Valve adjustment procedure

[EngineMotorMan]

Hey folks,

I just adjusted my valves and I think I have them too loose. I set them at .008 with my feeler gages with the engine cold. Should I have warmed up the car first? Before I loosened the eccentrics, I could not even slip the gage in. And yes, I did have the cam completely off of the rocker for each valve when I adjusted them.

Any tips or thoughts on valve tuning on the M-10?

[Tom D]

no such thing as "too loose", only too tight!!

spec is .006 - .008 cold, both intake and exhaust. valves have a tendency to tighten up as they wear, not loosen.

[epmedia]

And .008" is good if they have not been adjusted in a LONG time. Especially if it's never had an "Itallian tune up" to blow out carbon and squish the carbon down on the valve seats (this is where .008/bigger gap is good). If a head is fairly fresh with a new valve job, then .006" is good. Also - 20/50 oil may quiet them abit, if you not using that already. And as always stated in the past - they are suppose to make noise, like a "finely tuned sewing machine"

Those plugs have alot of deposits, how long they been in there?

[EngineMotorMan]

the plugs are about a year old. I probably should clean them up. The good thing is that there isn't really any oily stuff on there, just carbon.

the valves are certainly a bit louder, but the engine can rev a bit higher and seems to run more smoothly. the valves were adjusted about a year ago, but they were definitely set too tight, or maybe they were adjusted with the engine warm....

You are supposed to do it with the engine cold right?

[otto325e]

Make sure you have a feeler gauge that you can actually set independantly between the rockers and valve springs. With the adjuster/roller loose, just clamp the guage(I broke off a 5cm piece of mine from my guage set) it between then tighten the adjuster and take it out.

[epmedia]

...do it with the engine cold right?

yes, just like Tom stated for you.

[EngineMotorMan]

wow, how did i miss that part? I think I only read the first line of his post before. Why do they tighten when they wear?

[Tom D]

Why do they tighten when they wear?

the springs, for one, suck them into the head.

[kdanielson]

Valves don't ALWAYS tighten when they wear, it depends on what is wearing. If the valve face/valve seat is wearing the clearance will tighten, if the stem/adjuster eccentric/camshaft/rocker rubbing block is wearing the gap will open up. It has been my experience that the eccentrics wear the most-the good news is they are cheap and I recommend replacing them as well as the bolt/nuts.

I always set mine at a snug .006" with no issues and it reved to 7000rpm easily once I had the spring package sorted for my aftermarket cam though that was not necessary to make the power I was after.

Go down about 1/4 of the way on this page to see how I set the valves on a M10: http://www.kengineering.info/78%20bmw.htm

ken

[Tom D]

different approches with different results.

i have found over the years, that with older engines that were designed to run on leaded gas, the seat/valve is the weakest point. as Ken said above, this will tighten the clearance.

personally, with small BMW engines (i have two boxers and two 4 cylinders) i will run larger then spec clearances. this will change the personality of the cam just as much as Ken running tight spec values.

so you have options. don't worry about the valve lash noise. that just means your not burning valves.

[epmedia]

True with different results, even on the same engine.
I've had some loosen, and some tighten, but the loosening was not nearly as much as the tightening. The ones that tightened the most were after hotrodding, got down to about .003" (from .006") and started leaking past 2 exhaust valves. I'm certain it had to do with carbon build up, and thin valves I set mine to about .008" - .0010" after that, now about a year later - they are just starting to quiet down again... Knock on wood; I've been fortunate not to suck a valve yet, probably due to the weak valve springs

Hi ken - I like to use an 'allen key'/'round pin' to adjust the eccentric; gotta be careful not to let it slip out of hand though

[EngineMotorMan]

Duly noted. The car has a lot more power now with the valves loosened up to .008.

