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Tappet Gap


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#1 micrawavewindow

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Posted 01 March 2010 - 09:11 PM

hi i adjusted my tappets today and my mate said to adjust 10 thou on inlet ans 12 thou ion exhaust is this correct as i dont want to break my engine oh its a 1275 metro with 50 thou on the clock

#2 jameswhiles

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Posted 01 March 2010 - 09:19 PM

Do you have a Haynes manuel? If not it will be a very good investment for this sort of thing!!

#3 micrawavewindow

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Posted 01 March 2010 - 09:23 PM

i do have one but could not find the adjustments

#4 lrostoke

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Posted 01 March 2010 - 09:40 PM

From Haynes

Valve clearances
Inlet and exhaust (engine cold):
All engine types except 12A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 mm
12A engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.33 to 0.38 mm

0.30 = 12 thou approx
0.33 = 13 thou approx
0.38 = 15 thou approx

#5 micrawavewindow

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Posted 01 March 2010 - 09:47 PM

i am a little confused does this mean my inlet and exhaust are wrong and of so what should they be and also what page is that on pleasee

#6 micrawavewindow

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Posted 01 March 2010 - 09:59 PM

so should i set them to 14 thou both the same then

#7 lrostoke

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Posted 01 March 2010 - 10:03 PM

Somebody with more knowledge of that engine would be able to answer better, with 1275's seems a few sources suggest different settings depending on spec of engine.
I normally use the Haynes settings but I only normally set 998's section 2a at the beginning (newer edition)

More sporty spec engines anything from 15 - 18 thou is mentioned.
With standard spec 12 - 15 thou is mentioned.

I'd try them at 14 though see how it goes.

The amount of clearance you want is dictated by the camshaft manufacturer and the kind of rockers you are using and will be included in the documentation with any aftermarket cam.

The clearance for the standard cams is very easy to set and can be divided into two groups

All 850's all Non-Cooper 998s the MG turbo and all non-S or non-MG 1275s use 12 thou clearance with standard rockers, and 14 thou with 1.5 rockers.

Cooper 997/8s MG and S 1275's use 15 thou clearance with standard rockers, and 18 thou with 1.5 rockers.


Edited by lrostoke, 01 March 2010 - 10:04 PM.


#8 samsfern

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Posted 01 March 2010 - 10:14 PM

should both be 14 thou

#9 Darkscamp

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Posted 01 March 2010 - 10:14 PM

i'd do 12thou inlet and 14 thou exhaust if its a standard engine.

#10 samsfern

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Posted 01 March 2010 - 10:14 PM

should both be 14 thou

#11 Darkscamp

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Posted 01 March 2010 - 10:25 PM

i'd do 12thou inlet and 14 thou exhaust if its a standard engine.

didnt realise we were playing the repeat ourselves to get the last post game :) :(

#12 micrawavewindow

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Posted 01 March 2010 - 10:30 PM

thanks people much appreciated do you think i will do any damage until the weekend with them set and 10 thou and 12 thou just until the weekend or should i make it a PRIORITY

#13 lrostoke

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Posted 01 March 2010 - 10:34 PM

10 thou seems really tight, I'd guess theres a chance when engine hot of valve not fully closing as the gap reduces with heat.

#14 dklawson

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Posted 02 March 2010 - 12:58 AM

If anything... set the gap on the high side, not low. If you set the clearances tight you can get to the point that the valves will not close when the engine is hot. This will allow hot combustion gasses to go by the valve (which is not closed properly) and potentially burn the seat. There's an old saying "It's better to hear the valves than to burn them".

For what it's worth, early A-series engines called for a gap of 0.012" with standard rocker arms. When you go to longer ratio arms, the valve clearance is increased.

#15 micrawavewindow

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Posted 02 March 2010 - 12:14 PM

thanks everyone i have now gapped them all to 14 and it drives like a different car (alot faster) but it does rattle abit




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