The V8 Owners Forum -

I need to check the combustion chamber volume of my Buick 300 heads,I know to do it 100% accurately you need a burette but I just want to find out if they have been machined in the past, the heads are 43 years old so could well have had at least one skim in their lifetime.

I have a medical measurer which indicates up to 25 millilitres which I assume is the same as 25cc? if I level the heads and use parafin or white spirit and measure the amount I pour into the chambers will this be accurate enough to indicate whether they have been skimmed or not?

The original chamber volume is quoted at 54cc. and I need to know how much needs skimming off the heads to achieve a realistic compression ratio, and probably need to get the volumes down to approx 47cc.

I may still have to reduce the deck heights by a further 10-15thou.

Kevin.

CastleMGBV8 wrote:I need to check the combustion chamber volume of my Buick 300 heads,I know to do it 100% accurately you need a burette but I just want to find out if they have been machined in the past, the heads are 43 years old so could well have had at least one skim in their lifetime.

I have a medical measurer which indicates up to 25 millilitres which I assume is the same as 25cc? if I level the heads and use parafin or white spirit and measure the amount I pour into the chambers will this be accurate enough to indicate whether they have been skimmed or not?

The original chamber volume is quoted at 54cc. and I need to know how much needs skimming off the heads to achieve a realistic compression ratio, and probably need to get the volumes down to approx 47cc.

I may still have to reduce the deck heights by a further 10-15thou.

Kevin.

I guess it depends on the markings on your container, a burette goes down to 1/10 of a CC.

You need to knock up a perspex plate with a hole in the middle, stick it to the head with a small amount of grease then fill the chamber up making sure that there are no air pockets. Do this 3 or 4 times so that you are dead sure that you've got it right!

I've got a burette that you can borrow if your not a million miles from Bagshot, Surrey. (I've got a perspex plate as well!)

Edit....Sidcup....A fair few miles!

Pete

On Rover heads you can measure the blocks at either end of the head and it will tell you instantly if they are skimmed or not. Given the relationship between the two engines it wouldn't surprise me if your heads are the same. Have a search around some Buick forums and see if its possible. This wont tell you how accurate the volumes were to start with but then neither will the way your looking to do it as anything short of a burette just isn't that accurate. There is a post on here detailing the measurements for the Rover heads so have a search and see what your looking for.

Here's a thought and don't laugh, I actually did this ages ago before I bought a proper burette.

I made one from some thin plastic tube, the type that you get from wine making places, you can even get a nice valve for the end!

I attached about 1 metre of the tube to a stick with the valve sticking out of the bottom.

To mark the tube up you need to find out the ID as accurately as you can, I pushed a drill bit into it that was a good fit but did not stretch the tube. You can then "mic" the bit up and using some maths work out where to put the on the marks the tube. The smaller the ID the further the marks will be apart which makes the thing more accurate. (You must get the ID measurement right).

It was accuarate down to at least 0.25 CC. (I knew a 2 stroke tuner at the time, He laughed his head off when I showed it to him, we then checked it against his burette....he stopped laughing at that point!)

Pete

Pete, thanks for the offer of the loan of the burette, Bagshots a fair distance from me unfortunately and to pick it up and return it would probably cost me £40.00 in fuel! How much does a burrette actually cost?

Marki, thanks for the tips, yes that would be a good way to see if the overall head thickness is as original.

I'll see if I can find the measurement I need, or just stump up for a burette and do it properly.

Kevin.

Just did the crude test I outlined earlier and with the head carefully levelled all the white spirit I could get into a chamber before it started to overflow was approx 47.5cc which would indicate that the heads have had a skim at some point as their approx minus 6-7cc which strangely enough would be ideal. Apparently a 47cc. chamber is what they aim at in the states when they mod these heads.

I'll ask my engineering guy whether he has a burette to check them properly.

Kevin.

Marki,

I found that thread in the archives but it is difficult to tell where the measurement is taken from.

On the top diagram dimension A there is a step in the casting on the Buick heads not sure if it's the same on the Rover versions.

