Author Topic: Port timing.  (Read 5987 times)

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Offline jmester

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Re: Port timing.
« Reply #20 on: February 15, 2013, 07:23:38 pm »
I got .040 for squish. I do have a domed piston. Would you still measure the squish the same. Duration is from TDC to when the port begins to open correct. I was thinking of having the base milled and running a gasket. So I would mill the base .040. Put gasket on and raise .020 and leave a squish of .020.
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Offline Al Smith

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Re: Port timing.
« Reply #21 on: February 15, 2013, 08:13:16 pm »
You take it from the highest point of the piston to the head deck . 20 thou would be right close because most don't say get any closer than 19 thou .Now is that 40 thou with the gasket in or out when you measured it .Now is that a cut domed piston commonly refered to as a pop up or is it a factory hemi dome like an 038 Av ?

I can ever seem to get the danged things right on any way for some reason .I've used everything to regasket them from a front cover of National Geographic to the cardboard from a case of Budweiser to adjust the spacing after I screwed it up .

Offline jmester

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Re: Port timing.
« Reply #22 on: February 15, 2013, 08:30:15 pm »
It was .040 with the gasket. It is a factory dome.
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Offline Al Smith

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Re: Port timing.
« Reply #23 on: February 16, 2013, 05:02:33 am »
As I suspected then that being said if it has an offset combustion chamber meaning not concentric to the center of the cylinder it is a direct copy of an 038AV .Could be vica versa because I'm not certain which model was out first .

I've never taken the time to investigate what that 028 I have in the shed has .This has  caused my curiosity to arouse so I think I might just delve into it to see what design it uses . .

Offline 660magnum

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Re: Port timing.
« Reply #24 on: February 16, 2013, 05:21:46 am »
The 026 has the off-center small dome in the combustion chamber also
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Offline jmester

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Re: Port timing.
« Reply #25 on: February 16, 2013, 06:28:05 am »
From what is can tell is the 46mm piston is domed. And  the 44 mm piston is flat topped. I hope this does not sound dumb, I would like to set the squish at .025 and run a base gasket of .020. If I am correct I think I would need to mill off .045. Or would it be to mill off .035 to get a .025 squish with a gasket.  I tried to measure the squish at or around the dome or highest point , there is plenty of room to drop it down. With out any clearance issues.
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Offline 3000 FPS

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Re: Port timing.
« Reply #26 on: February 16, 2013, 11:33:31 am »
I do not understand why you want to run a base gasket.   Just leave it out and you end up cutting much less from the base of the cylinder which is better.     If you use some yamabond or similiar sealant there will be no problem with the cylinder sealing up.
PP 505, 475, 445.

Offline jmester

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Re: Port timing.
« Reply #27 on: February 16, 2013, 11:46:14 am »
I have used dirko before. But I like the way that if you have to pull it apart again it is a lot easier with a gasket than with sealant.  Imo.  I have used other things such as aluminum foil, cereal box with good results. Just like a gasket I guess.
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Offline man of stihl

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Re: Port timing.
« Reply #28 on: February 16, 2013, 02:58:14 pm »
I have used dirko before. But I like the way that if you have to pull it apart again it is a lot easier with a gasket than with sealant.  Imo.  I have used other things such as aluminum foil, cereal box with good results. Just like a gasket I guess.
I agree. if your going though the trouble of machining the cylinder base, i would use a gasket.
Ron

Offline Al Smith

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Re: Port timing.
« Reply #29 on: February 16, 2013, 07:27:50 pm »
If you have 40 thou with a gasket and you want 25 you'd mill off 15 thou .If you went without a gasket, sealant would probabley squeeze down to 2 thou .So 40 minus 20 is 20 thou plus aprox 2 for the sealant would be 22 thou . 3 thou wouldn't make that much difference .I dont think it's exactly 20 thou on the gasket ,like .5 mm which is almost 20 thou .I'm kind of an SAE type guy this metric stuff is un American . ;D

 

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