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ovanay elinquentday
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Having taken down my engine for an (unplanned) Timken conversion, I decided to get all of my winter upgrade projects out of the way. Although the shop that ported my heads said that they were set at 84 cc’s, since I am changing cams, pistons, and valve springs, I wanted to verify the combustion chamber size. If it’s of any interest, here is how I cc’d my heads.

Before I even get started though, let me say that I know nothing about head porting. I’m not an expert on this stuff. I just ride, and work on my own bike and the bikes of one or two daring friends…

These heads had about 8,000 miles on them when I pulled down the engine. The combustion chambers and exhaust ports were coated with carbon. I used a dremel with a fairly fine fiber sanding brush and a cloth polishing disk, to clean the chamber, exhaust ports, and valves. I only needed to wipe down the intake ports with solvent, and I stayed away from the valve seats as I worked. The end result was a set of pretty clean, and polished, set of heads.


Pic 1 – Cleaned up head

The intake valves cleaned up nicely with minor work. The exhaust took a bit of brushing, and I ended up having the seats on the exhaust valves touched up by a racing shop.

As I checked the heads, I was curious as to what the area of the combustion chambers were at the surface. While I wanted to know about their symmetry, I figured I could use the area measurements if I have to adjust the volume of the heads.

To check the chamber area at the head surface, I taped some graph paper (marked with 0.10” grid lines) on the head.


Pic 2 – Graph paper lined up

Since these were essentially stock-shaped combustion chambers, for me it worked best to try to line up a minor line on the graph paper with one of the straight sides of the chamber. I used my finger nail to locate the edge of the chamber through the paper, and then taped the paper down.

Using a pencil, I shaded the paper along the edge of the opening. (This is kind of like doing a rubbing on an engraving.) It worked best for me to hold the pencil perpendicular to the edge of the chamber and work around the perimeter of the opening.


Pic 3 – Pencil at 90 to edge

Once I had the chamber perimeter shaded,


Pic 4 – Complete perimeter

I simply counted the number of small squares within the perimeter.


Pic 5 – Count the squares

By approximating partial squares, I got a pretty accurate measurement of the combustion chamber opening. I did each head twice and averaged the results. (The individual measurements of each head were very consistent.)

What I found was that the area of my chambers at the surface were about:

Rear - 57.25 square cm
Front – 57.60 square cm

They were actually very close.

((I'm breaking this into multiple posts because of the image limit.))
 

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ovanay elinquentday
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Discussion Starter #2
CC'ing my Heads (2)

Once I had the surface measurements done, I got ready to figure out the volume of the heads. There are probably a lot of ways to do this, but I set each head on a glass plate and measured Marvel Mystery oil into the spark plug holes from a burette.

First, I put a very thin layer of Vaseline on the gasket surface of the head to help improve the seal. (Didn’t want any oil leaking out on my wife’s kitchen counter.)


Pic 6 – Light coat of Vaseline for seal


Then I layed a glass square on the head. (The tape is just to keep the glass from sliding in the picture.)


Pic 7 – Glass plate




Next I inverted the head and placed it at an angle, so that the spark plug hole was at the highest point. This would let air find its way out of the chamber.


Pic 8 – Head on angle


Then, using a burette, I measured in Marvel until the oil just touched the first spark plug hole thread. This way I was sure I had the chamber filled.



Pic 9 – Measure in the fluid


Using the burette is easy. It doesn’t matter how filled the burette is, you just write down your starting ml amount and your ending amount, and subtract the two to find out how much fluid you put into the head. Since my burette only holds 50 cc’s, I measured the oil into each head in two fills, and added the two amounts.


Pic 10 – Subtract the burette readings (two fills per cyl)

((One more break for the pic limit.))
 

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ovanay elinquentday
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Discussion Starter #3
CC'ing my Heads (last part)

The pink color of the Marvel oil helps for watching it during the measurement, and seeing the fluid if you have any leaks.


Pic 11 – Check for leaks



After measuring both heads, I found that my supposedly 84 cc heads were actually:

Rear - 82.3 cc
Front - 82.6 cc

So, while they weren’t the 84 cc’s I expected, they were essentially the same in shape and volume. With this info I charged off to see what the impact of my piston and cam change are going to have on my CR and cold cranking compression. (A thank you to Bigboyz here, for their online engine calculators, which I used to figure out the other effects of my changes.)

