Will these rocker arms will do ???

[Vagos]

Hi I started today some upgrades on the 2.7 strocker on is to replace the stock rocker arms.been reading about the rocker arms with push rods in here quite a while and it seems that there is the problem of spitting the push rods on higher rpms.I got one set of the german ebay for cih engine but meaning to ask if it the same type of rocker that is cuasing the problem as some pics of rockers i have seen dont have those ears around the surface that touches the valve.Here is a pic of them.Will i still have issues with them?Shall i install them or not?Also despite they are made from aluminium thay seem heavier than the stock ones.

[RallyBob]

Those look like the CatCams (made by Crane Cams) roller rockers for the CIH Opel. From what I've heard, the issue with throwing pushrods is only at very high rpms. I know of some people running them to 8000. Of course bad valve adjustment or over-revving (valve float) can cause this too!

[GTJIM]

There is not much choice in CIH rockers these days - you have got them so try them!

Another feature of this rocker type with the very short push rod is that with high lift cams the angle change through the lift cycle is quite large which changes rocker geometry quite a lot and affects the cam area under the curve - decreasing the valve open profile.

I would guess you are using something around 12mm to 13mm of maximum lift?
Take a look at the change in angle of the tiny push rod between valve on seat and full lift. It is much greater than that of a long push rod motor.

Let us know how they work for you.

[Vagos]

My total valve lift is 13,9mm.I will give them a try.Hope nothing will go wrong.

[wrench459]

Mr. Murphy(Murphy's Law) has an odd way to mess things up.
With your .547 lift its up to you and Mr. M good luck.
Or is the lift .820?

[Hiro]

Hi Vagos,
As Bob & Jim said this type of roller rocker are OK up to about 8000rpm,
But the rocker/pushrod geometry is very bad,
Thus you will loose the benefit from your big cam.
Anyway with our 2.7 strokers the safe max rpm is around 7500rpm,
Whereas the real benefit from the roller rockers is above 7000rpm,
Therefore IMO this application is borderline.
You will probably get better results in your 2.7 with the std rockers & custom made alu lifters from Jörg,
This way you could fine-tune the rocker geometry with your big cam which probably has a small base circle
(thus jams the geometry with std lifters).
HTH,
Hiro

[Vagos]

Hiro those rockers are Soooooooo out of my engine at once!!!I set them up today started the car and sounded awfull!!!like all the metal are loose inside the engine.let the engine cool down put the desire clearance again and stll the same awfull noise took the car for a ride even worse.put the stock ones inside set them up and now it sounds just marvelous!!!im putting those rockers in a box and up on the shelf for good.I also i think i made a kind of big error.the chevy valves are in lenght about 125mm versus 123mm stock opel ones.I thought for such a little difreence i would get the clearances from the stock rocker arms.But is there a possibility that the this small difreence in length to affect the geometry of the stock rocker arms??

I saw jorgs alu lifters on ebay but he says he only ships in germany.I would love to have a set of 16 for both my motors.

[Hiro]

Originally Posted by Vagos Hiro those rockers are Soooooooo out of my engine at once!!!I set them up today started the car and sounded awfull!!!like all the metal are loose inside the engine.let the engine cool down put the desire clearance again and stll the same awfull noise took the car for a ride even worse.put the stock ones inside set them up and now it sounds just marvelous!!!im putting those rockers in a box and up on the shelf for good.I also i think i made a kind of big error.the chevy valves are in lenght about 125mm versus 123mm stock opel ones.I thought for such a little difreence i would get the clearances from the stock rocker arms.But is there a possibility that the this small difreence in length to affect the geometry of the stock rocker arms?? I saw jorgs alu lifters on ebay but he says he only ships in germany.I would love to have a set of 16 for both my motors.

Ouch that was a risky test Vagos,
I hope you did not harm your camshaft!
Don't worry about the Chevy valves,
These were frequently fitted in CIH heads for racing.
Yes the 2mm extra stem length could affect geometry,
But this depends how the valve seats are machined in the combustion chamber.
If the seats are machined too deep then the stem will protrude a lot & the geometry will be affected,
But if the seats are machined correctly by carefully measuring the protruding stem length then the geometry should be OK,
To some extent this is also true with std Opel valves BTW.
Hiro

[Vagos]

I dont believe any damage might occour to the camshaft as the ride was slow and with very few revs.thanks for the relief on the chevy valves