More tests

This is whats been happening yesterday and today: Apart from family things, I started testing all 10 valves using the candle flame test. Moved the piston in the TDC position and pump it up to about 5 bar and hold the candle flame under the exhaust and the mixture inlet. Here are the results:

Candle flame leak test
CylinderExhaust valveMixture valve
#3OKLeaksFixed mixture valve.
#4LeaksLeaksFixed both.


So a bit disappointing but ah well, just needs more lapping I suppose, and hopefully that’s it and no machining.

So I started with cylinder #3, and yes lapping that mixture valve fixed it πŸ™‚ no problem !!!!

Then today I started with cylinder #4 and hoped to finish #4 and #5. Lapping both valves in #4, took two lap sessions πŸ™ This means cylinder off, lap valve, cylinder on : A lot of work……..

But anyway after a lot of work for this one, my candle flame test gave me a good result.Β No more time left for #5, so hopefully that one can be done tomorrow πŸ™‚ And then all valves are done !!!!!!!!!!!

Finished cutting the exhaust valve seat

Got a call today from Rob at Auto Restorations. He finished cutting the exhaust valve seat!

Picked it up at lunch time and spoke with him about my piston rings. He explained me how they work:

When the mixture is ignited, the rings are pushed down in its grooves in the piston, and then get pushed outside against the bore of the cylinder, sealing it.
Possibly just filling up with compressed air might not seal it, which is what I see.

So he convinced me to try and run the engine with the current rings.

And then I suddenly realized that there is a vent coming from the crankcase. So all I need to do is check how much (exhaust) gas is coming out while the engine is running. If I connect a hose and put it in a bucket of water I can see how much the rings are leaking!!! πŸ™‚

Oh yes Rob also lapped the valve, and reamed the valve guide as it was a bit pushed in halfway as it was pressed into the cylinder.

From Wikipedia: A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides.

So all good.

So tomorrow I will put this cylinder back on the engine and do my candle flame leak test for the 10 valves.

Are the rings leaking

Put the fourth cylinder on today and decided to start doing a leak down test on the 4 cylinders I have installed so far. A lot of escaping air, but none through the valves I think.

I will confirm that in the weekend after I have taken of the mixture inlets, so I can check those a bit better as well. Basically going to pump up the cylinders again and use a candle flame to see if any air comes out of the exhaust or mixture inlet.

The leak down test was disappointing. All four cylinders leaked down from 5 to 1 bar in about 5 seconds, same result as the worst cylinder last time.
With the one cylinder still off, I can definitely hear air coming past the piston rings.Β If the candle flame test in the weekend confirms that the valves are good now, then I am going to replace all the rings πŸ™

When will it ever stop!!!!!!

Valve seat machining company

Just been to an “Auto Restoration” place. They do the valve seat machining all the time. He showed me the tools they use. Just what I thought they would look like. Some creation that looks like a valve and sticks through the valve guide, and then the pull from the stem end, and twist it around till the whole seat is cut away and flush with the valve head again.

Talking with the guy, it looks like its quite normal for old valve guides to have a hole in it that is not central. So yes this is why the new one, where the hole is nicely central is creating this problem.

Yes the machining of the valve seat will be done this week, so I can put the last cylinder on for another test run this coming weekend. Still need to find out why the carburetor didn’t get enough fuel in the engine….

Seat needs machining

No engine work yesterday. Been helping a friend building a little shed most of the day.
So back on engine duty today πŸ™‚
First I put the #1 and #2 cylinders back on the engine after I quickly checked them for leaks through the valves. No leaks so yes these are on now.
Next cylinder to work on was #5. This is the one with the new valve guide. I had a quick go trying to lap it with a coarse lapping paste, but quickly gave up. Not possible, the valve seat needs to be machined first πŸ™

Valve guide issue

Hmm, maybe not so good news. More delays.

Yes I have my new valve guide, looks beautiful, but I think the the original valve guide didn’t have the hole for the valve stem to go through right in the centre. Will have to look into that soon.

What this means is that the valve head doesn’t sit right on the valve seat, meaning its going to leak, even if I lap the valve. There is just to much misalignment.
So now the valve is symmetrical, the valve seat might have to be machined. BUT this might not be so easy, meaning expensive, as the cylinder head is not separable from the rest of the cylinder as its one unit.

Ah well one issue at a time.

This is so far the only real issue I have found in this engine, so maybe I shouldn’t complain πŸ™

Just a nice description of all the parts around the valve, in case you are lost …..


Piston rings

Today I went to a shop here in Christchurch, Cliff Bond Ltd, who make piston rings !! πŸ™‚
They had the ring I needed, It’s a 4 1/8″ * 1/8″ compression ring. Was only $8.74.
The slot in the piston needed to be enlarged a tiny little bit. Was done in a few minutes. All perfect.

Just put the ring in and slotted the piston into the cylinder. Yes compression looks good ……..

New valve guide

Almost there. Did the last 3 cylinders, but with cylinder #5 I noticed 2 little cracks in the valve guide. This valve guide is basically a brass tube that slides into the cylinder and the shaft of the valve (see photo on right) slides up and down through this.

I managed to slide it out, and yes a piece at the top of the guide is about to break off. Well I don’t think it will just fall of, but its not right. If I grab it with a pair of pliers I can pull it sideways.

If it did fall off, it would fall on top of the backside of the valve and if I am lucky it would be blown out of the exhaust. Or if I am unlucky, it would fall on top of the piston, when the valve opens.

Don’t want to rely on luck, so this part needs to be replaced.

This valve guide (M302) would cost me US$0.75 in the good old days (1928). But no parts can be bought anymore, so needs to be made.Β Rang Tony, a colleague this morning from a previous work place who did this kind of work all the time, and I am going to meet up with him in the next few days, so he can make me a new one.

Should be very simple.

So the planning is still to get all the cylinders back on the engine next weekend!!

In the mean time I have been taking the carburetor apart to try and find my fuel problem. That’s still work in progress. Complicated things these aviation carburetors………

By the way, the compression on all 4 finished cylinders looks really good. No more leaking valves!!!!


Well all I did was try to push the piston down into the cylinder, and I couldn’t, as it kept on popping back.Β The real test comes when its back on the crank case, when I do the leak test.

Lapping valves

Started lapping valves today. Just grabbed the left one without thinking what the compression used to be on this one. But when finished, I tried pushing the piston into the cylinder. Beautiful compression here. No leak in exhaust and mixture inlet.

Then I noticed that this was originally the best compression cylinder. Ah well its good that the compression is still quite nice !

Second cylinder (#4) I did here was the one with the worst compression earlier on.Β After I was finished lapping the valves here, again, tried pushing the piston down, and again, really good compression!

WOW yes it’s working πŸ™‚ 3 more to go………