Magnum Heads

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73dartsport360

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I Was Wondering If You Can Use Cheby Rockers On The Magnum Heads?
Has Anyone Ran These Heads On A 360 Combo/408 Etc. I'm Trying To Find Out What Head To Use On My Next Motor Its A 360 Stock Rods And Crank Kb 107 Flat Top Pistons With The Deck Zeroed. I Had 587's Stock On It But I Know There Is More Power To Be Made!
Thanks Brandon
 
I know Eddie magnum heads have the 3/8 stud to accept chebbie rockers. I'm not sure about stock magnum or r/ts however. Maggies are also around 63cc if your watching compression ratio too being its decked or anything.
 
whitey said:
actually according to the MP catalog, the stock heads have a 60cc chamber.
Click to expand...

I cc'd my magnum heads and they were 64cc and most everyone else that has cc'd them has been in that are too.
 
73dartsport360 said:
I Was Wondering If You Can Use Cheby Rockers On The Magnum Heads?
Has Anyone Ran These Heads On A 360 Combo/408 Etc. I'm Trying To Find Out What Head To Use On My Next Motor Its A 360 Stock Rods And Crank Kb 107 Flat Top Pistons With The Deck Zeroed. I Had 587's Stock On It But I Know There Is More Power To Be Made!
Thanks Brandon
Click to expand...


Crane sells a kit that includes studs that are 3/8" on the rocker side and 5/16 on the block side. The kit also has guide plates with teflon inserts for the push rods. Crane list the same sb chevy roller rocker for the mopar application.

I purchased this kit and picked up a set of Proform sb Chevy for my magnum headed 360. The Crane kits states that you should be able to use the same push rods as you do with stock stamped rockers. When I mocked it up the conversion push rods MP sells for magnum heads on LA blocks are way to short to the point that the bottom of the rocker contacts the guide plate. Some one mentioned that they used 7.8" sb chevy push rods and I picked up a set of those cheap at a swap meet. It appeared like they were to long since the roller on the rocker was not centered over the valve stem.

I borrowed a adjustable checking push rod and there is no length that will center the roller on the valve and the 7.8" did infact produce the shortest sweep across the stem. Depending on what you read this condition is actually more desirable than the roller being centered with a large sweep.

I put the roller rockers on but the valve train noise was not natural. I couldn't find anything wrong; there was nothing hitting, springs weren't binding and retainers weren't contacting the guides.

I wound up going back to the stock stamped rockers.
 
73dartsport360 said:
I Was Wondering If You Can Use Cheby Rockers On The Magnum Heads?
Has Anyone Ran These Heads On A 360 Combo/408 Etc. I'm Trying To Find Out What Head To Use On My Next Motor Its A 360 Stock Rods And Crank Kb 107 Flat Top Pistons With The Deck Zeroed. I Had 587's Stock On It But I Know There Is More Power To Be Made!
Thanks Brandon
Click to expand...

I just installed the Eddy magnums on my 360/388 combo. yes they use a chevy style individual rocker 1.6 ratio. The Eddys are 58cc and have a double quench pad. The throat runner and bowl finish in stock form is very good. I did some blending at the port inlets and eshaust outlets and cut down the push rod pinch point a bit to hopefully improve flow a bit but otherwise a very good casting finish. I also went with the Eddy magnum Airgap intake and the finish was much better than the LA Airgap I had purchased 3-4 yrs ago - and the fit to the heads was dead on. As I am using a non-roller camshaft - making the pushrods longer - I added a bit of pushrod clearance into the heads just to be sure no binding. With a roller cam (taller lifters) all would e okay.
With flat top pistons @ zero deck and a .040 gasket you will end up with very good quench which should allow more compression and still run pump gas 91-92.
I ended up with 11.8 calculated compression and a final around 10.4 which may be a bit high for straight pump gas. I suggest you target for 10.8 - 11.0
if you go with the Eddy magnums.
 
I've got the Crane stud kit and 1.6 roller rockers. The push rods they sent were way to short. The MP pushrods were just the right length in my case as the block had been decked. As dgc333 said, the rockers make a strange noise, but like him I could find nothing wrong. I still have the rockers in there.

Jack
 
Coyote Jack said:
I've got the Crane stud kit and 1.6 roller rockers. The push rods they sent were way to short. The MP pushrods were just the right length in my case as the block had been decked. As dgc333 said, the rockers make a strange noise, but like him I could find nothing wrong. I still have the rockers in there.

Jack
Click to expand...

Jack, FWIW, my block was decked also (approx 0.020" was remove for zero deck on the pistons). Even with the decking the MP push rods only gave me about 0.025" of preload on the lifters with the stock stamped rockers. The size of the base circle of the cam has just as much impact on the preload as decking.

If you used the Crane rocker they may have more clearance on the bottom so they do not contact the guide plates but: Did you actually mark the tops of the stems a check the pattern? Again it may have been the Profrom rocker but with the MP length push rod the pattern started close to the center of the valve stem and the sweep was out to about 0.040" from the edge of the valve on the exhaust side. With the 7.8" long push rod the sweep was approx +/- 0.020" around 1/3 of the way in from the exhaust side of the valve stem. Starting with the adjustable push rod at the MP length the sweep would get smaller until I reached the 7.8" length and would start getting bigger again past that point.

The large sweep of the stock length push rod puts a lot of side load on the valve stem resulting in accelerated guide wear.
 
After I wiped out my second cam I had to do an inspection of everything. I checked all of the machining records I had, talked to the people that built the engine originally and made a lot of measurements. I was getting about .085 preload on the lifters. Way to much for a hyd. flat tappet cam.
As it turns out, the machinest had forgotten to tell anybody that he had decked the block by .070 to bring the pistons to zero deck. All is well now and the geometry for the valve train is good with the rollers not impacting the edges of the valve stems. I have been told by a couple of engine builders that the noise from the rockers I have now is how it is supposed to be. It was a little disconcerting at first though.

Jack
 
I wish mine were 60 cc's, they measured 66 cc''s. I have to cut them done to 58 cc's. I don't even know if they can be cut that much. I'm going to use Crans's 1.6 chevy rockers too. Check the clearance between the bottom of the rockers and the stud hex. Don't use the chevy size stud, there is a magnum specific stud with a very thin hex. I know that Hughes Engines and Comp Cams has them.
 
whitey said:
Guess Ma Mopar was wrong in print.
Click to expand...

Don't know about what mopar may have said in print but most everyone that has actually cc'd a stock uncut magnum head has gotten some in the range of 64cc's. Just like the older open chmaber heads that were supposed to be 68 but almost always were over 70cc or block deck heights always being considerably larger than the nominal advertised dimension.

It's these variations that make it mandatory to measure everything when building a high performance motor and not assume anything.
 
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