Valve Size Recommendation....
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Seasoned HDF Member
Joined: Mar 2010
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From: Poolville
Valve Size Recommendation....
I have a set of heads that I would like to use on my 117" TC.. I had them on this bike when it was a 103"er with a TW5-6 cam and the bike ran very well.. They currently have 5/16" kpmi valves w/1.90" intake and 1.61" exhaust with an intake port opening of 1.760".. Would a 1.940" intake valve be better suited and leaving the exhaust valve the same size but open up the intake port to 1.800"? Or will the .040" difference really make it worth the money? I plan on going back to the Woods 888 cam.. These do have 85cc combustion Chambers and I'm really not going for all out power this time but I would like the heads to breathe properly.. Thanks.
Last edited by 98hotrodfatboy; May 24, 2026 at 11:03 AM.
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Joined: May 2014
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From: florida
i run the 1.940 and 1.610 combo on my 107 that we have talked about. Kirby did those heads for me and during our discussions the 1.940 was the largest valve we wanted to use on that seat and considering the 9B cam.....bike runs great,,,currently gonn set up a 103 with the tw8 cam and Wes @ Cyclle Rama is going to do the same sizing for me. i had Scott do a set up for me as well with that sizing and it worked great too. the port sizing is good at 1.8 if you have enough intake, like the 55/58 HPI set up. if you dont, run it and see,,,,,if you think you can get more afterwords, you can always blend the port entry area to match the 1.8....you just taper blend it down.
m
m
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Seasoned HDF Member
Joined: Mar 2010
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From: Poolville
I thought the 1.94 would be better suited and am contemplating doing it but just might wait a little and see how the 1.90's do.. thanks Marco.. With the 888 cam I don't think it will make that much of a difference but I'm sure it will make some difference..
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Joined: Dec 2022
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From: CNY
When I was looking to do a 117, from questions I've asked, the responses were, the 1.94's are about as big as one can go on stock seats. Most 117's I've seen built have been done off 110 heads with the stock or larger 2 inch + intakes, I've seen some nice results with the 1.94's and I think intake size and cam size go hand in hand if you want to optimize your outcome, as in you need more cam to offset a lesser flowing head. I'd thought of running 1.98" intakes per Small Block Charlie with a cam that had a duration between the quite utilized TTS 150 and your tripple 8's. Would have really liked to have seen it through, but sometimes life happens, and now this build isn't!
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