Hot off the machining centre, here are the shots of the new CNC machined 9m/4T 911 cam follower before we send them away to be DLC coated. This is the first finished part for the new high lift valve train design that will allow us to run 15mm of lift with road or race cams, other parts on the way soon are matching race cams, some rather special valve springs and obviously spring retainers, platforms, collets and 8mm stem valves.

The photo shows the 9m follower alongside the early 993RSR adjustable version, aspects to note are the longer pad length to cope with the increased lift, better pad support and lighter weight at 87g against the motorsport rocker at 90g. The price estimate for the production version is in the order of £200 per unit, they run with the stock 911 elephant's foot adjuster and (with the 9m cam/valve/spring package) have a safe rpm design limit of 8500rpm.

 

Where does the weight reduction come from? At first glance it looks beefier. Also, I'm assuming it's a solid lifter design, correct?

 

Ooooh, very nice. Is the rocker bushed or not? One of the issues I found with the 993 cam towers and the older 911 style rockers is that the variance of the width of the rocker where the shaft goes through was not consistent. I had to machine most of my rockers so they fit in the cam towner. Will these fit in the 993 cam towers without modification?

 

Awesome! Nice job. Should be on everyone's Christmas list.

 

Very nice. Has anyone ever made a roller rocker for the 993?

 

The 9m rocker is CNC machined from solid bar stock, the weight reduction is in the detail of controlling the section thicknesses during the machining process. It is an adjustable design, not solid, as mentioned you use the stock 964 & earlier elephants foot adjuster. We have made double pad rockers that adjust with lash caps on the valves but we do not consider these to be acceptable for use in a road going engine, hence this design which still achieves our rpm requirements.

 

I hd the same problem but came to a different solution. If you look carefully at the 993 cam tower you will probably find that there is a clamping burr on one side of the shaft mounting face, this burr intrudes into the gap between the towers and causes the tight fit on the 964 rockers. I removed the burr with a file and all the followers fitted correctly. The 9m follower has been based on the 993 Porsche Motorsport rocker so will definitely be a direct fit in all our engines with 993 towers.
The bore of these prototype followers is not bushed, we know about the issue of wear associated with the non-bushed 993 rockers which is one of the reasons for having the 9m followers tribo-finished and then DLC coated, the other to eliminate wear on the pad which hard-faced or chromed followers suffer from.

 

There is just not enough space to fit a roller rocker on the SOHC 911 engine, besides which the roller design would add to the overall weight and reduce the rpm limit of the engine. Beyond using the stock cam tower, if there is demand for a better valve train for the aircooled engine than our current design we would redesign the tower to use twin overhead cams with bucket followers acting directly onto the top of the valves. We already have a design layout sketched for this configuration but it would be a £50k project to bring it to metal so it's not one that is going to happen in the next few months for sure.

 

Thanks for the info. The twin cam design would be nice, too bad I'm about £50K short.

 

Colin,
DOHC + 4 valve as well ?? Then you could get rid of that old hemi chamber and come right up to date !
Porsche did a lot of stuff on 4 valve for the 964 but that was one feature that didnt make it into production.
Maybe a 959 replica adjusted for 3.6 ??

All the best

Geoff