11 replies to this topic

[MayfairEdition]

Hi, I decided to set my tappets the other day, so I looked in the trusty Haynes manual for the clearences, when I found that, for a 12A engine number they are 033mm to 0.38mm. And for all other engines it is 0.30mm. Mine is a 12A engine so I wasn't sure.

When researching I found that 12thou seems to be the recommended setting for most engines, so that is what I did them to (0.30mm). I Carnt hear anything untoward, but it is a little awkward at the mo as my exhaust is blowing.

Does anyone know if it was correct doing a 12a engine at 12thou?

Thanks in advance for any help or tips. Cheers.

[HarrysMini]

12 thou when cold is the correct setting.

[MayfairEdition]

Ok thanks. I'll leave them as it is then. Why is it stated differently in the Haynes manual for 12A engines? If it is 12 thou for all of them. Cheers

[HarrysMini]

I tend to ignore anything the Haynes manual tells you, a lot of it is just terrible information.

 

I get all figures from the original BMC Workshop manual.

[sonikk4]

Not everybody has access to the BMC manual Harry so the Haynes manual does a good job for what it it. .015" is noted in the BMC manual for competition engines.

[A-Cell]

Yep .020inch (12 thou) or 0.30mm Cold is correct.

[Cooperman]

I tend to ignore anything the Haynes manual tells you, a lot of it is just terrible information.

 

I get all figures from the original BMC Workshop manual.

+1 on trusting the original BMC Workshop Manual.

 

The original 1275 Cooper 'S' had valve clearances of 0.012" cold and there is no logical reason to change this. You will hear all sorts of reasons given, but the clearances are to allow for valve train expansion as the engine heats up. The only reason for increasing this setting is if a different ratio rocker shaft is fitted, in which case multiply the BMC clearance (0.012") by the rocker ratio. e.g., if going to 1.5 ratio rockers, divide by 1.3 and multiple by 1.5, which gives 0.014"

[MayfairEdition]

Thanks everyone. From now on I'll take what the Haynes manual says with a pinch of salt. I can be certain I have done the correct thing for once now and not worry I'm doing it more damage than good.

Thanks again.

[sonikk4]

At the end of the day thats what the forums about. If you have doubts or questions then fire away. 

[sonikk4]

Check your email. There is something there that will help in the future.

[MayfairEdition]

Got it. Thanks Neil!!

[sonikk4]

No probs. Its a very useful bit of kit.