Speed INC said they saw a big gain switching. I think there was some other things factors involved. I put the crowers on in the beginning then switched to the comps and when the headgaskets were changed I went back to the crowers. Both are 1.6

 

It's always those 'other' variables that never get mentioned - maybe PR geometry was different, maybe the engine was in a better state of tune after the swap. Who knows? I do know that the RR themselves gained a minute amount, if anything at all.

 

Those suckers weigh almost 7 lbs. Don't know how much the others weigh or whether the weight of the Rockers has any affect on the performance, considering that lighter is supposed to be better, at least when it comes to valves, retainers, etc.

 

they are heavier...but the acctual wt. in the valve train is lighter. Look at a crower tip and a comp tip.

The crower trunion is alot larger

 

This is good point, but I wonder if that's actually the case. Ever since Comp came out with the ProMags and pointing out that steel is stronger than aluminium and therefore less can be used to brace the tip, it seems every manufacuture uses this line on their steel rockers.

I personally would not use aluminium rockers on street combo for two reasons:

1) Alminuim has a fatigue limit... steel does not. While it may be very high, there is a limit to cycles an Al rocker can handle without plastic (permanent) deformation. While failure is obvious, I don't think a deflction of say 0.005" is noticable without very careful inspection, it does affect geometry (specificly sweep accross the valve stem).

2) Spring OD size can limit arm strength. Pretty much any aluminium rocker is BIG because it HAS to be to have stiffness comparable to a steel deign. Aluminum rocker manufacturers brag about how large a spring OD can fit under it's arm... and it's always due to a big notch carved out from under the arm. This leaves you with either a thin trunion wall, and most likely a large arm. The trunion and arm sizes of Al rockers in general can be problems in some valve covers (nothing impossible to fix though) if there's enough lift involved.

The weight on the tip is obviously important to rocker design, but looking at similarities between brands it's hard to picture one make having a large advantage over others.

This is one reason I have non-self-aligning rockers instead of SA. Guide plates just seem to be a better solution to rocker alignement... put the horizontal stress on guideplates and the pushrod instead of the rocker's trunion/stud (and have a slightly lighter rocker tip). Probably a tiny difference, but the cost is comparable and worth it IMO.

As for a larger trunion... it's good for stablizing the rocker, but it also adds friction to the valvetrain. This is the same compromise builders have with main engine bearing size. A larger bearing has a faster surface speed (due to increased circumference) for the same RPM, leading to increased friction at the same RPM. Larger isn't nessesarily better... in fact you probably want the smallest trunion you can get that still retains rocker stability.

Engine building is an exercise in $$ vs. HP vs. durability... <zen> wise builders choose their own path. </zen>

 

I gained around 200 RWHP with my Crowers. I'll bet you can't say that about comps.

 

a larger trunion would reduce friction.....you would have more rollers

Also the crower tip is more narrow than the comp and a little taller. I have seen both many many tines...the crower is a higher quality....

But if you take them off and put on a set of japenese rockers from a salvage yard I don't think you would lose any h.p. IMO

 

That's my goal... new build will be done within a week or two... with ProMags. Hoping to get 200 over stock N/A it'll be close though. Might need to hook up this N2O plate to my monoblade to be sure.

 

No, that means you have a stronger trunion (less load per roller). The total friction from a trunnion is proportional to the number of rollers (n), times the force put on each roller (F/n), times mu (the friction caracterisics of the friction surface, and the radius of the friction path (R, similar to a lever multiplication factor of F).

Total force won't change by going to more rollers... but a larger radius will increase trunnion friction. Go as big as you need to ensure roller life and rocker stabilization, but any bigger and you're sacrificing hp. Same thing applies to rod and main bear diameters, or even to valve spring strengths. Bigger isn't always better.

 

For roller rocker applications in our road race cars that don't use shaft rockers, the Crower Enduro II are the only ones we use. They are higher quality than the comp's, and we had been using them before comp even released their copy of the Enduro.

You are not however going to see a 30hp gain by switching to Crowers. You are going to get a rocker that puts less "seen" weight on the valve, and one that will not loose lash as the Comp's are famous for doing. And I put more faith in the Crower name being behind a product than I do Comp.

In the LS1 world, the Crane Gold's are proven to give a significant gain over similar 1.7/1.8 rockers due to what crane calls "quick lift" just a way of saying that their rockers are designed to provide a true 1.7 ratio of lift from lobe to valve very early off the seat as compared to other manufacturers that drop the ratio to 1.3 and lower at low lifts causing less area under the curve.

 

Thanks for all the info guys.

 

Good info.

 

have you had a set of crane shafts yet?

I have not seen them in person...wondering how they compare to the T&D

 

I have not used the new Crane shaft rockers(quick lift type), but have used their Gold Race rockers many times. For shaft rockers we have used Jesel, Miller, Yella-Terra, Crower, and Erson.

 

im not trying to jack this, but do you have to change pushrod length when you put 1.6 rockers on?