CNC heads
- Thread starter JerboaJohn
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JerboaJohn
Well-Known Member
okies,, just about done with the bottom side. chamber cut and it looks shallow but it's deeper than stock, it's shape is hemi. polishing it now, then clean up the base mounting, then tap it and measure cc's.
I got a 10cc syringe to drip water in to see how much it holds, hope I didn't cut too much! lol if I did, then it's like 4 steps backwards the redo the mounting surface. I'm off next 2 days, so maybe I can get it almost done!
gawd i can't test it tho even if I do, it's cold and rainy
I got a 10cc syringe to drip water in to see how much it holds, hope I didn't cut too much! lol if I did, then it's like 4 steps backwards the redo the mounting surface. I'm off next 2 days, so maybe I can get it almost done!
gawd i can't test it tho even if I do, it's cold and rainy
Street Ryderz
Well-Known Member
It's alot of work! looking good though,where you have a lip from the crush ring to the chamber is not a good idea and is the problem with the shark head,even with that chamber the edge that meets the bore should have a tight clearence like a squish to help push the end gasses toward the center.A hemi style chamber is more spherical (dome shaped) you currently have a flat angle without alot of space for volume that a hemi style chamber provides.here's a pic of both styles of chamber.Top ones are squish type and bottom are hemi.okies,, just about done with the bottom side. chamber cut and it looks shallow but it's deeper than stock, it's shape is hemi. polishing it now, then clean up the base mounting, then tap it and measure cc's.
I got a 10cc syringe to drip water in to see how much it holds, hope I didn't cut too much! lol if I did, then it's like 4 steps backwards the redo the mounting surface. I'm off next 2 days, so maybe I can get it almost done!
gawd i can't test it tho even if I do, it's cold and rainy
View attachment 84726
gary55
Well-Known Member
Real cool. I would love to have the equip. to do that. I don't know where your at on head design so I'm not sure if this will help, but I'll throw it in so it's there if you want it. Heads start at pg. 33.Jennings: Two-Stroke Tuner's Handbook - tuners.pdfokies,, just about done with the bottom side. chamber cut and it looks shallow but it's deeper than stock, it's shape is hemi. polishing it now, then clean up the base mounting, then tap it and measure cc's.
I got a 10cc syringe to drip water in to see how much it holds, hope I didn't cut too much! lol if I did, then it's like 4 steps backwards the redo the mounting surface. I'm off next 2 days, so maybe I can get it almost done!
gawd i can't test it tho even if I do, it's cold and rainy
View attachment 84726
JerboaJohn
Well-Known Member
nice! thanks for helping this along with those pics and Gary for the link,,
I got it to where I can install a plug and it measured out just above 7cc, so I can bevel it a bit more for a squish band. it's really trial and error bcs I never tried anything like this so I'll hafta see how it feels vs. the stock head.
next step - bevel a squish band in, then I'll cut the cooling fins.
I taught myself machining. saved up n bought a lathe, some tooling and just played with it. this was before I got into mb's haha. originally I got it bcs I wanted to make brass steam engine toys (tho I never got past watching bunch of vids) then I discovered mb's and was like Huh? what's this?! Really? those r cool!
I got it to where I can install a plug and it measured out just above 7cc, so I can bevel it a bit more for a squish band. it's really trial and error bcs I never tried anything like this so I'll hafta see how it feels vs. the stock head.
next step - bevel a squish band in, then I'll cut the cooling fins.
I taught myself machining. saved up n bought a lathe, some tooling and just played with it. this was before I got into mb's haha. originally I got it bcs I wanted to make brass steam engine toys (tho I never got past watching bunch of vids) then I discovered mb's and was like Huh? what's this?! Really? those r cool!
FNTPuck
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You are doing awesome. I wish I had a lathe...I took courses for CNC lathe/Mill but never went beyond the basics and would LOVE to own one. I am familiar with modeling and CAD work, and own a 3d Printer, so I know I would have a ton of fun with one so a CNC lathe and Mill are both on my dream list...I have seen plans to convert standard old Lathes to CNC control for relatively cheap which really interests me...
FWIW there is a lot of different info floating around for the stock heads about them being 6cc but I have measured four different heads and all were 7.2-7.6ccs. Two Triple40s, one black Jet66cc, and one silver standard slant head(same as the Jet66 kit but silver instead of black lol)...not one was under 7ccs. I used the same method as I do for my SBC race heads...plug in chamber, syringe with easy to read ml's, plexi with a hole on each side of chamber(just a single hole in the center causes air bubbles, but two holes lets the air escape from opposite hole as you fill), and vaseline around chamber to seal it.
The generic silver slant head and Jet66 were both exactly the same, 7.6ccs. The two different batch untouched Triple40 heads I did were both 7.2ccs. Along with the extra stroke, that gives them real high compression stock compared to a normal chinagirl - almost 180psi if you use a single base gasket(ideally run one base gasket for better port timing and a thicker HG to make up for it). The high compression is what gives them tons of TQ, which is why they can get away with a 36t sprocket on a stock kit vs the 44t on the normal ones.
FWIW there is a lot of different info floating around for the stock heads about them being 6cc but I have measured four different heads and all were 7.2-7.6ccs. Two Triple40s, one black Jet66cc, and one silver standard slant head(same as the Jet66 kit but silver instead of black lol)...not one was under 7ccs. I used the same method as I do for my SBC race heads...plug in chamber, syringe with easy to read ml's, plexi with a hole on each side of chamber(just a single hole in the center causes air bubbles, but two holes lets the air escape from opposite hole as you fill), and vaseline around chamber to seal it.
The generic silver slant head and Jet66 were both exactly the same, 7.6ccs. The two different batch untouched Triple40 heads I did were both 7.2ccs. Along with the extra stroke, that gives them real high compression stock compared to a normal chinagirl - almost 180psi if you use a single base gasket(ideally run one base gasket for better port timing and a thicker HG to make up for it). The high compression is what gives them tons of TQ, which is why they can get away with a 36t sprocket on a stock kit vs the 44t on the normal ones.
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