Safe minimum valve clearance for my noisy tappets m20b28

[nickphine]

Hello, i've just finished my m20b28, build, runs really well but the tappets are noisy. Obviously.i set them during the buildas per haynes, but i'm sure i've read somewhere they just get noisy after a while and that's that. Can they be set closer safely to reduce tappet noise or do I need new eccentric adjuster wheels or just adjust them several times and hope it improves?

Any experience would be greatly appreciated, cheers

Nick hine

[daimlerman]

Did you set them up after fitting/torqueing the head down?

[nickphine]

I did, but before it was run. My feeble brain can't work out why it would make a difference if the head is torqued down or not, with it not being a pushrod an all. I'm probably missing something obvious.

I'm just going to redo them and see what happens, but there is wear on some of the eccentrics if I recall.

[daimlerman]

I used to set them with the head off,then learnt that torqueing the head down settles the alloy head onto the block face,which can change the settings...

I also set all valves to the exhaust clearance,with a 'loose' feel,as tight clearances can effect low speed running.
Injector 'click' can also be confused with tappet rattle,but I doubt that this is your issue!

I find that M20 is noisy at idle,compared to,say.M50,with auto tappet adjustment.

[nickphine]

Injector click, that sounds interesting. I have a stainless exhaust which again i think ive read can make injector clicks noisier? Could have dreamt that though.

[badassyas]

Having a six branch makes the m20 a bit noisier if you have one fitted..?
Also, you need to make sure your eccentrics are not flattened and your rockers too. It will alter the valve clearance and may make it noisier

[e301988325i]

I run my inlets at 0.15mm and exhaust 0.2mm.

I drive the car to warm it up before hand, and do the exhausts first.

[nickphine]

Thanks for your help, I read a post on checking for ticking injectors using a screwdriver and ones lug 'ole and mine are ticking away like little buggers. very little noise coming from the rocker cover though so I can only assume the injectors are to blame.

None of this will matter then when I go to Webers at some point so I'm going to stop worrying about it.

[HairyScreech]

this is the same trouble i have with mine, and yes i have found that even setting the rockers right down to 0.1 (only to idle it and listen not to run for more than 30 secs.) didnt stop the ticking, it was after that i started listening to the injectors to find as you have that they were ticking away like mad.

it dosent help that they fire at similar time intervals to the rockers opening.

not much you can do about the injector noise.

[hongkongfuey]

m20's should be 0.25mm (0.010 in)

i was told my old car which was cam'd and had 6 branch it should be 0.30mm (0.012 in) on the exhaust side due to extra heat

[HairyScreech]

yep, 0.25mm standard, you can get away with 0.20mm once the valve heads have worn to the eccentric a bit though as the dip worn in the top of the valve results in slack clearances when a flat feeler gauge is used to set them.
something which can cause tappet rattle on a lot of older stuff, particularly minis and ford kent engines.

who said to go for 0.3mm on the exhausts?
surely it would have to have been running a lot hotter to take up 0.05mm extra.

[Andyboy]

325i's idle better with 1-2 thou more exhaust clearance.

[nickphine]

not much you can do about the injector noise.

Triple Webers!

[nas786]

I need help on this as ive set my tappets at 0.10 on both exhaust n inlet side but the ticking is louder wat hav i done wrong?

[scjimbo]

not much you can do about the injector noise.

Triple Webers!

And a personal fuel bowser

[Eddie25]

Something that has bugged me forever;

I've just gone for Fully Synthetic Millers 15w 50 oil with a high ZDDP content. I believe ZDDP is a type of zinc additive that has been removed from modern oils but it is ideal for older valve train designs.

An M20 will always tap but i think the thicker oil does help. I also run a cam and 6 branch hence went for a 50 rated oil for the temperatures involved (the car is not used in the winter months).

I could be wrong but playing around that's what i've found out

[Eddie25]

If funds allowed i'd also like to try an M20 on more modern and possibly quieter running injectors. IIRC an variant of M50 injectors are pretty much plug and play.

[sean_318i]

The simplest way to silence a noisy m20 is to remove the badge from the centre of the steering wheel and stuff some tissue paper or a rag down around the nut that holds the steering wheel in place, and then refit the badge.

An awful lot of top end noise is transmitted up through the steering column and the tissue will dampen it out. This should be particularly effective on a 6 brancher due to the proximity of the exhaust to the column.

It’s made a difference on any of the m20’s I've driven.

Seán

[clipper]

yep, 0.25mm standard, you can get away with 0.20mm once the valve heads have worn to the eccentric a bit though as the dip worn in the top of the valve results in slack clearances when a flat feeler gauge is used to set them.
something which can cause tappet rattle on a lot of older stuff, particularly minis and ford kent engines.

I discovered that this had happened to mine while struggling to get a decent clearance set up.

In the end I fitted brand new excentric adjusters, then set and rechecked checked the "gap" at each valve head with a flat guage, which as you have said does not allow for the concave wear of the stem.

Then I calculated the corresponding gap between the rocker and the cam according to the leverage ratio of the rocker and reset the excentrics using that "corrected" measurement, which in theory takes into account the wear.

The maths showed me that the concave wear was actually responsible for an extra 0.01 - 0.02 mm when measured at the stem, so I would say that reducing to 0.2 is a bit excessive, mine would have required a reduction to 0.23 at the most.

It did, by the way make the engine noticeably quieter and run better.