Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 Engine Rebuilding Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Jul 2000
Location: So. Calif.
Posts: 18,301
Hot rodding rocker arms

Reducing weight from the valve train is an objective to help prevent the dreaded valve-to-piston kiss of death. People use ti valve retainers and valves and such to reduce the weight.

Has anyone ever gone through the anal-exercise of lightening the rocker arms? If so, any success stories (i.e. engine is still running) and/or verified areas to grind/not touch besides the "obvious" structural areas? Is there a desired weight to achieve? The classic books show how it's done on a Holden or Austin (or whatever). Any real-life 911 experience?

Some company/person awhile back was selling rebuilt rockers that were also lightened, surface smoothed, polished and shot peened. I realize the end result may be equivalent to polishing the valve covers, but I'm hoping for something a little better than that.

Thanks,
Sherwood
Old 09-05-2005, 02:19 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
HawgRyder's Avatar
 
Join Date: Feb 2002
Location: Langley, BC Canada
Posts: 2,865
Garage
Send a message via ICQ to HawgRyder
Lightening the arms will not give the same effect as the rest of the valve train.
Think of them as pivoting on the pin, and measure the distance from the center of the pin to the far end on each side.
The amount of metal actually moving is quite small.
You would get a better affect by removing the same amount of metal from the valve itself, because it moves further and has a larger push therefore on the valve spring.
Hollow valves or superlight ones will increase the valve float speed.
All this may be a moot point because you will be exceeding the piston speed allowed for the type and material used in the pistons themselves.
You will also need to address the oiling for all the bearings in the engine, because at higher speeds, the bearings will shed more pressure.
If you still want to explore these options....look at the latest technology in formula one and other high speed, long duration engines.
Good luck.
Bob
__________________
Bob Hutson
Old 09-05-2005, 02:56 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Jul 2000
Location: So. Calif.
Posts: 18,301
Hi Bob,
Thanks for your response.

Granted, the rocker arm mass is not hung out on the ends like the valve spring and valve, yet this unit does add to the inertial forces as it accelerates and decelerates at 1/2 engine speed, especially with more agressive cam timing. I'm not thinking of F1 revs to 18.5K and beyond; rather some extra insurance for those hopefully rare excusions beyond 7500 due to a limp shifting arm or acts of ever-increasing brainfade.

I've got a set of ti retainers ready to install. Not ready to replace w/ti valves just yet. The year-specific set of sodium-filled exhaust valves Porsche saw fit to install in my '69S heads will do for the time being, thanks.

I'm a cyclist too, so the thought of gram reduction permeates my cycling loins.

BTW, got any info on F1 pneumatic valve trains? (Just interested; not related to any of my mechanicals).

Sherwood
Old 09-05-2005, 03:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Still Doin Time
 
asphaltgambler's Avatar
 
Join Date: Nov 2004
Location: Nokesville, Va.
Posts: 5,442
I think there may be material that could be removed but I doubt the actual amount would make any real difference.

Unless you are building a high RPM engine (like 8K plus) lightened valve train other than the titanium retainers is a waste. Porsche guys are no dummies.
__________________
'07 Jeep SRT-8 - Hauls groceries and Hauls *ss
'85 Guards Red Targa - F@#king Money Pit
'95 Road King w/117ci - No time to ride, see above
'77 Sportster Pro-Street Drag Bike w/93ci - Sold to collector
'72 Yamaha CS5 200 Twin - Sold to fellow Pelicanite
Old 09-05-2005, 04:27 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
camgrinder's Avatar
 
Join Date: Feb 2004
Location: California
Posts: 921
I have seen a few modified rocker arms. Mostly lightened slightly, and / or polished. So far I havent seen anything cost effective that makes a big improvement.
The factory rocker arm with the right camshaft profile and associated valvetrain is good for 8000 rpms with 52.5 mm Titanium valves.
__________________
John Dougherty
Dougherty Racing Cams
Old 09-05-2005, 05:12 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
HawgRyder's Avatar
 
