rockers
Turbo Mini Forums

hi,

what type of rockers do you use on a 998cc turbo, the standard ones or uprated roller rockers?

Use what you Like Think on;y 1.3.1 ratio can be used on 998 though if you go roller rockers

why is that?

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

There is something in the yellow book about using 1.5 ratio's on a 998 and I think he found they gave worse results than the 1.3's. I guess it would depend on the lift of the cam that you are going to use as well. Kent Cams don't recommend using 1.5 ratio on 998 either.

Med do some nice roller rockers in 1.3 ratio for reasonable money.

There is no blanket rule to say that you can't use 1.5s on a small bore. The yellow book does talk about it, but there are plenty of engines that have benifited from them.

Anyway, back on topic. Get the best rockers you can afford. No real performance gains, but they do look nice.

Edited by Ben H on 31st Aug, 2012.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Roller rockers are only to stop premature valve and guide wear by stopping the rocker pushing the valve at an angle, theyre only necessary if there is excessive sweep on the valve stem top.
Having said that, you do get slightly more lift from 1.3 rollers as standard are about 1.25:1

Edited by paul wiginton on 31st Aug, 2012.

I seriously doubt it!

i was planning on fitting 1,3 minisport rockers but i have just ordered an xlite flywheel from med so the piggy bank is empty for now...

i will stick to the standard ones for now and when the build progresses i can always change them for roller rockers...

The minisport ones i have had in my hands after a bit of running where all quite sloppy. I would either keep stock or invest more .

The whole roller thing makes sense on a big V8 with 2 inch valve lift, but with the amount of lift on an aseries i personally doubt there is any gain
By proper setup you can minimize the sweep on the valve tip to a large extend anyway.

Edited by Sir Yun on 31st Aug, 2012.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Standard roller rockers are incorrectly spaced for a 998.

You need to re-arrange the rockers and add spacers.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

thanks for all the info guys, i'll keep the stock ones. i am now in the midst of building the turbo gearbox and engine and hope to get some decent process done in the next week. i'll stick to the standard rockers for now

So how far do you space them? Just so that the rollers are central on the valves?

http://www.turbominis.co.uk/forums/index.p...tid=469104&fr=0

It'll become obvious when you try to fit them. The roller tips are offset from the rocker. Some will med swapping over to align the tips with the valve stem.

In the 13's at last!.. Just