Engine Improvements #6

Most recent post


Decided to start a new page. It’s “2018” now, I am going to finish this engine ! 🙂

Very big tappet clearance

Yes decided to see if the Bleriot was still there. Have been busy getting my Advanced Local pilot license last year Oct and Nov, been on holiday to The Netherlands in Nov, then on Xmas holidays tramping in Aspiring National Park….

Its been since July that I last worked on the engine. So I checked the 5 front spark plugs that were still loose and disconnected, cleaned that one black one again, and connected the ignition wires. Next I thought, might as well check the tappet clearance, just in case.
And GUESS WHAT !!!!!! The exhaust clearance of the dirty cylinder wasn’t 15 thou (about 0.4mm) that is should be but 4 – 5mm !!!!!!!!! No wonder that cylinder had problems breathing. That exhaust would have been open for a very short time during the exhaust cycle.

So fixed that clearance setting and tried starting the engine, only to find out that my battery had died, well pretty sure, so will check it out later at home.

That was that session, but quite stoked having found this one issue. Its been there since July. Still think that my old carb is the way to go for now so will stick with that one !

Beautiful spark plugs again

After finding that massive tappet clearance last week, the engine is running again.

Took a few tries, and splutters, and help of Mike Small, thanks Mike !!

But yes running again. Sounding really good. No irregularities, just nice 🙂 One thing I noticed is that without the ring exhaust supplying heat to the carb, the carb is cooling down to a point where it freezes up when running now. Never seen this before with this carb. Ideally that means that its producing max power, but don’t like the freezing temperatures, so would like to introduce some heat again sometime in the future.

So now its just a matter of running in more, but after a little while running between 75% and 100% power I would have thought to have seen some improvement, but I don’t. Still hovering at the 1900 rpm mark.

The good thing is that the spark plugs all look right now. They all have a “nice brown tan”. That must mean that the mixture is sort of right again, this is with my original carb !

After talking with Mike, one of the many people trying to help, all with their own opinion, these are the few things to work on, and its all back to basics. It seems I have done all I can for now with what I have, its just rechecking a few things.

  • It seemed that the carb butterfly valve wasn’t completely open, only needs a little more, so fix that first. Not expecting miracles, but everything needs to be right to get the very last bit out of this machine !
  • Just quickly check the ignition timing again, and the valve clearance.
  • While doing the valve clearance have another look at the valve timing as well.
  • Now I am running with a higher compression, moved from 5.4 to something like 7, I could try a higher octane fuel. Don’t think 7 is high enough to really need it, but worth to try. And all this time I will be running the engine in a bit more…. Who knows 🙂
  • Currently running without an exhaust, and no carb heat. I am going to try to find nuts that fit my exhaust connection on the cylinder and make up 5 exhaust stubs, about a foot long. This will involve getting 5 exhaust bends making 5 rings, making 5 nuts with a washer welded to it…. Not to hard and expensive I think. Plus modify one of them to create carb heat. With the exhaust stubs I will create back pressure again, that could improve the exhaust cycle. Plus also prove one thing that I discussed back in April at the Omaka air show. This was about exhaust gasses being sucked in by one cylinder while another one was exhausting.
  • Then the last thing, is the prop !!!!! I am more and more getting used to the idea, that I have tried everything, and the last thing is modifying the prop a LITTLE !! Making the tip 10 or 20mm shorter. That should make it go faster and hopefully produce more thrust. Making that change is NOT making the prop look any different, so I am comfortable with that. BUT will talk with a prop guy first before I do this 🙂 don’t worry !

A step forward

Today I made progress ! 🙂

Started going through all the issues I picked up last week, and things to check on. So yes;

  • Fixed the butterfly valve in the carburetor. It’s now fully open with full throttle setting.
  • Rechecked the tapped clearance on all valve’s. Made a few little adjustments, nothing mayor, but has to be right !!
  • Checked the ignition time for both magneto’s. Yes both are 30 deg before TDC (top dead centre).
  • Checked the valve timing. All looking good with valve time overlapping; exhaust closing and mixture opening at TDC.
  • Drained the 91 octane petrol from the fuel tank, and filled it up again but this time with 95 octane petrol.

Because the carburetor butterfly valve is now a bit more open, starting the engine took a little getting used to. Needed 3 starts, but yes runs beautiful again. Pretty sure that after warming up the engine, it runs a bit better/faster now. The tacho needle is now on the 1900 and starting to touch the 2000 mark.

Some improvement, FINALLY !!!!!

At the moment I am running the engine without a exhaust. I am thinking that instead of putting the ring exhaust back, that I should try to make short stubs for all 5 cylinders. This will completely isolate the 5 exhausts. Read this post for the explanation.

The image here from the book, “Ghosts, the great war“, shows you what it will look like ! 🙂

Maybe a bit hard to see… The top cylinder and the next one to the right have two stubs sticking out to the right. The cylinder to the left of the top one has an exhaust stub sticking out to the left. I can’t see the bottom two stubs but they must just point down… And one of the down going stubs will be used to create carb heat, which will stop the carburetor from freezing up.

Measured the nuts that clamp the exhaust stubs onto the cylinder. I need to source or make 1 3/4″ nuts with 16 threads per inch. If I can do that, I will organise the exhaust stubs !

1 3/4″ nuts 16TPI

Trying to find 1 – 3/4″ nuts with 16 threads per inch. This is to clamp down new exhaust stubs I want to make, replacing the ring exhaust. Had a first look around today here in town, but no luck so far. Will try a few more shops….

What ever I get, I am sure they need to be machined. So maybe I just need to have some made up in the end if I can’t find any.

Other option of course is to put the ring exhaust back on again, and see what the power output does!


You can see 5 of them here in this photo. They looks like a ring slid over the mixture and exhaust pipe, shrewd onto the cylinder…… Mine will probably look different. Will see.


Old exhaust nuts and stub

After calculating the weight of the new exhaust I wanted to make, and getting the quote for making the exhaust bends, I decided to go for it.

Sorry Warren, I am going to cut the stubs with the seal and the fitting nuts of the ring exhaust. Tomorrow I am going to order the 5 bend bits of exhaust pipe.

Here you see 4 short and one longer stub. The stubs fit into the cylinder exhaust connection and are clamped into position with a nut (see previous post)

The longer one, is 1.5″ longer = the diameter of the exhaust. I have done this so the top exhaust stub that’s longer as well, can go side by side with the next one to the left. Below a sketch.

When I get the bend exhaust tubes, I will have them welded to the 5 bits in the photo above.

When it’s all welded and fitted you will see….. 😊