1.5 ratio rocker on magnum heads?

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moturbopar

moturbopar

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Hi all Im looking to find out what and if there are any 1.5 ratio rockers (ford/chevy?) that will work on a magnum head, with the correct conversion studs, and guide plates.
 
Expensive,check with Crane.On their conversin kit to screw in studs,I believe they list a 1.6 Chev roller rocker on that swap.Give em a call,might need different length pushrods though.Probably a custom length.
 
I gotta ask, why would you want to run the 1.5 ratio vs the stock 1.6 or a bigger 1.7 roller rockers?
 
Any SBC rocker will work. With the 1.5 rocker you "may" have some pushrod clearance issues.
 
thanks guys. The problem is with the 1.6 ratio rockers it puts my exhaust lift around .550, which is more than my head is machined for and puts it right at the limit of my valve springs. If I could use a 1.6 intake rocker with a 1.5 exhaust rocker that would get me where i need to be.
 
Im just going to sell my 60403 lunati and get something with less lift. thinking magnum 280h or similar.
 
You do realize that due to the complex angle of the pushrod to lifter to rocker arm on SB Mopar's (look at it from a front view and you'll see their not in a straight line) that you won't get the advertised lift, right? Even with perfect geometry you can figure you'll loose .025~.030 lift. Would that put you where you need to be? If you think so mock it up and measure the actual lift to see what it's got. My guess is that even with 1.6 ratio rockers you'll actually only have about .515~.520" lift at the valve.
 
I did, well they were 1.6 ratio, but I'm sure 1.5 would work. I used comp studs and guide plates. It was actually a pretty cheap conversion. Those are Chevy springs too. Don't hate me. LOL That little 318 ran good.
 

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Guys, so I can put a set of Chevy roller rockers in the Magnum heads? Any type of Chevy rockers? Could you recommend a good 1.6 combo with a good price? thanks!
 
JAmes Dodge said:
Guys, so I can put a set of Chevy roller rockers in the Magnum heads? Any type of Chevy rockers? Could you recommend a good 1.6 combo with a good price? thanks!
Click to expand...

Read the whole thread. Then replace the 1.5 rockers in my link above with 1.6.

Damn, why don't people read all of a thread?
 
Ok after doing some measurment. it looks like the stock magnum 1.6 ratio rockers, look to average between 1.52 and 1.55 I only tested 8 of them though. and with push rod deflection and the weird angle of the lifter and pushrod, fishy68 looks pretty dead on with the lift he listed. Checking another cam with advertise lobe lift of .313 with the 1.6 magnum rockers should come out to around .500. But with the measured rocker of 1.55 and and a lobe lift of .313 should equal .4856. But that not even close to what Im sitting at! Actual lift at the valve is .476!!!!!!!! The rocker is sitting pretty nice on the valve stem,sits pretty much in the middle through the whole lift. So I lost .024 lift from theoretical lift to measured!!!! So heck Im just going to use stock rockers, put the higher ratios on the intake and the lower on the exhaust, I think I should be fiine. Well I guess I will find out!
 
fishy68 said:
You do realize that due to the complex angle of the pushrod to lifter to rocker arm on SB Mopar's (look at it from a front view and you'll see their not in a straight line) that you won't get the advertised lift, right? Even with perfect geometry you can figure you'll loose .025~.030 lift. Would that put you where you need to be? If you think so mock it up and measure the actual lift to see what it's got. My guess is that even with 1.6 ratio rockers you'll actually only have about .515~.520" lift at the valve.
Click to expand...

So Fishy,
If I had a cam with lobe lift of .342" what lift at the valve do you think I would get with 1.7:1 rockers on a magnum head?
 
This is great info, for some dumb reason I haven't even checked the actual at-the-retainer lift of my new 360. That's a lot less lift than advertised using lobe lift x 1.6, I'm running the 60401 Lunati in mine also with Magnum heads. BTW runs great, like said in my sig on pump gas (87 mid-grade up here in CO) and 10.5:1 compression. The bottom-end torque is BRUTAL, even with stock 2.76:1 gears it feels like being shot out of a cannon when you step on the gas. Not to mention the throttle response is ridiculously quick lol... :burnout:
 
WHY??? It would waste cfm and hold back power......................
 
scrappydoo said:
So Fishy,
If I had a cam with lobe lift of .342" what lift at the valve do you think I would get with 1.7:1 rockers on a magnum head?
Click to expand...

As long as the geometry is spot on and are they a true 1.7 ratio you should see approx. .550~.560 at the valve. I haven't had the opportunity to do comparison measurements with different ratio rockers but theoretically the higher ratio the rocker arm is the less loss you'll have because higher ratio rockers move the pushrod socket closer to the fulcrum and that straightens out the pushrod angle a little.
 
AF.Y.I.,Mopar action,August issue,page 9.Scummitt ad,Comp part number CCA-1425-KIT. Comp s cast roller rockers,guide plates and studs,hardened pushrods.Cost 350.00
 
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