which heads to use

[duster360]

i recently picked up a 340 with a pair of x heads on it if i decide to build it which heads would be better x or magnums? before all of you start on the edelbrock kick, i already have the x and magnum heads, i already know what it takes to convert to the magnum heads, just curious how many of you have done this and what gains there might be from the mag heads

[Crank]

what are you going to use the 340 for? if its a race car and you need the rpm's up high and spin it at 6500 plus the x heads .if its a street strip car magnums all the way or neer stock magnums . the magnums are great at lower lifts to get you out the hole and you can get away with a little more compresion with the chamber desighn. the swirl ports fill the cylinders much faster in the ,3-.400 lift range than any other iron head i have seen exept the r/t head .thats why they use a 1.6 rocker because the cylinders fill at a much faster rate then the older style heads between 0-.500 lift you can run less gear and stall with magnums ,the x head likes between .450-600 lift range thats wear thay shine the best if thats what you are looking for it may be the way to go .

[dwc43]

Originally Posted by duster360

i recently picked up a 340 with a pair of x heads on it if i decide to build it which heads would be better x or magnums? before all of you start on the edelbrock kick, i already have the x and magnum heads, i already know what it takes to convert to the magnum heads, just curious how many of you have done this and what gains there might be from the mag heads

X heads are the best ones to use out of hte two you have. Besides, depending on which year 340 you have they wont fit anyways cause of the piston clearance.

[DartGT66]

Magnum heads all the way, the X-heads are of no comparation.

[72Challenger]

Crank's answer is the right one. Which head is "better" depends on how you're going to drive it. DW does bring up a point to consider however. If your pistons have a positive deck height, you're going to have to deal with it to use the Magnum heads. The easiest way would be to just use a .060 thick head gasket. That would give you the right amount of quench to take full advantage of the benefits. But measure first to be sure. Of course if you're mostly racing, keep the X heads.

To answer your question specifically, what you gain from the Magnum heads is higher compression and a better burn from the quench design, a better flowing exhaust, and better flow at low and mid lifts. What you lose is ultimate high RPM horsepower and valvetrain stability at high RPM or with high lift cams and the high pressure springs they require.

[BJSracing]

Yeah, well with the mags. you "or at least I" should always be worried about cracked heads. I have already had to replace a set on my 97 p/u. From most every thing I have heard that is a big problem with those heads. And being that this was my first and so far only encounter with the heads I am not that impressed with them. I have used X heads in many different configurations with out failure or problem. Just my insight.

[LA360Dart]

In a word Magnum over the "X" head unless your super stock racing and Magnum head is illegal. I own a 73 Dart Sport, car run 12.80's idles at 850 rpm. I get a lot of compliments on how well the car runs vs how it sounds. The heads are mildy ported bowl work and such. I would never use LA castings again.

Denny

[rumblefish360]

I'll base a decideing vote on the cam being used.
The magnum will out flow (More cfm) and have better velocity and better balance between the int and exh. valves.

[73scamp318]

Originally Posted by dwc43

X heads are the best ones to use out of hte two you have. Besides, depending on which year 340 you have they wont fit anyways cause of the piston clearance.

All lies here..magnums are the better head all the way around..just look at them and you will know. Listen to a pro..like ryan at www.shadydellspeedshop.com who only works on small blocks....way better flow, way better quench, way better exhuast % to intake....dcw will say the rockers make a difference, but are you spinning this to 8000rpms? no? then it won't matter.

So 1.92 and 1.60 vavles aren't better than the x heads? o..yeah..and the 1.6 rocker ratio..thats right these heads suck!!! dual quench pad? Man why would chrysler spend money to design a better head when they had 30 year old technology on the x heads? man stupid chrysler..they know nothing.

The w2 head is WWAAAYY better than the w8 w9 heads will ever be..well thats the same thing here.

sell your x heads on ebay..or dcw since he thinks that they are the only head mopar made that was worth its weight in gold.

Steve

[73scamp318]

Originally Posted by 72Challenger

Crank's answer is the right one. Which head is "better" depends on how you're going to drive it. DW does bring up a point to consider however. If your pistons have a positive deck height, you're going to have to deal with it to use the Magnum heads. The easiest way would be to just use a .060 thick head gasket. That would give you the right amount of quench to take full advantage of the benefits. But measure first to be sure. Of course if you're mostly racing, keep the X heads.

To answer your question specifically, what you gain from the Magnum heads is higher compression and a better burn from the quench design, a better flowing exhaust, and better flow at low and mid lifts. What you lose is ultimate high RPM horsepower and valvetrain stability at high RPM or with high lift cams and the high pressure springs they require.

man this is crazy..so the mags are better everywhere some how except upmost rpm hp? who needs that? a 1.8 honda? and better rockers? i forgot there is no harmonics in a single shaft with 8 diff rockers doing something different..thats right the perfect design..or wait..jesel uses individual shafts..but still the x heads are way better than the jesel rockers will every be..

[rumblefish360]

The X head can perform well. It could be better than the Magnum head. It is build dependent. Things like stated before, like positive piston height make a closed chambered head harder to use. Durations of the cam. Since the Magnum flows better and have better balance with better velocity, the need for a split duration cam is less. And when ported well, the split in durations is not really needed if at all.
Based on these 2 factors, the clear choice isn't there IMO.
(By the way Steve, have you been drinking tonight? )

[Crank]

the magnums will rev faster that means peek hp and tork much quicker if you look at the flow numbers it don't take much work to get really high numbers out of them .you can get 500 hp with magnums with vary little head work like stainless valves some bowl work gasket matching and taking the flashing out of the runners but after that you need a R block if you wont more hp.my vote has allway's been for magnums but i didn't wont to open up a can of worms.theirs only a few small block heads i would even put money into and i'm not a big fan of alluminum ,the magnum 's both stock and R/T ,w9,and the INDY small block package . but if i went that direction i would start with a R block ,bottom line the magnums will handle anything you can throw at them.go ahead ask me why thay don't use x=heads on stroker motors ?why don't they use open chamber heads no more like indy .b1, edelbrock,brodex, stage 5.hmmmm in fact the chambers are getting smaller and the runners are getting taller ,guess what that's all about i been studying heads for many years and not just mopar ,allot of people on this board rip on chevy pritty bad but they are well in the game with their heads on being high teck .you just need to now what to look for and how they work then what to do with it once you figure it out.

[rumblefish360]

Yep on that. Recent Vette engines are something/

[Slingshot383]

OK, there's a lot of "what the heads can do", and the "I already have these heads". Now comes the important part, are these heads ready to bolt on, or do they need valve jobs, porting work, new valves, springs locks and retainers? If so, then you would be money ahead selling them and buying either the Edelbrocks, the B1-BS, or the Indy small block heads. Weight is weight, and these heads have the advantage of modern port and chamber technology.

[duster360]

wow some real differences in opinon, specs, 69 340 going to get a hughs cam .500 - .520 lift range, hooker headers, b & m 2500 stall, also plus with the magnums you get hardened seats, motor wont see over 6500, and it might get a little spray, 3.55 gears, would like to make over 450 hp going in a 70 duster

[Slingshot383]

The one other difference is the intake mounting method. Of course you can by a jig to redrill the heads.