Hello Bricksters!

Just a couple of questions I have for You.

If one shave the cylinder-head one millimeter on a B230F, how many degrees will the camshaft then be retarded if one line up everything as it is supposed to be (the timing belt at the proper markings on the crankshaft,camshaft and so on)?

As I understand it the power will move up in the rev scale if the camshaft is retarded, less low-end torque and more high-end torque or how is it?

Next is it then suitable that I buy a adjustable camgear so Ican set the camshaft to proper settings?Advance it the amount of degrees that was retarded because of the milled head?

About the adjustable camgear, it is not the camshaft one actually move/adjust or, because if one do that I guess one also move the timing settings back in the distrubutor and that´s not wanted I suppose?One must hold the camshaft still I guess and move the crankshaft those little amount of degrees that is necessary to get the right distance in degrees when let say the intake valve will open against the piston when it is on its way up in the cylinder and then tighten the bolts on the camgear?

Lets make a scenario, in my case with the adjustable camgear on the shaved head which is bolted on to the engine block, the timing-belt is on, lined up on correct markings, the camshaft is retarded a couple of degrees cause of the one mm shaving which makes I suppose the valves will open a bit later, then for to get the correct distance between valve opening and piston I just loose the bolts on the camgear and hold the camshaft still while moving the crankshaft (with the belt and camgear of course) the right way until I get the correct distance in degrees between the valve and the piston and then tighten it up?

Hope You can understand what answers I am in need of, I will not do this myself but I want to know how it works although.I will let a Volvo-mechanic do this work but I would be very grateful if someone could straighten this up for me.

Thanks in advance! (Proper finish or)

Mikael

Sweden

Other listers will correct me if I'm wrong, but I think you're missing the point. Shaving the head has the greatest impact on the compression ratio. In a modern interference engine, you may increase compression sufficiently by taking off a full mm that you will launch the engine in short time if not compensated for by other means. Remember, the inside of the dome makes up the top of the overall cylinder volume. You effectively shorten the cylinder, which increases compression ratio.

Yes that is the point of shaving the head, but I think he is saying that he has to watch out for the side affects.

The thing about shaving the head, is that it makes more compression, but it also sometimes lessens the effeciency of the combustion cahmber, becase of a certain shape that is best.

The best cylinder heads have the combustion chamber more in the head than the piston.

The more combustion that is encaved, so to say, in the head, and trapped where the valves are, the better it will flow.

If you shave the head, it always lessens the amount of combustion in the head.

If you shave the block, that is a real good tuning trick though.

But shaving the head minimal amounts is ok IMO.

Also the factor of your timing belt tension. On these cars the tensioners are spring loaded so they can take out any looseness, but on some cars, the tensioner is a simple pivoting thingy and you can't take out as much tension that is needed after a shave of the head.

If your head needs to be shaved well then thats different, but if it doesn't I would go with a head gasket, and if convenient then the block.

So, if had the block out I would go for the block, and a thin head gasket especially (a copper custom made one).

Oh yah, the other thing is that you decrease the displacement, so maybe some gain of low end power but some loss of low end torque?

I dunno.

Here's a great theoretical question for the list. I don't think you affect displacement by shaving the head. I always thought displacement was basically bore x stroke x number of cylinders. The stroke doesn't change when you reduce the size of the cylinder. Only the CR.

I also remember reading that if you have a warped head, you can only shave a little bit before getting into trouble with the CR, as in thousandths of an inch as opposed to mm's. Anybody with real experience on this?

Yes that is correctI think. I have a 1970 Toyota Landcruiser that used to blow head gaskets after several valve jobs. Each time the head was serviced (burnt valves) the shop would shave the head. Each time the head was surfaced the compression would increase. Needless to say when the cruiser ran, the straight six put out a lot of horsepower. Finding gas became a problem, not enough octane. I finally swapped a chevy in it. Problem solved, plenty of power and better milage, plus no more head gasket-burnt valve problems.

I tried to answer this yesterday, but somehow the machine swallowed my posting. Shaving the cylinder head does NOT change your engine's displacement -- that can only be done by boring out the block for bigger pistons or changing the stroke of the crankshaft (which also usually requires new pistons and/or rods). Shaving the head just reduces combustion chamber volume, which raises the compression ratio because the compression ration is the ratio of engine displacement to combustion chamber volume -- and it also retards the cam timing slightly on an overhead cam engine like Volvoes after 1975. You have shaved the head enough so that you need super high octane fuel, that's your basic problem.

No, you didn't lose displacement, because that is the volume affected by PISTON movement -- you can only change it by boring out the cylinder for bigger pistons or changing the piston stroke (which requires different rods and/or pistons, too). What you did is reduce the volume of the combustion chamber, and the ratio of combustion chamber volume to piston displacemnt volume is the compression ration. Your problems were because you raised the compression ratio -- and, I suspect, because someone wasn't doing a first rate job of machining on the head or installing it.

How in the world is it possible to change teh compression ratio and still keep the same volume?

Compression is directly related to volume.

Shave the head, lose volume, gain compression.

Hello!

