596 casting or 308 casting for mild 360 4bbl

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popinsmoke

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Gentlemen,

I am building a mild 360 4bbl in my 78 Magnum, The short block is the stock low compression 360 2bbl that Ma Mopar made millions of.

Now I am in the process of installing a Comp Cams XE268H complete kit as well as an airgap intake and street demon 625 4bbl carb.

The lean burn system has been ditched in favor of the MP electronic conversion with the orange box.

Plans are at this time to run the big outlet dakota exhaust manifolds in to a 2.5 inch true dual with an X pipe.

So my question is the car has 596 casting heads currently sitting in boxes that came off the car and 103k miles, I have access to a pair of 308 castings at the local bone yard as not allot of Mopar guys frequent my yard.

Everything that I have read says that the 596 castings are the best of the smogger heads but the 308's are the best pre magnum head, my question is how much better?

If I am having 2.02 valves and bowl work performed anyway is there that much of an advantage to the 308 "swirl port" design $ for $?

Also looking for the MP head porting templates anyone know a good source to find them?

Thank you in advance for any advice.
 
308s are the way to go, should give you better low-end torque and response (better low-lift flow). Might want to check them for cracks though.
 
I seem to be doing well with 596 heads but what are your ultimate intentions street street/strip strip?
 
How's the block under the 308s? Both are open chamber heads, 308s are stronger on the exhaust and I think the 596s have better intake flow by a touch- very little difference between them. If you're talking about 302s- forget them completely, 318 trash heads. The bigger perk with 308s is that they're already in proper order for running a roller cam on a roller block, that's worth far more than the slight gains on the exhaust side. So if that's not a concern/consideration- I'd forget them.
 
I did the same thing in my '79 Magnum. IMO, you will be hard pressed to see and feel the difference between heads.
Ether head will do very well. Putting a 2.02 in the head is good. Open up the bowl under the valve. (I'd call it a waste of time and money if you didn't.)
 
Thank you, gentlemen, for your thoughts. I am thinking I will use the 596 heads as I already have them versus pulling the 308's out of the yard and having them checked.

At that point might as well swipe a set of magnum heads (any thoughts)?

My intended use for a daily driver with good useable power under the curve I am not going to to be racing it (I have my coronet for that) but I want a nice classy driver with all the creature comforts for those rare days I don't feel like being on 2 wheels.

This Magnum fits the bill except in the stock 360 2bbl form she is a slug, next improvement after the engine goes back together is going to be a set of gears that should really help get the big girl moving a little quicker.
 
Swapping to a Magnum head is OK as well. But it does incure a few extra costs that you may not be aware of.
Different intake is a starter and a possible balance issue that is easily solved with a B&M flex plate but it is a cost. The rockers are a 1.6 ratio over the stock 1.5 ratio which is nice but you have to constantly do a little math before you get a cam. And then there is new pushrods which is an added cost.
All of which are not a big deal but there.
Just food for thought.
 
Swapping the heads will not affect balance. Swapping the magnum short block may.

Magnum heads are excellent but need to find a set without cracks. As mentioned before valve train, valve covers, and intakes are differen . Magnum exhaust manifolds flow well though.
 
You do realize that Until the secondaries open, your new top end will not make a hill of beans difference right? So if she can't spin the tires now, both of them,then the new set up won't be but a tad quicker to 30/40 mph, depending on your current rear gears and TC stall.While the duals and freeflow exhaust will help some below 3500rpm(maybe lots depending on how restrictive your current single? pipe is; the secondaries may not open until 3000plus rpm.With 2.76s, that would be about 35mph.See what I'm getting at?
-If you put a bigger cam in it, all other things remaining, it may actually be slower to 35mph.This is because without a compression increase to keep the Dcr up, a bigger cam invariably trades away low rpm torque for high rpm power.
If you really need some giddy-up, the biggest bang for the buck will be a slightly higher stall TC. Then gears if you can afford to give up some hiway comfort; and you can never lose with a free-flowing exhaust.
-Since you already said gears, then that is the very first thing to do;before you spend a bunch of money on the engine. By itself a 20% increase in gearage will be dynomite, and absolutely none of your planned mods will make it any quicker below 25/30mph or so,than it now is, and it will not be felt until the car is really moving, and then you will be speeding;cuz 5400 with 2.76s in first gear is about 65 mph.
I'm not trying to ruin your day, but gears should be #1 for you;not last.
-Going from 2.73s to 3.55s is a 3.55/2.76 =plus 28.6%. This is huge. Your engine will feel like it grew by that same 28.6% or over 100 cubes. No other mod to a NA streeter will touch this mod for grin-factor.
-BTW, with a stock compression ratio, I would leave the cam swap for dead last. I mean it.It's really hard to beat that stocker for off-the-line giddy-up.And if after the gears are in, and the exhaust is hung, you still feel the need for more, a 4bbl set-up might kick in another 15 hp; but you might not feel it, until she gets wound up. You'll hear it,all right, but it will be awhile before it gets going.Worse if you stick that 268cam in there.
-I suppose I'd be remiss if I didn't take budget into account.If you already have the money earmarked for your plan, there's not much wrong with your plan, just so long as you have money to finish the combo.
-But if the cam is for sure going in, then at least cut the heads to get back some Dcr.
Whatever you decide;All the best to you
 
