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Magnum Heads
Hey all. You might remember my thread earlier about pepping up my LA318. So far I've done a mild cam, 360 4-barrel cast intake, Rochestor Quadrajet, double roller timing chain, and a set of Flowtech headers. Now I was wondering about putting a set of magnum heads on, replacing the stock 318 heads. I found a set at a local scrap yard, still on a magnum motor, for only $30. Now the only problem I am having, is that I don't know exactly what I will have to do, or buy to make these heads work on my 318. So can anyone and everyone help me out with this, and let me know if this will help my power, or hurt it. Thanks.
Eric |
#2
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I think it'll help, even if you don't port or mill the heads. The valves are bigger than the 318, but still small enough to keep the port velocity fairly high to help streetability.
You'll have to either redrill the heads or the intake manifold to accomodate the different intake-to-head bolt angle. You'll need different pushrods, and make sure you keep the valve covers from the Magnum heads because they're different from the LA units, too. Not sure about accessory mount bosses. I'm sure I've missed something, and others will chime in. |
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...and amc lifters that "oil through" those magnum rockers dont' oil through the shaft like your 'teen's.
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Im guessing you don't have a roller cam 318, so you need to get the heads, rockers, (you don't need the valve covers la's will work fine) i would go with a cross wind intake (has bosses for magnum engine $130 on ebay) its a edel airgap intake. You need lifters that allow pushrod oiling, pushrods and headbolts, Mopar sells all of this. most aftermarket lifters already allow this. Your compression will gain alittle, better flow and go with the better intake and you have a very very stout engine that is way more efficient.
Steve |
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I have never seen a performance test of a cross wind intake. I have no major problem with made in china unless the design is stolen. is it that close? |
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OK I Looked at this and it will not fit later 318 that need to have water neck moved to clear AC |
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How about we stick to the MAGNUM HEADS part of this thread, since that is what it's about. I know I will have to do something about the intake, but please don't hijack my thread.
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#9
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Go for it, I put a set on my 273, and my 95 ram has em, factory of course, and they have given me 180 some thousand miles of trouble free service.
I have the crosswind, and it really doesnt look like an ed air gap, it just has an air gap, thats it. |
#10
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Cageman,
What all do I need to make the magnum heads work on my 318? They are complete heads, with valves, springs, rocker arms, valve covers. I heard something about using AMC lifters, and oil thru pushrods, but is this all that I will need, and do you have part numbers that you used? Also, could I just use the lifters and pushrods out of the magnum motor, or would I have to swap cams, and is that even possible? Thanks. Eric |
#11
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Do you have a roller lifter cam already? If you do you can use everything off of the magnum if you do, if you don't you need to get new lifters and pusrods. I have a roller cam so im using the stock pushrods for now.
Steve |
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It's an Erson flat tappet cam, and I do have the correct Comp Lifter already, #822-16. So I all need to get is pushrods. The 400 horse 318 build in CarCraft uses these same lifters and the Comp pushrods #7960-16. I looked the part up at summitracing.com and they also list a substitute part TFS-21407650, which is a Trick Flow pushrod for about $60 cheaper. I am thinking of going with with the Trick Flow rods, to save some money. Now comes the part of the intake. I currently have a cast 4-barrel intake off a 360, and I need to know what I need to do to this intake, or what aftermarket intake to buy instead. I am going to be using a Quadrajet for a carb, so I just need an intake. Thanks again for the help.
Eric |
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id go with the trick flows also.
For an intake i would go with this for saving money http://cgi.ebay.com/ebaymotors/Mopar...spagenameZWDVW if not a M1 or Edel airgap. Remember head studs or bolts, they are differnt length than the la's. do you have a 1/4 pass with this engine? can you get one then run the magnums to show how big of a gain there is? Thanks Steve |
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This is a pulling truck, as in sled pulling, so I don't make any 1/4 mile passes. It didn't run too bad with the stock heads on it, but I've read quite a bit about the Magnum heads on a LA, so I want to give it a try. I think I will probably go with that crosswind with the Quadrajet. What does everyone think of this? Thanks.
