quadgod211 Posted February 13, 2009 Report Share Posted February 13, 2009 im building a 421 cub motor with cleanup port on alky and nos that i got off of 530grafix and i was told by a local builder that the bigbore pipes made 10 more hp then smallbore pipes..and he also said he could make 116hp on his dyno with his fully drag ported cub with the bigbores.... most the guys i know around here with 10 mill cubs run small bore with bigbore stingers on there pipes...only way they run bigbores is if there 72mm bore or biger.. i already have smallbore cpi's they aint much to look at since they have broke and cracked 10 or so times and been welded back...so i couldnt get much outta them if i decided to switch to the bigbores i guess what im asking is that...would it be worth selling and or trading for the bigbores or keep what i got ,,,10 ponies is hard to come by and is this dude full of shit???? also the dude told me that he built a 421 cub that went 3.96 300ft sand/dirt on alky motor w/no spray Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted February 13, 2009 Report Share Posted February 13, 2009 The 421 is a borderline motor for pipe selection and can work well with either pipe depending on portwork and carb selection. I would go with whatever your builder suggests. Quote Link to comment Share on other sites More sharing options...
KaosBanshee44 Posted February 13, 2009 Report Share Posted February 13, 2009 A local builder told you this? I don't know about adding 10 horsepower but i believe most of the guys that have a 421 cub run small bores. I forgot where i seen that chart but isn't small bore good to 480cc's or so and anything more than that big bore is more applicable Quote Link to comment Share on other sites More sharing options...
okbeast Posted February 13, 2009 Report Share Posted February 13, 2009 McCoy's got his 4mil's running the BB's if I'm not mistaken. Quote Link to comment Share on other sites More sharing options...
BB3 Posted February 13, 2009 Report Share Posted February 13, 2009 Ive seen a few 421's run 3.9's but there in a rigid frame. I always thought you would want to run the small bores so you have a little more backpressure. But then again i could be wrong again. Quote Link to comment Share on other sites More sharing options...
njbanshee Posted February 13, 2009 Report Share Posted February 13, 2009 i RUN SB Quote Link to comment Share on other sites More sharing options...
shanYE west Posted February 13, 2009 Report Share Posted February 13, 2009 Clean up port I'd run the small bores.. As far as BB's adding 10HP.. Thats bull shit.. The big bores dont add any hp over the small bores (on a 421 application atleast).. Just more power on the bottom and mid without losing any top. If it does add any peak hp.. it will be very minimal.... I used Big bore shearers on my Drag ported 421, But every motor and every builders port work is different and inturn will favor different pipes. Quote Link to comment Share on other sites More sharing options...
quadgod211 Posted February 14, 2009 Author Report Share Posted February 14, 2009 yea ill just stick with my smallbores becuase there welded up in 3 or 4 places where they have blew out and the stingers and mounting brackets have broke on each side...so i wouldnt get much out of them to get the new bigbores... im running a rigid drag frame thats +12 out the front and +10 out the back...i should run in the high 3.90's on motor i would think... im running the pro wedge 1's on a good fast dirt/sand track...i got nitrous but im having a hard time setting it up so i wouldnt have to run the button..i would like to set it up to where its on at wide open throttle but i have a twist throttle so im stuck for now.... also what kinda shot would you guys consider running on a 421...its got the hotrods crank so its welded but not the good kinda weld(you know what i mean)...i was thinking of runnin around a 10 per side or smaller with 18cc domes becuase i think ill blow the wheels off with anymore...also what kind of timing could i get by with on alky and spray?????? Quote Link to comment Share on other sites More sharing options...
moneybags Posted February 14, 2009 Report Share Posted February 14, 2009 Who is your local builder if you dont mind me asking? Quote Link to comment Share on other sites More sharing options...
2slow350 Posted February 15, 2009 Report Share Posted February 15, 2009 A 116hp is a lot for a 421cub, not saying is hasn't been done tho.. I kno McCoy has had his 421 cubs go 3.9's also and believe they were on full drag frames.. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted February 15, 2009 Report Share Posted February 15, 2009 Are u planning on running a wet system or dry shot.My friends are nitruos junkies and told me if I run nitrous w/ alky I wuold have 2 run a wet system and inject the nitrous with race gas in a converted coolent overflow bottle. I was told the intake charge of alky is too cold to react properly w/nitrous.I dont know anything about timing just wanted to give some fyi and ive never tried it Quote Link to comment Share on other sites More sharing options...
dajogejr Posted February 15, 2009 Report Share Posted February 15, 2009 A 116hp is a lot for a 421cub, not saying is hasn't been done tho.. I kno McCoy has had his 421 cubs go 3.9's also and believe they were on full drag frames.. Our buddy brady080 has a stock stroke, 68mm cub do 116 or 118 on a dyno. It was the guy who owned the dyno's personal motor....and he hasn't been able to duplicate that motor yet. As said...every motor and builder is different, run what they say. Matt Shearer himself told me unless I was hillshooting, I should have SB on my 10 mil, but my BB work just fine. My builder also said SB.... I'm gonna try and pick up some Shearer SB this year and test the two out back to back...just to see. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted February 15, 2009 Report Share Posted February 15, 2009 im runnin the big bore shearers on my 10mm cub. i would run small bore on a 421, but my 10mm seems to really like the big bore. Quote Link to comment Share on other sites More sharing options...
quadgod211 Posted February 21, 2009 Author Report Share Posted February 21, 2009 im sprying alky/nos mix into alky...ill just have to see how it will work im figuring on spraying a 20hp 10 per hole shot and run my timing around +4 and jim at pasion saidi should end up with 190lbs of comp on alky and spray......he 's the 1 cutting my domes... Quote Link to comment Share on other sites More sharing options...
2slow350 Posted February 21, 2009 Report Share Posted February 21, 2009 im sprying alky/nos mix into alky...ill just have to see how it will work im figuring on spraying a 20hp 10 per hole shot and run my timing around +4 and jim at pasion saidi should end up with 190lbs of comp on alky and spray......he 's the 1 cutting my domes... If I was you, I would recommend adding a small tank and spray gas with your nos.. Jmo Quote Link to comment Share on other sites More sharing options...
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