape but nothing to get worried about.

I was waiting for you to do it! (:

yeah, that's one thing I forgot to mention...standard LA headers/manifolds bolt right up.

Thanks for the info Patrick.

That's fine and all, but what are the biggest tires that will fit a...

never mind

I'll send out a heads up and try to help get this saved Pat.

Quote:

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Good info Patrick.

I think the Magnum Air-Gap is out now. The latest Edelbrock ad on pg 17 of the June '04 Mopar Muscle has it listed as RPM Air-Gap Magnum #7577 with a big "NEW!" sign next to it.

I also read that when putting Magnum heads on LA factory roller engines you can use the Magnum lifters and pushrods.

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What are/were the LA factory roller engines? Did they oil through the pushrods?

Also, has anybody actually ordered/received one of the new Edelbrock Magnum Airgaps?

Professional Products has their Magnum/LA Crosswind (Airgap clone) for the SB Chrysler listed in their 2003 catalog & its still not available yet.