4 Cylinder Inline Engine

[Rdean33422]

I use a drag knife on a vacuum table to cut my gaskets.
I would hate to think what they would look like if I did them with a scissors and knife.
Cutting two, one for a spare.


I drilled, counter bored and tapped the four spark plug holes in the head.
Then I installed the newly cut head gasket, cylinder head, and a small flywheel to check for compression..
All four cylinders give a good kick back when the the flywheel is flipped.
All good for now.

I need a proper flywheel so I found these pieces under the bench.


Here is the result.


The flywheel is 4" in diameter and 1" wide and weighs 3lbs.
That should be about right.
Now to give it a coat of paint.

Thanks for looking
Ray

 

[minh-thanh]

Looks great !

 

[Rdean33422]

Had a little time today so I made some risers to allow for the new flywheel diameter.





Thanks for looking
Ray

 

[Steamchick]

My first time reading this site. Just one point that seems unresolved...
The crank stiffness = resistance to destroying the engine at "whatever" speed.
Comparing 2 engines of same journal size and component dimensions and masses (pistons, rods, etc.):
Very simply: the crank of twice the length will have 1/2-cubed = 1/8th. of the stiffness, so will only tolerate 1/8th of the crank rotational forces/accelerations of the out-of-balance masses stung along the length. - I.E. will fail at 1/8th of the rotational speed. So if the 2 cylinder engine (= OK for 2500rpm) has simply been doubled in length, you are guessing to the gods of luck that the 4 cylinder engine can survive at the same speed. To put it another way, as you don't know what speed will cause failure of the 2-cylinder engine, you can't predict the safe speed to limit the 4 cylinder engine. But it should be OK up to 600rpm. After that "Good luck".
I am enjoying the build anyway.
K2

 

[Rdean33422]

To put it another way, as you don't know what speed will cause failure of the 2-cylinder engine, you can't predict the safe speed to limit the 4 cylinder engine.

You are right K2 we just don't know but will find out later.
Thanks for the comment they are appreciated.

Progress
I cutout and polished the cam support blocks and installed the cam bearings.
I also roughed out the cam shaft.


Then on to the upper cam pulley next.
The cam pulley didn't have a set screw but it did have a key way. I bored the pulley hole out past the key way and made a brass bushing, pressed it in, and bored that out to match the cam shaft.



Would you believe I had a timing belt the right length. It was left over from a previous build.
It looks like my calculations for the height of the cam supports will be right on but will need to make some cams first to be sure.


Thanks for looking
Ray

 

[Rdean33422]

Four brass cam lobes with set screws.


I also made up the timing belt tensioner and set the exhaust valve timing.


Another view.


I have good compression on all four cylinders.

Happy Dance

Thanks for looking
Ray

 

[Steamchick]

Wondering how you get from Cam lobe to valve head... For Inlet and exhaust from a single camshaft?
Still watching: I am sure it is "coming soon" - maybe in the next episode?
K2

 

[Rdean33422]

The intake valves are atmospheric so no cam is needed. They are opened by suction on the intake stroke of each cylinder.
Ray

 

[minh-thanh]

The intake valves are atmospheric so no cam is needed. They are opened by suction on the intake stroke of each cylinder.
Ray

That's really a challenge to do with 4 cylinders

 

[Steamchick]

Thanks Ray,
I'm sure it will work as you have done this before!
K2

 

[T.S. True sportsman]

Four brass cam lobes with set screws.
View attachment 155161

I also made up the timing belt tensioner and set the exhaust valve timing.
View attachment 155162

Another view.
View attachment 155163

I have good compression on all four cylinders.

Happy Dance

Thanks for looking
Ray

how doe the cam hit the other valve stems

 

[bluejets]

how doe the cam hit the other valve stems

Only needs to run on the exhaust valves, the induction are poppet valves as already stated.
The exhaust valve stems are obviously the longer ones as shown previously.

I'm curious which way the engine runs from the flywheel end........ I know which way it should run but........ ?

 

[Steamchick]

Should run with the cam belt tensioner on the slack side... timed so exhaust valves open around BDC, then close around TDC.
I.E. cam-belt straight from crank to cam on non-tensioner run. So from picture in post#46 flywheel = clockwise.
Do I get a gold star for the correct answer? Or a red "X" from teacher for being stupid and wrong?
K2

 

[Rdean33422]

Yes K2 you get a gold star as the flywheel does turn clockwise.

That's really a challenge to do with 4 cylinders

I have never done multi cylinder atmospheric intake valves before is there something about them that I should know?

 

[minh-thanh]

Well, there's one really important thing that I think you really need to know : I haven't built many cylinders with atmospheric intake valves yet.

 

[Steamchick]

A couple of historic principle for atmospheric intake valves:

• They need very light closing springs so they open with atmospheric pressure.
• Light springs don't close valves quickly for high revs.
• Good for demo engines that just idle.
• Not much good for today's standards of power per cc of displacement.
• As air-flow increases through the valve the pressure difference reduces, so the valves close, reducing air intake per stroke.
• When right and working, these were reliable, simple and effective.
• Modern 2-stroke engine reed valves can work better than automatic poppet valves, in some engines. But can suffer from combustion heat. (Not exposed to combustion heat on 2-stroke intakes).

K2

 

[Rdean33422]

The good news first.
I made a mount for my distributor and coupled it to the cam via 2 bevel gears.
It tracks and turns smoothly.


Now the bad news.
I was spinning the engine over with my drill and noticed a problem. Around 3000 rpms the flywheel was not tracking straight. When I slowed down it ran fairly true again so I believe I need center crank bearing to make it more rigid. In the beginning I said the crank was an experiment and it has proven to be a failure for me.
I will start on a new crank in a couple of days.

Thanks for looking
Ray

 

[NapierDeltic]

What about 2 small ball bearings on the sides, supporting the center of crank shaft? Just for fun...

 

[bluejets]

so I believe I need center crank bearing to make it more rigid

................... goto #23.

While you are there, rethink all this brass material (won't last) and the o'ring rings (yuk) nylon cam gears 2 x yuk.

 

[Nerd1000]

The good news first.
I made a mount for my distributor and coupled it to the cam via 2 bevel gears.
It tracks and turns smoothly.
View attachment 155182
View attachment 155183
Now the bad news.
I was spinning the engine over with my drill and noticed a problem. Around 3000 rpms the flywheel was not tracking straight. When I slowed down it ran fairly true again so I believe I need center crank bearing to make it more rigid. In the beginning I said the crank was an experiment and it has proven to be a failure for me.
I will start on a new crank in a couple of days.

Thanks for looking
Ray

Because you have full round crank webs, you can likely re-use your existing crank. A large diameter, narrow width bearing running on the web should suffice.

Alternatively you can try lightening your crank to work with the existing two bearing setup.