Kevin.

http://www.v-8.org.uk/forum/viewtopic.p ... +thickness

It might not be the same, it was just an idea based on the engines being related. The only way to really know is to find someone who knows these heads and even if it is possible it would be unlikely to be the same size anyway. Try a search over on http://www.v8buick.com or join and post a message.

katanaman wrote:It might not be the same, it was just an idea based on the engines being related. The only way to really know is to find someone who knows these heads and even if it is possible it would be unlikely to be the same size anyway. Try a search over on http://www.v8buick.com or join and post a message.

Marki,

Probably just easier for me to have the heads measured and then I'll know for sure.

Thanks for all the help.

Kevin.

I got mine measured professionally and they were all 54cc.

To get a decent comp ratio you need to determine the volume of the dish in your pistons, the thickness of whatever type of head gasket you're using and the piston tdc to block height.

I brought the combustion chamber volume of my 300 heads down to 37cc by getting the head shop (Airflow Developments) to weld up the combustion chambers behind the spark plug apertures. They then skimmed .082 off their faces (similar amount had to come off each face of the inlet manifold).

Using Buick 300 tin gaskets this brought the cr to about 9.3:1 using std 4.6 pistons (new block) which is about right for the crap pump fuel we get here lately.

If I was doing a rebuild on an old block I would have simply changed the pistons - ie put 4.0 pistons into the 4.6 block to raise the cr.

Robrover wrote:I got mine measured professionally and they were all 54cc.

To get a decent comp ratio you need to determine the volume of the dish in your pistons, the thickness of whatever type of head gasket you're using and the piston tdc to block height.

I brought the combustion chamber volume of my 300 heads down to 37cc by getting the head shop (Airflow Developments) to weld up the combustion chambers behind the spark plug apertures. They then skimmed .082 off their faces (similar amount had to come off each face of the inlet manifold).

Using Buick 300 tin gaskets this brought the cr to about 9.3:1 using std 4.6 pistons (new block) which is about right for the crap pump fuel we get here lately.

If I was doing a rebuild on an old block I would have simply changed the pistons - ie put 4.0 pistons into the 4.6 block to raise the cr.

Rob,

New Engine is 77mm. crank Bore 98.89mm for capacity of 4.35 I'm using the heavy duty 5.85" rods and Chevy 305 Pistons which leaves the pistons approx 33thou. down the bore at TDC. The pistons are flat top but have valve cut outs which equate to 5cc. With a tin gasket, 47cc. chambers I'll still probably need to have the decks skimmed 10-15thou to give me a static CR of around 10/1 which with the Crower 50232 cam should be fine, I hope.

Should have it all together in a couple of months, Ive got all the major components, just waiting for the pistons to come from the states.

Kevin.

I have never used a byrette for the simple reason that I don´t have one Instead, I have used different sized plastic syringes available from a pharmacy shop. 10 ml and 25 ml syringes do the job. I use water and mix some red penetrant fluid to aid in visibility. Like others already mentioned, I use a plastic perspex sheet fitted with grease. I have drilled the hole offset. I place it agjacent to an edge of the chamber and slightly tilt the head so that the air can escape easier from the chamber.

BTW, is your bore really 98,89 ? It sounds a lot for a Rover block .

That should be 94.89mm./3.736" for the bore size.

Kevin

In an Ideal world rather than reducing chamber volume by skimming the head, to get the compression up it would be best to get the pistons decked level with the top of the block (on a composite gasket) and down far enough to get the top of the piston between 25 and 30 thou from the cylinder head lower surface on a tin gasket. Only then start skimming the head if you have to. Also as Robrover has done if you can reduce the chamber volume by building up the squish area with weld by the plug it would be much better all round.
Mike

Spoke to the guy who's doing my machining work this morning, and he has got a burette so we can do the measuring properly on the heads and then know what base figures we are starting from.

We will have to do a test build of the bottom end with the four end pistons once it been bored to establish the actual deck heights.

I think we will aim for 47cc combustion chambers as recommended by Dan Jones, and use the composite gaskets, machine the decks probably 10-15thou to get the compression ratio in the right area, anything between 9.75 and 10.25/1 should be ok with the Crower 50232 cam I'm told.

Calculation.
Volume of cylinder 544cc

Piston to deck 3cc
Comp Gasket 6cc
Chamber Vol 47cc
Cut out in piston 5cc.
Total. 61cc. + 544cc = 605cc. divided by 61cc = 9.918/1

I'll be happy with that, and only minor machine work required.
If I've got anything wrong please tell me.

Kevin.