V8 nitro engine

[10K Pete]

Now put them in the oven at 600*F (most will go that high) for about an hour.

Pete

 

[Parksy]

Cheers Pete!

Testing the cams. No piston contact! Was my biggest fear, but all is good and compression is excellent.

 

[Parksy]

Probably another obvious question, but I've made this engine with a cross plane crank and each journal is 90 degrees apart. The cams I've made will have flats machined onto a shaft and held in place with a set screw. Are these flats machined at 45 degrees apart or 90?

 

[Parksy]

90 degrees. Got it.

Anyway, more progress. Clevis links, pushrods and tappets are all made and installed.

 

[stevehuckss396]

Probably another obvious question, but I've made this engine with a cross plane crank and each journal is 90 degrees apart. The cams I've made will have flats machined onto a shaft and held in place with a set screw. Are these flats machined at 45 degrees apart or 90?

Are your cylinder banks 90 degrees apart? If so I can give you the cam angles. Have you decided on a firing order?

 

[Parksy]

With regards to cylinder banks, are you referring to the V angle? If so I can't remember specifically what it is as I had to work it out with what materials I had on hand. Does this angle play a part in timing?
The crank throws are 90 degrees apart.
Timing I haven't worked out yet.

 

[stevehuckss396]

With regards to cylinder banks, are you referring to the V angle? If so I can't remember specifically what it is as I had to work it out with what materials I had on hand. Does this angle play a part in timing?
The crank throws are 90 degrees apart.
Timing I haven't worked out yet.

Yes the V angle will change things. If the V is not 90 degrees it can change cam timing and also ignition timing as far as when a cylinder needs to fire. You may need to make a custom distributor cap where the studs are not 90 or make a funny shaped copper strip on your rotor. Or will this be fired on glow plug?

 

[Parksy]

Will be a glow engine for starters. When I've got my head around the ignition side of things I'll convert it.

 

[stevehuckss396]

Will be a glow engine for starters. When I've got my head around the ignition side of things I'll convert it.

You will still need to measure the "V" angle so the cam lobes can be set correctly.

 

[Parksy]

I understand how the v makes a difference now that I think about it.

My initial plan with timing was this... Because it has two cam shafts, one for each bank, I was going to set the cam lobes at 90 degrees on the cam shaft, then time both sides accordingly. So really it's like two 4cylinder engines mounted together and the v angle isn't a factor to consider.

I hope this makes sense. Does this sound feasible?

 

[stevehuckss396]

It sounds like it would. Might have a real unique sound when running. Have you decided on a firing order.

 

[Parksy]

That I haven't worked out yet.

 

[pickleford75]

With a flat plane crank... depending on how you number your cylinders..... there really only 4 pontential fireing orders..... already been down this road.... assuming that your crank is made in the traditional manner

 

[Parksy]

Iv made this crank as a cross plane crank.

 

[pickleford75]

after going back an rereading i see that it is made in with 4 90 deg throws.... that still isnt too bad.... been down that road.... brings it up to only 16 poss combos

 

[pickleford75]

one of my v8s has a flat plane and the other is a cross plane... had to sit down with a notebook and a protractor:wall:

 

[Parksy]

after going back an rereading i see that it is made in with 4 90 deg throws.... that still isnt too bad.... been down that road.... brings it up to only 16 poss combos

Hahaha oh great. Well that's good to know. I think.

 

[Parksy]

Well the firing order side of things has turned out to be a lot more complicated than I first thought. And at this stage I really have no idea. I was wrong about machining the flats at 90 degrees on the cam shaft to mount the cams. They should (I think) be set at 45 degree intervals. But again, this will change the firing order depending on how I put the flats onto the shaft. If I do it this way, it will simply fire in order eg 1 2 3 4 5 6 7 8.


If anyone can provide assistance on this, I'd really appreciate it. I'm pulling my hair out with this one.
I hope my problem actually makes sense to start with...

 

[gbritnell]

The best thing to do in regard to this timing issue is to make a drawing. Start with whichever cylinder you're going to call #1, front left or front right. Now the crank will be rotated 90 degrees clockwise while looking from the front of the engine. (with a 90 degree bank angle) Now find whichever throw is at TDC. This would be your firing order #2. You should pick a cylinder order that kind of moves around the block. By that I mean not just 1,2,3,4 etc. Continue doing this until you make 2 complete revolutions which will bring you back to your starting point. Remember the cams are only turning at half speed to the crank so their rotation is 45 degrees to the crank's 90 degrees.
gbritnell

 

[canadianhorsepower]

George
mention everything there is to mention regarding
the Crankshaft firing order.

The fact that you seam confuse a bit I would remove the head
and forget about the cam timing.

Then when you have your firing order all set you can make
new cams accordingly. It might be a set back but with all the nice work
you did so far I think it would worth it.

good luck