Looking over my treats Eurokit, this head looks rather awful. I'm in too close for the focus to show that the entire combustion chamber is that rough, it's rougher than the fins even. And yes those are pits in the mating surface, not grit.
Is that okay to run? Ought I to hand polish it? Fork over to have it machined? Send it to Swaintech and have it coated?
Yeah I get a ceramic coating on it have done to the Piston to
You could hand polish it or have it machined. It's just raw casting on the chamber. The pits on the machined surface are porosity in the casting, not uncommon for low quality aluminum castings (see moped parts).
Those will be filled with carbon in a few minutes.
Looks like Not mating surface but squish band, Polish with dremel puffs both grits
Lia the Raven Wrote:
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> Looking over my treats Eurokit, this head looks
> rather awful. I'm in too close for the focus to
> show that the entire combustion chamber is that
> rough, it's rougher than the fins even. And yes
> those are pits in the mating surface, not grit.
>
>
>
> Is that okay to run? Ought I to hand polish it?
> Fork over to have it machined? Send it to
> Swaintech and have it coated?
Couldn't not find the post but Wayne talked about using tennis balls and golf balls with sand paper to remove material & smooth for squish band tunning. I would believe the same process would be fine just don't go crazy with the sandpaper, remove what you need then polish.
Just leave it and run it. Remember you get better atomization with rougher surfaces, smooth and polished surfaces you get pooling. If you do polish you dont need to kill yourself and get a mirror finish.
^^ Yes just run it.
My Derbi variant head looked the same.
will warn Wrote:
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> Just leave it and run it. Remember you get better
> atomization with rougher surfaces, smooth and
> polished surfaces you get pooling. If you do
> polish you dont need to kill yourself and get a
> mirror finish.
That's only during the intake process that atomization happenes, the particles should be good enough before reaching the head and compressing. Use a tennis ball and sandpaper it will clean it right up.
DPC Ryan Wrote:
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> Those will be filled with carbon in a few minutes.
Run it
And people were upset with the scalloping on the Gorgon heads from the ball end mill...
The rough and dimpled surface would induce more turbulence and in the way that a squish band increases velocity to aid in complete combustion I could see it having similar if negligible result.
Okay, so the roughness is probably fine. How about the shape of the squish chamber though, it's not so much spherical as it is cylindrical. Although if that's not good I don't suppose much can be done about it without significantly reducing compression.
Lia the Raven Wrote:
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> Okay, so the roughness is probably fine. How
> about the shape of the squish chamber though, it's
> not so much spherical as it is cylindrical.
> Although if that's not good I don't suppose much
> can be done about it without significantly
> reducing compression.
Ya that head is not finished
The band is the angled ring before the chamber. The size of the chamber is mostly what you are worrying about beyond the squish band width, angle and clearance.
I would CC that and verify it will work out to the right compression ratio . I believe Ken is correct and the dome was never machined so the displacement will likely be incorrect .
Sounds like a plan, I'll put a BU8H in there and 1/4 teaspoon in some oil probably. I don't know what the clearance will be as I haven't bored the cases out for this kit yet but it'll be an idea. I only just finally got the siezed kit off the engine today, it's like Chernobyl in there.
I wouldn't use oil. It's high viscosity can give an incorrect measure due to surface tension allowing the oil to actually sit above the level you want. Water or something thin that won't evaporate would be good.
wow thats a really wide squish band. run a loose squish tolerance or it's going to be HOT
one solution to this is take a piece of clear plastic and drill a hole in the top (add a chamfer if you can) and put on the machined surface and fill the chamber with oil that way with a syringe if you want to get the right CC without the surface tension giving an incorrect amount. or do what Ryan said. (edited)
If you want it really accurate you should assemble the kit put it on end and fill it through the spark plug hole with it at TDC. Record what it takes to fill it to where the plug electrode would sit . Then fill the ceramic around the plug and add it to the first number .like Ryan said use water and add a drop of soap to kill the meniscus .
Or just use a compression tester
Flagrant - Wrote:
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> Or just use a compression tester
Just curious ... How do you measure cubic displacement with a compression tester ?
If you are trying to figure engine displacement you don't include the volume of the head but just the volume the piston displaces. Your method as you know is good for head volume especially if you have a flat top piston. I thought you were trying to figure compession ratio. The ratio can be had buy taking the compression test number and dividing it by atmospheric pressure which is 14.7 psi at sea level. If you are above sea level by some measure and using a bourdon tube or similar principle guage you can figure that at 10000 ft atmospheric pressure is about half that at sea level and that the pressure is proportionate to the height. So like at 5000 ft you would say atmospheric pressure is at 11.025 psi. Its just easier than the oil method
By the time this guy gets that head carved out to make for a reasonable CR he won't have a squish band to worry about
If you're bore is 45mm,.
45x45x0.785x stroke that would give you your displacement.
yeah not a great head, you can probably just open up the bowl a bit with a dremel by hand and get pretty good results.
i'll machine it for you for free, but you'd have to pay shipping, if you want to do it shoot me a PM.
might not be bad if you can take advantage of a flat rate USPS envelope and put it in there, thats how i ship all my bigger-finned heads, 7 bucks anywhere in the US, not sure if HI counts?
Haha, I was waiting for you to weigh in. "Hm, people say this, and people say that, but I want to know what Graham thinks..."
yeah thats pretty turrible. we can't have you blastin' down a mountainside running that thing!
Using an old 3mL cat dewormer syringe I found in a drawer and soapy water, I can estimate the volume to be 7.0 cc. A lot of careful measurements of the old & new cylinder - and one assumption which will have to be verified later - suggest this should have a squish clearance of 0.60mm once set up, giving a volume of 1.04 cc. The exhaust port edge is 22.10mm below TDC, and the piston dome is 3.42mm high, assuming it is a spherical cap gives a dome volume of 2.99cc.
Compressed volume: 5.05 cc.
Swept volume: 74.6 cc
Trapped swept volume: 38.3 cc.
(74.6 cc + 5.05 cc) / 5.05cc = 15.8 : 1 theoretical nominal compression ratio
(38.3 cc + 5.05 cc) / 5.05cc = 8.6 : 1 theoretical trapped compression ratio
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