Eric |
#15
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ewatts, I think the stock manifold needs re-drilling to match the different bolt-to head angle of the magnum. Does the crosswind have a spreadbore pattern? If not- it might be a toss-up dollar-wise between re-drilling the stock manifold or adapting a spreadbore. Plus linkage changes, choke set-up (maybe not a prob. for you) etc. I have also read that the stock iron manifold is pretty efficient, and I'm guessing weight isn't an issue for your intended use.
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#16
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You would have to redrill the heads, which is not an easy task.
Steve |
#17
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There is a guy over at moparts who made a jig to redrill the magnum heads so that they accept magnum intakes and LA intakes He will send it to you for a small fee.
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#18
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Quote:
On the Moparts website you need to ask about this jig as I don't remember the user name that has it. By the way, the Magnum heads are perfect for a 318. Just make sure they are not cracked as this is very common with these heads. Depending on your cam you will probably also want to change from the stock valve springs. |
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No weight is definately not a problem for me. I pull in the 5500 Stock Class, and my truck with me in it currently weighs just over 5000. So I can use all the weight I can get up front.
Here is what I am pretty sure I am going to do, just need some opinions on what everyone thinks and if anyone has different suggestions. I am going to keep the bottom end stock for now, with my 292 214 449 cam, with Comp 822-16 lifters, Trick Flow TFS-21407650 pushrods, stock Magnum heads, stock 360 cast intake with a Quadrajet for now. Also I will be getting a set of cheap headers, probably Flowtech, and that will pretty much do it. The only two things I am not really for sure about is the intake choice, and also the carb choice. One of my friends has a Predator carb that he bought for his race car, and when I figure out what intake I am actually going to put on I think we might throw the Predator on there just to see how it does. So please help me with my intake choice. Thanks. Eric |
#20
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You will need new valve springs. Your lift with stock 1.6 ratio Magnum rockers will be .479, which is too much for the wimpy stock Magnum springs.
Assuming you want power in the lower RPM ranges I would use a dual plane intake. Performer, Stealth, Performer RPM or Air Gap should work fine. The Crosswind (which appears to be a Chinese copy of the Air Gap, some say there are quality control issues but I am not sure) and Magnum Air Gap will bolt directly to the Magnum heads. You might want to use a stock redrilled iron intake for the weight. |
#21
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I'm also thinking of putting magnum heads on my 318LA, and was thinking I would need a magnum head gasket... is that correct?
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#22
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Can anyone post the email for the guy who has the jig to drill magnum heads? I don't have a moparts username, and I don't really feel like signing up for another website. Thanks.
Eric |
#23
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I built a 360 this past summer with magnum heads. Here is some things to consider.
1. magnum valve springs are smaller in OD and are beehive shaped. LA springs wont' fit unless you machine the springs seats on the heads and you will need custom retainers (LA retainers are designed for 3/8" stems magnum valve stems are 8mm). The only other springs availble that are the proper height are from MP. I used the "R/T" spring which is good for .525 lift. Also any more than .525 lift requires the guides to be cut so the seals sit lower. When you change springs you need new retainers becaue these springs are strainght. MP has a retainer (no one else does at this time because of the 8mm valve stem) or do as I did and make a junk yard run and get them from a 2.2/2.5 mopar 4cyl. Remember what ever cam you use the divide the lift by 1.5 then multiple by 1.6 to get the new lift for the 1.6 ratio magnum rocker. 2. MP sells push rods for this swap, $39 for the set from Mancini. 3. As other stated aftermarket or AMC style lifters that oil through the push rod. 4. You will need magnum specific head bolts. The inner bolts are all the same lenght and the outers are longer than LA bolts. 5. LA head gasket is fine but you need a magnum specific intake gasket if you go with a magnum style intake. 6. No problem with accessories, all the holes on the end of the heads are in the same places. 6. Mangum valve covers use 10 fasteners but 5 are in the same place as the LA. I have no leak problems with LA valve covers. 7. The heads I have are 64cc's so take that into consideration for compresion calculations. 8. I am using the CrossWind manifold. Engine runs great in the 1500 to 6000 rpm range. |
#24
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But, I would not want you straining yourself www.bigblockranger.com click the upper right "the jig" |
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