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KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
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Forry,

Cool rockers! They look very light. I take it they have different geometry from original rockers to allow the larger lift (?)

Cheers,
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Andy
Old 09-07-2005, 10:56 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
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Nice project.

I see a couple of rocker designs there. One looks to be aluminum with a hardened insert on one rubbing end. The other one is nice too. Is the ratio different from the factory version or do these provide more lobe contact with increased lift?

Sherwood
Old 09-07-2005, 11:20 AM
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Quote:
[
On another thread, Bill Verburg also posted the weights for the 993 hydraulic rockers, 15g intake and 21g exhaust. How does this compare to the rockers we know and love?
I just happen to have 28 911 style rocker arms lying around, mostly awaiting me sending them off to have the faces reground.

A set of 12 from a 3.2 with a "B" cast into them and without the hardware, weighed between 129 and 132 grams, with one at 135.

The other 16 from who knows what engines (probably from the 2.2-2.7 era) weighed between 123 and 128, with one at 130, one at 119, and one at 116. Most of these had the delta symbol cast into them, but a couple had no marking at all.

I weighed a selection of adjusters and nuts. The assemblies came in at 13-14 grams, with the screw part at 10-11, and nuts at 2-3. A loose elephant foot or two also weighed in at 2 grams.

This is on an inexpensive digital scale which reads to one gram. I don't know its absolute accuracy or how it rounds (and don't care - I bought it so I could get a replacement piston down to the weight of its five older brothers with my die grinder and it is certain to give results within a gram or two of what it says something else weighs), but this should give a pretty good idea of what we are dealing with.

Weight did not seem to vary depending on anything that I could see, though I did not take the time to measure the side to side distance where wear (other than on the cam face) might occur. Teardropping (or whatever it is called) or the lack thereof on the oil holes in the bushings didn't corellate with weight either.

I can see a new tweak: weight match your rockers.

Bill got the weights he gives from a book. Either the 993 rockers are made from some enormously light but strong material, and not much at that, or the book editors got a decimal place wrong. A better guess might be that the weights are for the adjuster part, not the rocker itself.

Walt Fricke
Old 09-08-2005, 10:56 AM
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Quote:
Originally posted by Walt Fricke
Bill got the weights he gives from a book. Either the 993 rockers are made from some enormously light but strong material, and not much at that, or the book editors got a decimal place wrong. A better guess might be that the weights are for the adjuster part, not the rocker itself.
I made the mistake and misquoted Bill. His post said that the 993 rockers were 15g and 21g lighter than the 964. I apologize. Here is the entire post for reference:

Quote:
Originally posted by Bill Verburg
M64 05/06 ('94 993)

Advantages (compared to 964)
  • more rigid crankshaft, also heavier @ 15.4kg vs 14.4 for 964 M64 01
  • no crankshaft torsional damper to deal w/
  • cod rods are 520g vs 602g in 964 (mine actually measured out at 496.4 - 497.6 w/o rod bolts)
  • pistons weigh 602g vs 657g for 964
  • hyd rockers 15g I and 21g E lighter than 964
  • intake ports are 43mm vs 41.5 for 964
  • each valve is sodium cooled and 10g ea. lighter than 964
  • spring retainers are 10g ea lighter than 964
  • the entire rotating assembly is 800g lighter than 964
  • valve lift is 0.10mm greater due to hyd lifters zero lash
  • hot film MAF vs 964 flapper box
  • 3 into 1 exhaust headers
  • tuned for 98 rather than 95 octane
  • whole engine weighs 6kg lass than 964

The OBD1 euro vrams are better, and the 993RS much better
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Andy
Old 09-08-2005, 02:03 PM
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Walt, are you building a 66x95 motor? what cams are you planning to use and what max engine speed are you shooting for (shifting foibles excepted)?
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Andy
Old 09-08-2005, 02:07 PM
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Ah - I had access to Bill's original post too and could have figured that out.

Doesn't look like being 15g lighter is apt to mean much, given the variation I found. And we don't know where the weight came from - out at the ends where it counts most, or closer to the neutral axis.

The part not yet answered, I guess, is what do 964 rockers weigh? They kind of look like the earlier kind.

Walt
Old 09-08-2005, 02:11 PM
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