How to CC heads?

[74norton]

Hi
I am at the early stages of doing some head work to the 72 440 in my 70 RR.
I recently got a nice clean set of 906 heads from ebay and want to go through them before I begin milling etc. To get a good baseline and make sure I know what I have, I want to cc the heads.

How do I go about doing this? I have heard it involves a buret and stand. Any suggestions about where to get one and how to do the job?

Thanks
Charles Handler

[mr.b]

go to walgreens and such and buy a flask or any type of measuring cup that shows cc's. place a straight edge across the the chamber of the head and fill with water until the water touches the ruler or straight edge.

[John Kunkel]

You can't just fill the chamber with water due to the "membrane effect" of water, surface tension will allow it to rise slightly above the head surface.
You need to get a piece of clear 3/8" thick Plexiglass large enough to cover the entire chamber. Drill a 1/2" hole in the Plexiglass and seal it to the head surface with a thin film of grease.
With the valves and spark plug installed, pour liquid into the chamber from a measured beaker or burette until it reaches the lower rim of the hole. The clear material will allow you to see any air bubbles.

[74norton]

Thanks for the advice sounds easy enough.
Once I get a reading how do I know if the heads have been milled etc?

I plan on milling them .06 to bring the compression of the dished piston motor up to above 9-1.

What is the total vol that I am shooting for? I am guessing that once I cc the heads, I still need to check the distance the piston is down the hole to get the total chamber size. When doing this wont the fact that I have dished pistons make it hard to measure the volume of the cc in the bore?

Thanks
Charles

[sixpackcuda]

The 906 heads had 79.5 cc's so anything less and they probably have been milled already. .060 is a lot, you have to do the intake side as well. You might want to replace the pistons instead.

[sixpackcuda]

Here is a good Compression Ratio Calculator when you get your variables.

http://www.dvorakmachine.com/Calc_staticCR.shtml

[jlcoffell]

If you want to increase your overall compression why not
go with a set of closed chamber heads? The 516 castings
work almost as well as the 906's but are the closed chamber
version.
I was informed in an earlier posting that changing from a closed to open chamber head, will let you loose about 1 full number.
In theory this would also mean that going from an open to closed
chamber head will gain you 1.
I originally had the 516's with 11-1 pistons in a 440 and went
to the 906's. Big difference!!! much better with pump gas!!

Now as for a little help with cc-ing your cylinder. How good is
your math? I believe the formula is pie-r-squared-times the length.
measure both at bdc and tdc. add the volume of the head and
then calculate the volume of the dish in the piston. This will be added to both measurements. Also keep in mind the head gasket thickness. Divide the tdc/head cc/dish cc value into the bdc/head cc/dish cc value
and that will be you overall compression ratio.
Sound a little complicated (actually I hope I didn't miss anything)

I am in no way a professional and can even do some strange things at times so carefully recheck any help I provide. Basically just don't take my word for it but use it as a guideline to help find your answer. Good luck with your head change as I just recently went through it myself. BTW my engine has now been running great for a couple of months.
Hope I helped you a little.

[74norton]

Thanks for the good advice.

I do know that milling .06 will require the intake to be milled as well and may require a change in the rocker arm length and rocker angle. I will work all this out once I get the math done to tell me what I have to work with. Doing the math is the only way to be sure of my starting point so that is what I have to do first.

I would love to just change the pistons out but that will involve pulling the motor and extra machine work. I am pretty sure the bottom end is fresh. I do plan on doing a leak down compression test before rasing the CR. If the bottom end cant hold the increased cyl pressure then any changes up top are worthless.
If that is the case, then I will just change to some 9.5-1 pistons and that will be that.

Now that I am thinking about it, is is advisable to change the pistons with the engine in the car? I am guessing that while this may work, it is far better to just have the bores machined and the right sized rings added.

