9 replies to this topic

[backstreetclassics]

hi i have a 998 with uprated cam shaft inch and half carb what roller rockers would go best with this type of spec ??

cheers dan

[benpopham]

hey i have a heavily modified small bore and im still running standard rockers.. they are fine for the job.
but if your desperate.. go for some 1.5's

[Big_Adam]

NO!

NOT 1.5! They give too much overlap. You'll loose a few BHP. For a Small bore engine all you need AT MOST is 1.3 standard rockers are 1.25-1.3 so there's not much point.

If you really want you can spend £100+ on 1.3 roller rockers. Or get some diffrent standard ones, the pressed steel ones are nice. But over all rocker is a rocker is a rocker.

ROCKER!

[backstreetclassics]

so what yr saying is save my money and just put some standerd 13300 rockers on there

[Big_Adam]

Standard will do the job, if your REALLY trying to squeeze every last wee bhp from the engine (race stuff) then go for 1.3 roller tipped. Should reduce valve wear and side loading a little.

If not save your cash.

[backstreetclassics]

thanks 4 the advice

[Big_Adam]

It was my pleasure.

*goes back to reading vizard books to look smart*

Edited by Big_Adam, 10 May 2007 - 08:08 PM.

[backstreetclassics]

lol

[Dan]

Yes, the standard sintered rockers your engine was born with are fairly good. If you want to push the boat out get some repro 1.3 forged Cooper S rockers from Mini Spares which are excellent, IMHO rollers are not really worth it and as Adam says any ratio above 1.3 is wasted on most small bore engines. If you want to make a real difference for little cost, change the rocker shaft. This is a very easily overlooked component but the standard item can be fairly flexible, especially when worn. If it flexes in use, the valves don't open as far and they rock about in their guides causing excess wear to them. Thickwall shafts are a very good upgrade to consider.

You understand that no-one is saying use rockers from a 1275 here right? You seemed to say something about a 1300 above but we are saying 1.3 as that's the rocker ratio not the engine size. All late model rockers are the same, whatever the engine size.

Edited by Dan, 10 May 2007 - 10:09 PM.

[Yeti]

I was going to say what Big_Adam said. I am also a disciple of David Vizard......

1.5 is to much for 998 and the money is better spent else where as regard to roller 1.3's (my personal opinion!.... Im looking at suck through turbos.... have no money though....)

Mr Benn