CC'ing the combustion chamber?

[sierra3dr]

I've just done this on a cylinderhead from a 2.8 cologne engine. It's the first time I've done it,and got a result about 32cc,does this seem unrealistic?
I am aware the the CC measurement from a 2.9 cologne is 42cc.
Has anyone done it?

[graham bahr]

it cant be 32cc, even allowing for some space in the headgasket and that the pistons wont quite come flush with the top of the bores that would give a compression ratio of about 11:1

if you used a burette did you remember to zero it first?

[sierra3dr]

thanks for the reply Graham. I had used a 100ml syringe which is equivalent to 100cc. I did it three times,first attempt was messy :) . next two attempts came up with the same result.

[graham bahr]

i assume you had a thick piece of glass or plastic across the chamber which is sealed o the head with a smere of grease, with two small holes in it, one for the fluid to go in and one for the air to come out.

if you try to meassure the chamber size without the plate it will come up too small

[sierra3dr]

i assume you had a thick piece of glass or plastic across the chamber which is sealed o the head with a smere of grease, with two small holes in it, one for the fluid to go in and one for the air to come out.
sorry,forgot to mention that. So yeh,used a plastic perspex glass. Smear the sparkplug and valves with grease,and smeared the cylinderhead face for the glass to sit still.
I have few heads,so I'll give them a try.

[graham bahr]

could it of been a 2.3 head you CC'd?

that would have a much smaller chamber than the 2.8 doing a quick bit of maths and again allowing for the gasket a 32cc chamber on a 2.3 would give compression of about 9.2:1 which sounds about right

[Group4_Mark2]

Have you taken into consideration how far down the bore the piston is and the volume of the head gasket which all have to be added to the volume of the chamber when doing the calculation

Tom

[graham bahr]

Have you taken into consideration how far down the bore the piston is and the volume of the head gasket which all have to be added to the volume of the chamber when doing the calculation

Tom

the answers yes if you asking me although ive only guesstimated the figures, but suspect not if its sierra3dr your asking,

whichever way, allowing for gasket space and the piston being down the bore or not, a 2.8 head must have more than 32cc in it unless its been skimmed to death

[Group4_Mark2]

It was directed at 3DrSiera and I should have taken a bit more time reading all the posts as you have addressed the gasket thickness etc already.

Tom

[sierra3dr]

could it of been a 2.3 head you CC'd?
I very much doubt it,as I have never owned a 2.3

Have you taken into consideration how far down the bore the piston is and the volume of the head gasket which all have to be added to the volume of the chamber when doing the calculation

no,I was going to include this once I have established what the combustion chamber is. I was just following the guide from this chap http://www.merkurxr4ti.com/chambervolume.html In his calculation it appears that the cc measurement he got was only from the chamber

a 2.8 head must have more than 32cc in it unless its been skimmed to death
quite possibly,I do not know the history of the heads. What measurement would you expect from an standard head and a skimmed head?
I'll have to measure the other heads.

[graham bahr]

quite possibly,I do not know the history of the heads. What measurement would you expect from an standard head and a skimmed head?
I'll have to measure the other heads.

i dont know what the thickness of a 2.8 head should be but it cant be had to meassure, so you can compare the thickness of the one you have cc'd with some others

to be honest i have done very little with this engine other than std rebuilds and overhauls, so whilst i know what the engine is like internally when it comes to meassurements im working from basic principles, the engine capacity, that the pistons are flat topped and come near the tops of the bores are known facts so you can work out some basic things like roughtly the volme in the head gaskets compression etc,

i would expected the chamber volume in a 2.8 to be around 40-45cc, 32 just sounds way too small,

why not do all the sums youself, find how far down the bores a piston is at tdc, meassure the diameter and thickness of the fire ring on an old gasket so you can work out the volune inside it and do the maths to work the C/r using your 32cc if it comes out to about 9:1 then your 32 CC measurement is right and im talking rubbish

[graham bahr]

Smear the sparkplug and valves with grease,and smeared the cylinderhead face for the glass to sit still.
I have few heads,so I'll give them a try.



there should be no need to grease the sparkplug if its done up tight, and when it comes to greasing the valves, you want just a thin smere of the seats so that you dont get ANY grease in the chamber your meassuring, its very easy to "loose" a few cc

[Group4_Mark2]

I have done the following a few times and it works pretty well in some circumstances.

With the head on the engine with the correct gasket and head bolts torqued torqued up I spray some WD40 down the inlet and exhaust ports to seal the valves. I spray some more into the cylinder to seal the piston. Rotate the engine until the valves on the cylinder you are working on are closed and the piston is exactly at TDC. Then tilt the engine so that the spark plug hole is the highest point and using a burette fill the combustion chamber until the water/soap mix is just coming up the thread of the spark plug. Tip over the engine to remove the water.

