240 General: New (to me) 1980 Volvo 244

[Laird Scooby]

Originally Posted by Clifford Pope

Sorry, I still don't get it. How does knowing the gap tell you what size shim you need to close up the gap to say 16 thou?
You need to be able to measure the thickness x of the present shim, and then order x + 16 - 18 = ?
or else be able to measure the total gap with no shim y and then order y -16 = ?.

Let me try explaining a different way with a bit more information then.

Remember when Alan did the head gasket, changed the head etc a few weeks back?

He checked/adjusted the valve clearances then and recorded the clearances and/or the shim size for each valve. That's the important bit for this, recording the shim sizes.

He now has a record of what shim size serves which valve so when he measures the clearances in z years time, he'll be able to perform the calculations without needing to remove the shims indivudually, measure and then calculate.

With that extra information, he just has to measure the gap, work out the difference between what it is and what it should be then check waht size shim is in there to work out which he needs to get.

Then once the shims are obtained, pop the old out and the new in, recheck the clearances to be sure and job done!

Hopefully makes more sense now?

[Othen]

Originally Posted by Laird Scooby

Alan has created a spreadsheet and recorded the shim sizes of each valve so he can just measure in future, check his spreadsheet and work it out from there. At least that's what i think he means!

I should have read your reply to Clifford before I wrote my last Dave - you have explained it very succinctly. Yes, what you said is exactly what I meant.

My apologies if I forgot to mention keeping the spreadsheet record above, Clifford is right in that without it I’d have to take each shim out to measure its thickness if the clearance was out of tolerance. I thought I’d explained that bit, but I’d forget my head if it wasn’t attached to me.

:-)

Alan

[Othen]

Originally Posted by Bob Meadows

The older method:~ A sheet of flat glass- fine grinding paste (used for valves) lubricate with oil—get the muscles working & keep measuring. A disk or small item can be part sunken into a piece of wood if you find it easier.
Bob

Many thanks Bob, I notice (having now caught up with a few posts having been out most of the day) that Clifford used much the same method.

:-)

Alan

[Othen]

Originally Posted by loki_the_glt

I'll get you one with the various dimensions in the next few days - just as soon as I can locate a ruler and some suitable background material.

Many thanks; there is no rush whatsoever, I’m not planning to run the leak down test until October (then if I do discover an issue I can address it during the winter break).

Alan

[Othen]

Originally Posted by Laird Scooby

Let me try explaining a different way with a bit more information then.

Remember when Alan did the head gasket, changed the head etc a few weeks back?

He checked/adjusted the valve clearances then and recorded the clearances and/or the shim size for each valve. That's the important bit for this, recording the shim sizes.

He now has a record of what shim size serves which valve so when he measures the clearances in z years time, he'll be able to perform the calculations without needing to remove the shims indivudually, measure and then calculate.

With that extra information, he just has to measure the gap, work out the difference between what it is and what it should be then check waht size shim is in there to work out which he needs to get.

Then once the shims are obtained, pop the old out and the new in, recheck the clearances to be sure and job done!

Hopefully makes more sense now?

Exactly that Dave. You have explained the process much more succinctly than I suspect I did above ( I probably assumed everyone had read my previous passage some weeks ago about recording the shim sizes when I first set up the cam on the new head).

I see Clifford’s issue: when I set it up the first time I measured and catalogued all the shims I had (8 of them), fitted them to the new head pretty randomly and bolted down the cam (I did this on the bench), then measured the clearances and swapped the shims round to get a good fit. I needed 3 new shims to enable the maths to work.

You are dead right that once I’d calculated it all out and got a workable solution I recorded the actual shim sizes by valve number and I keep them on a spreadsheet for whenever I check the clearances again. I won’t have to remove each shim and measure again, I already have that information.

I’ve taken 3 paragraphs to explain what you did in one Dave :-)

Alan

[Clifford Pope]

Originally Posted by Othen

You are dead right that once I’d calculated it all out and got a workable solution I recorded the actual shim sizes by valve number and I keep them on a spreadsheet for whenever I check the clearances again. I won’t have to remove each shim and measure again, I already have that information.

You have the thicknesses originally, but if you find that the clearances have changed, how will you know what has worn? You are assuming the shim will have worn, so you just need a new shim of the original thickness.
But supposing the valve seat has recessed? Or both the shim and the valve seat have worn? Or the cam lobe?
You don't have a constant base point.

With an old-fashioned adjustable tappet the gap you measure can be adjusted regardless of the cause - the tappet, the cam follower, the push rod, the head of the valve stem, the rocker face, the rocker bearing, and the seating - anything could have worn, but you adjust-out all the wear until only the desired clearance remains.
But with a non-adjustable OHC all you have is a big gap of unknown size, because the shim might have worn. You've got to start either with a brand new shim of known size, or an old one that you measure.

