Tappets

[Derek Sheldon]

I’ve always set mine at 7 cold for both, quite an easy number to remember.

[Chris KC]

Quite aside from the obvious hazard, the main reason to set cold is consistency. The gap is temperature-dependant and unless you know HOW hot the engine is (at the valves) it might be 100 degrees either way, as well as cooling while you work.

[Tony Griffiths]

I'll upset the apple cart, since getting my first Seven in 1962 and a copy of  LM Williams Specials book I have always set the tappets at 0.004" cold. After an article on tappet clearances in the PWA7club  magazine last year I took one of the Sevens out on a blistering hot day up a long steep hill grinding away in bottom, at the top I quickly stopped and dropped (literally) the tappet cover off and checked the exhaust valve tappet clearances. All were an easy 0.002". Any engine rebuild includes grinding out the wear dimple in the tappet screw. I had to wait a while before I could refit the tappet cover.

Now that's the sort of empirical research I like to read about.

[Hobbo]

Hi just like to give an update. Checked and set inlet at 6, exhaust at 8 cold. Found quite a few that I think were very tight, quite a fiddly job. Could not conceive doing it hot or with manifold in place, thanks for all the valuable answers. Mike

[Roger Goldthorpe]

Not exactly Austin 7 but after fitting a trials cam to the Reliant engined Liege the following extract from my log relating to tappet clearances may be of interest

 

17               Set off for the Liege Club Meet but only got as far as Langtoft before the Liege began to loose power and started to run rough. Managed to crawl on to Dave Bogg’s where he tried to improve things but without success so left the Liege with Dave for him to sort out.

 

22               Collected Liege from Dave’s on our way back from a couple of days looking after A & G in Manchester. Liege is now running ok. Dave had telephoned Kent Cams and was instructed to set the tappet clearances to 16 thou and not 6 thou as for the Reliant!

Prepped Liege ready for Durham Dales Classic Trial.

Roger

[Bob Culver]

For anyone perplexed by the very wide clearances adopted for most makes post the Seven, this is because of opening and closing ramps designed to quieten and soften openings and closings and to reduce the effect of slight clearance variations on accelerations/decelerations. To avoid the vagueness associated with the ramps a wider clearance is usually stipulated for setting timimg and this confuses comparisons with Sevens.

[Dave Mann]

Thank you Tony, I still managed to scotch my left wrist on the exhaust down pipe, I should add this is easier to do on the RN and earlier cars with the raised exhaust manifold it would be difficult with the later combined manifold which is lower.

[JonE]

I'll upset the apple cart, since getting my first Seven in 1962 and a copy of  LM Williams Specials book I have always set the tappets at 0.004" cold. After an article on tappet clearances in the PWA7club  magazine last year I took one of the Sevens out on a blistering hot day up a long steep hill grinding away in bottom, at the top I quickly stopped and dropped (literally) the tappet cover off and checked the exhaust valve tappet clearances. All were an easy 0.002". Any engine rebuild includes grinding out the wear dimple in the tappet screw. I had to wait a while before I could refit the tappet cover.

old thread, but just out searching...

Is the point here that 6 and 7 thou gives an adequate safety margin, but that as long as the valves ARE physically released, then the engine will be more efficient if that release is as small as possible? i.e. Dave's "easy 0.002" in extreme circs shows that the cold 4 is ok for the rigorous?

[Ian McGowan]

Colin Wilks
"I was advised by a very experienced sevener to set all gaps to .010" cold. I have followed his advice and it seems to work. However, I have a feeling you may find this is a contentious issue on which opinions differ!"

+1  I much prefer a noisy tappet to a burnt valve.

[Robert Leigh]

For more than 60 years I have used 4 thou for inlet and 6 thou for exhaust, and have not had problems.