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Discussion Starter · #1 ·
Is there a big power difference in between a 65bore cub and a 68bore cub? thinking about building a cub over the winter..Thanks in advance
 

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The only reason I can think of to build a 65 mm 4 mil Cub would be to keep the ccs below 400 for class purposes. NOt sure of the power difference, but no doubt the 421 has more and wouldn't cost much more.
 

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Also theres the 66 bore at 397ccs if you want under 400ccs. Theres not that much difference . A 65 bore might be easier to find a 65mm wiseco piston locally at the dealer depending on where you are at rather than having to order a 68mm one. I'd go 68. But I've seen fast ones of each 65,66,68.
 

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Discussion Starter · #4 ·
thanks for the info..CC's dont really matter, the tracks I run at are open classes and a 0-425cc class. I'm leaning towards the 68mm. what hp numbers are coming out of the 68mm? 110ish? looking to run in the high 80s or 90s (hopefully lol)
 

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QUOTE (YGR4MIL @ Nov 8 2008, 04:09 PM) index.php?act=findpost&pid=15404thanks for the info..CC's dont really matter, the tracks I run at are open classes and a 0-425cc class. I'm leaning towards the 68mm. what hp numbers are coming out of the 68mm? 110ish? looking to run in the high 80s or 90s (hopefully lol)


You should have no problem getting 90 + hp on gas if it is tuned correctly and with the right size carbs (I like 39mm Keihns, but haven't tried any others to compare).

Go to alky and you should easily be 100+ hp (from what I've read). I've never dyoned my 421 Cub, but when I get it dialed in at the track it runs low 4 teens consistently all day long; sometimes 4.0s (stock chassis).
 

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Discussion Starter · #6 ·
QUOTE (J-Madd @ Nov 9 2008, 01:04 PM) index.php?act=findpost&pid=15470You should have no problem getting 90 + hp on gas if it is tuned correctly and with the right size carbs (I like 39mm Keihns, but haven't tried any others to compare).

Go to alky and you should easily be 100+ hp (from what I've read). I've never dyoned my 421 Cub, but when I get it dialed in at the track it runs low 4 teens consistently all day long; sometimes 4.0s (stock chassis).

thats what I was thinking, 100+ on alky. I'm looking to go some 3.8s or 3.90s in drag chassis. I've been 4.10 on my 4mil stock cylinder stock frame so far (i'm only 115lbs, so that helps lol).
 

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If your not restricted by cc's definately go 68 bore. My builder has a 421 that flat a** rips!!! On his dyno (on that day at that time, LOL) it made 114 hp. For everyones info, my 350 made 94, 535 Cheetah made 135 and his 18 mill made I believe mid 160's. I know how it works when a dyno # gets thrown out there. LOL
 

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QUOTE (YGR4MIL @ Nov 9 2008, 06:47 PM) index.php?act=findpost&pid=15484thats what I was thinking, 100+ on alky. I'm looking to go some 3.8s or 3.90s in drag chassis. I've been 4.10 on my 4mil stock cylinder stock frame so far (i'm only 115lbs, so that helps lol).

3.90's should be easy (with builder's help obviously) on a 421 cub. I have seen a Nate McCoy motor go 4.0x at a "slow" track that is supposedly 2 tenths slower than other tracks.
 
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