Cam Question

[998automan]

Hi, looking for help on the following: I have a 998 with a Kent 266 cam which was fitted at the same time as 1.3:1 roller rockers and double valve springs by the engine builder. The roller rockers are causing problems and I want to return to standard rocker gear and single valve springs, can anyone advise me if this will cause any issues? (other than a slight loss of performance of course!)

Thanks Mike 

[kalkat]

I would look out for a standard set of pressed steel rockers. If you are worried about their strength, they can be modded by welding. Why change to single springs? The doubles are to help get rid of valve bounce, as long as they are fitted with the correct caps and bottom spacers they shouldn't be an issue.

998s don't really like 1.3 rockers hence the use of standard, the pressed rockers are more accurate to the favoured 1.25 then the later sintered type

[998automan]

Hi, Thanks. The reason for changing to single springs is that the inner spring appears to be pulling the valve stem seal out of place. I am using the later type seals from Mini spares but otherwise all other components on the head are standard. 

[kalkat]

Hmm.....odd that as mine are fine. If the head is a standard CAM4810, you would do well to find a 12G295. It'll need skimming to get the compression ratio up, but is an enormous improvement.

Do you have a decent exhaust fitted?

[998automan]

Hi yes head is CAM4810, standard exhaust (as is everything else) apart from 266 cam and duplex timing kit. Gradually seem to be reverting to standard spec as once you start changing things you constantly seem to be running into problems like this! (Would be happy just to have it running right now!!) Having just stripped the head it seems as if the stem seals aren`t quite deep enough to fit into the groove that would/should hold them in place. They are supposed to be gen Rover parts but they`re probably not! (Anyone else noticed the quality of parts going downhill recently?) Is valve bounce likely with my cam?

[kalkat]

Valve bounce is probably unlikely......... 'less you're a loony like mee

[998automan]

Following on from this does anyone have a view on valve clearances with the 266 cam? Engine builder set mine up with standard clearances (0.012") but after talking to Kent about something else they mentioned 0.016" should be used (both inlet & exhaust). Having done this I have noticed a significant drop in power, especially when pulling away. Would like to revert to 0.012" but Kent have said this may cause damage?   

[kalkat]

Hmmm..... it's difficult to suggest what you might do with this. To be honest , the CAM 4810 is a lousy head - the valves are badly shrouded. The head itself may be robbing you of all the benefits of the camshaft. There is also the fact of still having a standard exhaust. The main idea with tuning is to get more fuel/air mixture burnt - this leads to more exhaust. I would suggest you go for a Maniflow exhaust (Somerford Mini are cheaper than Maniflow themselves) as you are almost certainly strangling the benefits of the cam and needle.

I have also found that Maniflow exhaust systems last a LOT longer than standard ones (usual disclaimer here) and sound lovely ;-)

[998automan]

Thanks, tried an LCB & RC40 but gave up as it was almost impossible to get the manifold lined up correctly as the auto box got in the way! Which manifold did you use and did you have similar issues with fitting it?

[kalkat]

I used a 'freeflow' manifold. I had no real issues, other than having to make a bracket up for holding the bottom end steady.

You shouldn't really use an LCB on a 998 as they don't respond well to them.

Manifold LM001 top right here ... www.somerfordmini.co.uk/eshop/index.php?main_page=page&id=194&pos=v&chapter=50

and LST001A exhaust lower down on the next page

[998automan]

Thanks for that, just need to find someone with a a ramp/pit now! (Getting too old to fit exhausts when car is still on the ground!!) 

[kalkat]

Naah! .....it's easy as it comes as separate parts.

[998automan]

Thanks, which inlet manifold did you use, some of the ones I have fitted in the past are not the same thickness as the exhaust manifolds they are supplied with (as with certain stage 1 kits from well known mini specialist!) so hard to get a decent fit/seal?

[kalkat]

Ah! .... my car is twin carbed

Proper Mini manifolds should fit, it's metro ones that don't. However, it's reasonably easy to make up some stepped washers. Another way would be to get the manifold machined to suit.

[998automan]

Thanks, will let you know how it goes!