This method is really only useful if you are going to do an overhaul on the engine and are taking the head off so that the water can be dried off and prevent damaging the bores.

Tom

[sierra3dr]

i dont know what the thickness of a 2.8 head should be but it cant be had to meassure, so you can compare the thickness of the one you have cc'd with some others
will do

to be honest i have done very little with this engine other than std rebuilds and overhauls, so whilst i know what the engine is like internally when it comes to meassurements im working from basic principles, the engine capacity, that the pistons are flat topped and come near the tops of the bores are known facts so you can work out some basic things like roughtly the volme in the head gaskets compression etc,
well your experience in overhaulling the engine is good enough advice:thumb:


why not do all the sums youself, find how far down the bores a piston is at tdc, meassure the diameter and thickness of the fire ring on an old gasket so you can work out the volune inside it and do the maths to work the C/r using your 32cc if it comes out to about 9:1 then your 32 CC measurement is right and im talking rubbishtalking rubbish?! Nah,not for me Graham,I'm open to opinions.
yep,I was going to come to the sums later. I was just hoping someone on the forum has done the chamber before and make a comparison,and move onto the next
I will add though,that the 2,8 on mine has an Eichberg turbo setup. But,I'm certain that it is not an original setup because Eichberg bored the block out to 3,0litre and put in deep dished pistons. So,I suspect that the previous owner got the bits from an Eichberg setup and just plonked them on. I would have expected the previous owner not to skim the heads,as that would be the wrong direction for a turbo.

[graham bahr]

your right if the engine has been turbo'd it unlikley the heads have been skimmed, if the turbo ran a very low boost the engine may still be the std 9:1, skimmed, dished or low compression hight pistons are the most likely way to lower the compression on that engine, extra thick head gaskets and or decompression plates would be another way but arnt very satifactory, as they will potientailly cause alignment problems with the inlet manifold.

i was once (about 20 years ago) very mildly involved in the a rebuild on a 2.8 which was being supercharged, we came to the conclusion the only way to really satisfactory lower the compression was to machine dishes in the pistons, as it wasnt really feasable to take enough material out of the combustion chambers or do it any other way.

you might be interested to know burtons do forged low compression pistons for the 2.8 engine ( they say they can be used in the 2.9 but you have to make the bowl in the piston bigger) i actually use 4 of these pistons in my turbo race car, they have a 25cc dish as std

[graham bahr]

This method is really only useful if you are going to do an overhaul on the engine and are taking the head off so that the water can be dried off and prevent damaging the bores.


using thin oil, or parafin ( or even antifreeze) you would only have to tip it the engine upside down to get it out again and not worry about taking the head of due to rust concerns

[sierra3dr]

if the turbo ran a very low boost the engine may still be the std 9:1
actually,high boost I recon,via a TO4B50 click here (http://www.dieselevante.it/turbochargers.asp?idfam=TO4B50) Before my existing renovation,some of the boost piping was split.

extra thick head gaskets and or decompression plates would be another way but arnt very satifactory, as they will potientailly cause alignment problems with the inlet manifold
I was considering the decomp plates from Ferriday,but I am glad you pointed the alignment problem out,I overlooked that,thanks.

i was once (about 20 years ago) very mildly involved in the a rebuild on a 2.8 which was being supercharged, we came to the conclusion the only way to really satisfactory lower the compression was to machine dishes in the pistons, as it wasnt really feasable to take enough material out of the combustion chambers or do it any other way.oooh machining dishes in the standard pistons? Now that has been mentioned to me before,that some people have done that,interesting to see.

you might be interested to know burtons do forged low compression pistons for the 2.8 engine ( they say they can be used in the 2.9 but you have to make the bowl in the piston bigger) i actually use 4 of these pistons in my turbo race car, they have a 25cc dish as std
Good god! I've been searching high and low for such pistons but couldn't find anything. I can't remember if I had looked at Burtons,but gave up.

[graham bahr]

Good god! I've been searching high and low for such pistons but couldn't find anything. I can't remember if I had looked at Burtons,but gave up.

they were commissioned by burtons, made by accralite, but because burtons commissioned then accralite dont list or sell them to anyone else.

[sierra3dr]

Had another go today,and I was nearing somewhere around 42/44 cc. The area around the sparkplug didn't need greasing

[graham bahr]

Had another go today,and I was nearing somewhere around 42/44 cc. The area around the sparkplug didn't need greasing

thats better :thumb::thumb:

i would expected the chamber volume in a 2.8 to be around 40-45cc, 32 just sounds way too small,


not bad working from basic principles ;)