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Thank you for well thought out replies and the advice,

Ultimately wat I am looking for is power under the curve and a nice fat powerband. Now I learned years ago that horsepower is for race cars torque is what is what rules the street. Horsepower, after all, is just a mathematical derivative of torque.

Now I know that you can either build torque or you can multiply what you already have I.E. deeper gears, I may have misspoken when I said gears are next after the engine I meant that the will gears be upgraded next but after the engine is back together but before the car hits the road again.

My plan for the heads are to concentrate on the bowl area, pockets as the factory back cut is less than ideal, the heads will be milled and a thinner head gasket used to help DCR trying to get to 9 to 1 if I can having the heads milled and running a .028 head gasket.

The ports are not bad as cast just need a little cleaning up.

My main concern would be not trading a few cfm for a loss in velocity as this will kill torque and more the powerband up in rpm's

I want to see most of my improvements in the low to mid lift range I could care less what the heads flow at .500 or what my peak power looks like I am building for a nice fat useable power at rpm's that are reasonable for a daily driver.

My original question was between the 596 heads and the 308's what is a better starting point?

My conclusion thus far is that the 308's offer a slight advantage on the exhaust side but this is countered by the fact that I already have the 596's and the 308's in the local yard are in unknown condition.

Thanks for again one and for the advice and let me know if you have any thoughts on my plane listed above.
 
That 78 Magnum is a pig. Ditch the 360 and blueprint you up a nice stone stock 375 HP 440. No more needed.
 
Here are some DIY porting results on a set of 596 castings. This was about a 3rd set of heads I ported, pleased with the results. Your are probably not going to go that extreme in terns of the port work though.

LIFT I E

0.100 67 57
0.150 99 79
0.200 130 104
0.250 162 125
0.300 189 140
0.350 215 152
0.400 235 160
0.450 253 167
0.500 262 172
0.550 261 175
0.600 248 177

The finished chambers/ports looked as follows:

head_port2.jpg


I would assess the situation from the perspective of how much $$$ are you going to sink into either stock casting to make it perform? These days, that type of money will buy you a decent aftermarket iron head.

At the very least, consider optimizing your static CR to work with the heads and camshaft in particular. That will be the key to making good torque.
 
Nice job M body. Doing that yourself is a home run. Now, for the folks that can't, won't or do not want to be bothered in doing it themselves, a W2 head flows in this area more or less. There are some OOTB flow tests around the web. It's a lot of work to learn and port your own iron heads but only costs as much as the tool and bits to do the job. (More or less) and a new set of heads cost money! It's allways a catch 22.

I hear and read experianced head porters spend 40 (plus) hours porting a set of iron heads. And YOU, will take a bit longer due to learning and finding your way around the head in terms of what works and doesn't. (Purchasing a second set of heads could be a result!) Now comes the second catch 22. Port your iron heads or purchase new heads? The cost is close. And money is the easy part. Just the hardest to part with.
 
popinsmoke said:
Gentlemen,

I am building a mild 360 4bbl in my 78 Magnum, The short block is the stock low compression 360 2bbl that Ma Mopar made millions of.

Now I am in the process of installing a Comp Cams XE268H complete kit as well as an airgap intake and street demon 625 4bbl carb.

The lean burn system has been ditched in favor of the MP electronic conversion with the orange box.

Plans are at this time to run the big outlet dakota exhaust manifolds in to a 2.5 inch true dual with an X pipe.

So my question is the car has 596 casting heads currently sitting in boxes that came off the car and 103k miles, I have access to a pair of 308 castings at the local bone yard as not allot of Mopar guys frequent my yard.