Again, I’m not a head expert. I didn’t factor in the volume change of the spark plugs for instance. But, it was interesting info. Also, it was good to see that I did not leak any oil from the surface of the heads or the valves. Everything seems to be square and sealing.

GPO
 

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Premium octane member
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Great thread! Definitely interesting for the do it your selfer and home builder. I dont remember, but whats the new build?
 

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ovanay elinquentday
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Discussion Starter #5
TXCHOP said:
Great thread! Definitely interesting for the do it your selfer and home builder. I dont remember, but whats the new build?
Thanks.

No radical changes. I am changing from a 9.7 CR RevPerf 98" with Andrews 37g cams, to a 10.7 CR RevPerf 98" with RedShift 577 cams. It was just one of those things. With the engine apart, I couldn't resist tweaking things to try to get it to keep building HP up above 5000 rpm. I'll be claying the build and doing some other misc measuring, so maybe I can post some pics of those DIY checks.
 

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0043--Licensed to Doof!
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You're making the rest of us look bad!!!

Actually, that's a really neat way to figure your cc's. Good luck with the new build.
 

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GPO03FatBoy said:
The pink color of the Marvel oil helps for watching it during the measurement, and seeing the fluid if you have any leaks.


Pic 11 – Check for leaks



After measuring both heads, I found that my supposedly 84 cc heads were actually:

Rear - 82.3 cc
Front - 82.6 cc

So, while they weren’t the 84 cc’s I expected, they were essentially the same in shape and volume. With this info I charged off to see what the impact of my piston and cam change are going to have on my CR and cold cranking compression. (A thank you to Bigboyz here, for their online engine calculators, which I used to figure out the other effects of my changes.)

Again, I’m not a head expert. I didn’t factor in the volume change of the spark plugs for instance. But, it was interesting info. Also, it was good to see that I did not leak any oil from the surface of the heads or the valves. Everything seems to be square and sealing.

GPO

Very Impressive..............:thanks:
 

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Greg,

Good post man. Did you factor in head gasket and valve pockets (if any) into the volume?
 

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IronButt
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You should have the spark plug in place and drill a hole in your plate. If you have the springs on a coffee can will hold the head up nicely for the do it your self guys. As well you need to over fill the burrett and then drop to zero. And really to have it accurate you need a 100 cc capacity tube. And the oil may not give you a accurate measurement either . That is what I was told you can make your own or just buy the water based cc fluid from goodson.




And many times you are figuring in the true piston volume not a valve relief as you have to work from the top ring up. Being very close to the same figure is the most important , as 1 cc has a very small effect on overall compression. If you figure in the amount of volume to the top ring that is where you may see a smaller chamber to get a static number. Every piston is different as they move the top ring up or down use a thinner or thicker ring, bore size will effect it as well. Plus the head gasket thickness is another you must really mesure not just say it is a .030 etc. A used gasket is best and you must measure the bore of the gasket. cometic will move the size around some. You can figure that in with a piston with rings on it grease the bore and drop it down X amount and use the math to find out what the true piston dome volume is.
 

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ovanay elinquentday
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Discussion Starter #10
vafatboy said:
Greg,

Good post man. Did you factor in head gasket and valve pockets (if any) into the volume?
This was just the heads by themselves. I figured I'll check the deck height and other engine factors separately.

I used a smaller (50 cc) burette to have finer gradations on the measurement. You can actually start at any point in the burette, provided you record the starting point. The key to an accurate measurement in adding fluid, is to read flat and level through the meniscus of the burette. (Odd term meniscus, it's just the band that that the surface tension of the fluid produces along the walls of the tube - reading in the middle of it is supposed to give the most accuracy.) Marvel seemed to be preferred by some of the engine guys I read info from, because it is a light and colored oil. Others recommended using tinted alcohol. The nice thing about having a glass plate is that you can see whether there are any bubbles in the chamber. Getting a measurement within 0.1 cc doesn't seem to be much of a problem.

just some thoughts.
 

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HDWRENCH said:
You should have the spark plug in place and drill a hole in your plate.
This is the way I do it. Most accurate.

Regards,
NC​
 

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ovanay elinquentday
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Discussion Starter #13
nc-renegade said:


This is the way I do it. Most accurate.

Regards,
NC​
I would certainly agree that it is most accurate to measure the real working volume of a head with the spark plug included. When I initially measured my heads though, I was only looking for the volume of the heads without other factors.