Join Date: Feb 2002
Location: Langley, BC Canada
Posts: 2,865
Garage
Send a message via ICQ to HawgRyder
You might also investigate titanium rockers....as strong or stronger than stock and about 1/3 the weight.
You know the old saying...."speed costs money...how fast do you want to go?" .....LOL
Bob
__________________
Bob Hutson
Old 09-05-2005, 05:14 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
Registered User
 
Join Date: Jul 2000
Location: So. Calif.
Posts: 18,301
Were it not for the fact the factory rocker arms are the designed weak link in case of a valve-kiss-w/piston scenario (the rocker will usually break first), we'd probably see more improvements in this area (forged aluminum/ti, roller bearings, roller tips, etc.). A titanium rocker would be the last thing to yield in case of a valve crash.

However, most engines are of the interference type and many have little reservation using state of the art materials in the valve train. Maybe I'm reading too many domestic hot rod catalogs where replacement pieces are a fraction of the cost of the equivalent ones from Stuttgart.

It's been many years since imports first equipped their 4 cyl., DOHC, cross-flow engines with low-friction rockers with roller-tipped ends. There are potential gains to be made in reducing frictional losses in this area, but we'd prefer to have that margin of error in case of a 9000 rpm mis-shift.

Sherwood
Old 09-05-2005, 09:10 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
Quote:
Originally posted by camgrinder
The factory rocker arm with the right camshaft profile and associated valvetrain is good for 8000 rpms with 52.5 mm Titanium valves.
John, I assume you're referring to the regular factory ones here, not the racing shim type forged ones?

Cheers,
__________________
Andy
Old 09-05-2005, 11:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
camgrinder's Avatar
 
Join Date: Feb 2004
Location: California
Posts: 921
Andy,
Yes I am talking about the regular ones.
__________________
John Dougherty
Dougherty Racing Cams
Old 09-06-2005, 08:51 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
Porsche Crest

The forged "racing shim type" rockers look like they are lighter (I was gazing at the lineup of rockers in Wayne's book). Anyone know if this is so? Changing those cup shims (which look a lot like the "valve savers" you could use with VWs when the tip of the valve stem got messed up) is a real pain (you have to compress the valve spring some), but with the 993 style rocker shafts it would be a relative breeze. Does someone sell a racing rocker?

How would titanium hold up on the cam?

The Major (I'm blanking on his name, but he retired from messing around with Porsches to raise horses or some such) is the guy who magnafluxed, polished, and shot peened rockers so you could be fairly sure they wouldn't break all of their own accord. They sure have a rough finish, but all this was kind of expensive.

Me, I sort of favor old rockers from my race engines - if they had cracks I figure they'd have broken by now. But lightening them out toward either end where the polar moment is at work would be attractive. There are guys running 9,000 rpm 911 race engines out there - that's how you get your power to displacement ratio up without forced induction.

Walt Fricke
Old 09-06-2005, 09:28 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
camgrinder's Avatar
 
Join Date: Feb 2004
Location: California
Posts: 921
Walt,
The guys name is Dopke, I dont remember his first name.

I know CMW is converting 993 rocker arms over to solids, and then using a lash cap. Again they are kind of expensive.
__________________
John Dougherty
Dougherty Racing Cams
Old 09-06-2005, 10:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
Right - Clay Dopke.

Everything in racing is expensive.

Walt Fricke
Old 09-06-2005, 10:17 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
 
Registered User
 
KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
Porsche Crest

Quote:
Originally posted by camgrinder
Andy,
Yes I am talking about the regular ones.
Thanks, John.

