CC'ing some late cylinder heads,.not sure what I'm seeing

[Ron LaDow]

Ron; check your math. .010" times the area equals closer to 1.4cc, not 7cc.

(embarrassed face icon) Not only did I blow it, I then repeated it.

[Steve Harrison]

Ha Ha Ron,...I'm no math guy, far from it, so it never registered to me to "do the math" on your suggestion, but even if it's not too much volume, it still is something. I should have done that before anyway so thanks for the reminder.

Hey Vic,
You've seen hundreds of head chambers. Here's a close up of the heads I am CC'ing.
They look untouched to me and have the "factory grainyness and waves", at least that's what it looks like to me. What do you think? (I know it's hard to do from pictures)

The second picture is the chamber of some old race heads I have here. Lots of unshrouding, and the finish looks different.

P.S.,...that's not a crack at the spark plug hole pointing towards the intake valve. I checked it out closely, it just looks like it in the picture.

[Vic Skirmants]

Top photo does look stock.

[Paul Kust]

The unshrouding at the plug looks like the difference, or am I just stating the obvious?

[Dick Weiss]

The exhaust valve seat looks like it's been cut excessively deep and the shown valve itself has corrosion
on its face; The other 3-valves look the same and were they reground, seats cut deep, and lips still
w/in specs? Also, a lot of shims will be needed for the spring stack-heights and will require shims under the rocker stands to make sure the valve adjustment screws won't block the oil flow to the rocker shafts @
the clearance settings!

Dick

[Larry Coreth]

At the risk of belaboring the point that Vic made, the 1.4cc number assumes 82.5 dia but in actuality the I.D. of the pocket into which the cylinder fits is approximately 92mm. See below.
This then equates to 1.7 cc (1.68 to be precise). Still far less than 5 or 7 cc's !

"Does that seem reasonable", is the question I always ask my self when finishing a calculation. The answer has on occasions has saved me some embarrassment but not always.

[Vic Skirmants]

LARRY! The 92mm dimension has NOTHING to do with the bore size.

[Jacques Lefriant]

Hi Vic
they are using that no(92) if the plate is off the surface by .010" one thing they can do to check is to use their plate on a very flat surface and just grease the periphery and cc the gap.
j

[Ron LaDow]

Hi Vic
they are using that no(92) if the plate is off the surface by .010" [...]j

This is the reason I suggest getting the sealing surface cut before you take any measurements; you're guessing unless it is flat on the surface.
I'd also suggest getting the ink off and using petroleum jelly to seal the edge. It is VERY visible and you'll know if the liquid is sneaking into the presumed peripheral seal.

[Larry Coreth]

Vic,
That is the point the cyl. bore size does not come into the calculation of the head cc's if the glass cover is held up by a theoretical .010" raised edge on the head's cylinder mating surface. This is at least how I understood the originally proposed explanation for the extra 7 cc. A very unlikely possibility considering the actual numbers.

The bore size does come into the calculation when spacing the cylinder up with a base gasket or in cylinder/head design that uses a head gasket and two or more head gaskets were to be used.

[Martin Benade]

Isn't the ridge a little bit of aluminum that is forced into the cylinder bore, creating a ridge at bore diameter? Everything at the larger diameter is out of the calculation, as it is sealed with grease and not getting measured.

[Larry Coreth]

Martin,

As I imagined the situation, the measuring fluid was getting between the glass and the sealing surface of the head/cyl. interface where that distance was supposedly the nominal .010".
Now if when cc'ing the head the glass is sealed at the head/cyl. interface as it should be, the 92mm dimension is irrelevant and the cyl. bore (82.5) dimension becomes academic also, as the point here is to measure the head volume directly.

[Matthew Devereux]

Has anybody seen a combustion chamber that looks like his? I couldn't find any pics.

[Jacques Lefriant]

Hi Steve
are you sure you are not getting 57. i ask since the normal range is 58-62 and early heads 57-60 the heads have been resurfaced so the volume should go down by as much as 2-4 cc sinking the valves will not be very effective since the surface area is small. Your combustion chamber looks as cast. If the 60.0 was stamped by someone who measured it appears the heads have had a subsequent resurfacing anyway which should decrease the volume. since you have access to other heads you might prove your methodology.
j