Another 906 head question

[footin70rt]

So I have a set of 906 heads that and was just trying to find out if it's worth milling them down to get the compression up. I know the chambers stock are 88 - 90cc's so how much can be taken off to to reach a 75 - 80cc chamber? I understand that I may have to mill the intake to fit but that doesn't bother me, this is going to be a "budget" build. I also have a set of 2.14 1.81 stainless valves I was planing on using also.


 

[Chryco Psycho]

you would have to basically remove the quench part of the chamber approx .080 or more which leaves the deck too thin .
 Better of to use 516 / 915 heads or use an aftermarket alum head

[footin70rt]

So what would be the smallest the chamber size can safely be?  I have heard of people taking .100 off these heads and ending up with 65cc, and running them. One I know of ran his for several years, is he the lucky one?

Also do you know what would be the approximate cc  for each .010 off?  Like I say under 80cc would be great but I could live with something around 82-83cc. Trying to keep costs down as much as possible.

[Chryco Psycho]

LEt me see if I can figure this out
 we need Pi R 2 x the diameter of the chamber approx 4.35 X .010 & then convert to cc
 I am not sure how much you can mill off & get away with it , I know there is a limit to the amount you can deck before the deck gets too thin , your friend maybe lucky with a thick casting or maybe it is not subjected to extreme pressures?

[Chryco Psycho]

well if the Chamber is 4.35" removing .010 from the head removes 1.12 cc ....... so milling .100 will remove 11.2cc
so a 90cc chamber would be 79 cc approx , you will need to mill the intake side of the head or the intake .012 for each .010 milled from the deck .
 you will have to have custom pushrods made .100 shorter , you will really need to watch piston to valve clearance where you are generally safe to around .600 lift with relieved pistons now .500 lift may be tight unless you deepen the reliefs in the pistons , be careful with bore notches too smaller bore blocks may have the valve hit the side of the bore with big valves .

[footin70rt]

Thanks Chryco. Looking at these heads I don't think I would trust them after taking .080 off. The thickness at the water ports is maybe .130 ( hard to measure accurately)  I was hoping to get the static compression up close to 11:1, and if I can get it down close to an 85cc chamber it calculates out to 10.31. Decisions to make now,..... anyone want to buy a couple of kids? That would free up some cash!   

[Chryco Psycho]

Hmm Kids .............       ummm 

[footin70rt]

Just kidding on the kids, besides my 10yr old little girl argues with me that the Chally is "her" car. It's always fun when her friends come over and point and ask is that Kylee's car?