Better heads
BJR were those 318 magnums you referred too as "the biggest dogs you'd ever seen" in stock trucks with original computers, etc? Reason I ask is I had a 93 Dakota I bought new with a 318 mag and when I got it it ran adequate but wasn't all that impressive. I added short tube headers with dual exhaust and a Mopar perf. computer and nothing else. It was like a whole different truck. With a peg leg 3.55 rearend it ran a best of 14.46 @ 96 mph and 14.60 consistently spinning 10-20' out of the gate. I found it was the computer that really made the diff. Apparently they had the timing very conservative from the factory. I have throughout the yrs. known numerous guys with 70's LA 318 Dodge pickups, a few of which I helped tune for best perf. and none of them came anywhere close to the way mine ran. I'm not trying to make it sound like I had some sort of a race truck but rather stating that in comparison my 318 magnum with it's ports that you say are too big for a 318 would run circles around the older ones. I have also driven one other 318 magnum full size Ram (short bed , reg. cab. all stock) and it ran stronger than my Dak did when mine was stock. I know you know more than I do about heads and perf. in general but to say the 318 magnum is the doggiest 318's ever I can't agree with. JMHO
Yes that what I was referring to, in the stock form. But then with what you added to yours it should have picked up something but then so would the earlier version engines with the same amount of mods done to them.
For a comparision to your 318 magnum engine in your truck, we have a old version 318 with a standard bore and a .501 comp cams cam and 3675 set of heads with stock valves and a M-1 intake and a set of hedders on pump gas and the car weighs in at 3330 lbs. and just last week even being out of tune ran 7.89 @ 88 mph in the 1/8 which this puts the old style 318 engine in the low 12's or upper 11's. The heads have a good VJ and a 75* bowl cut only and have been gasket matched on the intake side, the exh. was left untouched other than what the machine cut at the VJ. Were looking for some low 7.70's or upper 7.60's this week, with the carb jetting that we did.
You also have the advantage of being double quenched in the heads and we have a open style chamber, which this is a advantage for you and for comparision sake would be closer to the 302 heads. So yes I in my own opinion I personnally wouldn't ever use a magnum head on a 318 engine. And my reason for this is too much port volume, too big of intake valve, the bowl in the heads are too large for short stroke and small bore engine. This is where the 5.9/360 engine works much better with the magnum heads. Because they have everything that the 5.2/318 engine doesn't in reguards to bore and stroke. My personal opinion is that they tried to pattern the magnum head after the likes of the 440-1 head when they first came out. The bowls were so large that they wouldn't make any power til you turned the crap out of them. They are also in the 160+ cc range from the factory which doesn't bode well for Tq on a NA engine of this size and bore.
The reason that they work better on the 360/5.9 engine is the piston speed is much faster and the larger bowl will work better, something along the lines of a BBC engine. Now this isn't to say that they wouldn't work well on a 349 style engine as the stroke would be much longer and could make better use of the larger port volume, and piston speeds. Once again similar to the BBC.
Also to in your comparision to the older version engines that your friends have is that your also fuel injected which should be a gain on any engine. And you never mentioned weather the older engines had small 4 bbl carb or 2 bbl carb on them. So were not really comparing apples to apples here.
Sorry for being so winded but IMO I won't use the magnum head on any 318 that comes from me. Maybe thats why I'm getting the performance that I do. But this is MPO.