318 Head Opinions

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ValiantMike

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I'd like to get some opinions on some different heads for my 318. Its a late 70s, early 80s block thats in good shape currently with stock heads, Edelbrock Performer, 750 Holley, headers, 4spd, 8 3/4 391s, in a 1964 Valiant. I want to keep it as a rarely driven street car with an occasional 1/4 mile run. I've got a line on a pair of 302 heads and a pair of mid-90s 318 Magnum heads, both sets are done up to stock specs. What I want to know is, which ones would you go for? I really don't want to change pistons at this time, but cam, intake, carb, etc., is all to be changed with head change. So what do you think would be a good combo for me. I want it to sound good, and go as good as I can within limits listed above. Give me some ideas. Mike
 
I would say magnums. do you have all the necessary parts to do the swap? You will also need to redrill the heads to accept a LA intake manifold. just imo
 
Mike, I don't mind buying what I need to do this. I'll probably get another intake too. What do think for a cam?
 
ValiantMike said:
I'd like to get some opinions on some different heads for my 318. Its a late 70s, early 80s block thats in good shape currently with stock heads, Edelbrock Performer, 750 Holley, headers, 4spd, 8 3/4 391s, in a 1964 Valiant. I want to keep it as a rarely driven street car with an occasional 1/4 mile run. I've got a line on a pair of 302 heads and a pair of mid-90s 318 Magnum heads, both sets are done up to stock specs. What I want to know is, which ones would you go for? I really don't want to change pistons at this time, but cam, intake, carb, etc., is all to be changed with head change. So what do you think would be a good combo for me. I want it to sound good, and go as good as I can within limits listed above. Give me some ideas. Mike
Click to expand...


The Magnums have 59cc chambers & 1.92"/1.65" valves. They are also better flowing.

More compression, bigger valves &better flow, what's not to like.

Only drawback is the intake manifold selection, but some say the LA manifolds can be adapted. The Magnum heads seem to be prone to cracking, but if you found a good set & ran a cooler TSTAT, I'll bet that problem would disappear.

Hey, I'm learning.

There's some good poop on the Magnum heads here. http://www.moparmusclemagazine.com/techarticles/mopp_0409_318_engine_build/
 
PlumCrazyDuster, thats what those 302 heads are and they have 56-62cc chambers already and are a bolt on. People are telling me that I'll get better flow with the Magnums though. The only thing with the Magnums, aside from changing lifters, pushrods, etc., is that they will have to be milled on both sides to get compression up to mid 9s, plus intake will have to be replaced or Performer will have to be drilled to fit. I wish I knew how much better over the 302s that the Magnums would be.
 
Some people have said the swirl port heads flow as well, and with light porting can exceed them (the magnums, that is). I am looking for some 308's, myself. There are also issues with the rocker geometry, magnum's have 1.6:1 ratio, which translates to faster, higher lift. On an la block with a high lift cam I have read on the hughes engines website that the holes for the pushrods may have to be milled out in some cases. If you have access to magnum heads, they are newer, more efficient technology, quench style, heart shaped chambers and etc., right? and bigger valves, too, I'd run 'em if I had'em. Why not? Milling the heads requires custom pushrods, too. But if you don't mind spending money to do it nice, There is an air gap manifold for magnums, now, too. But you'd have to mill that, too. A change of piston would solve the chamber issue, but which is a better track, to change pistons, or mill heads, intake, and custom pushrods, or port other heads to flow like you want? What a mess, I haven't helped at all, have I? LOL
 
You said this would be a rarely driven street car and once in a while 1/4 mile car. I think the choice is dependant on how serious you want to get. I think that both heads would have great street manners. From previous posts with BJR and several others I tend to lean towards the magnum heads for performance. The 302 casting has just as much potential but, probably would take alot more machining than the magnums just to get to the bolt on performance of the magnums. If initial cost is not an issue I would go with the magnums. You can find magnum valve train parts at most salvage yards too. Of course matching your components is just as important.

Also, If your going this far you should really think hard about going the extra step and swapping to some higher compression pistons. The 318 stock pistons sit way...... down in the hole.
 
