1972 heads CC

Hello,

I would like to know if anyone has CC'd stock 1972 heads. I have a 2nd 455 stock engine that I was told was low mileage and came out of a big car. I pulled the heads and found no cylinder ridge that I could feel, just a slight discoloration. I used my new jegs CC kit to check the combustion chambers to verify the 71 CC number that I have seen on several pages online. The surface of the head has been scraped clean, the chambers left untouched with a bit of carbon on them. I checked 2 chambers on the same head and got 77 CC. I was hoping to use these on my current build until TA heads came available. 77 CC seems like a lot and kills compression with the pistons in that engine down measured at .055 down, standard size stock 1972 take out pistons CC'd at 36 and a .038 head gasket (TA Orange) for calculation. This should work out to about 7.85 to 1 if I calculated correctly. Does this sound right for a stock 1972 455 engine?

I am more concerned about the correct cc volume of the heads, but was hoping for an easy 2nd 455 with a cam for this one in the future since the heads would be fairly fresh after getting redone. Not sure I want to cut .030+ to get to 71cc.

Please let me know what you have seen.

 

We put a set of 73 Stage 1 heads on my buddy's car that were shaved .015" to get them cleaned up. They came back at 69.5cc each. His piston tops and how far in the hole were like yours. His CR was only a little better at 8.33:1.

77cc sounds more like a 75-76 head. They were about 78cc.

Your calculations are about the same as mine. The size of the head gasket diameter might be all we differ on. So, if you could get the heads shaved about .020, it would help. Otherwise you would need to take it apart to deck the block.

 

The Team Buick reference section lists head casting numbers , the cast numbers on your head has 2 listings for 72-74 @71cc and 75-76 @76cc ,this would explain your result of 77cc , cheers

 

Thank you. I thought the 72 cast in the head near the exhaust port meant 1972. How much cut do I need to get to 71? I thought I read .005 per cc. Is that true?

 

What would it work out to if you milled them down to 66-66.5cc?
Chris

 

I cc’d my ‘72 heads and got 71cc. Unfortunately, I don’t have access to my casting number right now but I can post it early next week.

When I first cc’d the heads I was getting higher numbers (I don’t recall how high). Then I realized I was putting too much grease on the head to ensure a good seal and the grease was holding up the plexiglass so it was giving me a false measurement. So the next several times I just put a very, very thin layer of grease and I got repeatable results of 71 cc. Just make sure your confident with your measurements before you cut the heads.

 

This is my first time trying to use my cc kit. I will try again with less sealing grease. I did have a nice bead I squished down.

 

Yeah, I did the same thing my first couple tries. All you need is a super thin (transparent) film of grease.

 

I believe.004 per cc is correct , I think the 72 on the head is a mould no , there is also a month, letters , A to M , and a year , number , 0 to 9 in the cast to indicate the manufacture date. 76 heads are open chamber and less desirable than earlier closed chambers heads , however 76 blocks are a stronger improved and heavier and the best to build . Check the Team Buick forum for all the cast numbers , valuable information.

 

Here's a picture of one of my heads. It has the same casting number as yours. It also has M17 under the GM mark. I think that's the month and day the head was made. Unfortunately, the heads are out getting a valve job, so I can't look at them, but I recall the heads having a 72 on them. Like you, I thought that was the production year, but I did not verify that. However, per rjay's comments, this assumption seems incorrect. I'm not sure if this info helps at all, but I figured I'd share.

 

I will try to get out to the garage this afternoon and try cc with less sealing grease. I do recall this head has a different date mark than the block and other head which have the same letter and number.

Does anyone have a picture of the open chamber on the 75/76 heads? I can't seem to find one that I can compare my head too.

 

Thank you Larry for the pic. I am certain mine are closed chamber.

I also need to try and get more practice/consistency in my cc abilities. I tried all 4 chambers. Best I got was 73 the rest 74-75. Plan on trying again when they dry out.

4 pics.
#1 casting date on head in question
#2 chamber on head in question
#3 block casting date
#4 2nd head casting date

Are these heads close in date or is the odd one most likely a replacement?

 

Maybe a silly question, but do have a spark plug installed when you’re cc’ing the head or are you plugging the hole some how? You should have a spark plug in otherwise you’ll get an inaccurate number.

 

Spark plugs are in. I try to put less Vaseline on each time. I am amazed at how little it takes to seal.
Once I can get consistent with my cc technique. I will send them out to be cut 20-30 to get them down to 68ish cc.
This should net 10 to 1 on my 4.32 bore 0 deck 26cc dish piston engine that is waiting on ta heads.
It will also bump this one up a bit if I put the heads back on on the future.

Thanks for the help.

 

Casting dates would indicate mid December and early January( accelr8 is right) ,i could not remember exactly . With the cc’ing , the spark plug appears a little short, and both valves are the dished which could possibly account for the extra cc’s.I don’t see a steam hole on the inlet side between the chambers check the deck for a corresponding hole , this may be characteristic to this cast , someone will be able to inform , if there is a steam hole in the block and not in the head it might a good idea to drill one . Cheers

 

It's important you cc with the same plugs as you will be using.
The plugs that are in there look to be short.
IF the TA heads are aluminum the compression can go to 11-1 or higher & still be safe.
To get the same performance from aluminum heads as cast iron the compression needs to go up 1.5-2 points since the aluminum dissipates heat so much faster.
You can lessen cc's by replacing the tulip valves with flat faced valves then you wouldn't have to cut so much from the heads as the tulips have about 6cc's or more between both.

Tom T.