1953 Tappets

[Ian Richmond]

Hi, I am new to the Ariel fraternity and have found this forum incredibly helpful. I am sure I am going to ask lots of (probably very dim) questions but for now I just need advice on tappet clearance. I have a 1953 NH which I presume was manufactured prior to June 1953 as it does not have a letter R after the four digit engine number. According to the Maintenance and Instruction Manual the clearances for the pre June engines are Inlet Nil and Exhaust 2 thou, whereas the June 1953 onwards engines are 6 and 8 thou respectively. As my NH has the earlier engine, (to play safe) I have set inlet at 1.5 thou and exhaust to 3 thou, just to run the engine following a full rebuild. I am a bit nervous of setting a clearance of zero. Is the theory that the clearances will increase as the engine warms up ? Any help/advice would be very welcome.
Ian Richmond

[Ian.Taylor]

My Oct 52 built VHA has Nil & Nil clearance . I set my rockers snug then back off until they move back & forth freely with NO tappet clearance.
I cruise between 55-60 mph with no issues even when it was close to 40c here recently.
My old 32 OHC was Nil & Nil .On a hot motor i discovered the clearance increased say to about .001-002

I suspect the VHA is the same.
I'm still using the original steel pushrods.

[Simon.Gardiner]

Hi Ian (R) - welcome.
I used to run my '53 NH at nil and 2 thou - as I remember in practice that resolved to just 'disappearing' the clearance but still able to slide the rocker across the end of the valve cap for 'nil', and just able to feel the slightest bit of clearance for 2 thou (and making sure that the exhaust lifter was well out of the way) .
Ran that engine for a year or more as the 'daily driver' - including some very long excursions, never had any trouble with the valves or timing gear.
However, always start off with appreciable clearances if you've renewed the rocker-box gaskets as they will sink pretty quickly initially (unless maybe you're using Drags' ally gaskets).
The pre-'53 iron engines (or is that pre-52??) were nil and nil, I did a lot of miles on my '51 VH using the nil/nil settings, again no problem.
In my experience, if you've set the tappets slightly tight (or they've got tight because of the rocker box gaskets compressing) you find that you've got good compression when hot but poor (or very little) compression when cold, and I'd say you can use that as a yardstick for whether you need to slacken something off slightly. (I guess that also reinforces the theory that the clearances increase as the engine warms gets hot!)

SG

[Ian Richmond]

Hi Ian and Simon,
Thank you both for your detailed information, I now feel very comfortable following your advice. I will take the bike for a short run leaving the gaps at 1.5 and 3 thou., then re tighten the rocker box bolts and then set the clearances exactly as you suggest. I do have some Drags ally rocker box gaskets but when I lined them up with the boxes and cylinder head, in some places there was only a very narrow contact patch, perhaps 1.5mm, and as the main purpose for a total engine strip was to make the engine as oil tight as possible I (reluctantly) fitted new fibre gaskets. I realise that I will have to continually re tighten the rocker box bolts as these fibre gaskets compress, and then reset tappet clearances. My engine also still has the original steel pushrods.
Thanks again for your advice, I will undoubtedly have many more questions as I get to put miles on the bike.
Ian