What happened to the rockers

[SappySE107]

Im not sure if aluminum pushrods would work at all honestly. You will have a lot of heat/friction on the guides and pushrods so you want them to work well in that environment.

[AaronGTR]

Oh I get it, Ok thanks
Why cant I just use them with out Guides, and why odesnt my engine have any already.

Because your stock rockers are pedestal mounted. They are self aligning and they automatically set the valve lash (or lifter pre-load in our case) when you tighten them down because the pedestal sets the rocker height.

The crane rockers are adjustable rockers. They don't use a pedestal and instead "float" on a stud and their height is determined by your valve length, pushrod length, and pre-load. Since there is no pedestal to keep them straight, you have to use pushrod guides from the older style 60v6 that used the same type of rocker and the pushrod guides keep the pushrods and therefore the rockers straight. You need heat treated pushrods to work with guide plates since there is extra friction there, or they will wear out faster. Stock pushrods don't come heat treated since they don't use guides plates. You need to find out if Milzy's pushrods are heat treated or not (I doubt it). That's why I ordered custom heat treated chromoly rods from www.pushrods.net.

So you will need the rockers, the guide plates, and possibly new pushrods. You will also have to clearance the bottom of some runners on the lower intake manifold and also put a radius on the top edge of four of the rockers in order to get them to fit. I ruined a LIM trying to grind metal off the bottom and went thru the bottom of the runners and the rockers were still too close, which is why I had to radius the rockers. You only need to take off very little and they will clear.

[john_V63400]

Wow thats starting to sound to complicated. Could I have you do it for me if I pay you. That would save me alot of hassle.

[SappySE107]

I would need a whole engine here to determine where to grind and how much since I haven't done it before for these rockers. I will not modify the rocker arms.

[AaronGTR]

Well, um... I live in MI and u live in CA... otherwise I'd do it for beer. It's not terribly complicated, but you do need to understand how it works and what you're doing because there is some potential for engine damage if you do things wrong. The most important thing is following the directions that crane gives you for adjusting the rockers. You have to rotate the engine by hand so that each rocker you are adjusting has it's valve fully closed and the lifter at the lowest spot on the cam (basically opposite the lobe).

Here's what the modified rocker looks like.

http://rides.webshots.com/photo/1121342809052938416uZTYMW

This is were they go on the heads.

http://rides.webshots.com/photo/2859606210052938416gDIJqP

You'll see which runners need to be sanded and which rockers need moddifying when you line the LIM up. It will be pretty obvious. Just a quick note... some think doing anything to the rockers is a bad idea. I haven't had any problem with mine though and they won't fit any other way. If you do it right you take very little off and it's all on the outside end, not from the area above the pushrod cup, so it should not weaken the rocker in any way.

[john_V63400]

Wow that really helps thanks. Did you get them installed and running on your car, if so how does it run.

[SappySE107]

It says in the directions from crane to not modify the rockers in any way, which is what I follow. I am aware that some people have modified them to clearance the lower intake however. If I were to do it, I would cut the lower and weld it so that it clears and open up on the top side for the airflow if there is room. I will have to do a mockup eventually but its nothing I am doing until I get this other engine together and ready to ship out.

[john_V63400]

If thier made to fit the 3400 why would you need to grind the rockers down anyways. Wouldnt they have noticed that when they made them.

[SappySE107]

They are made for the 2.8 iron head actually. They also fit the splayed valve heads since they are narrow body rockers. I haven't test fit the intake manifolds through every cycle to know how much and where to modify anything else.

[john_V63400]

So these rockers will show a great amount of HP gain though. For all this hassle it better be worth it.

[AaronGTR]

Yeah, they aren't made specifically for the 3400. They are made for the earlier 2.8 which had different intake manifolds and inline valve heads which placed the rockers in a different position. The splayed valve heads move the rockers further up, so an aluminum rocker like the cranes that are thicker you run into the clearance issue. Anyway, I would modify the rocker before the LIM. Crane tells you not to modify them just to cover their butts if someone does something to compromise the rocker's strength you can't go and blame them if they break. It's not a problem.

I certainly wouldn't want to start cutting and welding my LIM though and having pieces intruding into and/or changing the path of air flow. As Ben has already shown with his flow numbers, even ported UIM/LIM's lower the air flow compared to ported heads alone when they are connected to the heads. I wouldn't want to make it any worse. Besides, the small amount of clearance needed doesn't warrant going to those kind of lengths and you gain more clearance from the rocker than changing the LIM. It has to do with the angle they approach the runner at when they are moving. You have to see them on the engine to understand what I'm saying. Anyway...

It would be nice to find a steel or chromoly roller tip rocker that would work instead of the aluminum ones because they would be smaller and shouldn't have that problem. Several have been found that might work but no one's tested them yet.

[AaronGTR]

Wow that really helps thanks. Did you get them installed and running on your car, if so how does it run.

Yes, they've been installed on my car for a long time now and they run fine. I was the second person to try it and the first with a GA. As for gains and if it's worth it?...

I don't think anyone's actually dyno'd them independant of any other mods so it's hard to say the gains. You have less friction from the roller tip, but then you add friction from the pushrod guide. They're actually not much lighter than the stock rockers. The biggest difference is probably they are stronger and a more precise ratio. You'll have to decide if that's worth it or not. Personally I'd like to test one of the steel rockers.

I installed mine at the same time as a set of RSM ported heads and swapping to LS1 valve springs. RSM's heads are far from the greatest though. I massaged them slightly myself, but they've never been flowed so I can't say if I'm really gaining much from them. I did a before dyno but it was with a straight pipe and I added a high-flow cat before I did the after dyno so I probably lost about 5hp right there from the gains with the heads/rockers. I saw a 10whp total increase but I can't say if any of that was from the rockers or just the heads.