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Discussion Starter · #1 ·
I am going to swap out the 273 heads for magnum heads this year. I have everything for the swap. What I need help on is choosing a hydralic camshaft. Remember the magnum heads are 1.6 rocker ratio
'77 Aspen R/T
The short block is stock '77 318
4spd trans
3.23 SG gears.

My choices;
XE268
268/280 @.050 224/230
lift(1.6) .508/.512

XE262
262/270 @.050 218/224
lift(1.6) .493/.501

MP4452761
268/272 @.050 ????
lift(1.6) .480/.485

I know the 318 slugs are usually far down in the hole. I am leaning towards the MP cam. I think with the 1.6 rocker ratio, the comp cams are too excessive in regards to lift.

Recommendations please?


 

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I would use the 262 in the 18, im no fan of the magnum heads though.
 

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I would use the 262 in the 18, im no fan of the magnum heads though.
 

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I say either of the last two but leaning towards the 262 or you might consider the MP cam that is 260/268 adv duration. I've used it in a 318 with ported 360 heads and it runs hard from 1000 rpm to redline.
 

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Discussion Starter · #5 ·
I went with the MP cam, I think my PV clearance should be good. Those stock 318 slugs are usually down in the bore quite a bit.
 

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Discussion Starter · #6 ·
Evildriver-3 said:
I would use the 262 in the 18, im no fan of the magnum heads though.
Close chambers, good flow, 1.6 rocker ratio, vertical intake manifold bolts, good valve size. What's not to like.
 

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The rocker set up, not really good flow it doesn't out flow the 915 or the x, small valves
 

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Discussion Starter · #8 ·
Evildriver-3 said:
The rocker set up, not really good flow it doesn't out flow the 915 or the x, small valves
Magnum as cast
LIFT----AS CAST---------IN/EX
.100"--67.3/N/A
.200"--131.3/97.3
.300"--185.6/132.5
.400"--212.5/144.9
.450"--213.9/146.3
.500"--212.2/146.3
.550"--212.5/146.3
.600"--213.9/146.6
.650"--214.2/147.3
.700"--215.3/147.3

#302
302's
LIFT----I-------E
0.100--55.2----34.5
0.200--105.2---70.7
0.300--152.0---104.2
0.400--187.0---113.2
0.450--189.8---115.5
0.500--190.1---117.3
0.550--190.4---119.0
0.600--190.4---120.4

596's
LIFT----I-------E
.100--62.8----48.3
.200--117.3---98.3
.300--174.2---120.8
.400--193.2---125.6
.450--192.5---127.7
.500--192.5---128.3
.550--192.5---129.0

Magnum R/T(1.9 valve)
200"--135.6/110.4
.300"--194.9/154.9
.400"--227.4/173.5
.450"--233.9/177.3
.500"--239.4/179.4
.550"--244.9/180.8
.600"--245.0/181.8
.650"--245.0/181.8
.700"--241.5/183.2

and
http://www.geocities.com/alwest_83/sbheads

Not to shabby. There is nothing wrong with the rocker set-up other than it's generally foreign to Mopar people.
 

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Yea i've argued this with ED-3 before. The Rocker set up isn't a shaft like he is use to but the way its designed is just as stable as the stock rockers on LA engines. Magnum heads do have a problem with cracking though
 

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Ok for a stock motor the rocker set up is fine, but when you look for more hp there junk, just like gm.

As for the flow #'s you have that is the 1st i have seen a rt mag head come close to a W-2 or Econo head with smaller valves, unbelieveable a smaller valve head not nearly as good a port and only 10 off a W-2 and Econo, you know there are ways to make flow benches lie and dyno's, just ask hughes he gets big #'s too
 

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Discussion Starter · #12 ·
Evildriver-3 said:
Ok for a stock motor the rocker set up is fine, but when you look for more hp there junk, just like gm.

As for the flow #'s you have that is the 1st i have seen a rt mag head come close to a W-2 or Econo head with smaller valves, unbelieveable a smaller valve head not nearly as good a port and only 10 off a W-2 and Econo, you know there are ways to make flow benches lie and dyno's, just ask hughes he gets big #'s too
RT heads from MP come in two versions standard magnum valve and 2.02. The flow numbers posted above are the standard valve. Yes I view flow numbers from comerical companies with a grain of salt. The above numbers are all from the same bench, from a guy who does excellent porting on the side. He is very good and has ported just about evry small block mopar head there is. So, yes I take his flow numbers a little more seriously.

That valve train set up on the magnum heads are not junk ::)
 

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Well you'll find out when you want hp that they are in fact junk when you have to replace everything and go to a shaft.
Lol you guy's make me laugh i love telling you things and you don't want to listen, you know what call mopar or a real mopar engine builder and ask them what you do for the junk rocker arms on a mag head, better yet go and look up mancini MP or whoever else sells the rocker arm conversion or build a good motor and then tell me the problems encountered and how the rockers suck, and then think why? why did they make this head with this junk set up? why did they change it just so you gotta spend more money on rockers going back to what the old heads have? do you ever wonder why the gm guy's go to a shaft rocker?
Again on the flow #'s are you really and trully saying you believe the mag head flows just below a W-2 and Econo head all not being ported as cast?
 

