318 Magnum

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Bills70dart

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I am building a motor for my 1972 Dart. I am on a budget so take that into consideration. I have a good running 318 la motor. I am looking in to EQ magnum heads with a 340 hp intake becuase i already have it. I am going to port according to the article in the mopar enthusiast magazine. I was looking at either a XE274H or a xe268h I am also using 1970 340 Hp exhuast manifolds becuase I like the stock look and I have them. The car is a 4 speed with 4.11 gears what do you guys think?
 
Is this a stock LA bottom end? Stock pistons and all that?

If so, I'd definitely recommend a thin head gasket to try and get the compression up. Mr Gasket makes one that has a compressed thickness of .28 (I don't know how well it seals). You might try having a small amount milled off the heads as well.

I'd also probably try the heads without porting to start with.

If you're not going to run headers or buy a big converter, this cam might be a better choice.

http://www.voodoocams.com/Product.aspx?id=1544&gid=287

You'd want to check to be sure the lift wouldnt cause problems with the Magnum heads though, as on the exhaust you'd be at .526 with a 1.6 rocker.

Steve
 
I agree with LX. And to elaborate the LA 318 have the pistons way down in the hole that's why he said to mill the heads to get the compression up. A cam as big as your looking at will work fine with 4:10 gears and a 4spd but not with a 8 to 1 compression engine and stock exh. manifolds. That's where the problem lies. That's why you need a smaller cam. Otherwise you'll just give up 40-50 lbs of torque to gain 10 hp. (est.) That's not a good trade off. Those heads flow real good in stock form and porting usually looses some velocity so with the smaller cam and only 318 cubic inches stock would probably be better. JMHO The absolute biggest cam I'd consider is the 268. If you gain much from porting it won't be allot. The Lunati cams also have a bigger split between the intake and exhaust so with stock exhaust manifolds I believe they'll make more power than their Comp Cams counterparts. Again JMHO.
 
I am not sure about the pistons in the 318 as i have not pulled the stock heads off I am not running stock exhuast manifolds I am going to run 340hp manifolds.
 
What the pistons are will give you a much better idea of what cam you can run. If they've been replaced and are anywhere close to zero deck the 274 cam would be fine.

340hp manifolds are stock manifolds. They perform slightly better than low perf manifolds but according to a dyno test I saw it wasn't much difference. That was performed on a 300 hp crate engine. If they are put on a 400 hp engine it'll be even worse cause it needs to breath better.
 
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