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1.5:1 Roller Rockers With 286 Cam.


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#1 Howie1000

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Posted 11 October 2019 - 08:03 PM

Evening chaps!

My MED 1380 has a stage 3 head and 286 cam with standard rockers (from the Victorian times by the look of them!)

Would there be any benefit to 1.5:1 roller tip rockers with that cam, or is that a bit overkill?

Cheers.

#2 imack

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Posted 11 October 2019 - 08:23 PM

I thought the 286 was designed around the use of 1.5:1 rockers

#3 nicklouse

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Posted 11 October 2019 - 08:36 PM

You would lose torque and gain not much.

 

dont forget to strip it down and measure for the changed rocker geometry. 



#4 nicklouse

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Posted 11 October 2019 - 08:37 PM

I thought the 286 was designed around the use of 1.5:1 rockers

Nope.



#5 Howie1000

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Posted 11 October 2019 - 08:42 PM

You would lose torque and gain not much.
 
dont forget to strip it down and measure for the changed rocker geometry.


So a standard 1.3:1 roller tip rocker would be better then? (Is 1.3 the standard one??)

#6 Cooperman

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Posted 11 October 2019 - 10:46 PM

In my 1964 rally 1310 cc Cooper 'S' I use a 286 with 1.5 roller-tip rockers.

When I changed from the standard 'S' forged rockers to the 1.5's I got 2 extra bhp at over 6000 rpm but lost some low-end torque. With the 286 think of 3000 rpm as 'low end'.

To keep it 'on the cam' under competition conditions I run a SC CR gearbox with a 3.9:1 FDR. Then I try to stay between 5000 rpm and 6800 rpm for the best performance available.

Unless you drive at over 5000 rpm most of the time there is no point in having a 286 as you will be 'over-cammed'.

For road use a 266 is probably better as it will pull from 2500 rpm and give peak power at 5700 rpm so a standard ratio gearbox can be used with, ideally, a 3.44:1 FDR. If the engine is nicely and accurately built with good flow in and out, that gives an ideal result for the road, although for fastest times in competition a more aggressive set-up is needed.

Don't bother with the 1.5:1 rockers with the 286. Just get the gas flow in and out optimised, match everything accurately and keep the gearing low to keep it on the cam.






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