buret - where to get one?
 

Anyone know where to get a buret - you know, for engine builders to measure CR? I poked around a little and found class A lab grade for $200. Hopefully there is a non-glass one of reasonable accuracy for engine builders. I checked - none here on Pelican.

Thats what I use as I need accuracy when making CR measurements. :)

Try "plastic burette" in google.

Plastic Burette - 50 ml ~ Burettes ~ Burettes & Accessories

get the 200 glass one
50ml will not fill the head

I saw these

Burets : Best Value Class A Buret Kit

Cool, $40 for a 100ml. Actually, I'm a chemist, but haven't used these prehistoric things in many years. I'm tempted to bring it into the lab to compare with a true class A.

If you do make a comparison between the budget plastic Buret kit and a real deal true class A buret, please post your results.

The one I found was through a quick google search and I have no knowledge of the vendor or the manufacturer. I'm sure made in China, but I figured for those using the device for measuring volume of cylinder heads occasionally and using water, plastic should hold up for a long time if one takes care of it.

Calculated volume.........
 

What is the measured volume for a typical 3.0 or 3.2 cylinder head dome? I'll be doing (CC'ing) one pretty soon for a friend's engine rebuild project and in need of a burette too. I thought a 100-mm capacity burette would be sufficient. Feedback highly appreciated. Thanks.

Tony

I recently cc'd my 3.2L heads that had been twin plugged and chamfered for 98mm cylinders. They came in right at 90cc and I used a 100cc burette.

Yep, 100cc buret works for me.

Really, it is no problem to refill a buret. this is common practice taught in first year chemistry class. yes, you have to compound the error but for a typical build this is not an issue as the percentage error in measurement will still be much lower than your significant digits on the final CR value.

I noticed while surfing on their site that FVD Brombacher sell a 100cc burette, p/n FVD 721 103 99 -->

FVD Online Shop

€155 on their UK/German site, but they also price in $$'s

When I cc'd my motor, I did a trial fitting of one cylinder/piston/head, put the piston at TDC, and filled the head through a spark plug hole. I made a fitting from a piece of clear plastic and a junk spark plug so I could overfill a bit, and subtract what was in the ersatz spark plug and tube.

The formula is swept volume plus measured volume divided by measured volume. I got 13.something to 1, but then had valve pockets cut deeper for clearance, ending up with 12 to 1.

Made me wonder, short of doing every head to be sure that they are all exactly equal, why this method is not more common than measuring the chamber, then measuring the deck height (and worrying if you got it right measuring to a sloped surface), and then depressing the piston into the cylinder, measuring that depth, and filling the cylinder to determine the piston dome volume, and so on.

50mm burette would have worked, as TDC volume is a lot less than head volume without a piston stuck up into it.

buret obtained - now C/R calculation issues
 

Walt, I may try your method. I'm just concerned about bubbles that could not be seen once the head is bolted on.

Well, resurrecting this dormant thread, I bought the budget buret mentioned herein and got to work expecting solid answers so I could atlast move forward. Instead - confusion.

Engine is 98mm bore x 74.4mm using Mahle/Max Moritz 9.8 CR pistons, assembled up to P/C with total 1mm shim under cylinders.

1. Mount my plexiglass plate on head and use buret: 90cc

2. rotate engine to BDC and buret to top of cyl: 552cc

3. rotate engine so top of piston dome is level with top of cyl:

a. measure from top of cyl to perimeter of piston: 9.2 mm. There is a cylinder here containing dome + empty space = 3.14 * 49 * 49 * 9.2 = 69.4 cc

b. mount plate on cyl and buret empty space : 41.8 cc

c. dome = 69.4 - 41.8 = 27.6 cc

4. rotate engine to TDC. Measure from top of cyl to perimeter of piston: 1.3mm
Deck volume = 3.14*49*49*1.3 = 10 cc

Sooo, with 1mm base shim,

CR = ( BDC + Head) / (Head - Dome + Deck)

CR = (552 + 90) / (90 - 27.6 + 10) = 8.8

But these are Mahle 98mm 9.8 CR pistons. What gives? What if no 1mm shim? Then remove 3.14*49*49*1 = 7.5 cc from top and bottom...

CR = (552 + 90 - 7.5) / (90 - 27.6 + 10 - 7.5) = 9.8

Anybody still awake? Somehow this doesn't seem right. If Mahle says this is a 9.8 CR piston, I would think it means that you should be able to shim it to this spec, not that 9.8 is the theoretical max. And these heads have been rblt before. Somethings not right. Anybody see what's wrong? :confused:

I think 90cc's in your heads is stock, so it appears that there have been no modifications.

If I understand correctly, your calculations show that you get 9.8 CR without the 1mm shim?

That seems correct, the 1mm base gasket moves the cylinder away from the case, which would increase the volume of the cylinder and increase deck height, the increase in volume would reduce your CR.

I think that stock usually had a .25mm base gasket which would still get you around 9.5 CR.

As another data point, 100 ml unit should get the job done. I've had some work done to my 3.2 heads and measure 86.1 to 86.3.

I use blue windshield washer fluid. Beats mixing solvent with ATF, smells nice, flows quick, easy clean up.

This works quite well....

B&B 40310 B&B Buret and Stand

If I followed correctly, I think you need to include the 10cc for the deck in the numerator too? In the denominator, I believe you are also missing the calculation for the (piston to cylinder radial clearance) x height to top compression ring, although that's a pretty small volume.

Other than that, try to refine your calculation for the piston dome. Otherwise, Walt probably has the best way to do this. Measuring is always more precise than calculating.

Air bubbles are certainly a possibility.

Because I had a clear plastic tube screwed into the upper plug hole to aid in getting my fill quantity correct, I was able to rock the motor around maybe 45 degrees each way from having the plug hole straight up. Don't recall seeing bubbles coming up. At one point I drained and did it again, though perhaps doing it on several cylinders might have been better. Figures were comfortingly close. Then, after I had the intake valve pockets deepened, I got a suitably lower figure when remeasuring. So I trusted my results pretty much.