Everything that I have read says that the 596 castings are the best of the smogger heads but the 308's are the best pre magnum head, my question is how much better?

If I am having 2.02 valves and bowl work performed anyway is there that much of an advantage to the 308 "swirl port" design $ for $?

Also looking for the MP head porting templates anyone know a good source to find them?

Thank you in advance for any advice.
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The swirl port design is junk. Again, it is JUNK. It takes a massive amount of work just to correct the chamber. This has been published in the latest Chrysler small block manual that I know of.

Do not get caught up in crap that was designed for CAFE standards and missions bullshit. It does NOT translate into HORSEPOWER.
I will give you one example. In the 1980's you couldn't pick up any tech article and not have it be full of crap about swirl and tumble and how to get it so you can raise your compression to the moon and still run pump gas. How you could improve fuel economy with tumble and save your money back in just a year. It was total BULLSHIT. I do anything I can within reason to kill swirl, because I want the incoming charge to have every single bit of its potential to fill the cylinder, not waste energy trying to force the charge to swirl or tumble.

That is one quick, nontechnical fact about not getting sucked into using emissions crap to make horsepower.
 
For a Lo-Po motor like this, it is not even worth the worry. I read his intentions as cam it, 4bbl. intake and carb it, drive it. (Headers or no.) Give it a little head work and call it a day. It is just the most basic upgrade to do.

Poppinsmoke, to split the advantages and disadvantages while comparing the 2 heads is fine and great for a bench race session like this, you will never know the difference between the 2 heads. Stock, large valves or not and/or ported. If there both done the same way and I installed, then swapped them out on a blind drive by you, you'llnever ever know. It is truly splitting hairs.

I like your build though I would use headers.
 
rumblefish360 said:
Nice job M body. Doing that yourself is a home run...I hear and read experianced head porters spend 40 (plus) hours porting a set of iron heads...
Click to expand...

Thanks rumblefish360...yeah, I found porting heads to be one of the more rewarding undertakings...but you are certainly right on the money with the time estimate...it probably took me a good 60 hrs/head and this is already having some experience with using various bits, shaping ports, etc, etc....it really is some serious "elbow grease"...and as someone told me before: "...once you try the serious style porting on your own you will understand why the pro head-porting effort costs the money it does...", no argument there!!!
 
RustyRatRod said:
That 78 Magnum is a pig. Ditch the 360 and blueprint you up a nice stone stock 375 HP 440. No more needed.
Click to expand...
All that weight though? Also don't forget if he goes BB to let him know about the host of other cost that will go along with it.
 
j par said:
All that weight though? Also don't forget if he goes BB to let him know about the host of other cost that will go along with it.
Click to expand...

All of what weight? There's a 150 pound difference in the two engines. I can throw that across the yard.
 
j par said:
Where did you get that #? And all of the other cost?
Click to expand...

I got that number cause that's what the difference is. What about the cost? In for a penny in for a pound. If not you may as well get out of it.
 
RustyRatRod said:
I got that number cause that's what the difference is. What about the cost? In for a penny in for a pound. If not you may as well get out of it.
Click to expand...
The difference in the empty block? Translation - if I'm going to cyber spend a dime it might as well be a dollar?
 
j par said:
The difference in the empty block? Translation - if I'm going to cyber spend a dime it might as well be a dollar?
Click to expand...

The difference between the whole assembled engines.
 
RustyRatRod said:
That 78 Magnum is a pig. Ditch the 360 and blueprint you up a nice stone stock 375 HP 440. No more needed.
Click to expand...
For a driver I'd be motor shopping at the u-pull it before building a 440. A 44re behind a 5.2 or a 5.9 would be worlds ahead of a 440 if it's gonna be driven day in/out and the driving part is primary to power and other concerns.

popinsmoke said:
Ultimately wat I am looking for is power under the curve and a nice fat powerband. Now I learned years ago that horsepower is for race cars torque is what is what rules the street. Horsepower, after all, is just a mathematical derivative of torque.
Click to expand...
And so then you'd know that to increase torque, you will be increasing horsepower. If you are keeping HP static or losing it you will not be increasing torque. This is something people often lose sight of, they want to improve what they have but do not make beneficial changes. Chrysler made 245hp with <8.4:1 compression- why do you need more to achieve it from the same engine? Planning on making over 245hp, why use a cam smaller than Chrysler did to make less?
 
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