17 replies to this topic

[087dave]

Hi all
I have a weekend driver with a metro 998 flat top pistons,stage 1 kit, stage 3 head sw5 cam Aldon dizzy

The car is great to drive but I was looking at MED site and they have a nice set of 1.3 rockers but

If I was to fit them to my engine would I notice any power gain with the mods in my engine?
Cause I know the sw5 gets it's power from the lift it produces....so would there be too much lift?

Any done this?
Thanks dave

[Ethel]

Isn't the SW5 supposed to have been designed with hi lift rockers in mind? Though that's probably more for large bore A's. You can't really have too much lift, though it will waste a little bit of power compressing valve springs, then higher ratio rockers require less spring poundage to start with. The issue is the faster rate the valves will open, this is basically a good thing, but it also has the effect of increasing the effective duration of the cam.

 

The SW5 doesn't have much duration (244 degrees), so I don't think you'd end up with anything undriveable.

[gazza82]

1.3 rockers aren't a lot more than normal 1.2 rockers but they will be more accurate that the old pressed or sintered rockers.

 

They won't lose you much in performance as 1.5s might

[Cooperman]

With 1.3:1 rockers you will notice no increase in power because the standard ones are just under 1.3:1.

If you fit 1.5:1 rockers to a 998 you might notice no improvement in top end power,  but a loss of mid-range and bottom end torque.

[Mini Manannán]

Going to highjack this one

 I've been considering the same MED 1.3 rockers for my 1293, could I expect any worthwhile power gains other than top end (which I'm not too bothered about)?

[Cooperman]

You will notice no difference at all.

[087dave]

Thanks for the input guys

I have the earlier type rockers that came of a 75 car
Are these the best ones for a 998?
But I also see there are cooper s ones? Are there
Any good for a 998?

[Scoop77]

Cooperman, could you explain why and when you would use 1.5 rockers please. They appear to be a popular 'upgrade' and modification?
Thanks

[Gremlin]

With 1.3:1 rockers you will notice no increase in power because the standard ones are just under 1.3:1.
If you fit 1.5:1 rockers to a 998 you might notice no improvement in top end power,  but a loss of mid-range and bottom end torque.

Depends what cam you use

[087dave]

Sw5...

[KernowCooper]

IMO you would use 1.5 rockers if the extra small amount of bhp you gain at the top end of the rev range is important, 2 cars built to the same spec and one with a extra 3bhp on a circuit where maximum revs are in use

[Gremlin]

Sw5...

I know your using the SW5, I was just saying that not all cams produce the same results once 1.5 rockers are fitted

[gazza82]

Thanks for the input guys

I have the earlier type rockers that came of a 75 car
Are these the best ones for a 998?
But I also see there are cooper s ones? Are there
Any good for a 998?

 

There were three standard types:

 

The pressed steel ones fitted to most early and lower capacity engine ... one trick is to weld them down the joint to make them stronger.

Sindered rockers fitted to later engine like the A+ ... good to around 6000 rpm

Forged rockers fitted to the Cooper ... and rare as hen's teeth!

 

All should be interchangable and all around 1.2 lift. The forged ones are the most accurate.

 

 

The you have roller rockers from people like Minispares, MED, Moss, etc .. usually 1.3 or 1.5 lift.

Edited by gazza82, 23 May 2014 - 03:22 PM.

[Cooperman]

It is generally accepted that 1.5:1 rockers work best with standard or mild cams. I've never tried them except on my 'S' engine which has a 286 cam and everything else to make a lot of power. I found that when I fitted 1.5:1 rockers I gained all of 2 bhp at 5700 rpm and over, nothing below that and I feel that I lost a bit below about 4500 rpm, although I didn't measure it.

They don't work well on a 998 and, for a 1275, they are expensive for what you gain. Maybe useful on a racing Mini where 2 bhp might knock a 1/10th of a second or so off a lap time, but for a road or rally Mini probably a waste of money.

[087dave]

Hi again

I see mini spares have cooper s rockers reproductions
Are these the nearest to 1.3.1?

Thanks