Decarbonizing the head

This is  a follow up to the cleaning the valves post and its my experience with the Utube recommended method from that post. https://www.youtube.com/watch?v=7GEmuQa3dPY

I used a brass wire brush fitted into a Dremell flexible shaft drive. Overall it worked well but the job really needs a beefier driving system. Mine is battery operated and kept stalling, needing a few moments to reconfigure.

Starting condition, exhausts (top) much dirtier than inlets

Dremell flexible drive

Brass brush fitted into drive.

The Dremmel works well on the valve seats, when using it be careful to avoid in-out motions that might score a line right across the seat- try and stick to circumferential movements. The seats cleaned up easily and very well, the brush was also useful for polishing minor blemishes off the alloy inside the chamber. It was also possible to try and get the carbon off the ports... this is a VERY messy job. Dremmel or no, there is no way of avoiding getting extremely dirty and spattering the stuff everywhere! I found liberal use of diesel EGR cleaner immediately followed by the Dremelling could swirl the cleaner around the port and help to loosen the carbon- but it comes off as a sticky paste- really Yukk!

Exhaust ports nearly done...

OK- well an observation- for effective decarbonising with a Dremmell- make sure its fully charged! Overnight on the charger helped the performance of mine no end!

Lapping (Grinding) in the valves.

This spare head isn't perfect but it seemed to me that getting it ready for use might at least let me use it in emergency- or alternatively at least it keeps all the bits together in case I need any spares! I decided therefore to lap in the valves before refitting them to this head.

I started with the inlets- nos 1 and 2 went really well, the amount of grinding needed was very small- in fact "fine" paste only was needed and the effect was to create a lovely smooth grey area encircling both vales and seats.
I ground these using a hand grinding tool and using the spring under the valve approach to aid in lifting the valve between grinding sessions.

I used the time-honoured spring-on-the-valve-stem approach to aid lifting the valve for partial rotations between grinds.

Valve in position- spring lifts it from its seat

Finished effect- smooth and even circular grey region around valve and seat seen here for number 2 inlet

However it was only when I moved to valves 3 and above that the significance of something I had noticed earlier on struck me: Valves 1 and 2 are different from the other 6. They have been replaced! It seems likely that these valves have been changed (possibly their guides as well) and in all likelihood their seats have been recut at that time. I don't think the other valves received this attention and my attempts to grind the remaining valves proved far more difficult.

Inlet valves 1 and 2 (left) and 3 and 4(right)- valves are different design, although all have Lotus numbers on their stem tops. Nos 1 and 2 differ from the remaining 6.

Inlet valve 2- wide, even and smooth seat

Inlet valve 4- seat narrower than that on cylinder 1 and not even: it's narrower on one side (app 10 O'clock) than the the other (app 5 O'clock), some pitting still evident at 11 O'clock

Although I could get a nice smooth grey colour to the seats and valves it took much more work. Furthermore the seats didn't seem even, they were narrower than the bands around the valves in no 1 chamber in all places, but worse, seemed to be wider on one side than the other. Its hard to see in the pictures because the flash makes them look pretty shiny all over but it seemed clear enough to me. The chances are that these valves would seal all right but it was clear that their seats were more worn and possibly out of concentric alignment with the guides. If I was to use this head I think at the very least I would want to recut all the seats in cylinders 2-4 and probably renew valves and guides as well.

Grinding these seats is laborious and there is probably nothing to be achieved in doing so. I decided therefore to thoroughly clean the head and valves and reassemble for storage against future need. I have however got a drill-mounted lapping tool on order so I may try this when it arrives just to see if it improves matters but for the time being I'm going to stop any work on head 2 and return my attention to the reconditioned head returned from Southern Rebore.