Rover V8 lifter preloads....

[Jono FD3]

Right, here we go.....
The engine I am rebuilding is a twin plenum engine from the SD1 and as a result it has group A pushrods (Or hopefuly if the previous owner can find them) and adjustable rockers (Like the older cars where you set the tapet gaps) but they are tack welded so they don't move.

So what I'm wondering is this: do the rocker arms stay in contact with the valves at all times and the slack maintained by the lifters, or do they have a gap between the rocker and valve aswell??
And now for what I'm thinking.... if they stay in contact with the valves, I would be able to adjust the pre load of the lifters by adjusting the screw and lock nut on the rocker arms instead of buying a shim kit, correct??

Jono

[sidecar]

Right, here we go.....
The engine I am rebuilding is a twin plenum engine from the SD1 and as a result it has group A pushrods (Or hopefuly if the previous owner can find them) and adjustable rockers (Like the older cars where you set the tapet gaps) but they are tack welded so they don't move.

So what I'm wondering is this: do the rocker arms stay in contact with the valves at all times and the slack maintained by the lifters, or do they have a gap between the rocker and valve aswell??
And now for what I'm thinking.... if they stay in contact with the valves, I would be able to adjust the pre load of the lifters by adjusting the screw and lock nut on the rocker arms instead of buying a shim kit, correct??

Jono

You are right, there is basically no 'slack' in the valve train on a standard RV8, the rocker is always in contact with the stem of the valve and the lifter is always in contact with the cam. If you can get hold of the tack welded rockers and can carefully remove the weld then you would have a nice setup where you can set the lifter preload of each valve to whatever you want. Some people are of the opinion that the preload is not important as long as there is some, I do not subscribe to this, I think that it is quite important if you are building a 'performance' engine.

Shims is another way of setting the pre-load, I really don't like them, whenever I've tried to use them I've just wasted hours of my life pratting about trying to get the preload on all the valves within 20 though of what I was aiming for. The other bad thing with them is that they make the valve train geometry worse than it is already and it ain't great to start with. (Even with a standard cam). All the engines that I've been involved with run adjustable pushrods. These are easy to setup, once you have done a couple you can work out a 'method' You can just carefully remove all the slack then wind the adjuster an number of nut-flats more. (From memory 4 flats is around 25 thou which is what I go for).

The slight bad side of adjustables is that the holes at either end of both heads quite often need to be ovalized. Adjustables quite often need to be shortened a couple of mm before they can be used. (Head skims and pedestal boss skimming causes this).

Just my humble!