Anyway, there are several different ways to go about doing what I am doing. I chose the present path because my bottom end seems good and has low miles on it (for a 72) and because I got some 906s off ebay for cheap. OF course by the time I have em milled and have hardnend seats put in and do some porting and relief work to them, well I guess I couldve just gone out and bought some Indy heads but that just be too easy

((((((((((((((O

-Charles

[23T]

You will need two holes in the glass/plexglass plate that covers the chamber. One to put the fluid in the other to let traped air out.

You can also use a large hypordermic syringe to mesure the cc's injected into the chamber and I have found colored alcohol works better than water( less serface tension)

[rustycowl]

The glass burett, stand, etc is available from Goodson. I bought mine a coupla years ago. It was kinda expensive as I recall, around $100.

[jlcoffell]

One note that I should have added in my earlier reply was that
you should look into aftermarket aluminum heads.
Like I said in my earlier reply I just completed putting some 906
heads on my motor.
I originally paid $ 175.00 for the pair. After machining, hardened
exhaust seats, new guides, stainless stock size valves, etc. was done I looked at the overall price tag and it totaled right
about $ 1000.00.
Edelbrock aluminum heads complete are like $ 1300.
If I had it to do over I would go aluminum.

[John Kunkel]

The factory blueprint spec for the 906 chamber volume is 79.5 CC's but, in reality, they'll be a long way from that. Most will be in the 88-90 range. Milling these heads .060" will remove about 14 CC's.
To determine the amount any BB head has been milled, mike the outer head bolt boss. This boss was exactly one inch from the factory.

[74norton]

Everyone says the same thing about just sucking it up and buying the already done heads. If I get aluminum heads can they be milled to rasise CR?

Thanks
Charles

[jlcoffell]

I believe the aluminum heads can be obtained with different size combustion chambers. You can check online at like summitracing.com, and I believe Jegs carry them. You also may try
looking at a company called mancini racing. I think another company Dvorak machine may have them as well, Dvorak is where
I got my valves and head gaskets.
The aluminum heads will also give you the larger 2.14 and 1.88 valves.
If at all possible don't shave the heads. I have known people that have done that and end up with intakes that just don't fit
quite right. They also fight vacumn leaks after a while.
I know I like to work on a vehicle and then only work on it again
when I want to, not because I have to!

[DartGT66]

Chamber sizes have to be measured always to know where you are at. Some 516 were measured recently and they showed 84cc in stock condition, so the closed chamber heads are not necessarily that much smaller. Milling them will also reduce the CC's less than milling an open chamber. I like to measure the chamber using a piece of lexan sealed to the deck with vaseline ans installed so that it leaves one "corner" of the chamber open. Then I put the heads in such a position that the corner points upwards. After that I have some water in a glass, I weigh it with an accurate letter weight scale, take water out of it with an injector and fill the chamber. I have a scale in the injector I use, so I get a picture of how much water is injected in to the chamber. Then, when it's full I weigh the glass again; one cc of water weighs one gram, so it's easy to egt the cc's out of the glass's weight difference.

[jimm II]

The method used by 23T also worked for me the coloured added makes it a lot easier to see...
One major causion DON"T ...DON'T.....DON'T do the head cc ing on the Wife's family kitchen table that has been in family for ages, a little spilled alcohol and the stain is easly removed. This causes additional cost to the engine rebuild.....

[turbododge]

23T has it right about the syringe, they work really well. You can get a 35cc syringe at your local feed mill or horse supply for a couple of bucks. Also correct is the need for air bleed hole(s). Instead of coloring for the water, I use 50/50 antifreeze mix, that way it also helps prevent rusting, which can get into the seat areas very easily.

[69rrunner]

I just took "Reher Morrison" Race engine building course this summer ( It was offered through my work so I had to go for it)
We cc'd a couple of heads and they used the buret and stand method plexi sealed with grease but they used a GREEN colored alcohol, I don't remember the name of the stuff but it was something you would get at Walgreen's or any drug store. Even though their book says to use water! It was really pretty easy. just make sure you don't get any leaking through your valve seats. later Ed