Magnum Heads

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Woody'sScamp

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Hi all,
I'm trying to learn as much as I can and I'm looking at all options for upgrades for my '75 318 smog, (except a $$$ 390 stroker., can't afford.) No racing, just a cruiser with a little more HP. The 302 head is in my head now as I've got is a LD4B, 600 Eddy carb and 340 HP manifolds. I've read a lot of threads and articles about 300 to 400 HP 318's and one had to do with using magnum heads.
1.If I use 360 Magnum Heads on my 318 smog motor will it work with my LD4B manifold?
2. If not, what is the best aftermarket manifold for magnum head?

Thanks
 
you have to use a magnum intake manifold if you use actual magnum heads.
if you use something like the EQ318-B head, then you can use the LA style intake manifold. The Engine Quest heads come in an A and a B head. The B head is a magnum head with LA intake bolt holes in it.
 
Hi all,
I'm trying to learn as much as I can and I'm looking at all options for upgrades for my '75 318 smog, (except a $$$ 390 stroker., can't afford.) No racing, just a cruiser with a little more HP. The 302 head is in my head now as I've got is a LD4B, 600 Eddy carb and 340 HP manifolds. I've read a lot of threads and articles about 300 to 400 HP 318's and one had to do with using magnum heads.
The 318 & 360 Magnum heads are identical.
1.If I use 360 Magnum Heads on my 318 smog motor will it work with my LD4B manifold?
2. If not, what is the best aftermarket manifold for magnum head?

Thanks
Q1. No
Q2. Edelbrock’s Magnum RPM. The cheap chick knock off intakes will work OK as well. But you asked for the best.
“Edelbrock”
 
Hi all,
I'm trying to learn as much as I can and I'm looking at all options for upgrades for my '75 318 smog, (except a $$$ 390 stroker., can't afford.) No racing, just a cruiser with a little more HP. The 302 head is in my head now as I've got is a LD4B, 600 Eddy carb and 340 HP manifolds. I've read a lot of threads and articles about 300 to 400 HP 318's and one had to do with using magnum heads.
1.If I use 360 Magnum Heads on my 318 smog motor will it work with my LD4B manifold?
2. If not, what is the best aftermarket manifold for magnum head?

Thanks
Well, for "just a cruiser with a little more", You're shootin' a bit high in the 300-400 hp range!....lol. First a decent cam is up, and the final squeeze & fast burn the 302's provide combined with that intake will be more than a little more, plenty for fun & cruising. Mags mean $$$, pushrods AMC lifters, new intake etc. You have enough to burn tire & have fun even w/o changing heads, good cam & carb with that intake & go...
 
Use a magnum head and buy a magnum intake manifold from edelbrock or SM or somewhere...and all the rockers, push rods and the rest to make them work.
302 heads?? only if you put a lot of work into them.
They flow less then other 318 heads...they are the #516 of 318 heads. Period.

Screenshot_20210916-075454_Video Player.jpg
 
What about re-drilling the Magnum heads?

Not a "right now" solution since the first jig got lost (as I recall) and the one floating around now has a couple of people in line currently. But it would mean he could use the LD4B intake even though the ports would be small.
 
... 340 HP manifolds...

I am running those same manifolds on my MP R/T heads and I had to get some plates cut to run them. The material around the port on the head was too small to seal the port in the manifold. I've seen OEM Magnum heads where there wouldn't be an issue, but I've also seen one's with the same configuration as my aftermarket ones that would be an issue. Just an FYI and warning.
 
I am running those same manifolds on my MP R/T heads and I had to get some plates cut to run them. The material around the port on the head was too small to seal the port in the manifold. I've seen OEM Magnum heads where there wouldn't be an issue, but I've also seen one's with the same configuration as my aftermarket ones that would be an issue. Just an FYI and warning.
Glad you caught that.
Agree 100%!
I know some aftermarket along with the r/t do have less flange around the end ports.
I had bought some Summit shorty headers for my truck that I just put some aftermarket Magnums on 'not even gasket matched on the exh side'.. to find that there was only about .030 width of sealing surface at the lower corners. In fact...I had to weld up the bottoms of all header ports and the lower corners and file flat to make them seal up... I also die ground out all the welding that protruded into the port window they were .150 too small all around!!! ..and when I got done...it finally felt like I put headers on. Avoid summit headers. They are total ****. Just look them over with a mic and good header gaskets...they are garbage.
What a pain in the *** it was to fix them. I would have returned them if I hadn't already modified my down pipes to fit!

Bringing it back...
..So be careful which exh manifolds you use and with what casting heads.
 
Glad you caught that.
Agree 100%!
I know some aftermarket along with the r/t do have less flange around the end ports.
I had bought some Summit shorty headers for my truck that I just put some aftermarket Magnums on 'not even gasket matched on the exh side'.. to find that there was only about .030 width of sealing surface at the lower corners. In fact...I had to weld up the bottoms of all header ports and the lower corners and file flat to make them seal up... I also die ground out all the welding that protruded into the port window they were .150 too small all around!!! ..and when I got done...it finally felt like I put headers on. Avoid summit headers. They are total ****. Just look them over with a mic and good header gaskets...they are garbage.
What a pain in the *** it was to fix them. I would have returned them if I hadn't already modified my down pipes to fit!

Bringing it back...
..So be careful which exh manifolds you use and with what casting heads.

My final solution will be the Doug's D453 headers at some point. Pictures I have seen make it look like they match up well.

I have thought about a Jeep Magnum manifold on the right side and filling the bottom of the port on left side free flow, but no idea what you could fill cast iron with that would stick and stay at those temps.
 
My final solution will be the Doug's D453 headers at some point. Pictures I have seen make it look like they match up well.

I have thought about a Jeep Magnum manifold on the right side and filling the bottom of the port on left side free flow, but no idea what you could fill cast iron with that would stick and stay at those temps.
Brass, or iron.
Maybe lightly slotting the holes on the manifold down .060 so that you could raise it up more or some.
 
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