Strokermike,63 Dartman, now you know where I'm at with this. Since squeezing every last hp out of motor is not main issue I'm guessing that the 302 heads would be the easiest, less expensive route. But then again, if I'm going to do this, why not squeeze every hp out of my work and money, and with a little more work and money the Magnums would be a better choice, but if Magnums are used then pistons should be changed to maximize Magnum heads. So now, if I'm going to do all of this, why not just get a 360 block and start with it. Oh where does it end? One thing is for sure, I'm going to do something in the next few weeks, so opinions are appreciated. Mike
 
63dartman,Valiantmike,
Are you sure I ment magnums? I really prefer the 302's, they have a better chamber design (fast burn- heart shape) than the typical wedge style of the magnum. Also port velocity should come into play along with port volume.
We all know that the 318 magnums are the same casting as the 360. So the problem comes in that this is mainly a street car and occasional trip to the track. With the larger ports the engine will be some what of a dog on the bottom as with the smaller ports it will pick this up greatly. Larger ports need a looser converter to make them work and the larger the port the looser the converter needs to be, also over camming is a another issue that comes into play here. You only have 318 CI so this is easily done, then you'll have the issue with valve shrouding in the cylinders as with the 302 you don't have this, as the valves are smaller. The best part is no extra machining and you already have the parts. A simple cleaning of the bowl's and a gasket match to fit the intake and you'll have 350 hp on tap. I know as I'm makeing just under 400 HP with 87 octane and 302 heads, and a stock short block and a 280H cam.
 
BJR, you've answered my question. I'm going to get the 302s and go with them. Now before I lose you, can you give me any ideas on a good cam for my application? The car is 1964 Valiant, 4spd, 8 3/4 with 391s and it has fenderwell headers now but I just bought Spitfires that will go on after heads, etc.. I know the fenderwells will flow better than Spitfires, but they are in bad shape and I don't have money right now for TTIs. Thanks Mike
 
No BJR, I meant that is what I prefer.....I don't want to get caught writing anything that would mislead people about you.

Guys, I have talked to BJR on the phone several times and He really knows What he's talking about. I have alot of respect for BJR and his knowledge of mopar heads.....for that matter Any heads!!! BJR Has been doing this for a long time. Also he is a great person too.
 
Valiantmike,
I would suggest a XE284 with the 4 spd. or the XE284HL both will work great and get you some lope. But you'll have to check the piston to valve and the retainer to guide clearences as the guides will have to be machined. If this is too much for you then go down to something in the 268 range. But you'll still have to check the afore mentioned things.
 
ValiantMike said:
I want to keep it as a rarely driven street car with an occasional 1/4 mile run.
Click to expand...


That's the important line. I wouldnt go Magnums there either, just as BJR said. I would not, however, use a cam the size of the XE284 or the XE285HL. Way too much cam even for a stick car with low compression. I ran a 318 for a while with the oldschool High Energy 268H, that had a noticable idle, and really strong low and mid range, and pulled to 6800. That was with X heads, but in any case...A modern equivelent would be the XE268. I dont think any of the HL series is in the range you should be looking at. Keep it in the [email protected] range, with more on the exh side, and you wont be disappointed.
 
The thing that we have found is that when you have a large port head, such as the X or J heads or any 340/360. That the 318 just can't utilize the port to it's advantage as go's for the valve size. I know I'm going to catch some slack on this but, we did this years ago, also as this was the ticket and none of us were the wiser. But about 10 years ago we tried a set of 302's and we also used the 1.88 valves, and thought that bigger was better with the small chamber head, but boy did we get a rude awakeing. The heads actually ran a bit slower and the bottom end (starting line) was where we did the suffering at. It was due to the loss of low end torque and later found out that the valve size was too large and slowed the velocity down in the port. So about 4 years ago we went back to the drawing board and used the same casting heads so not to have to repair the ones that were on the engine and to give a good comparision, and utilized a stock sized valve on the intake side with the same modifications done as the 1.88 valved heads had. The torque and performance was marginally different to the tune of 30 ft.lbs. and 40 more HP, and this was useing a .480 280 comp cams grind which is very close to what moper has stated(228 @ .050). But because the fact that the heads have more velocity in them and are more efficent for the 318 bore they work better on the engine. Thus allowing you to get away with more cam as the 228 @ .050/280 cam sounds fairly stock. We just finished a 318 engine and ran a .501/292 comp cam in it as we already had the cam and we knew that the other cam didn't have much sound and wanted more. The engine is a bone stock rebuild in the short block with a mildly ported set of heads (318's) with stock valve sizes, the engine idles at 800-1,000 rpm's. Yes we have a stall converter in the car but he (Valiantmike) has a 4 spd. and this cam is 244 @ .050 and is a straight pattern cam. This is why I like the XE284 as it has a 106/114 centerlines and helps to build cylinder pressure by keeping the overlap lower. We are useing this cam in a lower compression 360 engine, I know it has more stroke but this cam sounds very tame much like the 228 @ .050 cam in the 318. Being that it was so tame in the larger engine with larger heads we figured that the smaller heads would tame it even more, which it did when installed in the 318 with smaller port 302 heads. This is partially why the engine idles at 800-1,000 rpm's with the old style 292 cam which is 244 @ .050. Port size and velocity has alot to do with what cam is used in a engine more so than airflow and valve size. Obviously if we had the 340/360 heads on the engine the engine would be a dog in the low end as torque and hp would be down, and the need for low gears and a higher stall converter would be needed with the same cam. Also smaller ports that have higher velocity will use less fuel and be more efficent and make more power. With the 340/360 heads I was buring about 1/2 gal. per run and now with the 318 heads I might be burning a Qt. 9 runs was just under 4 gals. of fuel in the 1/8 mile.
Sorry for being so winded but I wanted to give a real world account of what small changes will do and the reasoning behind it and the change it made in performance. I hope this helps everyone to have a better understanding that bigger isn't always better in the case of the 318's, but the right parts in the right places will make bigger gains with less $$$$ out of the pocket.
 
