MP Magnum rocker conversion?

[sharpie]

Anyone done this? It changes the pedestal-mount rockers to stud-mounted rockers, much like Chevy heads. I was thinking this might be an economical way to get a bit more power (more lift) with a smaller pricetag than edelbrock heads.

What do you think?

 

[70aarcuda]

more lift?

stock magnum rockers are 1.6 ratio.....what ratio do you plan on using?

 

[sharpie]

more lift?

stock magnum rockers are 1.6 ratio.....what ratio do you plan on using?

There's two choices, either 1.6:1 or 1.7:1. If 1.7 would cause a problem, I could use 1.6, which wouldn't change the lift necessarily, but might produce some more power due to the lack of rocker friction? I am just thinking that if I am going with a new cam, I am going to need new heavier valve springs, lifters, and pushrods (I need new pushrods anyway), so why not change the rockers out?

Mainly, I just want to know if anyone's had issues with this setup or not.

 

[rumblefish360]

If 1.7 would cause a problem, I could use 1.6, which wouldn't change the lift necessarily,

OUCH!

The 1.7 will change the lift for more lift and intenseify the cam.

but might produce some more power due to the lack of rocker friction?

Whhhhhhhhhhhhhhhhhhhat?!?!?!?!?!??!
Lack of friction? LOL, no bud, the amount of friction is not a big HP netter and the amount of friction on a rocker arm due to it's ratio is more likely increased due to it's higher ratio. The higher ratio is moveing the valve more.
More movement on the arm and valve and spring.

 

[sharpie]

OUCH!

The 1.7 will change the lift for more lift and intenseify the cam.


Whhhhhhhhhhhhhhhhhhhat?!?!?!?!?!??!
Lack of friction? LOL, no bud, the amount of friction is not a big HP netter and the amount of friction on a rocker arm due to it's ratio is more likely increased due to it's higher ratio. The higher ratio is moveing the valve more.
More movement on the arm and valve and spring.

I guess my point didn't come through. My point was that if I used 1.7, I'd have more lift (more power), but even if I went with the stock 1.6 ratio, I wouldn't achieve more lift than stock, but I'd still have some gains, right? Mopar Muscle's article says that it would add a little bit, even at the same ratio.

While most will assume that the only benefit of roller rockers is reduction in friction, the other benefits of aftermarket roller rockers include true, blueprinted, at-the-valve ratios and precision motion.

http://www.moparmusclemagazine.com/howto/38620_rocker_arm_upgrade_install/index.html

I was just trying to obtain some opinions. I know the engineering some, I just don't know if they're reliable/useful or not. O


edit: I don't know if that was your intent Rumblefish, but your post sounded pretty condescending.:-?

 

[71DartGuy]

What type of heads are you talking about? You mentioned stock ratio being 1.6, which would mean that you are talking about Magnum heads. Going to 1.7 wont reduce your friction any that I can see but will cause some disastrous retainer to guide clearance on the valve end unless you go with a mild cam. Why dont you tell us what you are working on and what you intend to do with it so we can get some more details and in turn give more advice.

 

[sharpie]

What type of heads are you talking about? You mentioned stock ratio being 1.6, which would mean that you are talking about Magnum heads. Going to 1.7 wont reduce your friction any that I can see but will cause some disastrous retainer to guide clearance on the valve end unless you go with a mild cam. Why dont you tell us what you are working on and what you intend to do with it so we can get some more details and in turn give more advice.

oh, sorry. I thought I had explained, but I didnt:

I have a 360 magnum. Going to use stock heads/crank/rods/pistons, new cam (not sure which, but definitely a street cam). Electronic distributor, OEM oil pan, high vol. oil pump, harder valve springs, roller lifters, and stock valves.

 

[muller]

if your not sure yet what cam you want to use....why als about the 1,7 rockers????

just get a cam with more lift and save money

 

[sharpie]

if your not sure yet what cam you want to use....why als about the 1,7 rockers????

just get a cam with more lift and save money

because I want to change to stud-mounted rockers (cheaper, widely available, roller tips available), and my only choices are an Edelbrock head (1500/pair), or this conversion.

 

[71DartGuy]

Magnum heads already have stud mounted rockers. LA heads have the shaft system. Edelbrock heads use the chevrolet style rockers. If your going to run a mild street cam I wouldnt worry about roller tip rockers.

 

[sharpie]

Magnum heads already have stud mounted rockers. LA heads have the shaft system. Edelbrock heads use the chevrolet style rockers. If your going to run a mild street cam I wouldnt worry about roller tip rockers.

Magnum rockers are bolt-fulcrum pedestal mounted. A chevy rocker won't work on the Magnum heads without the stud conversion.

 

[dgc333]

What type of heads are you talking about? You mentioned stock ratio being 1.6, which would mean that you are talking about Magnum heads. Going to 1.7 wont reduce your friction any that I can see but will cause some disastrous retainer to guide clearance on the valve end unless you go with a mild cam. Why dont you tell us what you are working on and what you intend to do with it so we can get some more details and in turn give more advice.

Goin to a 1.7 ratio rocker is not going to cause any retainer to valve guide clearance issues unless the valve lift is going above .525" with the 1.7 rocker. Using the stock stamped 1.7 ratio rockers from a Viper V10 motor is a very common and inexpensive up grade on magnum motors.

I tired the Crane conversion kit on my magnum headed motor and because of the thickness of the cast guide plates the bottom of the roller rockers contacted the base of the studs. The nylon inserts in the guide plates also caused a funny sound that I did not like so I took them out and went back to the stock rockers.

If you plan to go with stud mount rocker arms I would suggest using the stamped metal guide plates and studs rom Hughes Racing over the Crane kit.

 

[Coyote Jack]

I have the Crane kit. As Dave said, they do make a funny sound. I likened it to a bit of a sewing machine sound. I would stick with the 1.6 ratio rockers. Just a little less pressure on the rocker. You have to watch your final lift numbers. Anything over .525 and you are asking for trouble in the retainer and guide area. The only problem I had doing the conversion was, I had to grind out grind out a little of the pushrod hole in the head to get the proper clearance. Other than that it was a painless conversion and works well.

Jack