roller rocker arm for the 911

William Jones · 05-06-2003, 05:05 AM

I have been informed that Lasiter Racing Engines (678) 479-6473 has developed a roller rocker arm for the Porsche 911. These rocker arms are supposed to "free up" about 15 to 20 hp on a stock 911 engine. This sounds like a development whose time has finally come. High performance V-8 engines have had roller rocker systems for years.
He says that a roller cam profile is currently being tested. Is there an advantage in using the roller rocker/cam package for the 911?

Zendalar · 05-06-2003, 05:15 AM

The amount of HP sounds too optimistic

I thought the oil film between the rocker arm and camshaft is enough to make the friction low.

I don't know so much about these, but sounds like it has 2 more moving/wearing parts than normal rocker arm.

William Jones · 05-06-2003, 05:47 AM

Based on a quick survey of roller rocker products on the market - they all look more complex than the non-roller design. I questioned the hp gains myself. The published information on similar products seem to indicate that they (roller rocker/cam) may be worth the money.

doug petty · 05-06-2003, 05:57 AM

I WAS TOLD ONCE THAT ROLLER BEARING ROCKERS DON'T LIVE LONG SINCE NEEDLES ARE DESIGNED TO GO ROUND & ROUND.
THE SHAFTS GET PITTED FROM ONLY TRAVELING ABOUT 50 DEGREES, THATS WHY MANUFACTURERS THAT ARE CONCERNED ABOUT QUALITY USE BUSHINGS.

makaio · 05-06-2003, 06:34 AM

How would you adjust valve lash?

I'm thinking these are for the water boiling 996 motor, not the air cooled motors?

William Jones · 05-06-2003, 06:41 AM

All NSCAR teams use roller rocker arm packages. They indicate these systems use less inertia and friction which results in more torque and horsepower. These cars run 9,000 rpm for approximately 500 miles. I think the rocker arm durability issue has been solved.

William Jones · 05-06-2003, 06:51 AM

Valve lash is adjusted in the same manner as a stock 911.

brokke · 05-06-2003, 06:54 AM

Most likely the roller of the 911 design is on the camshaft side. This makes it possible (and necessary) to use a more agressive camshaft. Similar to a roller follower design in a engine with a central camshaft.

Peter
911 2.4S

TimT · 05-06-2003, 07:37 AM

Ill be a test mule for the roller rockers. pm me and ill give you shipping info....

911pcars · 05-06-2003, 11:54 AM

The valve train is a major source of engine friction which takes HP to overcome. Reducing HP requirements in this area can only be good. Lightweight rocker arms also reduce valve train weight to help prevent high speed valve float. I'd be interested to see what they have.

However, a big "plus" with the factory rocker is the "built-in" safety margin. If a valve happens to kiss a piston in an over-rev situation, the rocker arm will break and absorb most of the valve train trauma since it is made of cast iron (cast steel?). Most aftermarket rockers are made from billet or forged steel or aluminum which are so strong they won't break - so something else does. But then again, with a lightweight valve train, an over-rev, kiss-of-death may not happen as readily.

Keep us up-to-date. Thanks.

Sherwood Lee
http://members.rennlist.org/911pcars

RoninLB · 05-06-2003, 12:15 PM

It would make sense to me if I wanted an agressive cam ramp.. otherwise, I don't have a cam wear or rocker foot problem.. and I don't hang above 7k rpms.........Ron

William Jones · 05-06-2003, 12:26 PM

Wayne's book seems to indicate that the "safety margin" you mentioned is somewhat diminished by the fact the piston would now hit the valve at an angle. I plan on installing them later this week and test them out over the weekend. They tell me the "roller cam" is coming! I can't wait!

911pcars · 05-06-2003, 12:32 PM

[b/"Wayne's book seems to indicate that the "safety margin" you mentioned is somewhat diminished by the fact the piston would now hit the valve at an angle.[/b]

Why now? How has the valve-to-piston collision angle changed?

Sherwood

William Jones · 05-06-2003, 12:41 PM

I don't have the book in front of me right now, but I thought he said the initial design changed - the valves are now placed in the head at a greater angle. I will confirm this information with the proper citation.

JWest · 05-06-2003, 12:59 PM

Quote:

the valves are now placed in the head at a greater angle

Sounds like it not an affordable solution if that is true.

Roller rockers are popular on American iron because you can buy a set for $150 to $300.

What you are talking about must be in the thousands if valve angles are altered.

carter_gordon · 05-06-2003, 04:06 PM

Just my .02, I think that a big plus of roller rockers is not just the friction reduction, it allows you to run a more aggressave cam lobe. If this is the case I think 15-20 HP is resonable. I have tons of SB Chevy friends that run them, and have not heard of issues with reliability.

Bud Gordon

Lukesportsman · 05-06-2003, 06:43 PM

There are some OEM engines running roller rockers, so durability doesn't seem to be an issue anymore. The Mustang Cobras, before OHC, used them from factory. I've ran them for many years without failure.

HawgRyder · HawgRyder's Garage

Do the new roller rockers have needle bearings at the pivot point and a smaller roller at the valve tip end?
If they do...then OK...but if they still exert side pressure on the valve tip..then no real gain for the buck.
Bob

makaio · 05-06-2003, 08:11 PM

So lets see some pics and prices already.

911pcars · 05-06-2003, 11:25 PM

"There are some OEM engines running roller rockers....

There are quite a few not-too-special Euro/Japanese econo-boxes using roller bearing-tipped rocker arms to reduce a little bit of friction here and there. Many use twin-cam, four-valve, cross-flow heads. What's the rev limit of an S2000 Honda - 9000 rpm?

Sherwood Lee
http://members.rennlist.org/911pcars