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#1
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Can someone summarize the difference between 5.2 and 5.9 magnum heads? Same castings? What are the stock valve sizes for each?
------------------ 1994 Ram 2500 4x4 RC 318, 14" k&n, 3" exhaust, MP PCM, 180 stat NV4500 5spd, 4.56 gears, detroit rear, 255/85/16 MT's |
#2
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The 1995 Ram Field Service Manual - and the "Magnum Engines" book by Larry Shepard - have paragraphs in the engines section that say you can tell 5.2 from 5.9 cylinder heads by a casting marking inside the valve compartment where there is either a 'NH' or a 'CN'.
But - Larry Shepard later wrote in Mopar Performance News magazine that the two Magnum cylinder heads are identical. This was in the article about the new aluminum Magnum heads. I emailed Richard Ehrenberg of Mopar Action magazine once 2 years ago about this same subject, and he said he thought the 5.2/5.9 cyl head was the same too. My best guess is that post 1994 Magnum cylinder heads are the same on 5.2/5.9 V8 engines. I believe the section in the two books listed above are mis-prints that were written in 1993 when the 5.2 Magnum was out and the 5.9V8 was still pre-Magnum design. This writing was not properly revised when the 5.9 became a Magnum style engine too. The Magnum combusiton chamber size is supposed to be 62 cc. Inlet port volume is 170 cc and inlet port length about 5 inches long. The inlet port flows about 207 cfm at 0.400 valve lift at 28 inches H20. Head gasket is 0.0475 crushed. My best guess is that the tops of the pistons are 0.041 inches down in the magnum spec block's 9.58 deck height { old pre-magnum spec was 9.60}. The exhaust flows about 171 cfm at 0.400 valve lift at 28 inches H2O. There is some more info and pictures on the Magnum head online at: http://www.hughesengines.com/heads/magnum_heads.asp Chrysler cyl heads W5/W7 info at: http://www.chapmanracingheads.com/or....html#CHRYSLER Edelbrock Chrysler cyl head info at: http://www.martelbros.com/edel/autom...ownumbers.html Brodix aluminum cyl heads for the small block Chrysler at: http://www.brodix.com/Catalog/Heads/.../b1-ba_mc.html Picture of the Magnum 4.7 cyl head: http://coulterc.home.mindspring.com/hemi/4.7Lhead_1.jpg Look here to see how GM copied the Magnum head and called it a 'fast burn': http://www.paceparts.com/fast_burn_cylinder_head.htm |
#3
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So it sounds like the 318 has the same size valves as the 360. I think the MP catalog shows 2.02" and 1.60" intake and exhaust for the stock replacement magnum heads. These seem like awfully big valves for only 318 cubes.
Another thing that strikes me as odd is that my manual says the 318 valve lift is .434" whereas the 360 is supposed to be only .405" or something. I figured this was because the 318 had smaller valves, but now I'm even more confused. RS |
#4
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The heads are the same, same valve sizes.
I wouldn't swear to it but I think the cam might be smaller for the 5.2L. If no one else answers your question for sure I can look in the service manual tomorrow. What year of engine are we talking about though? ------------------ 70 challenger r/t conv, 72 383 swinger, 90 5th Ave, 98 V-10 Q/C SWB 4x4 |
#5
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It has been my understanding that the only real difference between the 5.2 and 5.9 is displacement. This would be the cheapest way for the factory to build the engines. This also helps explain why the 318 has 42 less cubic inches but has a very close HP rating to the 5.9 If you look at the MOPAR PERFORMANCE catalog, there are a boatloads of parts listed only as Magnum V8 with no distinction between size.
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#6
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As far as I know, the stock heads are the same w/ 1.92" intake and 1.625" exhaust valves.
High performance heads with 2.02" intake valves for a 318 is not too much! Thirty years ago or so, Chevy was putting their "camel hump" or fuelie heads w/ 2.02" intake valves and 1.60" exhaust valves on their HP 283s., 302s and 327s. Mopar Performance offers ported and polished cast iron heads for our Magnum V-8s with 1.97" intake and 1.625" exhaust valves, heavy duty springs and retainers as P#4876257. Hughes offers ported and polished heads with stock size intake and exhaust valves in their "Stage I" heads and 2.02" intake and stock size exhaust valves in their "Stage II" heads. Here's 2ยข for the pot |
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