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Notching Top Of Cylinder Bore?

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Old 01-12-2010, 11:52 AM   #1
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Default Notching Top Of Cylinder Bore?

I was just curious if anyone has done this or not.

I have a set of cylinder heads that were used on a larger bore (4.125") so the combustion chambers were opened up for that larger bore. I blew that engine up late last season and I'm in the process of building a 6.0L shortblock (371ci) that will have a final bore size of 4.040". I was just wanting to know if anyone has notched the tops of the cylinder bores for a larger combustion chamber cylinder head to work on a smaller bore. I'm on a super-tight budget with this build, and would like to try to use these heads I already have instead of selling these and buying new ones etc... From what I can tell, I'd only need to notch the tops of the bores out about .030 - .050 more than final bore size. In other words, the combustion chambers measure about 4.090" across.

To give an example of what I'm talking about, here is a link:
http://www.turbomalibu.com/gn1r.htm

Mike
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Old 02-12-2010, 04:55 PM   #2
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Anyone think this is a good idea? I am toying with this idea as well on my build. Don't see how it could hurt, except lower compression.
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Old 02-13-2010, 09:05 AM   #3
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Originally Posted by whitesmokels1 View Post
Anyone think this is a good idea? I am toying with this idea as well on my build. Don't see how it could hurt, except lower compression.
I didn't get any response on here so I talked to my machinist about this. He has an engine dyno and used to build stock car engines. He said he's seen it done but it only picks up 5-6hp (average) on old school SBC's. So,,, it definitely doesn't hurt as long as the head gasket clears the notches. I just got my block back from machining so I'll be doing this as soon as I finish up the rollcage.

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Old 02-13-2010, 09:41 AM   #4
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Been done since at least the late 1960s.
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Old 02-13-2010, 10:26 AM   #5
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Sweet. As they say "Every little bit counts"
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Old 02-16-2010, 06:13 AM   #6
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not sure if this will work very well with the thin cilinderliners in an alu ls engineblock
might be a good option for the iron (truck) underblock though
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Old 02-16-2010, 09:03 AM   #7
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not sure if this will work very well with the thin cilinderliners in an alu ls engineblock
might be a good option for the iron (truck) underblock though
I agree.
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Old 04-28-2016, 10:41 PM   #8
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Lightbulb notching top of lq9 cylinder

Hey guys, I know this is an old thread, but I got my 4.030' block 6 liter back, and thought id post pictures of the valve interference with the cylinder walls. The funny thing is it appears the valves, don't interfere with the cylinder walls, until roughly .225" down the cylinder. The pictures show the marks, the very bottom of which are being pushed free, to the top of the valve guide, like 1.5" which is not realistic lift lol.My question has 2 parts...

How far down the cylinder wall would the valves travel from the seat with say an .051" ls9 head gasket?

And second, would it be okay to notch the cylinders above the said depth, to help clear/unshroud the valves???

Again I know this is an old thread, but I couldn't find much information, about this being done. Thanks again, please no critisizm, just advice......
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