V8 engine build part 4 – cylinder heads

V8 engine build part 4 – cylinder heads

I’m making some good progress here getting on with the engine build during my lunch breaks, and quite honestly it’s a lot more fun than crawling around on the floor doing bodywork right now, so onto the top end.

I bought an extra pair of old Range Rover heads from eBay last year and had them stripped, skimmed and completely rebuilt with new valves to Stage 1 specification by my local engine shop. I think I mentioned previously that one of the heads that came with the engine had a mysterious hole torn into one of the sides which had been badly patched up and looked ugly, so I thought it was worth the peace of mind of building up from a better starting point.

They look fantastic now, and after sitting on a shelf for months, their day has finally come. I’ll obviously be fitting them using brand new composite gaskets, but I’m also using an ARP stud kit instead of the factory stretch bolts, which generally seems to be the preferred method.

First off, the bolt holes were all checked and cleaned, before inserting the studs and screwing them in finger tight.

New composite gaskets on next.

And then the heads themselves go on. The nuts have to be tightened in a 3-stage process using a specific tightening pattern to achieve the correct fitment and minimise the risk of any future gasket failure. The first stage is a fairly low 20Nm, but the second and third stage involve tightening a further 90 degrees beyond the previous stage, and gets quite hard work quickly… time to break out the big torque wrench!

Looking more and more like an engine again at every step.

Next job is to fit the tappets and pushrods, followed by the rocker assemblies. The rockers had been rebuilt with new parts fairly recently by the previous owner and are still in good shape, so I just gave them a good clean. I checked all the pushrods for any distortion or serious wear, but all looked good, so will be re-using them too.

Here the 16 new tappets have all been inserted after a dip in engine oil, followed by the pushrods.

The rocker assemblies were then carefully positioned and bolted down to the correct torque.

Any Rover V8 expert will tell you that at this point it is critical to check the “tappet pre-load” and adjust it if necessary using shims placed under the rocker pedestals. The pre-load is determined by measuring the gap between the inner top lip of the tappet and the circlip beneath it when the rocker is fully assembled. It has to be checked when each tappet is resting on the back of the cam lobe (i.e. not under compression), and a useful guide with more details can be found here. I used the tails of two pop rivets to measure mine, one filed down to 40 thou and one to 60 thou, and thankfully found they were all within tolerance first time round.

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