The V8 Owners Forum -

Hi guys, just thought I'd put up my issue to see if anyone can throw any light on the subject (Rover 3.5)!!

Here goes, I'm rebuilding the engine and have now converted from Group A rocker setup, back to the std rover alloy units, running a compasit head gasket (which aparantly compresses to 40thou / 1mm when torqued down) so what I have done to check everything is this:

Cut a section out of a 1mm sheet of alloy (dummy head gasket) loosely bolted the head down with 2 valves fitted (with no springs so I can measure clearance), now the gap between the valve spring retainer and the valve guide should be about 80thou (2mm), but to get this clearance (from the top of the guide not the stem seal) the lash on the cam follower looks to be about 80 thou instead of 40 (I know extra shims need to be fitted under the pedastils)!!! Now with these gaps I wouldn't be able to run the std rubber washer valve seals as there would be about 10thou clearance....... I knew I would probably have to mill the top of the vave guide slightly to fit the newer oil seals, but looking at it I would need some drastic mods to do so!!!

Am I missing something or does it look like I have got massive valve lift? I know the cam is an RC28, but thought that was a mild cam! LOL

Cheers
Jono

The pre-load on the follower being set to 20, 40 or 80 thou won't make any difference because when the engine is running there is no 'free play'in the system. Basically the valve will lift the amount that the cam grinder decided to make it lift.

You could use two old lifters, take them apart and fill them with candle wax so that they are solid.
Then fit weak valve check springs, (cut a rocker shaft spring in half, each half makes a good checker spring)

As you don't now have any means of setting the preload other than shims you could fit shims or even washers for the test under the rocker shaft pedestals. (you only need to do it on the two either side of the rockers that you are working on).

Basically when the solid lifter is on the base circle of the cam you want no slack in the valve train but you don't want the valve open at all. You may have to fiddle about with the number of shims/washers. Spinning the pushrod with your fingers can help you feel how much slack/load there is on it.

Now you are ready to test the setup, turn the crank until the valve is at peak lift, if anything locks up then don't force it! Now with the valve at peak lift measure how much more you can push it down by hand, if it 2mm then that's the clearance.

If that all works OK then things aren't too bad. This will be the clearance when the engine is running even with 40 thou preload, most of the time! The one time the clearance will reduce is when the lifters pump up, they will then hold the valves open by 40 thou X 1.6 (The rocker ratio) so that figure will get added to the total lift. That is one reason why I run adjustable pushrods and set each preload to only 20 thou.
With shims?.....Good luck!

Personally I would do whatever it takes to either keep your group A setup or at least avoid shims.

Hi
If these are 3.5 heads intended for tin gaskets and you have put on comp gaskets then you will need to skim the pedistal bases not add shims, that is unless you have skimmed the heads to compensate (assuming standard base circle cam).
What I am saying is check it as described but don't assume you will be shimming the pedistals. I don't see why people think shimming pedistals is a bad thing anyway, always strikes me as better than the added weight of adjustible push rods. I must confess it would strike me as the best and simplest solution would be to stick with the Volvo rockers.
Best regards
Mike

kiwicar wrote:Hi
If these are 3.5 heads intended for tin gaskets and you have put on comp gaskets then you will need to skim the pedistal bases not add shims, that is unless you have skimmed the heads to compensate (assuming standard base circle cam).
What I am saying is check it as described but don't assume you will be shimming the pedistals. I don't see why people think shimming pedistals is a bad thing anyway, always strikes me as better than the added weight of adjustible push rods. I must confess it would strike me as the best and simplest solution would be to stick with the Volvo rockers.
Best regards
Mike

I've spent a couple of hours checking the valve train geometry using engineers blue on the end of the valves, even the standard setup is not good, the rocker pad contact area gets very close to the edge of the valve stem, shims make this worse.

With regards to the weight of adjustable pushrods I believe that they are lighter than the standard solid ones.

One thing going for shims is that they are cheap!

I would have loved to stick with the Group A setup, but I couldn't find any pushrods for the job as mine were lost by the previous owner (bought the engine partly stripped!) and yes I have had the heads skimmed as the engine suffered HG failure!!

Oh well.... looks like a few hrs measuring and testing when I get off the water then! LOL
Cheers guys!

Jono

Jono FD3 wrote:I would have loved to stick with the Group A setup, but I couldn't find any pushrods for the job as mine were lost by the previous owner (bought the engine partly stripped!) and yes I have had the heads skimmed as the engine suffered HG failure!!

Oh well.... looks like a few hrs measuring and testing when I get off the water then! LOL
Cheers guys!

Jono

did you try the comp cams website? or summit racing? or iskidine? all do push rods with pretty well any end you want and in any length, diamiter and wall thickness.
best regards
Mike