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while 300 cfm is stellar for a OEM 96" casting,but its not near enough for anything but a very mild 124.

 

Yea that's what I figured.

This will be more of a hot rod build so I'm looking to maximize hp.

Ill be on the lookout for some 110 heads or MVAs.

Thanks

 

What would the minimum CFM for a 150hp 124" be?

I built mine to be around this numbers, didn't put it yet on a dyno but im pretty sure that is closer to 140 than to 150, I would say around 135hp based on my butt dyno, I have a set of 110 heads @ bit over 300 and i'm not sure if they're the bottleneck, or maybe the 58mm HPI unit.

 

The 58 tb is not the bottleneck. Typically if all components are matched for peak hp the restriction for 150+ is often exhaust, even if it’s a good 2-1.

 

I'm running the FM e-series for dynas, I know for a fact that it does support 150 hp as FM themselves run one on a 117 and Jamie told me that he is using it on another dyna pushing 160 without issues, I was between the e-series and the boarzilla and ended with the FM mainly due to being quieter.

 

With purpose built G.W. heads and a wood 68 sure it should go 150. But if a stock head casting worked for typical street use and a more street friendly typical big motor cam, 150+ hp unlikely.

 

You're right, they had GW heads and probably 12:1 or more comp with those cams, still it was a 117, a 124 should reach the 150s easier, I have a feeling that something is holding me back because the engine wants more fuel in low-mid range but wants less at upper rpms, Im running the woods 9B set at 11.2 comp, my heads are 110 castings ported to a bit over 300cfm, that's why I asked since Kirby said that heads pushing 300cfms won't get you past a mild 124 (I consider mild around 135-140 hp)

 

I like to see my 110 heads in the 325+ area,really hard to put a number on what 300cfm heads would do on a 124" without knowing the rest of the build,but even on a very aggressive build I wouldn't expect more than 130,maybe 135

 

On my 124 build using 110 heads Cycle Rama had them flowing @ 340 cfms and set the compression for 11.8 running there 650 cams and its reached 150 hp so your going to need more flow and raise up the compression and a better exhaust, I built a Fm 117 using DVR heads and a TW999-6 cams along with a 58mm TB running the dyna FM E series exhaust for forum member the MADD GHOST and his numbers are very low for a 117 build, the tuner told him the same that something is holding him back on the power department. the tuner removed the baffle out of the pipe and the bike picked up 10 hp. but its too loud for his liking!