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Discussion Starter · #14 ·
Evildriver-3 said:
Well you'll find out when you want hp that they are in fact junk when you have to replace everything and go to a shaft.
Lol you guy's make me laugh i love telling you things and you don't want to listen, you know what call mopar or a real mopar engine builder and ask them what you do for the junk rocker arms on a mag head, better yet go and look up mancini MP or whoever else sells the rocker arm conversion or build a good motor and then tell me the problems encountered and how the rockers suck, and then think why? why did they make this head with this junk set up? why did they change it just so you gotta spend more money on rockers going back to what the old heads have? do you ever wonder why the gm guy's go to a shaft rocker?
Again on the flow #'s are you really and trully saying you believe the mag head flows just below a W-2 and Econo head all not being ported as cast?
Of course stock magnum heads dont outflow W-2's. Christ I ran the Econo's on a Duster back in the mid-late 80's. You call them junk if you like. There are just as many nay-sayers as there are supporters. If I was building a 600 hp race motor than you damn right I would use the shaft style rockers.

These heads are going on a stock 1977 318 short block. The magnum heads are replacing the '67 273 small chamber small valve heads. The solid lifter cam is being replace with the MP___761 cam. Why that cam? Lift issues with the 1.6 rocker ratio on the other two cam was too much (IMO). Though I will clay the pistons with the MP cam, it should be OK.

When the 360 magnum short block, from which the above heads came off, is ready I will put ported R/T or Edel aluminum magnums on (when they come out.). Even then that engine wont exceed 500 hp at the flywheel. The magnum style valve train will do just fine

Enough said, you do what you want, and I'll do what I want.
 

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Well the point im making is you posted flow numbers SAYING DIFFERENT so you are saying they do out flow W's, and wtf does 14,000 posts have to do with anything as far as i know you ran 1 motor with a good set of heads and now your saying mags are better, riiiight ok

 

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Discussion Starter · #16 ·
Evildriver-3 said:
Well the point im making is you posted flow numbers SAYING DIFFERENT so you are saying they do out flow W's, and wtf does 14,000 posts have to do with anything as far as i know you ran 1 motor with a good set of heads and now your saying mags are better, riiiight ok
Re edited the post so lighten-up. I never said the stock mag heads would outflow W-2's.(re-read the thread please) Only that they would run very close to the older stock LA heads. YOU are the one that brought the W-2's into this thread. The magnum R/T heads as cast will out flow the stock X, J, 587, 519, 308, and have a smaller chamber.
Flow results Ive seen with as cast W-2, is they flow an average of 260-270cfm (intake) at .550 lift. With the magnum R/T's doing 240 at .550, so they dont outflow the W-2's. Never in this thread did I ever compare the two until now.

Again you brought the W-2's into this.
 

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I haven't seen a mag rt head break 220 let alone a mag head break 210, whereas a j head will break 210 and a x head as cast, but the #'s you have up there are showing it equal to a W at 500.

Mopar states the only new head outflowing the x and j is the alum big port version which isn't a mag rt head either it's known as the commando head, what happened to the rt head? i wonder why even mopar doesn't compare the new heads to the mag heads but still comparing them to J's and X's
 

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Discussion Starter · #18 ·
Evildriver-3 said:
I haven't seen a mag rt head break 220 let alone a mag head break 210, whereas a j head will break 210 and a x head as cast, but the #'s you have up there are showing it equal to a W at 500.

Mopar states the only new head outflowing the x and j is the alum big port version which isn't a mag rt head either it's known as the commando head, what happened to the rt head? i wonder why even mopar doesn't compare the new heads to the mag heads but still comparing them to J's and X's
I dont know what flow #'s you have seen, but the R/T will out flow the older stock LA heads.

To the last paragraph, post a link to that claim by Mopar.
 

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To make 600 hp reliablely you would have to get rid of the stamp steel rockers on LA heads to so either way your replacing stock rockers on LA and Magnum heads. The magnum setup is just as stout if not stouter then the rocker shafts. In a way the Magnum rocker is riding on a shaft or really the bottom half of a shaft. They are nothing in common with the Chevy ball stud setup.
 

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Discussion Starter · #20 ·
I agree 300le, but Im going to stop the pissing contest. I hope ED3 has no hard feelings.

As I went with the MP4452761 I am counting on those stock pistons being down in the hole a ways so I dont have to cut valve reliefs in them. Fel-pro head gasket is being used. I will clay the pistons unless someone says different. Cam specs are below with the 1.6 rocker ratio. Any comments?

268/272 @.050 228/231
lift(1.6) .480/.485
 
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