[Tom D]

motorman, the second part of your post was "Any tips or thoughts on valve tuning on the M-10?"

the following are old mechanic's tricks for tuning engines. this was before hydraulic valves and computer controlled engines.

i'll start with some insight on cam timing.

by retarding or advancing the timing of the cam, you can move the power band up or down a few hundred RPMs. if you retard the timing you'll get better top end and advancing will move the power towards the bottom.

you can also do this by changing the valve lash. decreasing clearance moves power up, same as retarding the cam. increasing the gap has the same effect as advancing the cam.

this is why i run small BMW engines with large valve lash. puts the power in a spot more suitable for daily driving.

retard cam/decrease gap = top end power
advance cam/increase valve gap = bottom end power

[EngineMotorMan]

thanks Tom. That makes a lot of sense because since I have opened the gaps on the valves, the engine has more power at lower RPM. This is good for me because I live in a town with lots of hills and I don't have to down-shift all the time now!

[goinstrong]

I was aware of the timing changes and effects of retarding/advancing the timing, but thanks for the clarification about the valve lash! I have a tired M10 in my '81, and it might help to set the gap at .08. Thanks!

Tim

[RedLantern]

Couple of noob questions:

1. Is there a particular order I need to do the cylinders in? If so, what is the cylinder order from the firewall to the radiator?

2. I'm going to replace the valve cover gasket at the same time - do I have to do anything to the gasket before I install it? Lube it up with oil or anything?

[otto325e]

No but it's easiest and quickest to do them in firing order because once you have the first at top dead center, the next cylinder to fire will be the closest to top dead center.

The firing order on the m20 engines is 1-5-3-6-2-4

1-3-4-2 or 1-2-4-3 is your firing order I think

[RedLantern]

I would be able to figure it out by observing the motion of the camshaft as well as the resulting lift on the rocker arms/tension on the valve springs, no? Rocker arm lifted=spring compressed=valve open, correct? I want to adjust the valve when closed right?

[epmedia]

I would be able to figure it out by observing the motion of the camshaft as well as the resulting lift on the rocker arms/tension on the valve springs, no? Rocker arm lifted=spring compressed=valve open, correct? I want to adjust the valve when closed right?

Standing at the front of the car, the engine turns clockwise. The fireing order is 1 3 4 2, #1 is the front (displayed on valve cover). It's easiest to remove the spark plugs and put the car in neutral and rotate the engine with the fan belt, otherwise put the car in 2nd gear while rolling forward to turn the engine.

Yes, the valves are adjusted while closed/cold (the round on the camshaft).

[Tom D]

thanks robert.

[epmedia]

1-3-4-2 or 1-2-4-3 is your firing order I think

it's "usually" best to go by your first instinct.
I cannot for the life of me, ever remember the order of a 6, very confusing...

thanks robert.

"tag teaming" it... I'll be slacking later, so you are "it" for the rest of the day...

[RedLantern]

Thanks guys. Now I just have to wait for my parts shipment (with the valve cover gasket) to arrive! Will I need to prep the new gasket in any way before replacing the old one?

[epmedia]

Thanks guys. Now I just have to wait for my parts shipment (with the valve cover gasket) to arrive! Will I need to prep the new gasket in any way before replacing the old one?

The gasket goes on clean and dry. (unless the front timing cover height is improper)
The gasket does not have to be replaced every time either, just so you know.

[Rushfan1]

The gasket goes on clean and dry. (unless the front timing cover height is improper)
The gasket does not have to be replaced every time either, just so you know.

Eventually I am going to be replacing my valve cover gasket. So the procedure is simply to remove the old one and clean the gasket surface area such that it is dry? When tightening the valve cover back on, what's the general rule for the amount of pressure to use when tightening?

I realize this is a newbie question from a long time E21 owner, but my valve clearances haven't never been touched (187000 km). Engine runs just fine with a quiet valve chatter coming from the engine bay. Is ignoring the valves dangerous to my M10's health (and thus mine)?

[ekr470]

Yes, if they are too tight you can burn valves. Definately go and check your clearances.