2004

Magnum R/T head porting w/pics

https://www.motortrend.com/how-to/mopp-0407-magnum-rt-cylinder-heads/

For clarity:
Are these used factory production Magnum cylinder heads.
What casting number?
A guess as to year of vehicle they came off of?

They are not Magnum R/T heads, correct?

For a period the MP catalog listed ported Magnum heads for sale.
Perhaps someone here on Moparts would know who did the actual porting for MP ?
Mike Leach did Tri-Y Magnum tube headers, did his shop also do the ported Magnum cylinder heads?

I think one can state with confidence that these cylinder heads were designed with a top priority to reduce NOx pollution using the concept of Fast Burn.

But the cylinder head design was not enough alone for NOx.
EGR still had to be used from 40% throttle opening to 60%.
In those years, once past 60% throttle opening,
the “Rep. John Dingle Jr. Passing Power legal exception” kicked in
and emissions did not have to met at all.

My gut tells me to bet that
a MPI intake manifold combined with untouched R/T cylinder heads and cam
will out do any home porting job.

But if it is fun by all means do it.

These are early 90's magnum heads out of a Van.
They have the dual intake bolt hole patterns tapped from the factory.
I will never know how much power is picked up because there will be no baseline.

14.7 psi boost will double what ever gains are made, plenty for a 19 to 20 year old kid.
I'm sure after some time there will be project creep when his car gets spanked by dear old dads. LOL

Out of the box he'll say WoooooHooooo, this is waaaaay faster than the 390FE in the truck. (which he thinks is peppy now compared to his Echo)
Later he be like, Hmmmmmm

I have never seen any factory heads with dual drilled intake bolt holes. I think what you have there are either aftermarket castings or modified factory castings.

I agree 100% either someone drilled them or they are EQ heads (EQ heads of Odessa, Fl. - does both holes on magnum heads)

either way they are getting some more modifications from the sounds of it.

My fuzzy memory seems to whisper that EQ cylinder heads have larger ports than the factory Magnums and flow better, but not quite much as Mopar Performance sold R/T Magnum cylinder heads.

The early ones that are no longer made.

I remember way back when a member here made a jig he would loan out to drill the heads intake bolt pattern. Never seen or heard of a dual pattern from the factory.

These came off a van sitting in a junk yard back in early 2000s.
No way my memory gonna recall the specifics. lol
It looked 100% factory.
318 came with roller camshaft about 2 years before 360 started to get em.

Pretty sure I read on here a couple decades ago that during crossover the factory drilled the heads with both patterns.

NO.

the early magnum blocks were drilled for rocker shaft oiling, magnum head/gasket blocked it a deck surface. in 92-93 it was either a magnum or a pre-magnum LA head no duel bolt holes on mag heads. roller lifters were the crossover.

that's why someone made up a jig and started swapping on carb/intakes/t-covers hiding magnum roller cam engines in old mopars in the 90s and head rebuilders like Odessa head company in Odessa fl. started doing it to all magnum heads they rebuild and IIRC they cast the EQ heads new and machine them duel pattern. IIRC they do other head work custom order.

the early 92-93 5.2 blocks are best for LA head hybrid mix as they will oil the shaft rockers..

the early pre-magnum 5.2 roller lifters were not oil through and had a solid PRs, then they got oil through roller lifters with the solid PRs. 91-92 pre-mag LA 318 oil through roller lifters/w hollow PRs & through the shaft rockers. then they all swapped to the magnum head/blocks by 94.

any trucks with the 318TBI or a 360headed 4v 318 all got a roller block with a flat tappet cam/lifters.

correct 318 went roller cam in 85 with 360 in 89 with the #308 head (which are the good ones to find)

I remember the moparts rent a jig. seems it went MIA and never showed up again. late 90s

plenty of EQ heads went and still going out as replacements. JYs are full of them by now.

Roller lifters predate the magnums by several years, I doubt that's the crossover.

Nice Mopar Prochargerman!

We need more 71 Plymouths doing the 1320 lol...

Hopefully my 71 GTX will be back out after 20+ years doh...

I've been doing some small block porting too for my 64 truck.

But if I was gonna have a trick 71 it would be a 400 stroker methinks?

There is lots of info on heads and the all say ''don't go bigger than 90%' in the throat''...

But if you do the proper throat cut with a decent 'cutter' the the throat angle is already done for you...75 degrees or even 70 is OK!

The exhaust has a wonderful shape in the bowl area, so 'easy peasy'...

what I mean by crossover was on lifters. the non-oil through with the solid PRs then they got a oil through roller lifter with the solid PRs. then the last of the pre-magnum roller cam engines got oil through lifters & hollow PRs oiling up the PRs & up through the heads/rocker shafts.

next change was magnum head/pedestal rockers/oil-through roller lifters & hollow PRs - LA pre-mag & magnum share same oil through roller lifter but different length hollow PRs.

which is why I said you have to watch the roller lifter you use on a magnum engine as early non oiler roller lifters do not cross over to a magnum head engine.

and when looking building a LA/magnum hybrid, I have only found the early 92-93 magnum 5.2 to have block drilled for shaft mount rocker oiling.

also why I said most 90-91 pre-magnum 318s seem to have more of a VC leak issue/PCV-oil consumption issue as they oil both ways to the rockers and that is a lot of oil in VC area splashing around.

of course this is all just my opinion from what I have found working on them.

Mopar did a great job designing the magnum's exhaust port then did a piss poor job on the intake ports. You can grind the intakes some to get that pinch cut down. I ground an intake port on a 5302 magnum head and intensionally cut into the pushrod area to see how far is safe (see pics). I cut .129 (5/32") deep before I went through. So it looks like you can take 3/32" (.093) off the restriction and be safe.

I grind it out then patch with braze. Then find 8 bent pushrods (gets away from the port) works like a charm.

Haven't done the intakes yet on this head.
Just got back from "vacation" and will get back on them soon.