SBM Rocker Arm Comparison

[Earlie A]

This post is to show a comparison of the INITIAL contact location of several different SBM rocker arms on a few different heads with their stock valves in the closed valve position. Please read that carefully because that is all that is being demonstrated here. This is not a demonstration of complete rocker arm geometry. This is to show the initial contact location. That's it.

Three heads will be shown. The first head is a Trick Flow. The second head is a factory iron 915J small valve. The last head is a Speedmaster.

Six different rocker arms are shown. Rocker arm number 1 in the list will show up on the left in the first picture. Rocker arm number 6 will be on the right. Here's the list:

1. Hardland Sharp for Trick Flow
2. Harland Sharp for Edelbrock
3. Hughes
4. PRW
5. Speedmaster
6. Factory Mopar

Here's the pictures of the Trick Flow head. The first pic shows all the rocker arms being tested. Picture 2 shows the contact location of 1 & 2. Picture 3 shows the contact location of 3 & 4. Picture 4 shows the contact location of 5 & 6. The rub marks on the top of the valve were made by sliding the rocker arm from left to right while the valve remained closed.

 

[Earlie A]

Next up is the factory 915J head. Same format as before.

 

[Earlie A]

And last is the Speedmaster. These pictures would be the same if the head were a ProMaxx. I have taken all the measurements that Mike at B3 needed for a correction kit. The SM and ProMaxx are within a few thousandths of each other. I have not measured an Edelbrock but I bet it would be the same.

I will note that rocker number 5 (the red Speedmaster) would not be usable on this head with a 1.5" diameter spring. The rocker arm hits the retainer. This problem has been well documented.

 

[gzig5]

Great information. Interesting to see the various contact locations. I am surprised that the SM was only one that hit the retainer. I tried to use PRW on my ProMaxx heads and it they had a lot of interference on the retainer and need to move up and back to clear. Looking forward to more, appreciate your efforts.

 

[Icetech]

that's crazy how far some of those are off... I am using the mancini/HS rockers on my trick flows and they sit pretty much centered..

 

[Earlie A]

that's crazy how far some of those are off... I am using the mancini/HS rockers on my trick flows and they sit pretty much centered..

That is one set I would like to have in this comparison. Are they bushing or roller bearing?

 

[Icetech]

That is one set I would like to have in this comparison. Are they bushing or roller bearing?

Bushed.. i only have a couple of hundred miles on them.. no issues, but i haven't taken them apart to check how bad they are scuffing or anything

 

[Icetech]

well actually they aren't even bushed. the rocker rides right on the shaft.. so it's like bushed but no bushing.

 

[Earlie A]

Great information. Interesting to see the various contact locations. I am surprised that the SM was only one that hit the retainer. I tried to use PRW on my ProMaxx heads and it they had a lot of interference on the retainer and need to move up and back to clear. Looking forward to more, appreciate your efforts.

You can see in the pictures that on the SM head test springs were used. Real springs may have rubbed.

 

[Icetech]

 

[Earlie A]

well actually they aren't even bushed. the rocker rides right on the shaft.. so it's like bushed but no bushing.

So it's like the Hughes rocker arm. The aluminum is the bushing?

 

[Icetech]

So it's like the Hughes rocker arm. The aluminum is the bushing?

yeah.. i'm hopefully building a new motor this winter (block is gonna be 6 months in the machine shop) and will be checking them over at that time

 

[NC Engine Builder]

I'm gonna stick my nose in here and give my opinion of what's going on, hopefully @Earlie A doesn't mind! It seems that the aftermarket heads when designed, were based off of the factory blueprints for rocker stand location. And that would be fine for a stock stamped rocker and STOCK length valves. But, invariably, most end up with something other than stock length, and when using a roller rocker, your pivot point is the CENTER of the roller tip, not the pad of the stock rocker. Then you compound the problem with variations in rocker manufacturers. These are the reasons its almost mandatory to do geometry correction on these heads.

 

[MoparLeo]

Was the installed valve height the same between the different heads ? That would affect the rocker tip location.

 

[Earlie A]

Was the installed valve height the same between the different heads ? That would affect the rocker tip location.

The valves used in the SM head are SM valves. The valves used in the Mopar head are stock Mopar valves. The valves used in the TF head are TF valves. The point of this was to show people using an all stock head what they can expect.

Your observation is correct. Valve length and installed height (relative to the shaft) do affect the geometry.

Edit: The rocker shaft saddle in the TF head has been relocated (by TF) to improve geometry.

 

[NC Engine Builder]

The valves used in the SM head are SM valves. The valves used in the Mopar head are stock Mopar valves. The valves used in the TF head are TF valves. The point of this was to show people using an all stock head what they can expect.

Your observation is correct. Valve length and installed height (relative to the shaft) do affect the geometry.

Edit: The rocker shaft saddle in the TF head has been relocated (by TF) to improve geometry.

I forgot about the trick flow saddle, I have successfully used PRW rockers on those with no correction

 

[Earlie A]

I forgot about the trick flow saddle, I have successfully used PRW rockers on those with no correction

You are correct. Mike at B3 told be the TF needed 0.015" shims to be correct with the PRW rocker. Not worth the effort.

The PRW contact point is not great on the TF since it is quite off center, but the mid lift geometry is good. So basically the arm is not quite long enough.

 

[cookietruck]

I was told by Harland Sharp that the Mancini rockers they make are copies of the old aluminum crane rocker arms.

Fyi

 

[cookietruck]

Prw steel rocker
SM head with SM valves, rocker hit the SM retainer so used a beehive retainer.

Cycled through .600” or .650” lift. Can’t recall exactly now..

 

[Earlie A]

Prw steel rocker
SM head with SM valves, rocker hit the SM retainer so used a beehive retainer.

Cycled through .600” or .650” lift. Can’t recall exactly now..

View attachment 1716446986

No correction kit? Do you recall the valve length? That looks more centered than the PRW/Speedmaster pic I posted this morning. Wonder if your valve is shorter than the one I used.

 

[cookietruck]

No correction kit? Do you recall the valve length? That looks more centered than the PRW/Speedmaster pic I posted this morning. Wonder if your valve is shorter than the one I used.

No correction kit, heads bought complete last November, the rockers are about 3 or 4yrs old, though I doubt those would’ve changed.

I didn’t measure valve length

 

[PRH]

The Hughes rockers look a bit short on all of those heads.

 

[PRH]

PRW rockers & SM heads……. Not even close to fitting.
A Crane Gold I have as a mock up tool……. Room to spare.

No pic of it on the head, but this Comp rocker also had room to spare.

 

[Earlie A]

PRW rockers & SM heads……. Not even close to fitted by.
A Crane Gold I have as a mock up tool……. Room to spare.

View attachment 1716447045

View attachment 1716447046

No pic of it on the head, but this Comp rocker also had room to spare.

View attachment 1716447053

Crane gold and Comp no longer available, correct?

 

[PRH]

Crane golds are long gone, but the HS made Mancini rockers are supposedly patterned after them(even though they look nothing alike).

Comps are still available, although they are bushed now.