6X-8 Heads - CC at 109 ???
 

I acquired a 455 motor with 6X heads while looking it over I noticed that both heads have been stamped 109 CC. That seems to be a large chamber volume for 6X-8 heads. My other set came back at 101 CC after valve job. So questions: How do you get 109 CC from 6X-8s? The heads have been worked on supposedly by a Pontiac shop. Any one know what shops stamp the CCs on heads?

I had a set CC at 106.

I valve job in conjunction with Tulip face valves and or some unshrouding work will do that when you start off with 98 CC to 101 CC head.

Are Tulip face valves usually stock valves? About to pop the valley pan and look around. I guess the looking for the exhaust seal on valve will identify a stock valve? Any other way to spot a stock valve?

Thanks good to know about the CC on the heads. Going to pull current cam to see what it is. Hoping to get a bore scope to check piston tops.

If you are popping the valley pan off safe to assume the intake has been removed. Use a small mirror and flashlight to look down the intake ports.

Intake and valley pan now removed, thanks for the tip on the mirror. I'll check it out. Motor looks clean, cam doesn't seem to have much wear. Should be pulling it later today. Then the dreaded "what cam should I use", depending on what I found.

Ones I have are 105 but the "eyebrows" in the chamber are smoothed. My original 78's motor are 97.5.

well, I'm going to pull the heads and CC them to be sure they are still 109CC. Also going to elongate the push rod holes while there off and check spring pressure. I don't have a spring tester, should I bring the head to a machine shop and have the spring pressure tested?

Also the motor has a few issues, no wonder there is not much run time. It had some old 1.65 Erson roller rockers on it but the pushrods were rubbing the heads. If 109CC head then compression lower than I like. But what got me, someone had installed a 305H cam with that compression?

I just want to get the car on the road so I might just use a 2801 cam that I have on the shelf and not pull the heads.

This motor was supposed to be ready to run. Saw it running in car and thought I would drop in my car to get me going. After checking this motor over it has some issues.

Yes. They can also check for coil bind, and see how much they can shim to get pressures right if they are not already.

I just reread your post here and it seems your are going by what the heads have been stamped in regards to the CCs since it seems you still have them bolted on the motor.
If it where me I would pull them while changing out the Cam to confirm there CC's and to maybe Mill them to get them down to 101 CCs.

Part of me wants to throw the 2801 cam in and go since I have the cam. But I really want to do it right. Its only a few more bolts to remove the heads now so I'm going to have them checked out and do it right.

Good, that's the best way to do it!

If you mill them 0.050 or more you have to mess with intake and valley pan sometimes.

I have a 2801 in a low compression 400 and it runs well for a stock type cam.

[ATTACH]Attachment 470018[/ATTACH]

Took the heads off, domed pistons, that changes everything.

Anyone seen a dome like this? any idea on CC?

I wiped one down looking for numbers, didn't see any. The others look oily. any ideas?

The largest I can remember from yrs ago were 15cc most were 8-12cc. I don't recognize those in particular but that may get you in the ballpark of a cr range without cc-ing them.

Just from looking at some pics from Summit, these appear to be Keith Black KB-347 pistons. If I'm reading it right there are zero CC. Still need to CC the head but if its 109CC that is about 9.5 to 1 comp? From the pics about something wasn't happy, really oily pistons tops.

Do the Pistons rock in the Bore?

Do the back side of the Intake valves look oily?

What do the heads have for valve seals , white Telfon type's?

I wonder if those pistons are cast.........

With two different depth valve notches I do not think it's cast, besides I think I see maching marks on the flat of the piston tops which would confirm that they are not cast!

????
 

Pistons oily or just nasty from a bunch of idle time with the 305 cam?

What's the hone marks in the cylinders look like....fresh or shiny from running a while

Clay

Attachment 470074

Attachment 470075

Here are the heads and bores. Car didn't have much run time on it so hoping it was the big cam, low compression situation.

I have any other set of 101CC 6X heads that are fresh so I will end up using those instead of the 109CC heads.

So what do you think from pics?

Those valves are pretty darn sunk !
No wonder the heads are checking in at 109CCs!

The Bores look good atleast!

Yeah, sunk, and are the center punch marks for marking cyl position???

On taking a closer look at the Intake valves it looks like a 15 degree top cut of considerable width was added to the valve the valve job .

This will pick up very low lift flow which the 455 does not need as it only makes for more reversion up the Intake port during Camshaft over lap which then makes for degraded idle and a motor that comes on the Cam latter in rpm , but also cuts down on high lift flow a tad!

The factory guys / designers new what they where doing in the heads by using a 30 degree intake seat with no top cut!

I hope your next set of 6X heads does not have the same type of valve job?

Good assumption it is #6 cylinder. Valves are mismatched manufacture, at least the two we can see. Not inspiring work.

The Intake valve with the circles is a stocker and the six punch marks means in what back into the valve guide it came out from which further means that some if not all of the valve guides where likely not replaced during the rebuild.

How wad the oil usage on this motor?