[Othen]

Originally Posted by Clifford Pope

You have the thicknesses originally, but if you find that the clearances have changed, how will you know what has worn? You are assuming the shim will have worn, so you just need a new shim of the original thickness.
But supposing the valve seat has recessed? Or both the shim and the valve seat have worn? Or the cam lobe?
You don't have a constant base point.

With an old-fashioned adjustable tappet the gap you measure can be adjusted regardless of the cause - the tappet, the cam follower, the push rod, the head of the valve stem, the rocker face, the rocker bearing, and the seating - anything could have worn, but you adjust-out all the wear until only the desired clearance remains.
But with a non-adjustable OHC all you have is a big gap of unknown size, because the shim might have worn. You've got to start either with a brand new shim of known size, or an old one that you measure.

Hi Clifford,

Well, you have me there: it had never occurred to me that there would be significant wear at on the shim or the cam lobe. Most of my experience is with bikes, where DOHC/OHC arrangements are very commonplace, and I must admit that in about 40 years of adjusting them I've never come across a valve clearance that increased, they have always decreased due to wear at the valve seat - not once - in dozens of times.

I suppose you are right, but I can't help thinking the chances of wear on a well lubricated cam lobe and follower running at perhaps 100C is much less than an un-lubricated valve seat running at 800C and with a steel valve smashing into it 50 times per second. I could be wrong.

Whenever I take an old shim out I notice that if I take a few measurements of the thickness with my micrometer it hardly varies, whereas if it was wearing significantly wouldn't one expect to see the middle where the lobe touches much thinner than the edges where it doesn't? I've never measured a camshaft's lobes for wear, but saying that I've never noticed one wear out either.

I completely agree that it a screw or eccentric adjuster is much easier, be it OHV or OHC design, but that is not what I have with the B21 motor, so there is not much point me pursuing that line, is there?

Alan

[Clifford Pope]

Well, it seems our experiences differ then.
In my experience with 240s what gradually happens is the valves become noisier as the gaps slowly widen - I've assumed because the shims wear from contact with cam lobes. There isn't usually a visible groove because the buckets should rotate freely, so the wear is spread over a dish shape, not concentrated in a groove because the bucket isn't turning. Also the cam lobes wear, increasing the clearances.

I've never actually had a 240 with any significant valve seat recession. The heads are I think all built to run on unleaded fuel, unlike most other older cars.

So I come back to my point - you need to know the thickness of the current shim before you can fit a new one, in order to have a base point. Or of course you put in temporary shim of any known thickness, eg a new marked one, measure the gap, and then calculate the size you need from that.

If only the shims ever wore, then you could just put in new ones of that size to get the valve clearances correct. Or if shims never wear, then you just need to get new ones to take up any wear in the other components.
But if wear takes place in an unknown mix of shim, valve, valve seat and cam lobe then you don't have a known starting point.

Finally of course, the engines go for hundreds of thousands of miles without any significant change in valve clearances, so you probably only need to reset everything once in your lifetime anyway.

[Othen]

Good morn chaps,

I thought I'd post a photo of the leak down test instrument I bought, and that has led (somewhat indirectly) to the recent discussion above:



I like owning tools, and as has happened a few times, I bought this not because I particularly needed it, but because:

a. I'm intrigued by this - I've never used one previously, I'd heard of them and always thought the logic made sense. This may be old hat to many of you chaps, but for me it is new ground.
b. I have an ideal test bed (the RB - 40 years old and with a simple and easily accessible petrol engine). I don't think I'd try this on the Porsche (probably have to take the engine out to get access) and the Škoda is a diesel.
c. It only cost £17.50 delivered to my door. As some may know, I'm a tightwad and always thought something like this would cost several hundreds, I have no idea how a factory in China can manufacture it, ship it to me and everyone along the line make a profit for the cost.

The instrument has been sitting in the garage for several weeks since it arrived. I have just had a look at the (English, and quite good) instruction book and can see it should only need to run at 20-50 psi, so I don't think there is much danger of it forcing the crank bolt, which is good news.

I'm quite looking forward to trying this one out - in October - in the meantime I'm going to enjoy driving the Royal Barge for the rest of the summer and autumn.

:-)

Alan

[loki_the_glt]

Originally Posted by Othen

I'm quite looking forward to trying this one out - in October - in the meantime I'm going to enjoy driving the Royal Barge for the rest of the summer and autumn.

:-)

Alan

And so you should!