Quote:
Originally posted by Walt Fricke
The forged "racing shim type" rockers look like they are lighter (I was gazing at the lineup of rockers in Wayne's book). Anyone know if this is so? Changing those cup shims (which look a lot like the "valve savers" you could use with VWs when the tip of the valve stem got messed up) is a real pain (you have to compress the valve spring some), but with the 993 style rocker shafts it would be a relative breeze. Does someone sell a racing rocker?
Walt,

I know you were following this thread, but Bill V. posted a picture of the 993RSR shim type rockers there. I do not know if these are the same part as the older shim type rockers (e.g. 3.0RSR), but they do look similar. Until John mentioned the CMW conversion of 993 rockers, I was not aware of any other source of shim type rockers than the factory.

964 heads on 911 3,2?

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? the 3rd post has some other interesting info:

C2 3.6 vs 993 3.6

Bill also said somewhere that the 993 hydraulic rockers were lighter than the regular rockers but not as light as the shim type rockers. I doubt that CMW can shave much weight off of the 993 rockers by converting them to solid, but what do I know. I bet the real solid rockers would be lighter and stronger than converted 993. Maybe more unobtainable, too!
__________________
Andy
Old 09-06-2005, 11:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Mar 2003
Location: Oklahoma
Posts: 2,373
If I thought there was something to be gained in the rocker area I would have done it.........The CMW stuff is very expensive and they did not recommend it to me even though I have a very extreme engine.

Eric Hood
Old 09-06-2005, 11:27 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered User
 
KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
Quote:
Originally posted by strokher racing
I have a very extreme engine.
what is your redline? and what rockers are you using?
__________________
Andy
Old 09-06-2005, 11:47 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Registered User
 
Join Date: Mar 2003
Location: Oklahoma
Posts: 2,373
stock 91 turbo rockers with a custom grind from John. I have lightweight ss valves and titanium retainers and locks. When I said extreme I meant over 30 pounds of boost. Going to shift around 7800rpm.

Eric
Old 09-06-2005, 11:52 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Registered User
 
KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
Thanks for the response. by locks do you mean keepers? those won't be Ti, will they? what compression ratio, off topic but I'm curious?

Cheers,
__________________
Andy
Old 09-07-2005, 12:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Registered User
 
Join Date: Mar 2003
Location: Oklahoma
Posts: 2,373
Yes locks and keepers are the same thing. You can get them in titanium as well. Compression is just under 8 to 1.
Old 09-07-2005, 12:36 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
Registered User
 
Join Date: Oct 2003
Location: Cincinnati, Ohio
Posts: 76
We have been working on rocker arms for the last year, see attached photos.

It is our experience that RPM is really not the limiting factory in the factory rocker arms, but that the rocker arms are the limiting factor in the amount of lift you can run. As you see we have built rocker arms with needle bearings, out of a space age alloy and a forged arm. Each has it's own limitations are are currently testing (on the dyno) one of the designs.

The comment about the oiling is very true, and we extensively modify the oiling circuit when we run above 8K. We also have gone to great extremes to match all of the valve train (valves, springs, retainers, etc.) It is very important to have all parts working with each other and not against each other.

This being said, remeber when you make one change, you MUST check everthing else to make sure you did not create a problem elsewhere.

__________________
Forry Hargitt
TD Performance
Cincinnati, Ohio
forryh@tdperf.com
http://www.tdperf
Old 09-07-2005, 05:52 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)
Registered User
 
ChrisBennet's Avatar
 
Join Date: Aug 2001
Location: Nashua, NH USA
Posts: 8,089
Quote:
Originally posted by camgrinder
Walt,
The guys name is Dopke, I dont remember his first name.

I know CMW is converting 993 rocker arms over to solids, and then using a lash cap. Again they are kind of expensive.
Clay Dopke (Dopke Design) used to sell those polished X-rayed (?) rocker arms. I bought my Ti valve spring retainers from him years ago.
-Chris
__________________
'80 911 Nogaro blue Phoenix!
'07 BMW 328i Coupe
http://members.rennlist.org/messinwith911s/
Old 09-07-2005, 06:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 01:12 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.