setting up rockers

[KA2S4]

Hi guys,

What is the best way to set up rockers?

I have an original set of S ones to recondition, so new shaft and bushes, but what about springs for between the rockers? or is it best to use solid spacers instead?
How about setting them up so the rockers are exactly centred over the valves? is this recommended?

Cheers,

James.

[Spider]

Before we get too far in to this, what is it for / what's the intended outcome?

ie, original restoration, max power, best reliability?

[KA2S4]

It's for my 970, I don't want to run rollers but do want to optimise the standard S rockers in a way similar to what they may have done in the 60s.

[Spider]

OK, cheers on that.

S Rockers are notoriously inaccurate and inconsistent in their ratio, so if it were me (and I was fixed on the S rockers), I'd be be getting a few sets and picking the eyes out of them, to at least end up with a set of 8, or even 2 sets of 4, that had the closest matched ratios. If you are using the new ones that are available these days, I don't know if they are any better, they may well be.
The original S rockers weren't bushed, so check the bore of them isn't worn, although, I see no reason why they can't be bushed.

Then, between each of them, try them one at a time on each valve to pick out which are going to be closest to centre over each valve stem. They can be ground or shimmed as need to adjust, I know Mini Spares (for one place) have shims available. I usually don't get super fussy with this aspect on the forged rockers though.

Check the pillars are steel types and those suited to the S rockers, though, they can be shimmed or ground as needed to optimise the heights. As for the optimum height, there are a few published guides floating about, however it also need to take in to account the cam profile. Your camshaft grinder man would be best to advise you on this.

Also, if the rockers have been used, be sure to have the tips refaced. You can do this yourself, with a diamond lap and a steady hand, however, it is tedious.

Spacers vs Spings - I've never found any advantage using spacers.

I'll also just add that the best of the factory rockers were the pressed ones, in nearly every aspect and these are what I always use if I'm not using rollers. There are 1275 and small bore versions, however, with some work, I have fitted the small bore types on the big bore heads quite OK. These also have the added advantage of being bushed.

[mk1]

All excellent advice Spider & I agree with every word, apart from "The original S rockers weren't bushed".

I have never seen an S rocker that didn't have a bush fitted.

[Spider]

Ha, I have to say, it has been a while since I looked at an S rocker! I somehow recalled they weren't bushed. Thanks Mark.

One other thing I do recall is that S rockers have the lowest advertised ratio of the Factory Rockers.

[KA2S4]

Thanks for the advice people, all good advice by the sounds of it.

The cam is a 544

Do new bushes need reaming or are they just fitted? reason for asking is I thought they may be able to be ratio-matched at that stage.

I had read a ST thing about the spacers but maybe not a worthwhile mod to do...

J

[mk1]

The bushes need reaming 9/16 if memory serves correctly.

The old ST rocker bushes are good, but fitting them so the all give the same offset is almost impossible, I made a jig to do this years ago, but the results were only "average" to say the least.

[Spider]

If you did want to try to correct the rockers you have by off setting the bushes, then as Mark has said, it would be extremely difficult to fit off set bushes to achieve the desired outcome. Fitting bushes and then attempting to off-set ream them would likewise be extremely difficult as the reamer will want to follow the hole that is already there.

If it were me, I'd fit bushing material, possibly a solid slug, in to each rocker, then clock up the rocker and bore the bush. You would be assured of getting very good results.

I'll also add, while slightly OT, that the late sintered rockers are very under-rated, they are no performance rocker for sure, but they are considerably better than is perceived.

[KA2S4]

I'll also add, while slightly OT, that the late sintered rockers are very under-rated, they are no performance rocker for sure, but they are considerably better than is perceived.

Embarrassingly that is what I currently have on the car.

J

[Vegard]

http://bit.ly/1ac8Xu1

Why not fit these?

[mk1]

Vegard,

As has already been said fitting them to give equal amount of "offset" is almost impossible.

[1977peter]

I fitted offset rocker bushes in the mid 70s its true that it is very difficult equalise the lift-but the other problem is that by altering the ratio the rocker tips move forward of the valve stems,also the adjusting screws will be out of alignment with the pushrods! If you are using a head with sleeved pushrod holes you may find it necessary buy another set of bushes and fit four of them to your rocker posts to restore the alignment.Nothing is as simple as it seems!! PETER

[carbon]

iirc BL special tuning used to supply different rocker pillars to correct alignment for the ST offset bushes

[Vegard]

iirc BL special tuning used to supply different rocker pillars to correct alignment for the ST offset bushes

Indeed. I've gotten Longman posts on mine.

[KA2S4]

Seems to be a lot more to this than first thought!

J

[carbon]

As with many things the devil's in the detail... the other factor which can affect rocker set-up are the pushrod lengths. I have found that even 'std' unmodified pushrods can vary in length by up to 60 thou. And cam followers can also give different pushrod heights.

[970s]

James,

I think you better forget about the perfection in old rockers set up!
It won't cause you a lot of HP!
But fun to learn!

Al