27 replies to this topic

[Dusky]

Dusky - for measurement of combustion chamber cc's and chamber balancing I have been using an alternative method which avoids the need for burette and liquids. It seems to be repeatable to better than 0.1cc, so at least as good as burette.

 

You should be able to get hold of all the kit to do this for less than 20 Euro. If you would like more details let me know.

Pmming you ;)

[Cooperman]

Don't make it more complicated than it is. A 5 ml syringe from a chemist's shop for a couple of Euros, plus an electronic calculator and a digital vernier (with end probe)is all that's needed. A digital vernier is a tool that is needed for a lot of work on a Mini and it's easy to borrow one.

[Dusky]

Is a burette also good? I can lens a burette from a mate

[timmy850]

A burette is probably the most accurate way, as they are normally calibrated before sale. The chemist syringes aren't nessecarily accurate. Just make sure on your first one that you make sure the liquid has made it down to the tip, otherwise you'll get a high result.

My 295 head has 27cc chambers

[Dusky]

I'll use the burette with some fluid that doesnt suffer too much from surface tension Now in waiting for.the happy arrival of the head ^.^

[Dusky]

But I have zone syringes too actually... Ill just measure all the chambers twice , once with the buretta and once without the syringe

[dklawson]

Surface tension is not an issue if you cut a disk from thick clear plastic and make about a 1/4" hole in it near the edge.  You smear grease over the head around the chamber, press the plastic down locating the hole in the plastic near the edge of the chamber.  Tilt the head slightly so the hole in the plastic is "up".  Then fill the chamber through the hole in the plastic. 

 

I no longer have a burrett.  I use a very accurate gram scale and a full syringe.  I weigh the full syringe at the start, fill the chamber, and measure the ending weight of the syringe.  The weight change in grams equals the volume in cc.  The scale I use is accurate down to about 1/10 gram.

[Cooperman]

Surface tension is not an issue if you cut a disk from thick clear plastic and make about a 1/4" hole in it near the edge.  You smear grease over the head around the chamber, press the plastic down locating the hole in the plastic near the edge of the chamber.  Tilt the head slightly so the hole in the plastic is "up".  Then fill the chamber through the hole in the plastic. 

 

I no longer have a burrett.  I use a very accurate gram scale and a full syringe.  I weigh the full syringe at the start, fill the chamber, and measure the ending weight of the syringe.  The weight change in grams equals the volume in cc.  The scale I use is accurate down to about 1/10 gram.

That is the best way to do it. I use a piece of 1/8" thick Perspex and I have two 1/4" holes, one to put the fluid in and the other to let the air out.

[carbon]

Doug - I like your method of using syringe with weight before and after. Likely to be more accurate than trying to read off a burette...

 

The method I use is similar, only difference is I have been using Plasticene (modelling clay). With cheap and accurate digtal balances now widely available I think this is the way to go. I bought a 0-500g balance that reads to 0.05 gram from Maplins a few months back, and a 500g block of Plasticene from Hobbycraft for £2.

 

I use the Plasticene to completely fill the combustion chamber, once full cut off any surplus dead level with the surface of the head. Remove and measure weight of the plasticene on the balance. This works very well for balancing chamber volume, readings seem to be repeatable to 0.1g or better. Here's a set of readings I took from a 12G940 head when I was getting the chamber volumes equalised ...

Cyl 1 = 35.45, 35.60, 35.65, 35.70

Cyl 2 = 35.10, 35.35, 35.50, 35.65

Cyl 3 = 35.30, 35.50, 35.50, 35.70

Cyl 4 = 34.95, 35.35, 35.70, 35.60

 

All of above are weights, need to divide by 1.625 to get volume. So 35.65g = 21.9cc

 

For accurate cc readings you will also need to measure the density of the modelling clay you are using as this will vary from manufacturer to manufacturer (and probably from batch to batch).

 

This is where Doug's method of weighing the syringe has the advantage, as the density of water is well defined.

[Dusky]

The head is comming in tomorrow ( says the tracking website) so I'll be able to measure tomorrow #excited

[Dusky]

Sent the head to the machine shop for a 1mm ( 40 thou) skimm after measuring everything.Will report back whn it is installed etc.

The head itself is in superb condition by the way. Not too rusty, no damaged threads,...

Will have a look at valve guides etc when it returns, but those looked okay.

 

Any advice on cleaning the inlet and outlet trackts of the head? A good degreaser? Or could I try my new jet-washer? ^^

[dklawson]

Before they cut anything, have them check it for cracks and leaks.  Once you know the head is good they can proceed.

 

My advice is to have the machine shop check the guides while/when they have the head for skimming. They will also have the press to remove and install new guides if needed.  New guides need to be checked for size anyway and reamed if necessary.  Once new guides are installed, the valve seats need to be cut again (if even just slightly) to insure the valve seat is concentric to the guide.  Then... the valves need to be re-ground and lapped to the seats.  All of that will be easier for the machine shop to do than for you to do at home.  Again, have them check/do the whole head while they have it.  It will be quicker and less frustrating for you.

[Dusky]

Before they cut anything, have them check it for cracks and leaks.  Once you know the head is good they can proceed.

 

My advice is to have the machine shop check the guides while/when they have the head for skimming. They will also have the press to remove and install new guides if needed.  New guides need to be checked for size anyway and reamed if necessary.  Once new guides are installed, the valve seats need to be cut again (if even just slightly) to insure the valve seat is concentric to the guide.  Then... the valves need to be re-ground and lapped to the seats.  All of that will be easier for the machine shop to do than for you to do at home.  Again, have them check/do the whole head while they have it.  It will be quicker and less frustrating for you.

The head was tested by the previous owner ( with receipts of it).
Sadly this machine shop doesn't press valve guides and I'll need to go to another one to let them do that.

Belgium is a sad place to live in when it comes to cars... I could have let another shop done it all toghether, but they were charging 250 euro's for the skimm, and that's a bit too much for only a skim ( imo).

 

Cheers and thanks for the advice too ;)