Magnum rocker arms..any problems??

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DusterKrazy

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I am thinking of doing a 318 build up using Magnum heads. Are the Magnum rockers reliable? I know they are 1.6 but I do enjoy the shaft mounted rocker system that the LA engines use. Any known problems with the Magnum rockers
before I make the plunge???
 
If you just want the 1.6 ratio, just get 1.6 rockers for LA heads. Hughes Engines has shaft mounted rockers for Magnum heads. It's actually 4 shafts per head, each with 2 rockers.

I have Magnum heads (EQ, not stock) with a cam that has just over .600 (not including the loss for pushrod angle) lift with stock 5/16" size studs. If I did it over, I wouldn't use Magnum heads. Haven't had any problems, it's just that there are better out there for about the same price. My Magnum heads can't handle a cam that will allow them to live up to their full flow potential due to the weakness of the stud mounts, at least not comfortably. With the Hughes stud mounted magnum rockers, they probably could, but that would be another $400+ that could be spent on porting, springs, etc on a set of LA heads.
 
Whats the intended useage? They make an excellent street head/daily driver and can be ported to flow maybe 250ish. Never will flow the same peak #'s as an la head,but will spank it all over the lower rpm range under 4000
 
I have 45k miles on my 360 LA/magnum hybred using the stock rockers with a .509/.512 lift cam. The engine regularly sees 6000+ rpm shifts and I haven't had any issues with the stock magnum rockers.

I tried stud mounted aluminum chevy roller rockers but could never get the geometry right so went back to the stock rockers. Remember, the magnum rocker is a pedestal system not a stud mount like a chevy so there is a lot more surface area to resist bending.

If you plan to run a lot of lift and spring pressure drilling out the 5/16 holes to accept 3/8 or 7/16 threads would be the way to go. Also, if you plan to go the high lift route you are already going to be doing machine work to the spring seat and guides so adding on drilling and tapping the mounting holes is not going to add that much more cost.
 
The Magnum heads seem to be a great alternative to LA heads and using a 1.6 rocker. They have decent size valves and better flow along with small combustion chambers to increase compression. I bet they would really flow
great with some porting...

I am curious about this..
 
Well it's a big debate whether they will outflow an LA. I like the velocity on the magnum as it helps with throttle response. But the ports are too small to be used on a serious 360 etc. A teen would repond really well. As siad the magnum will NEVER touch an LA's peak flow #'s.

However,add all the flow #'s together and divide to get an avg. you may be surprised at how much the mag really does flow.
 
DusterKrazy said:
The Magnum heads seem to be a great alternative to LA heads and using a 1.6 rocker. They have decent size valves and better flow along with small combustion chambers to increase compression. I bet they would really flow
great with some porting...

I am curious about this..
Click to expand...

do some research, the CFM ceiling is lower than an LA.

And when ported, theres no diff in low lift numbers, if fact they get better on the LA head to an extent, [theres usually a trade off at a certain point when it comes to high lift flow vs low lift flow.fwiw
The magnum head does have a better chamber which raises the compression and uses factory 1.6 rockers that will lift the valve more and faster so there's the power diff between the 2 in stock form.
And when people start talking velocity, I wonder how they know or if they are just assuming....have they checked the actual port vomume, measured it?, did they flow it and use a pitot tube, did they check the fps?

but now back on topic, the magnum rockers are pretty durable and you should have no problems running them to .550, but if you do run a cam in this range or bigger...I recommend you get some roller tip rockers that way you don't side load the guides to death and start ruining the valve job and sucking oil down the guides.
 
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