Cam/Valve timing

[Dousi]

Hey guys

I'm in the planning of mi first ICE, a simple single cylinder sidevalve Engine. I've got it all drawn in my CAD, but have no clue about the timing of the valves, when should the inlet open, close, when the exhaust. haven't found anything on here, an nowhere on the net which relates to modelengines, only thing I found is on read Engines and I don't think that this will be the best timings for a simple model engine.

so, is there a number to tell wich will/should work, or doesn't it matter that much?

I've the dream of building a model V8 and found a 3D model on a Website wich shares 3D files. on this model engine, the Cams are all 90° one to another. is this realistic?

what are you using on your engines? an when do you ignite?

Hope somebody can help me, thanks in advance!

Florian

 

[stevehuckss396]

There was a thread on this recently.

All the cam lobes being 90 degrees apart would only work in an inline motor. With a v motor the lobes need to be adjusted for the v.
Where is the website you got the files. I could take a look and see what else wont work.

For your single, everybody's different. Depends on your max rpm, do you want to hand start it, ect.

I have made a V8 cam. I went 280 degrees duration, 110 degree lobe seperation, and timed it at 35 degrees

 

[Dousi]

found de engine on Grabcad: here

max rpm is below 10k, electric starting, but i want it to idle as low as possible.

you timed it at 35°, does this mean you ignite at 35° btdc?

thanks

 

[ausdier]

That engine is called "Little Demon V8" by Steve Huck.
His build log is here http://www.homemodelenginemachinist.com/f31/small-v8-8892/
and his cam question here http://www.homemodelenginemachinist.com/f26/modelling-350-chev-camshaft-13666/

other builds
http://www.homemodelenginemachinist.com/f31/demon-v8-slow-build-15532/
http://www.homemodelenginemachinist.com/f31/my-start-steves-v8-15275/
http://www.homemodelenginemachinist.com/f43/small-v8-offically-done-14788/
http://www.homemodelenginemachinist.com/f31/1-10-scale-v8-14470/

 

[stevehuckss396]

Were you able to download the files for the engine? I own the rights to the Demon V8. If so could you ask the person who posted them to take them down please.

 

[Mosey]

I am curious about people copying this V8 engine, as the statutory penalties in Federal court for copyright infringement are astronomical. That might be worthy compensation to the guy who built it.

 

[dman]

cam selection is a complicated engineering problem with no one solution. its weird because there can be a wide range of suitable choices yet the wrong cam can be detrimental to performance. if in doubt smaller is better. David vizard wrote some articles on the subject for full size racing engines that could be worth taking a look at. though others who I believe to have more expertise in camshafts seem to have a different method for choosing parameters. proper selection has a lot to do with air velocity and displacement. more port velocity and the can will be bigger and lobes closer together. bigger ports and the lobes will be smaller and farther apart.

when it comes to installation after the cam is manufactured you can put the engine at tdc and use the valve spring pressure to balance the cam in the overlap period to get things close. if you wish to do additional timing with a degree wheel and indicator it couldn't hurt.

 

[Dousi]

Were you able to download the files for the engine? I own the rights to the Demon V8. If so could you ask the person who posted them to take them down please.

Yeah, I have the file on my pc. I'll send a message to the person.

 

[Goldflash]

If my understanding is correct you are building a side valve engine
These do not need radical cam timing or lots of valve lift to run.
follow this link that gives cam timing figures of early engines especially ford flat head engines
However side valve engines can run radical cams and high lift and get impressive results ie the Harley KR racing engines of the late 1950s and 1960s http://www.tildentechnologies.com/Cams/CamHistory.html

Hope this helps

 

[dman]

http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/viewall.html

this is david vizards cam choice guide. worth a look.

 

[Dousi]

Thanks to all of you, these links and other posts are very informativ! I will study them and think Ill be able to do my cam with the help of these.

Thanks to all of you!

 

[stevehuckss396]

Thanks to all of you, these links and other posts are very informativ! I will study them and think Ill be able to do my cam with the help of these.

Thanks to all of you!

If you need a visual aid I have a solid model of a chevy with the standard 18436572 firing order in stl format.

 

[Dousi]

If you need a visual aid I have a solid model of a chevy with the standard 18436572 firing order in stl format.

This would be perfect!

Ill send you my email adress as a Private message

 

[stevehuckss396]

If you need a visual aid I have a solid model of a chevy with the standard 18436572 firing order in stl format.

I forgot to mention that the cam was designed to rotate clockwise with the crankshaft.

 

[petertha]

.. but have no clue about the timing of the valves, when should the inlet open, close, when the exhaust. haven't found anything on here, an nowhere on the net which relates to modelengines
Florian

Here is a post I started on somewhat similar question a while back.
http://www.homemodelenginemachinist.com/f26/valve-timing-4-stroke-glow-17093/

As indicated, I excluded gasoline/ignition model engines in the tabular comparison because of what I'm working on (methanol/glow), but somewhere I maybe saved those model engine timing specs too.

I've also built an Excel spredsheet that accepts typical 'engine language' input parameters like: "intake opens 25 BTC, closes 82 ABC
exhaust opens 65 BBC, closes 42 ATC..." then it spits out cam phasing angle at reduction ratio & little pictorial sketch etc. The idea was to help make cams & set them up in a model. I dont think I can upload Excel files, but if its of interest I will dig it up, show some screen pics & maybe have some pro's here validate it before distribution.