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watercooledguy Samba Member
Joined: September 03, 2012 Posts: 6 Location: United States
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Posted: Thu Sep 16, 2021 5:32 pm Post subject: Valve size for bore size?? |
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I'm in the process of building a 1967cc 92x74.ive been looking at cb and the 501 heads both available with 44 or 42 valves.is there pros and cons of each.would 44 be a over kill for a 92 bore?
Running a w120 and 44s |
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txoval Samba Member
Joined: January 23, 2004 Posts: 3540 Location: The Woodlands, TX
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Posted: Thu Sep 16, 2021 7:25 pm Post subject: Re: Valve size for bore size?? |
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Yes, run the Panchitos (40x35.5), CNC chambers |
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Glenn Mr. 010
Joined: December 25, 2001 Posts: 76760 Location: Sneaking up behind you
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Posted: Thu Sep 16, 2021 7:32 pm Post subject: Re: Valve size for bore size?? |
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txoval wrote: |
Yes, run the Panchitos (40x35.5), CNC chambers |
Agreed.
Last year I built a 2017 (90.5x78.4) with those heads and it runs great and pulls to redline. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare |
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Maxpower Samba Member
Joined: March 30, 2009 Posts: 26 Location: Arizona
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Posted: Thu Sep 16, 2021 8:28 pm Post subject: Re: Valve size for bore size?? |
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I totally agree with you guys but usually you ask what hes using it for. And the main question was pros and cons which is obviously powerband related (kinda)is it a Baja or track only. There is guys running small motors with big valves would
be nice to hear more than run this head and the reason why I know a lot cuz I respect your opinion but I read too much. |
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Paul.H Samba Member
Joined: April 03, 2015 Posts: 613 Location: England
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Posted: Thu Sep 16, 2021 11:19 pm Post subject: Re: Valve size for bore size?? |
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Smaller valves will seat better for longer and pick up less heat especially on the exhaust , they are lighter requiring less spring and they are stronger so if you want a high mile engine then stick with a 40mm intake. If you are a "horsepower hero" then put the biggest valve available |
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txoval Samba Member
Joined: January 23, 2004 Posts: 3540 Location: The Woodlands, TX
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Posted: Fri Sep 17, 2021 4:07 am Post subject: Re: Valve size for bore size?? |
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A 42 or 44 valve would be lazy down low with that engine combo and I doubt the increase above 4500 rpms would be much. That cam is also done at 6000 unless you run ratio rockers.
If you haven’t bought the cam, switch to the W125 |
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bugguy1967 Samba Member
Joined: January 16, 2008 Posts: 4338 Location: Los Angeles, CA 90016
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Posted: Fri Sep 17, 2021 12:28 pm Post subject: Re: Valve size for bore size?? |
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Depends on how much power you want. A 42mm valve can support over 200hp. A 40 can supply around 180hp with good ports. _________________ "A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine" |
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[email protected] Samba Member
Joined: August 15, 2002 Posts: 4394 Location: Brew City
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Posted: Fri Sep 17, 2021 12:42 pm Post subject: Re: Valve size for bore size?? |
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watercooledguy wrote: |
I'm in the process of building a 1967cc 92x74.ive been looking at cb and the 501 heads both available with 44 or 42 valves.is there pros and cons of each.would 44 be a over kill for a 92 bore?
Running a w120 and 44s |
With your cam and carb choice, 40mm x 35.5mm valves(in a head with the proper ports) will give you the best HP/Torque numbers. Anything bigger and you will actually lose HP and/or torque _________________ Please "LIKE" us on facebook to see what we are working on.
https://www.facebook.com/mofoco?ref=ts&fref=ts
www.mofoco.com
Cylinder Head Reference Sheet |
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