Two Heads are always better than One
Part 1: by Grant Rodman
This is one of those projects that goes in multiple directions, and grows exponentially by the minute!
Pearl had a bit of an issue with an exhaust valve clearance closing up on one cylinder for some unknown reason. Even though easily resolved, there are a couple other issues, so I thought that her original head should be prepared as a possible replacement one day in the future. Unfortunately once removed from the engine, revealed the water jackets are now in need of major repair (which is another story on its own).
Luck would have it, I knew of a partially complete late S3 “big valve” head for sale.
But being only partially complete & not personally knowing its history, it really was a “pig in a poke”, so before investing any money on the missing bits, the cams are installed to see if they spin freely, (these heads can easily be warped beyond service), then it’s dismantled to inspect the valves & guides for wear/damage. (The exhaust valves will be replaced regardless)
Converting S3 heads to fit earlier engines is not uncommon, so while waiting for the parts to arrive, I started preparing it for the bits I want to transfer from mine.
First up, the tacho encoder – no major drama – just transfer the coupling to the inlet cam, & drill/tap some holes on the back of the head for the encoder.
The tricky bit is with the cam cover seal. On early heads, the rear bearing cap is extended to incorporate the seal for the cam cover. To allow me to still use the Tach encoder & my polished cam covers, I had to manufacture an adaptor to retain the seal (with a couple extra steps, as it would only be retained by the cam cover itself now).
I thought the Exhaust side would be easy (fool am I!) – the step heights between the S3 head and the old cover differ by 5mm, so using the original blanking plate is out the door (discovered after I had already drilled and tapped the holes!), so will now be replaced by a pair of S3 rubber grommets.
To make this head look the part, I chose the polish the front to make it look “period proper”. This is a rather tedious task, and I now have a deep appreciation of those that had to do it ‘day in-day out’ at the Jaguar factory.
Onto the business side – All later heads have extra coolant ports at the rear – these have to be plugged, as they are half exposed by the shorter block of the earlier engines. Later ‘Slotted’ S3 Engines also have coolant ports between the head chambers – these are also partially exposed by the early head gasket, and as I would prefer that my head studs to remain “dry”, I chose to plug them as well. They are then filed down to with-in a few thou proud of the head surface, and will be machined proper when the head surface is machined.
The valves are all lapped in & checked with bearing blue for good contact faces.
Even though it is standard practice to ‘skim’ an alloy head every time it is removed, the norm is to remove the absolute minimum – not the case here, as there are a couple nasty pits where the 3.8 head-gasket will sit. I was allowed to watch the last couple passes in the planer but foolishly forgot to take a photo!
I want to give credit to Doug at the machine shop- even ‘hand dressing’ the cutter tool for the final cut to ensure a good finish(those brass plugs can do funny things to the finished surface (yes I probably should have plugged them in aluminum!).
Deviating from the ‘norm’, I chose to fit modern valve-stem seals on both inlet & exhaust (Holden Commodore V8) – they nearly fit straight into the S3 head (as it has the shorter collets & retainers), but I machined 1/32” off them to be certain
Even though I took heaps of measurements prior to assembly and calculated the shims needed, I still mucked up half of them, (my high-school math’s teacher would have been so disappointed!), Final assembly with ‘Cam Lube’ on all the critical surfaces.
And then, all the exposed surfaces are coated on grease, cams linked together, a storage box fabricated (with the gasket set secured inside the lid), and then sealed up for storage.
The next bit is now to revisit Pearl’s original head!
