Double Valve Springs

[petert 577]

There’s little information regarding fitting double springs or experiences on this forum, so I thought I’d share my recent experiences in fitting the Catcam kit, as sold by Pug1off. I had two heads to build and the owners had both purchased the kits without advice. Pug1off will openly warn buyers that the kits are not for the inexperienced engine builder.

 

The kits contain three parts. The double springs, retainers and spacers (or bottom retainers). I’ll detail the bottom first, as this was identical in both heads I built. The tops differed, as one head had XU9 valves, the other XU10.

 

The spacer is designed to fill the spring base cavity, creating a new flat platform. Once they drop in, they’re hard to remove, so beware. Whilst the spacers are made from anodised aluminium, you can’t allow the springs to sit directly on that. Additionally, the inner spring would sit on the casting aluminium. Neither ideal. Thus you need to add a thin hardened shim, which both inner and outer spring can sit on.

 

Next issue is that there is nothing now to locate the bottom of the springs. They’ll wander around and create havoc. Pug1off advise to turn up steel rings, which slip over the guide and locate the inner spring. The seal is then fitted which retains the ring in place.

[petert 577]

Fitting with XU9 Valves

The first head was a normal D6B head, fitted with new, oversize stainless steel valves. With the thin base shim fitted and new Catcam retainers, the fitted spring height came in nicely at approx. 95lbs of seat pressure. All good there. However, it soon became apparent that an extremely thin valve clearance shim would be required if oem buckets were used with the oem camshaft base circle.

After some researching, I found a BMW S14 bucket which has a thinner pad and uses a smaller and thinner shim. This worked out perfectly, as this head needed new buckets anyway.

Edited July 14 by petert

[petert 577]

Fitting with XU10 Valves

The owner of the second head, in this case a Grp A casting, wanted to use low mileage XU10 valves & buckets he had. I hadn’t really given it much thought and it provided unexpected challenges.

When using the Catcam retainers, the top of the XU10 valve is extremely low. This means it’s impossible to fit a normal shim. The shim would sit on the retainer recess, not the tip of the valve. After much deliberation, I concluded that it was impossible to use the Catcam retainers with XU10 valves & collets. The solution was to turn a small step in the oem retainer to locate the inner spring. The outer spring locates perfectly on the standard retainer.

I turned up a 7º mandrel to hold the retainer and used a small tungsten carbide tool. High speed steel won’t cut it.

 

It’s not over yet however. With the top and bottom of the springs located satisfactorily, I could now measure installed spring height. Unfortunately, it was too high and I had to add more shim at the base to obtain acceptable seat pressure.

 

Edited July 14 by petert

[SRDT 169]

6 hours ago, petert said:

After some researching, I found a BMW S14 bucket which has a thinner pad and uses a smaller and thinner shim. This worked out perfectly, as this head needed new buckets anyway.

Those are aftermarket "shim under" buckets right? Genuine BMW S14 buckets have the shim on top like some Italian and Japanese cars.

[petert 577]

Yes, I found them in the Supertech catalogue.