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The rocker shaft diameters are the same between the 901 rockers and the 993 hydraulic rockers. However, as Joe mentioned, the 901 rockers have two holes through to the bushing because in a non 993 cam tower the rocker shaft / bushing surface is lubricated via splash lubrication from the oil pipe in the cam tower. The 993 cam tower feeds pressurized oil through the rocker shaft into the rocker shaft / bushing surface AS WELL as pressurizing the lifter. If you simply install 901 rockers in a 993, you effectively create an oil leak in the pressure side of the oiling system as oil is pumped through the rocker shaft, around the bushing and OUT the splash lubrication hole. This may cause bottom end oiling issues in engines that rev high. The proper thing to do is to have the 901 rocker bushed to prevent the oil leak through the holes
...and reprogrammed the computer for 100 octane and a 7400RPM revlimit. Everything else is stock, down to the rod bolts (hope that doesn't bite me) with 57,000 miles and it laid down 315hp at the wheels.
What shop? Do they have repeated, satisfied customers?
After considering all the options I am going to have the stock rockers machined to accept the adjustable elephants foot. The reason I went this route instead of rebushing the early style was the weight savings and what appears to be a stronger rocker design. SCARGO has done this to one of the race cars and is has been through the test of time.
I agree with Steve that this route is not for all. The amount of work needed to adjust valves every 10k would frustrate most people. Given my goals and the layout of the car this is the best thing for me to do.
I will let you know how much it cost when I pick em up tommorrow. I will take pictures as well. I can't remember how they plugged the hole on the last set. IIRC it was a small BB.
Ok the conversion is done. The shop machined the nose down and plugged the oil hole with a small allen set screw. This rocker weighs 22 grams less than the early style does. The car now sounds like an early car. I love the extra mechanical noise.
Now here is the supprising thing. The before and after butt dyno says there was a performance increase. The motor seems much more responsive and pulls stronger to redline. I was very supprised to say the least.
The only disclaimer is that I also changed the plugs (same type and old ones were not to bad) and fixed a vacuum/boost leak on the IAT. I wish I did a more controlled test but hey while I was in there it seemed like a good time to fix these other things.
...and you're going to post a pic of the finished rocker, right?
Here is a side by side with the early style.
There are two versions of the 993 rocker. IIRC 2820 and 2850 are the stampings. The 2850's are thinner and appear to be made of harder material. I will have a hardness test done on all 3 versions to satisfy my own curosity.
Spoke to the guys at patrick motorsports. They said oil is no longer supplied to the valve tip like the hydraulic style. He said it should not be a problem because thats the way the factory has been doing it since the 2.7 days.
Old thread but I was looking for information about lubrication of the rockershafts and pumped into this.
What Marin writes above is actually not correct. Or it could've been at the time Marin posted it but currently PatrickMotorsports solid lifter conversion kit for 993 has rockers and shafts with oil journals.
i.e. not spray lubricated like on the 964s.
The Patrick kit has special rocker shafts with a reduced size for the oil hole to meter less oil to the rocker. This is because the solid rockers are designed for splash lubrication with large holes to capture oil from the cam lube spray bars. Solid rocker shafts thus have NO flow to them at all, thus do not need a lot of flow when pressure lubricating them as well - the extra will just be bled out the big "capture" holes in the rockers anyway filling the cam housing with oil.
Another thing is that the RS cams don't have the lobe ramps ground correctly for solid use - they work OK I understand though. If one wants to do it right then use a cam ground for solids like a 964 C2 grind or some after market grind for solid rockers.
Making this simple, there are two options: 1) Have mechanical adjusters added to 993 rockers, or 2) re-bush the pre-993 style rockers to eliminate the splash lubrication hole in the bushing. I did the latter (through John Dougherty) for my 9M build.
The photos are courtesy of Patrick Motorsports. I posed the question to them yesterday.
I think there is a third option; use 901 rockers with modfied 993 shafts that have smaller oil passages (ala Patrick Motorsport or similar).
I wonder how the GT2EVO rocker shafts are....? I know the shafts have motorsport part#, so most likely they have smaller oil passages. Also the EVO spray bar has motorsport part #.
...I wonder how the GT2EVO rocker shafts are....? I know the shafts have motorsport part#, so most likely they have smaller oil passages. Also the EVO spray bar has motorsport part #.
I noticed that too, I wonder if the holes in the spray bar are larger than 993?
Old one - Not exactly the same but some of the info applies - I'd like to use 993 cam housings on a 964 - get the benefit of direct rocker oiling, less places to leak and then also retro solid rockers. I've been reading a few different threads and this one does have some good tidbits - but is there a complete list to accomplish what I'm after?
So far:
993 housings
check me on this one - Rebushed 964 rockers (not sure how important it actually is to block off the splash holes considering the next item)
993 shafts with reduced orifice
So what now about the spray bars? Also is there anything extra needed to route oil to the passages that feed the rockers through the housing?
Google a pic of a 993 cam. There is an oiling grooved machined into first journal on the cam. oiling to the other journals goes through this oiling path.
I use the 993 rocker shafts without any modification to the hole size. Race motor with 80+ hours no issues. I had a groove machined in the center of the rocker bushing so pressurized oil goes all the way around.
I think the 993 cam boxes (which I have) have larger oiling passages due to feeding all the rockers.
I did have issues on one or two intake valves where the rocker foot became dry. Maybe less oil splattering with the more compartmentalized valve covers. To solve this I drilled a small hole in the normal oiling hole in the intake rockers to squirt more oil in the upper part of cam tower. Solved the problem.
I'm also running gt3 oil pump that puts out a lot of oil... took quick look at some data and 155F oil temp, at 1k rpm around 40psi oil press, and at 4k 80 psi
10-27-2009, 08:40 PM
