OEM vs HD rockers with Schrick 284/272 Cam

[zaq123]

Even though they "look" good, they need to be refinished for a new cam (and technically if you change them from lobe to lobe).

It's hard to capture since so little is being taken off. Tried using some layout dye but the coolant in the machine washed it off the pad for the most part.

Used rocker (m30, but same concept):



One brush on the grinding wheel:


Second pass:


And the Souix machine:

Have you checked the cam/rocker pad wear pattern after these regrinds have been ran for a little while?
The reason I asked: in your setup, it looks like the grinding wheel applies side pressure on the rocker pad during regrind. Since there is a clearance between the rocker bushing and the shaft, the grinding wheel would sideload the pad and won't grind it true, side to side. It looks like your are using conical support (both sides of the bushing?) which will help a lot for this but i thing it's still not ideal IMHO

Is there a way you can rig the setup so it grind the pad front to back (using the edge of the grinding wheel vs its side)? Basically keep the grinding wheel axis and the rocker bushing axis on the same plane.Than would probably help to keep the grind true across the entire pad surface.

[ForcedFirebird]

Have you checked the cam/rocker pad wear pattern after these regrinds have been ran for a little while?
The reason I asked: in your setup, it looks like the grinding wheel applies side pressure on the rocker pad during regrind. Since there is a clearance between the rocker bushing and the shaft, the grinding wheel would sideload the pad and won't grind it true, side to side. It looks like your are using conical support (both sides of the bushing?) which will help a lot for this but i thing it's still not ideal IMHO

Is there a way you can rig the setup so it grind the pad front to back (using the edge of the grinding wheel vs its side)? Basically keep the grinding wheel axis and the rocker bushing axis on the same plane.Than would probably help to keep the grind true across the entire pad surface.

Of course. I had all the major critical components on the machine trued up/ground etc that couldn't be done on my surface grinder. They are located between center cones and the fixture rides on a 1.5" way shaft. There's a diamond dresser also attached to the way, so when you dress the stone it's exactly 90° to way since it sweeps across the grinding wheel. Then the 90° fixture is attached to the way. Next you locate the pivot of the swing arm over the rocker pad radius center and lock the allen bolt in place. Then the rocker is swept across the grinding wheel, much in the same manner the valve faces are done on the other side of the machine. Since the stone is spinning and you are running the part across the stone, it will be flat and true unless your stone is horribly out of dressing. If you measure radial play with a rocker on a shaft, it's far worse than my machine with the cones.

[ForcedFirebird]

Here is a good read about how these rocker refacing jigs work, and how to make sure the machine is square:

https://bbs.homeshopmachinist.net/forum/general/47856-rocker-arm-attachment#post961060

The rocker shaft is a .002" slip fit, so in reality the rockers are "rocking" during use - that's why in my pics you can see the edge of the pad still didn't grind. The cam is ground so that it pushes forward to use the front thrust plate, the rockers will wear accordingly, and usually more on once side than the other. Just like flat tappet push rod engines, the cam contact area needs to be refinished when installing a new cam since they wear together during break in.

[RobE30]

When I put my engine together years ago 284/272 cam), I just reused the stock rockers. Its been about 14 years or so and still working but thinking back, I wish I would've spent the extra money. I think I've been damn lucky

[ForcedFirebird]

When I put my engine together years ago 284/272 cam), I just reused the stock rockers. Its been about 14 years or so and still working but thinking back, I wish I would've spent the extra money. I think I've been damn lucky

Most of the time it will work, but you are excessively wearing the surfaces during break in and run the risk of wiping a cam lobe (I have seen this a handful of times on m20's), so you end up with less lift - however minute, it's still a loss of power.

The rockers in our endurance car have been reconditions many times and are still ticking at a 7100 red line in racing conditions (we typically shift at 6800 in most cases). In the 7-8 years we have been campaigning this car we have only lost ONE rocker arm, and that was a NOS batch of the HD rockers that had the pad issue. I had them in a box for years and used them on the car, second race the pad came off and got pounded straight through the water jacket under the cam. The only other time was in a car we support (also an e30 with m20). Against my advice, not only were they taking the engine to 7100 every shift during that session, data showed an over-rev to 7400 on a rev match down shift. I drilled a hole in the firewall since it was #2 intake and shoved the rocker shaft into the car and replaced it (also a HD rocker, but it snapped at the eccentric end).

[nando]

I used to bang my car on the limiter at 7500 all the time. lol.

[E30-TourZing]

Thank you everyone for your responses.

I decided to buy a HD set from Bimmerheads, and inevitably spent a bunch more money there to while I was at it.... I am assembling my 3.0L right now, and it will be reassuring to have new and stronger rockers to help out when the RPM's get above 7200.

[zaq123]

Thank you everyone for your responses. I decided to buy a HD set from Bimmerheads, and inevitably spent a bunch more money there to while I was at it.... I am assembling my 3.0L right now, and it will be reassuring to have new and stronger rockers to help out when the RPM's get above 7200.

Make sure you check P to V clearances well. HD rockers give you more lift that what stock rockers do so the clearance will be less than what you expect to see from just a cam spec. Sent from my iPhone using Tapatalk

[dstevenson]

With a stock bottom end the only cam upgrade I trust is a 272/272. As far as heavy duty rocker arms go? All of the ones you find (especially from Ireland BMW) are complete shit. I speak from experience. If you are not racing the car and constantly hitting the rev limiter the stock rockers should be fine. The OEM valve springs are already a performance design with one spring inside the other (double springs). The more aggressive the cam is, the more stress on the rockers.

[ForcedFirebird]

With a stock bottom end the only cam upgrade I trust is a 272/272. As far as heavy duty rocker arms go? All of the ones you find (especially from Ireland BMW) are complete shit. I speak from experience. If you are not racing the car and constantly hitting the rev limiter the stock rockers should be fine. The OEM valve springs are already a performance design with one spring inside the other (double springs). The more aggressive the cam is, the more stress on the rockers.

To the defense of IE, I also have been racing these m20's for some years. Particularly endurance racing.

Several years ago we had an issue with rocker pads snapping off, but that hasn't happened to us since 2016.