Out of curiosity though, I took a cc reading on my spark plugs alone. As best I could determine, considering both their cavity and electrode, the additional volume of a spark plug is about 0.3 cc.

Curiosity overwhelmed me though, so I did a couple of repeat measurements on my heads, including the plugs, and using alcohol as the liquid.

Originally I measured these supposedly 84 cc heads by adding Marvel through the spark plug hole until the oil just touched the 1st thread of the spark plug hole. The results were:

Front: 82.6 cc
Rear: 82.3 cc

Remeasuring the heads with the spark plugs inserted, the heads inverted so that the plate was on top, and adding alcohol until the air pocket was gone and the alcohol was just level with the head surface gave:

Front: 82.3 cc
Rear: 82.0 cc

The interesting thing is that measuring the head upright and without the plug did induce error. But, checking with the spark plug did not add volume to my measurement. The reason is because with the plugs inserted the area is level across the plug opening until the plug cavity is reached. When I measured the heads without the plugs, the liquid rose slightly into the hole and then the surface tension of the oil added a slight bit more volume as the liquid rose to the first thread line in the plug hole. The net result – measuring with the plugs showed that the true volume of the heads, with plugs, is actually 0.3 cc less than what I had originally measured.

So, I have to agree, if you want to measure things exactly, the best way is to measure with the plugs. On the other hand, practically speaking, the 0.3 cc error induced by measuring through the plug hole was less significant to me than determining that my supposedly 84 cc heads were actually 82 cc.

Just some ramblings...
 

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GPO03FatBoy said:
So, I have to agree, if you want to measure things exactly, the best way is to measure with the plugs. On the other hand, practically speaking, the 0.3 cc error induced by measuring through the plug hole was less significant to me than determining that my supposedly 84 cc heads were actually 82 cc.

Just some ramblings...
Good post and information! Just goes to show that some of this stuff does drives us all a little crazy when you want to be exact!

Regards,
NC
 

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Nice work. I will have to check mine as well when i pull the heads off my bike. I had what i though was i real high ccp(205) for a 9.7 37g build. Maybe this explains it a little. I know my pistons were almost 0 deck and i also used a .030 gasket.

Thanks for the write up.
 

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TXCHOP said:
Nice work. I will have to check mine as well when i pull the heads off my bike. I had what i though was i real high ccp(205) for a 9.7 37g build. Maybe this explains it a little. I know my pistons were almost 0 deck and i also used a .030 gasket.

Thanks for the write up.
Depends how you are measuring the ccp. If you are taking the reading after it the gauge stops building pressure and you are reading 205 PSI, then write down your 4th stroke reading, this should be around 185 PSI for that cam.

Regards,
NC
 

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FXSTBI
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Excellent Post

Like the detail and information I'm next. Mine is coming apart middle of this month for the Timkin upgrade along with balancing my crank and some much needed gearbox work. Guess I'll have to add this procedure to my down time waiting on the crank work. I hope my heads are a little closer to what I paid for. The difference between your heads wasn't bad but paying for 84cc and getting 82cc that will throw your cam selection off any where from .010 to .090 in lift which is a major issue, that's the difference between a .510 lift cam and a .590 lift cam when squeezing HP and TQ. Were these CNC heads or hand ported? I guess either way they should have been cc'd before and after porting.
 

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IronButt
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Really if you do it the same way each time and take into account for it , it would work fine. If any thought I was saying it was wrong that is incorrect more so that being accurate is important. If you take one person reading on something and then anothers you will find that you get a slightly differenet result. That applies to most things. But being accurate is important. I would say that Gregg got a very close number and the small amount of change from one to the next is not going to make any real change. When you are doing heads you shoot for being with +/- a few tenths of the number you shoot for. Now until any one has done heads this is not as easy as one would think. As the work in the bowl, shape of the stock chamber, and starting cc volume can make the job more difficult. And you end up going back and forth a few times to get both heads with the spec you have choosen. I get customer calling on heads they have that may or not need milling and they have cc'd them and the biggest error we see is using a tube that is not large enough and they make a mistake in that process. You can start with the tip full and the next time it is empty and your final number is off.
 

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nice post; have not done any internal engine work yet myself, but found the info you provided interesting and educational. the quantity of technical info i have gained form this forum never ceases to amaze me .
 
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