1/3 scale DOHC V8 Engine

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satech04

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Jun 12, 2024
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Hi all,

After building Steve's wonderful Demon v8 I decided to try building an engine of my own design. Having built a pushrod v8, I decided to try a DOHC engine... with 32 valves. We'll see if I regret that decision. I'm about 1/4 of the way through designing it up in CAD, then I'll start on the fun part: machining!

The engine is based off of a Ford Coyote 5.0. I'm going to try building a helical supercharger to go with it.

Specs:
1.2" bore x 1.2" stroke so 178cc
Full oil and water systems
HUGE valves at .479 intake and .415 exhaust
.120 valve lift

One head almost finished, except for oil and water porting.
1718233774311.png


Crank and pistons are basically done
1718233863999.png


More detail on the head. It's going to be a very complex part
1718233924069.png
 
That is a nice start.

I would think the 4-valve design could be challenging, but I think it is possible, and you never know what is possible until you try something.

Good luck.

.
 
So shim under bucket design? A ton of work there!
 
It's actually got a shim on top of the bucket. It sits in a little pocket. Hopefully it'll stay put!
 
Long time coming, but time for an update. I enjoy the actual machining far more than sitting and doing CAD... but it has to be done.

I've made a good bit of progress on the motor. I've gotten the water pump, oil pump and related passages done, finished up the various covers, and started on the timing and serpentine belt arrangements. I like seeing the belts move, so I decided to do the timing externally.
1723331991980.png

1723332027737.png


Detail on the water pump. I'm trying an impeller design, hopefully I can get enough flow. It's 1.5" in diameter, and I'll be spinning it at about 1.25:1 to the crank.
1723333127893.png


Oil pump:
1723332302800.png

It took a while, but I figured out how to model a proper gerotor oil pump. We'll see if I can manage the tolerances needed:
1723332383037.png
 
Last edited:
Still a lot left to be done! CAD says there's already over 700 parts, but about 250 of them are fasteners. A lot of this will be CNC milled, because as much as I enjoy manual machining you can do a lot more with CNC.

I've started my research on the supercharger. I want to do a real screw-type blower, which means some crazy complex shapes for the rotors. I'll have to see if I can find somewhere to have them 5-axis machined, maybe one of those Chinese machining/3d printing sites?

I found this compressor online, even though it's 3d printed he actually gets a little bit of boost!
 
satech04 said:
Still a lot left to be done! CAD says there's already over 700 parts, but about 250 of them are fasteners. A lot of this will be CNC milled, because as much as I enjoy manual machining you can do a lot more with CNC.

I've started my research on the supercharger. I want to do a real screw-type blower, which means some crazy complex shapes for the rotors. I'll have to see if I can find somewhere to have them 5-axis machined, maybe one of those Chinese machining/3d printing sites?

I found this compressor online, even though it's 3d printed he actually gets a little bit of boost!
Click to expand...

I am wondering if you could pull it off on the lathe using a form tool and a threading operation? Probably another of my crazy ideas.
 
Looks like an interesting project 👍

Just machining and no casting?

The gerotor oil pumps used in various Chinese GY6 engines engines can be found dirt cheap and the quality seems OK. I have one on my desk (for a GY6 50 139QMB engine) that I can measure if you want to test it in your design.
 
mayhugh1 said:
First class modeling. What are you using for source documents? Do you have one of the Tritons to work from? - Terry
Click to expand...
Thanks. I've just been using a spec sheet I found online, and lots of pictures. It's probably not a perfect scale replica, but pretty close.
 
Adaware said:
Looks like an interesting project 👍

Just machining and no casting?

The gerotor oil pumps used in various Chinese GY6 engines engines can be found dirt cheap and the quality seems OK. I have one on my desk (for a GY6 50 139QMB engine) that I can measure if you want to test it in your design.
Click to expand...
Thanks, and yeah, everything will be completely billet. I don't have much experience with casting yet.

That's an interesting idea about the oil pump gears, I have worked with that engine quite a bit. I currently have the outer gear at 1.35 in, not sure if the GY6 gears are about that size?
 
satech04 said:
Thanks, and yeah, everything will be completely billet. I don't have much experience with casting yet.

That's an interesting idea about the oil pump gears, I have worked with that engine quite a bit. I currently have the outer gear at 1.35 in, not sure if the GY6 gears are about that size?
Click to expand...
Nah, for this particular engine it's smaller. Perhaps more suited for 1/4 size engines.
Outer gerotor ring gear has a diameter of 23mm and the width is 8,75mm.
 
That's an interesting idea about the oil pump gears, I have worked with that engine quite a bit. I currently have the outer gear at 1.35 in, not sure if the GY6 gears are about that size?
Click to expand...
Have you thought about motorbike oil pumps, this is one out of a Yamaha 500 single, 29mm dia, only problem is it is 12mm thick. Just a thought.
Cheers
Andrew
 

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