I've been reading a lot lately about the pro's and con's of milling the air horns down. Just wondering who has done it successfully as well as any thought on the K&N Stub Stacks.

http://www.clubcobra.com/forums/showthread.php?t=101214

My old Barry Grant Holley's do not have the them. I do not know exactly what BG did to the Holleys to put their stamp on them, but there are no air horns.

I saw dyno reports on them years ago..did pick up a little, nothing there is night and day but it all helps air flow and thus H/P

I have milled a few, but I can't say if it helped or not. I have never done any back to back testing. They look a lot better, for what that's worth. I'm sure they do help air flow but I doubt it will be a huge difference. I don't think it will be anything that show's up on the speedo.
Eddie

Back in the day when we use to do them flow charts showed that removeing the air horn would give you 25-35 more cfm..

We did back to back dyno pulls on Holley 850's #8381 in the early 1990's. One was stock the other with the BG mod's including the air horm removal. The engines were 466 CI making about 520 HP at 5500 RPM. The BG carb made about + 8 HP. The engine builder was surprized and we did the test about three times....we ordered a second one!

I think I might cut mine with a little blending however I'm not going to go any further than what was illustrated in the above link. What I am uncertain of is if the metering blocks would need work as well. Some have claimed a leaning condition that can't be resolved by jetting. Not sure how much truth there is to that. I'll do one and leave the other one stock with the air horn and choke in place and run to Valakos and put them on the flow bench. I can't help but think this would help flow anyway. Does anyone know if the internals are different between the HP carbs and stock Holleys?

I don't thing the metering blocks were changed. Not sure the jetting was even changed. I may still have the dyno sheets...we don't throw much out

Thanks for your input. Every little bit helps when it comes to HP.

Usually the hp series holly's have a screw in air bleed jets..