stock heads limit?

[VernDiesel]

Where does stock unmodified heads start to impead horsepower gains? 

[rigidthumper]

There's been a couple guys post 130ish HP with stock M8 heads on the big bore kits with the bigger throttle bodies.

[VernDiesel]

Thanks thats better than I expected.  I converted a 107 to a 114 so I do have the bigger 4.075 bore. (11-1 fwiw)  I do also have the extreme heavy breather AC, 64mm TB & manifold. Only I stuck with the more moderate 492 cam. Maybe with a good aftermarket cam, stepped header 2 into 1 exhaust and PV dyno tune they would do 120 - 125 ish HP without cam-airflow magic? 

[rigidthumper]

Big bore as in 124/128 kits- I haven't seen a stock headed 107/114 with any cams tested yet, that broke 120 HP. Need more airflow- that can come from displacement or porting ( altho having both is fun )

[VernDiesel]

I followed what you meant big bore as in the 4.250 bore S&S jugs. Love to go there down the road. I meant Stock bore 107ci 3.917, 114ci 4.016, stage 3 114ci 4.075. IE the big or bigger bore of MoCos options.   MoCo uses CNC heads with their Stage 4 at what 120 - 125 HP.  But I am not sure where the stock heads with say the 4.075 bore start impeding flow or power.  I am sure cam matters as well just kind of a general HP for stock untouched heads with like the 4.075 bore.

From the stage 3 dynos I've seen 108 to 114 HP but I don't know if its the heads that sort of stop it there or just the cam and or other intake & exhaust restrictions.

[Txwezl]

https://harleytechtalk.com/htt/index.php/topic,104122.msg1233958.html#msg1233958

[VernDiesel]

Wow thanks for the link. 121 HP & 130 TQ on a stock head 114. 

[Hillside Motorcycle]

With re-worked OEM heads, we have seen north of 150, 124" engines, S&S cam.

[yobtaf103]

Wow thanks for the link. 121 HP & 130 TQ on a stock head 114.

Think Andrews 504 requires springs

[Don D]

Here is a 117"
http://www.rocketcams.com/m8cvo117
Now the kicker
Stock exhaust and air cleaner
125/136 STD

[Durwood]

Where does stock unmodified heads start to impead horsepower gains?

I have seen 137 horsepower on a 124" build from stock heads and throttle body using a CR-482 cam.

Next up is an SE 64 throttle body and then a set of heads that WFO Larry worked over for me.
[attach=0,msg1325711]

[TXChop]

Where does stock unmodified heads start to impead horsepower gains?

I have seen 137 horsepower on a 124" build from stock heads and throttle body using a CR-482 cam.

Next up is an SE 64 throttle body and then a set of heads that WFO Larry worked over for me.
[attach=0,msg1325711]

When is that being built/tuned? 

[Tail Ridr]

Here is a 117"
http://www.rocketcams.com/m8cvo117
Now the kicker
Stock exhaust and air cleaner
125/136 STD

Would an AC change along with exhaust change and corresponding tune, fix what looks to be a soft low end and then hold or improve those numbers in SAE?

[Don D]

I am sure it would improve. 115tq at 1900 is not soft. There is nothing soft about that torque curve just a jagged line and like you said at least pipes and a tune would go a long way to fixing that. Time to shop for a clutch fix too.

[Durwood]

Where does stock unmodified heads start to impead horsepower gains?

I have seen 137 horsepower on a 124" build from stock heads and throttle body using a CR-482 cam.

Next up is an SE 64 throttle body and then a set of heads that WFO Larry worked over for me.
[attach=0,msg1325711]

When is that being built/tuned?

As soon as I get the heads back and the opportunity.

Going to bolt the throttle body on and tune. Then install the heads and retune.

[bigcraig]

Here is a 117"
http://www.rocketcams.com/m8cvo117
Now the kicker
Stock exhaust and air cleaner
125/136 STD

That's pretty impressive, really.

I have been shopping for a cam for my CVO that already has a Fulsac MX headpipe, 2.25" cores (I have 2" cores as well on the shelf) and a Tman zero-loss AC.

Thinking about adding a HPI 62mm TB when I finally decide to the cam. (HPI is less than 2 miles from my house.)

Makes a fella really think about the possibilities.

[Heatwave3]

Here's 140hp on my FM 128 M8 with stock heads and upgraded springs.

[Hillside Motorcycle]

Our company Facebook has a 124" that rang a bell.
Headwork, build, tuned by us.

[Buglet]

     It looks like the stock heads gave it more torque.