906 heads Misc. Info for the Masses

[zyzzyx]

I am starting to assemble my heads and am finding that the information that I have read here is not quite right. Me thinks! Anyway, I ported my heads, un-shrouded the valves, and polished
the combustion chambers. Put the head gasket on the head and used it as a template to un-shroud the valves. Didn't want to go too far! After all this I decided to cc the combustion chambers. Some here were saying that the chambers on 906's were 86,88, and some were 90 or more. Here are my findings in pictures. As you can see by my Mic reading, the head has only been machined 0.007 from stock. They measured 1.007 generally before I had them
"cleaned up".

 

[Lefty71]

I measured up a set of 906's and also a set of 452's, with a burette just like you are showing. They were both cleaned up, never cut and had stock valves in them, 1" flange in the lower bolt area. Both sets measured out to 86cc. At the same time I did my 915's that were worked a little with new valves, and I'm sure they were lightly decked. They came in at 79cc. Just a little reference for comparison. I'm sure all the factory cared about is they were "in the ballpark".

 

[super-bee_ski]

I measured up a set of 906's and also a set of 452's, with a burette just like you are showing. They were both cleaned up, never cut and had stock valves in them, 1" flange in the lower bolt area. Both sets measured out to 86cc. At the same time I did my 915's that were worked a little with new valves, and I'm sure they were lightly decked. They came in at 79cc. Just a little reference for comparison. I'm sure all the factory cared about is they were "in the ballpark".

+ OR - 10 percent!

 

[Jerry Hall]

This puts an understanding to why some cars equipped equally from the factory ran so much better than others.

 

[#41]

This puts an understanding to why some cars equipped equally from the factory ran so much better than others.

I would attribute that to tuning far before a small percentage of compression.

 

[Kern Dog]

A few years ago I checked the chamber volumes of several BB heads. 346. 452 and 906 castings. One was 90 ccs, the rest were 88-89. Your number is unusually low.

 

[4406bbl]

I would say his valves are sitting higher in the chamber than stock. You may want to put the head gaskets on the block and mark the bores for a notch if you unshrouded the valves all the way out to the gasket, or put the heads on and look up there. I used to do that but I now put the heads on the bare block after it is bored, mark them left and right, then scratch the circle of the bore on the head, and never unshroud past that line. You will see mopar big blocks have a weird shape head gasket and porting unshrouding all the way out is not the best idea.

 

[Don Frelier]

A few years ago I checked the chamber volumes of several BB heads. 346. 452 and 906 castings. One was 90 ccs, the rest were 88-89. Your number is unusually low.

They sure look like they've been milled to me.

 

[zyzzyx]

I had hardened valve seats installed and used Milodon valves. My installed spring height didn't change after I got them back so the valves are where they need to be. All the tops of the valves are even with a straight edge, and the valve tips were not touched.

 

[70bigblockdodge]

The 452s I have on my Charger are ~90 I have a set of 516 castings that are hacked down to 73 CC's and the 906s that I'm using on another are hacked down to 80cc. All of these were decked long ago. I've picked them up at swap meets over the years.

 

[PRHeads]

OP’s heads have aftermarket over sized valves with thicker margins and smaller dish volumes.

Not stock heads with stock valves........ of which I have cc’d many........ at around 88-90cc’s.