I recently asked this question on the metalworking group on USENET.

The normal way to do this for full-scale engines is to clamp a piece of clear acrylic onto the head, then drop oil from a burette into a hole in the acrylic until the chamber is full, then check to see how much volume you've used up.  This gets awkward with little engines, so here are the suggestions that I liked best from that thread:

• Talk a diabetic friend out of a syringe & needle, and use it as your burette, with isopropyl alcohol as the working fluid.  The syringe will have very small graduations, the needle will be fine (so you can use a really small hole in the acrylic), and isopropyl alcohol is cheap and has very low surface tension.  Use the 99% stuff.
• Same as above, but weigh the head before and after, then calculate
• Drip wax into the chamber.  Either melt it out and determine volume, or weigh the head before and after.

Good luck.  That reminds me, I need to stop shaving or changing cloths for a couple of days, then drink lots of coffee and go into a pharmacy and see if I can talk them out of some needles...

Clarence Lee of RCM fame, once wrote years ago how he figured volume. If I remember right he used a syringe with oil. Been a long time ago that I read that. Might be able to find it in the RCM web site.

Here in Aus you can buy over the counter, If you know the Pharmacist he-she may give you one, not an expensive item, not concidered dangerous even for illicit drugs,not that I would know about that. Noel.

 . . .  Just use a syringe and oil, if it is a lapped  ABC or AAC motor it will be easy to go thru the glo plug hole, and not have any leak thru a ring gap

Randy

My 1.0 syringe has a scale with major divisions of .1 cc and minor divisions of .01 cc. Doing some quick feasibility cipherin', that looks pretty decent. You probably have some similar calculations you have done, so these are sort of a "sense check" for you.

For  example: An LA 46 has a bore of 23.0 mm, stroke of 18.4 mm, and a volume of 7.64 cc. "Guessing" an arbitrary 10:1 compression ratio, the combustion chamber volume is .76 cc. Adding a .010" head shim gives us a new (Randy Smith method) volume of .87 cc, or a delta of .11 cc –  right on the edge of what the syringe will measure.

A practical feasibility test might be to do just that – measure the head volume with no shims, then a variety of shims, and see if the volume changes agree with your calculations as to what they should be. It is clear the measurement system  will not as robust as you would like, but maybe good enough for what you are trying to do. I'm sure you are not interested in the head shims, but we can use them as a way of testing our measurement accuracy.

You will post a follow up what you are trying to do, won’t you 

       Larry Fulwider

. . . I tried this years ago, and couldn't get the syringe to meter accurately due to the plunger friction.  It wouldn't move, and then would come free, overshooting the mark.  . . .

.\ . . .
  Tom Hampshire

Maybe we can get Jim Lee to make us some high-zoot 1.0 cc syringes 

       Larry Fulwider

Larry
Put that order in now, there will be  'bit' of lead time   

Howard
Put the piston at tdc and count the drops of oil ( I use MMO ) If I remember correctly an average 40 will have about 23  - 25 drops when its level with the hole for the glo plug....  FWIW
thanks
Jim