So guys, how much boost/HP you running while still on a hydraulic valvetrain? And what rocker arms?

 

Do you think there is a limit on hyd. lifters when you introduce boost into an engine? I wouldn't think so.

 

absolutely there is. As intake pressure increases you need to run more spring pressure to make up for the boost pushing on the back side of the intake valve, more spring pressure requires heavier valvetrain components. the extra spring pressure and heavier components put a beating on those hyd lifters.

With that being said, Mark Kohler ran mid 7's with a hyd roller valvetrain, so it can be done at high boost. I would think you would ok in the mid 30lb area

 

Shawn,

does compression play on this also? like 9:1 compression with 30 psi = 10:1 compression with 25psi? this make sense?

PS Shawn you get my Private Message???

 

Thanks. Any idea of which rockers? Most of the heavy hitters are solid, I'm just very interested in who is still hyd.

 

Mark is using the Harland sharp rocker arm.

Kurt

 

That's interesting. I've heard of a couple people breaking those. You guys must have them along with everything else set up correctly / very well.

 

Attached is a couple pics showing the rockers in place. I believe the highest he ever spun the engine was 8100rpm, although his normal shift point is down in the low 7XXX range. I think he ran just over 30psi.

Kurt

 

Holy Toledo those look monstrous! I don't plan on turning my ls2 past 7500...

 

Do those come with the girdle or are those customs?

 

The girdle is a custom part, does not come with the rockers.

Kurt

 

Dang. I've looked around and I couldn't find LS bars or they just don't look as Porno Hot as those in the pictures.

 

Wow, yeah those are pretty beefy.

 

You have to have a huge money. max effort, big RPM setup to NEED solid roller.

 

Most rocker problems seem to be connected to losing control of the valvetrain. When boosted I believe your best bet is safe lobes with proper springs and the strongest pushrod you can get into your combo. Keep everything in control and add boost, the power and durability will be the fun part!

Kurt

 

I noticed that Mark is switching to a solid setup this year.

 

That was the plan all year, he is ready to step away from the street car stuff
ERL will be building his engine, and it should be a nice gain over what he was running!

Kurt

 

what would you consider "safe" lobes 427?

 

Did he decide on what size twins yet?

 

Mark has decided to stay with the single turbo after considering all his options.
The cam lobes are something you need to work out between your engine builder and the cam company. In a boosted engine the ability to move air is a given, control is really the thing that is sometimes comprimised with aggressive lobe designs that get the valve open quicker, even though guys are running big heavy valves and hardware that can put that type of lobe into a bad place.

Kurt