Hey BJR and Moper, I hold both of you guys as well as some other FABO members in my highest regards as far as Mopar performance knowledge, and I could read your stuff all day long. Your views and advise are greatly appreciated. And I'm not just blowing smoke either. Mike
 
BJR Racing said:
GEEEEEESSSSSSSSSS,
I wrote a novel! Sorry guy's I didn't think it was that large.
Click to expand...

Nothing wrong with a novel if it contains that much useful information, Bobby. :) To most of us, head technology is akin to black magic, and it's great to have guys like you and several other very well versed people on this board that will share their knowlege with us neotypes. I've been building engines and cars for the past 40 years, and I've learned some do's and don't from first hand (read: Expensive) experience. I probably couldn't give another person a difinitive scientific type answer to certain questions, especially relating to head technology, but I know what works and what doesn't for my machines. Guys like you and Scott, Moper, Rumble, Headsbikesmopars, etc., have imparted a LOT of real world experience and a wealth of knowledge here on this board, and I, for one, really appreciate your patience and willingness to share. Thanks to all of you.
Oh, damn, another novel. :toothy7:
 
Quote: Oh,damn, another novel.

Sid,
You AINT RIGHT! Thats Southern to YA'LL.

Glad that we could be of some help to you.
 
Go for the Magnum heads (FYI, there is no difference between any 318/360 magnum heads, thay are all the same), be especially vigilant for cracks between the intake and exhaust seats. Lightly smooth the exhaust ports with some cartridge rolls, no need to remove much metal. Get an Edelbrock Performer RPM Magnum Intake (or an ebay Crosswinds RPM knock off), stick with the same carb, get an cam that has a max of .520 lift and a duration of about Int 220/ Exh 230 @.050. Get your self a 2500 stall converter and a set of at least 3.55 gears or deeper. I knew a dakota that properly set up for drag racing was doing 13.0's, figure an a-body is about 700lbs lighter, so mid 12's should be possible with the right chassis setup. Add a tickle of juice (125hp), and spray your way into low 12's or high 11's. :thumbup:
 
The problem with the 318/360 magnum heads is the port volume is too large in comparision to the 302's. Also he's running a 4 spd. and 3.91 gears.
The 318 we just finished runs in the upper 11's in a 72 Duster on 93 octane gas and NO nos.
 
Port volumes larger than 140 cc's on a 318 will kill the low end performance. Most 302 heads were in the 118-120 cc range from the factory, and stock 340/360 heads were 150-152 cc's from the factory. Will they work and run, sure, but the performance that may be desired may be tougher to get. Also you better gear and converter the heck out of it, and now it isn't streetable any more, or efficent.
When they put magnums on the 318 they also reduced the camshaft to help create more low end torque this is why most people that have a magnum 318 say that they are a dog and would have rather have had a 360 instead. What the magnum 318 is to the magnum 360 the 3.9 is to the magnum 318.
 
I have actually run my above combo in a Dakota a few years back and I had no complaints about torque or HP, top end was great, but I had FI, 4.11 gears, and a 5 speed. If I was going for Max HP, I would go with the Magnum heads.
 
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