Blorton

iTrader: (2)

I'm strongly considering a set of the General's cnc ls6 heads.

However, I'd like to smooth out any cnc marks they may have. What's the preferred method of doing that? I've got a die grinder with a nice selection of attachments, but am afraid I may end up doing excessive material removal even with a high grit flapper wheel.

Could I just wet sand them by hand with various grades of sandpaper, or what would you guys recommend?

Thanks!
Dan

66deuce

iTrader: (1)

i don't know if there is any real benefit to sanding out the cnc marks,maybe a sponsor could chime in?but i did sand them out on my heads.it sounds backyard,but i just sanded mine by hand with 80 sandpaper.i was careful not to change the shape,just smoothed them out.i'll find out if i screwed anything up when i get it on the dyno in a couple of months

robertbartsch

i left mine with the deep scratches...

i was going to sand them down and was advised not to...

Blorton

iTrader: (2)

Did whoever advise you give a reason why? I'm thinking because some turbulence on the intake port can be good, but I'd like to hear what they were saying.

Thanks,
Dan

quickWS6

I don't see any reason why you shouldn't. Jantzer is hand finishing my Patriot heads right now. Most of the shop cars have "hand-finished CNC heads" that I have seen.

BTL FED

iTrader: (9)

There is nothing wrong with hand finishing them, just dont change the shape and dont try and make them a mirror finish, a little rough is good, now the exhaust can me made to be a mirror finish it helps so carbon doesnt stick as well

annil8r

You will not hurt anything by hand finishing your heads, but be careful not to take to much off. The best thing to use would be a 60 grit stone, thats the finish you need. The rougher you leave the intake the better the runner keeps the mixture churned up which in the longrun builds more power. Roughness in the intake does not hurt the flow.

Steve - Race Eng

iTrader: (1)

I do quite of bit of flow testing at my shop as well as cylinder head development work. I can tell you from experience, leave the intake side as is. The flow will drop in most cases if you smooth out the machining marks. The ridges also help to keep the fuel mixed with the incoming air charge.

The exhaust side can be carefully sanded (don't hit the valve seat) using first sixty grit sanding rolls then finishing with 120 or finer depending on how much time you are willing to spend. I use a high speed cable driven Dumore grinder for this work.

Steve Demirjian
Race Engine Development

Blorton

iTrader: (2)

Thanks very much for the feedback, Steve! I'll leave the intake side alone and see about following your advice on the exhaust side. I've got a dremel with a remote cable option, so that may be a workable option. Time won't be a big deal as I'll be accumulating parts for the job over time and will have plenty of time to do the finishing.



Dan

M6HuggerSS

so make the exhaust port like a mirror.
dont touch the intake.
but what about the chamber? can you polish it?

-Joseph-

iTrader: (12)

The intake port volumn is 250cc on those GM CNC heads, I would try not to make it too much bigger.

99 Black Bird T/A

iTrader: (4)

250cc intake port volume? That's got to hurt velocity.