Half Scale Ford Quadricycle Engine

[vascon2196]

Looks like I have to make a new valve.

I just spiked the leaky valve on the concrete like a football.

I almost threw the manifold out into the woods but I'll hang onto it until I make yet another valve.

Amazing...this must be my 12th valve I've made and I don't think a single one has worked properly. I either really suck or these f-ing valves are harder to make than I thought!!!

 

[cfellows]

Gotta agree. For something that is seemingly so simple, poppet valves seem to be the trickiest part. On my very first gas engine, the valves worked perfect, first time, right out of the chute. Every engine since then has been a challenge. Keep after it Chris, don't let the little bugger get you down, you'll win eventually. The good news is, once you get it working, it'll probably never give you any problems again.

Chuck

 

[vascon2196]

Thanks Chuck. I can hear air leaking from somewhere. I'm not sure if I scored the cylinder wall by accident and it needs to be re-honed. I'm not sure if it is the valve or the intake valve.

I brought my engine in to work today so the Machine shop instructors can figure out where the air leak is coming from. One of the instructors has built many model gas engines so I'm hoping it will be more obvious to him.

The damn thing was running last month and then something happened I can't seem to find.

 

[vascon2196]

So...........machined a new valve...still leaking air but have not lapped it yet. Took the piston out and the piston ring was pinched in the groove and not springing open. So we used some fine grit sandpaper on both faces of the ring to make it a little thinner which seemed to help.

I'll fire it up tomorrow...my brain hurts.

 

[cfellows]

Have you thought about replacing the piston rings with o-rings? I know some people think that's cheating, but boy it sure works well.

Chuck

 

[vascon2196]

Yes Chuck...each Piston has one piston ring and one O-ring.

I originally used 2 piston rings but it leaked too much air...the O-ring puts the compression through the roof.

 

[barnesrickw]

What type of O-rings do you use for I.C. Engines. Cheating or not, it sounds much easier.

 

[vascon2196]

Currently I am using regular rubber (Buna-N) O-rings but once I fix all the little bugs in the engine I will replace them with Viton. The Viton seems to handle the heat much better however I've had a rubber o-ring in my Ford plumbing engine for 3 years now and no problems.

 

[barnesrickw]

Since I'm getting some great free information, do you change the piston fit any when using o-rings instead of steel rings?

 

[cfellows]

Since I'm getting some great free information, do you change the piston fit any when using o-rings instead of steel rings?

Not sure what others do, but I fit my pistons pretty loose, up to .003" clearance on a bore of 1" or bigger. I generally use an o-ring with 1/16" cross section. The depth of the groove is around .060" and the width of the groove is around .075".

Chuck

 

[barnesrickw]

Great information, thank you.

 

[vascon2196]

After several attempts to get this engine running I have decided to re-make the manifolds. The current exhaust manifolds are in 2-pieces and between the air leaks and valve misalignment issues I will make the new ones out of 1-piece.

This will eliminate 2 extra potential air leaks and allow me to make the valve seat correctly. There is no store within 100 miles of me that sells 90-degree C'sinks or the flipping V-Belt I need for my lathe so I have to wait yet another week before I can do all of this.

Anyway...I think new exhaust manifolds, new valve seats, new valve guides, and new valves will finally get me the compression I am looking for.

 

[stevehuckss396]

Ok! I guess we wait. Keep us posted.

 

[vascon2196]

Attached are pictures of the new one-piece exhaust manifolds. I bought a set of 90-degree C'sinks to cut the valve seat. I cross drilled for the exhaust hole making sure the new manifolds look like the two-piece versions that Ford made.

The plan today is to make a new gasket, fasten in place, and hope I have compression!

 

[vascon2196]

More pics.

 

[vascon2196]

Oh boy....all that work and no compression.

Air was leaking past the spark plug so I added some Permatex liquid gasket. I also put one of the manifolds in the 4-jaw and turned an O-ring groove to try and seal the air in internally. I have to make yet another gasket and continue to look for leaks.

Funny...the smallest leak will prevent compression...I mean there is no compression at all...very strange. Oh well, I'm on vacation this week so hopefully I will have time to fuss with it.

 

[bobsymack]

This might sound like a stupid question but is your valve timing correct,it is very strange to have no compression even with bad valves etc. Hope you find the solution soon as I know it must be frustrating.
Vince.

 

[vascon2196]

This might sound like a stupid question but is your valve timing correct,it is very strange to have no compression even with bad valves etc. Hope you find the solution soon as I know it must be frustrating.
Vince.

I hope it is correct! I'll double check this...thanks Vince.

The air leaking past the spark plug is due to the tapped hole being on a conical surface. I should have given it a small spotface first to give the spark plug a flat surface to seat against. I added Permatex liquid gasket and it no longer leaks. As of this morning it has a little compression but not enough. It must be leaking elsewhere. I feel like a detective searching for clues.

 

[vascon2196]

I have really good compression in one cylinder and absolutely none in the other. Another problem is that one of the cranks is coming loose...again. Since I did not use hardened crankshaft material the keys are galling. Even after drilling and tapping through the crankshaft and crank it is still spinning and throwing the timing off.

I'm going to weld the crank directly to the crankshaft and be done with it.

 

[stevehuckss396]

How tough would it be to hog a one piece crankshaft. I know they are a pain but you just cant beat them for strength.