V8 nitro engine

[stevehuckss396]

The effect on cam lobe seperation

widening lobe separation will do the following

Raise Torque to Higher RPM
Reduces Maximum Torque
Broadens Power Band
Reduce Maximum Cylinder Pressure
Decrease Chance of Engine Knock
Decrease Cranking Compression
Decrease Effective Compression
Idle Vacuum is Increased
Idle Quality Improves
Open Valve-Overlap Decreases
Closed Valve-Overlap Decreases
Natural EGR Effect is Reduced
Increases Piston-to-Valve Clearance




If you want a good running V8 I would suggest about 280 degrees open
with 110 degrees lobe separation. Give you a nice warm sounding engine
with a good idle under 1000 RPM. Sound about like this.

[ame]https://www.youtube.com/watch?v=FnbwsLysqGk[/ame]

 

[Parksy]

That is just an amazing looking and sounding engine! Thank you for your help and figures. With those figures, are the exhaust and intake lobes the same(280 degrees open)?
Are the valves opening at any specific point?

Thank you again Steve.

 

[stevehuckss396]

Cam timing in the V8

 

[Parksy]

Brilliant. Thank you Steve.

 

[canadianhorsepower]

Cam timing in the V8

Hi Steve
where does the program came from ??
looks pretty good

cheers

 

[hussien95]

Cam timing in the V8

What is the name of this program please؟

 

[stevehuckss396]

I wrote the code many years ago.

Sorry I cant post the program. Got this error.

EngineCalc.zip:
Your file of 3.90 MB bytes exceeds the forum's limit of 3.81 MB for this filetype.

 

[canadianhorsepower]

I wrote the code many years ago.

Sorry I cant post the program. Got this error.

EngineCalc.zip:
Your file of 3.90 MB bytes exceeds the forum's limit of 3.81 MB for this filetype.

Can you PM it
it looks good

 

[stevehuckss396]

Can you PM it
it looks good

I don't think I can. Anybody who wants a copy Email me at [email protected] with the subject engine calculator and I'll send it to you. Double click the setup.exe file and it will install.

 

[Parksy]

More progress. Will hopefully start on some rocker arms tomorrow.

 

[Parksy]

Made the rocker arms today. Started with some steel bar, cut them, machined to shape, filed the contact tip by hand then case hardened it. I will nickel plate them when I get a chance. Happy with my progress.

 

[michael-au]

Good work on this engine, looking forward to seeing it run

Michael

 

[Parksy]

Thank you Michael.

Nickel plated the rockers today.

 

[petertha]

Prior posts on timing with some methanol examples. But I think you have some better qualified input already. Another thing I've noticed that sometimes gets glossed over in cam discussions is the Rocker ratio + Pushrod & Lifter geometry possibly acting at 3D angles + any clearance gaps between lifters etc.... can all affect end result timing in terms of valve physically opening & closing. I'm not sure by how much or if it makes a hill of beans difference, but just mentioning FWIW.
http://www.homemodelenginemachinist.com/showthread.php?t=21808
http://www.homemodelenginemachinist.com/showthread.php?t=17093

 

[Parksy]

Thanks Petertha. I have thought all about those things you've listed and it does worry me if I don't do thinks correctly. But I have tried to keep things as simple as possible. The rocker ratio, which I'll be honest, I don't understand, but assume it is in reference to where the pivot point is in the middle of the rocker? I've kept this in the centre so I'm assuming this gives me a 1:1 ratio.

 

[petertha]

I think I jumbled too many things in one sentence. The rocker ratio I think is just a teeter-totter. If the valve side length = pushrod side length then resultant valve lift = pushrod displacement. If the rocker axle is not centered, for example pushrod side is 0.8" and valve side is 0.7", then the valve lift will be reduced 0.7/0.8 (87.5%) of pushrod displacement. So this doesn't affect intake/exhaust timing, just lift.

But where this gets funky is how the cam throw acts through the pushrod/tappet assembly onto the rocker because typically these components don't line up all neat & perpendicular and sliding faces & sockets etc. There could well be some 3d geometry acting through the assembly as a whole. So just designing a cam profile to yield open/close duration (in isolation of the other components) may not yield exactly the same open/close timing at the valve itself. Again, whether this is small or large or worth fretting about is another subject. Hope that clarifies what I was trying to say.

 

[Parksy]

That makes sense Petertha.

Thanks for the clarification.

 

[Parksy]

More progress. Machined the cams out tool steel. Went with the 280 degree intake and exhaust duration with 110 degrees lobe separation. Will heat treat them when I've finished cleaning them up. What is the preferred liquid to use for quenching this type of steel? I believe it's oil hardened silver steel.

 

[10K Pete]

If it's O1 steel then..... oil!!! 1575*F, quench in room temp oil, temper to suit.

Pete

 

[Parksy]

Cheers Pete

Quenched them with oil and they are super hard. Can't file them any more.