Rockers and other thoughts
 

I was digging thru my stash of rockers and though it would be interesting to weigh some different types and see how much difference their was in weight.

First up is standard cast Porsche factory rockers. I weighed a couple and they were 132-134grams.

http://forums.pelicanparts.com/uploa...1611023985.jpg

next up aftermarket cast rocker. These were quite a bit heavier at 142grams.

http://forums.pelicanparts.com/uploa...1611024098.jpg

Next a early forged rocker with screw adjuster. These are lighter at 122grams.

http://forums.pelicanparts.com/uploa...1611024229.jpg

The lightest rockers I have are 993 forged rocker modified to use standard screw adjuster. These are only 110 grams.

http://forums.pelicanparts.com/uploa...1611024411.jpg

The adjusters weigh 14grams.

http://forums.pelicanparts.com/uploa...1611025078.jpg

Pauter says their rockers weigh 85grams and I believe that includes the adjuster.

So if you can get more rpm with less spring weight with lighter components how much does the weight effect this. Many people go with titanium retainer to save weight. The information I found says stock retainers are 19.4 grams and titanium is 11 grams. I could save more than that with a rocker change.
The 993 used 8mm stems instead of 9mm and those should be less weight as well. I would imagine that if you used lighter valves, retainers and rockers you might be able to use stock spring weights and still have a good safety margin for higher RPM's.

John

We’ve gone a bit nuts w my build on modern rotating assemblies:
Gt3 ti rods save 220g each
Custom cp pistons (i don’t have weight handy)
Custom dlc coated pins, hollow and light
Pauter rockers
Xtreme worked heads with ti bits

The total is several pounds of rotating weight saved. Lots in the valve train.

You could save even more weight by going to a modern beehive valve spring and retainer.

Beehive springs are around 40-45gms and the matching steel retainers are 8gms.

Forgot to post this pic. One down side of 993 is the pad is slightly smaller than earlier rockers. pad length in inches on rocker face,

http://forums.pelicanparts.com/uploa...1611115481.jpg

john

Dan
I've been interested in beehive springs since I first read about them in Circle Track (RIP) years ago. The assertion is that they don't need a two spring system to deal with harmonics and other nasty effects found in a single cylindrical spring, and of course the retainer can weigh less.

Do you know of any successful application of these to an air cooled 911? Custom retainers, maybe?

Why didn't you go with actual Xtreme heads?

We found that bushing friction in the rockers in a huge issue. We have developed a bushing that reduces that friction greatly. Less friction=less drag=less heat.
The next big step to reducing parasitic loss is to convert to single row chains and straight cut gears. At that point things start to get serious.

http://forums.pelicanparts.com/uploa...1611148513.jpg

I'm putting together a 930 engine right now that will have beehives and tiny retainers. I'm working with one of my usual circle track valve spring vendors and it turns out they have an off the shelf spring that will work. And as you said, the harmonics issue is practically eliminated with beehives, and the seat and open pressures, even for race applications, fit quite nicely with what Neil recommends. I'll keep you posted.

I purchased a bunch of used rockers, and amongst them was one un-bushed rocker. The shafts fitted it as they did the bushed rockers. What application might it have come from?

unbushed rocker
 

Around 1968 they used unbushed rockers but the shafts had a black nitrate finish.Galling was an issue over time.Fred

These very early unbushed rockers are actually very high quality cast iron.
We bore them and install bushings to make a high quality rebuilt rocker.

During the process we remove the old bushing (if there is one) and adjuster.
Bore/Ream the bushing hole
Black Oxide the rocker
Press in the new DP-4 bushing and burnish
Surface the contact pad
Coat the contact pad with Moly dry film (TLML 2)
Drill the bushing oiling holes
Treat the rocker to a Cryogenic conversion process
Clean adjuster threads with 8x1.0 forming tap.

http://forums.pelicanparts.com/uploa...1611156744.jpg

2x cost. Mainly. Discussed this with a few big power 993/964 builders (400+Hp) and feedback was positive but difference in fully worked head vs their head wasn’t worth the 2x cost to me. I want to say 10hp at the top on a big 964 build but please don’t quote me.

Shop has some of their heads for a few build they are doing they are very nicely made. But so is his rework stuff.

I am sure I get some extra power out the Xtreme heads on my race engine....but the main reason for getting the Xtreme heads was so I had heads that would not crack after 40 hours. I figured I was saving me money in the long run.

Oh I’m sure you do get more power. Interesting on cracking and likely a good roi there... this is a street car... it’ll be flogged hard but nothing like my track cars are (i don’t race just occasional de now...)

I've heard from others that 3.6 heads are good for 30-40 race hours on big hp engines. Not sure it's the case for earlier heads. And probably less likely on an engine that sees mostly street use.

For Cup car engines, Porsche has rebuild/replace hour standards. My understanding is that, at least for the 996 Cups, among other things the heads are replaced at that interval.

I think the typical air cooled race engine, normally aspirated, has valve seats dealt with, and valve guides, when it looks like this is needed when the engine is apart to replace bearings or for other work. At least for typical PCA amateur use, DE or CR (not talking 24 hour races). Anyone have a rule of thumb on this? Lots of late 60s/and 70s heads being used on track. Mine have never cracked - but then I have yet to reach 110 FWHP/liter, either.

What’s the cost of the Pauter rockers?

Pauter rockers are about $2500 a set plus the swivel feet as they are not included and of course you would probably want new shafts and bolts.

john

What years were the early forged rockers used? Part number?

Thanks

David

Well, abort the mission here to avoid any engineer stuff.

Mass on rocker arms is more detrimental the further from the center that it is. The characteristic that affects revability is moment of inertia. If the geometry of the parts is the same, you can use mass and moment of inertia interchangeably, otherwise you can’t.

Friction affects the power consumed by the rocker. It does not affect the rev limit directly, but since power consumption is proportional to rpm, you obviously want a low friction rocker for higher revs.