I must thank You all for the answers.It is always good to have someone ells looking into a problem or question that one have.

David what You are saying seems logic when one thinks about it that one mm don´t should make a big difference on the outer side of the cam pulley.I didn´t think about that.I know some buy those VX camshafts with a adjustable camgear and advance it 4 degrees to gain lower end, is it correct?Then I thought that a adjustable camgear would be suitable for me also because if I haven´t read it all wrong so when one shave the head the camshaft will be retarded and then I thought it would be good to advance the camshaft forward to the correct position.Do someone think that this 1 mm shaving can retard the camshaft as far as 4 degrees or will it just be a fraction as You David mention and then the adjustable camgear isn´t necessary at all?

David You are curious why I have had the head shaved, well I write You how it is.As I said I have a B230F 88 740 GL and I have searched for some tuning equipment for the car so it will be little different then ordinary 740:s.Lets make a very long story short (if possible), I wanted a modified head and camshaft that wouldn´t be to extreme because I´m a daily city/highway driver.I just would like some more punch in the upper rev scale and I know the M-camshaft that we have has its limits when one come up to that region.

I got in contact with a 240 GL 90 owner that had bought a complete tuning kit from SAM-Steffansson.It contained a modified 531-head with theirs SAM-1 camshaft and gaskets for the change followed with it.I talked to this fellow and he was really happy with the result.Well I thought it was the easiest way for me to get some extra power to my engine so I bought this kit in last fall.It has been resting under my bed all winter and now I will have it changed at Volvo in beginning of June.

As You know we have the 530-head on our B230F:s, the combustion chambers volume in the 530-head is 4,3cc x 12mm (height of the chamber)= 51,6 cc (got these figures from Mike Aaro).

Now I will have the better breathing 531-head (it sat on B230FB/FX and some B230E and all B230ET I think for example), the combustion chamber on 531-head is little bigger and have also I think little better shape than the 530-head, it also has the spark plugs a little bit deeper into the chamber which should result in better and faster burning (this is what I have read).The combustion chamber is 4,5cc x 12 = 54cc.

If SAM would stay with the head unshaved You can see I would get lower compression and that is not good for the power or the fuel economy either I think.Thats why they had it shaved 1 mm, shaving a head is a way to gain power for a N/A brick here in Sweden.So Michael Yox I know by shaving the head it will increase the compression ratio but I´m sure that the people on SAM knows what they are doing and has the new compression ratio in their mind.The 240 owner has driven his car for 4 years and more now, without any problem.

Lets count on my compression, now it is 9,8:1 with the 530-head.My combustion chamber volume is 51,6cc.With the new head which is 54cc - 4,5cc (the 1 mm shaving) = 49,5cc it results in.

My combustion chamber volume will get smaller from 51,6cc to 49,5cc, 51,6 - 49,5 = 2,1 cc.

Mike Aaro did help one that had trouble to count his compression on a page, I use his kind of calculations.

A B230F has 9,8:1 = (2316/4)/(9,8-1) = 65,79cc in total combustion volume.

Why he takes the compression ratio minus 1 in the calculation I don´t know but I guess it must be correct because if someone should know he would.

Now one can be a little confused about the result we got 65,79cc it is much more than those 51,6cc it should be.But in the KG:Tunings catalog I read that one must count in the gasket and they use a number of 9cc for the volume that the gasket takes up.Okay 65,79cc - 9cc = 56,79cc.Well it is not correct yet, but then I remembered that the piston isn´t flat at the top, it has a little round room which one must counter in.56,79cc - 51,6cc = 5,19cc.Those 5,19cc (not a correct value I think because I am not sure about how much the gasket really takes up in volume, just used those 9cc for example) is held in piston top I suppose or can someone ells correct me if I am complete wrong with my calculations.

Now to the important calculation, to calculate the new compression I will have to use this formula ((65,79-2,1) + (2316/4)) / (65,79-2,1) = 10,09:1 in my new compression.The number 65,79 was my old combustion chamber volume with the 530-head minus the loss I get with my new 531-head.The 2316 is the whole volume of the four cylinders divided by four.

You see it is not a dramatic increase of the compression if my calculations now is correct of course.The man I talked to on SAM did say that they were aiming on 10,5:1 so I guess I can have missed something here.They didn´t say they would shave it 1 mm, I have measured the height of the head and it is approximately 145mm tall, original it is 146,1 mm tall.If they would get near 10,5:1 it would be necessary to shave it 1,5mm I think.

The SAM1-camshaft lifts the valves more and have a bit longer duration so I guess I will probably loose some of the good low end torque I have now but hopefully will fly away on the upper part.I like to rev the engine and then You also "clean" it up on the inside I think from all carbon deposits and other things.One wrote it is good for the fuel mileage if one "blow through" the engine now and then so one get rid of those unwanted products.

With a more high-lifting and longer duration camshaft one gets less cylinder volume filling on the lower revs I have read.There is something called compression pressure (like 12kilogram or I think You use psi over there, seen You described it like 150 160 160 150psi on a certain engine and respective cylinder, it is for looking after a bad head gasket for example)and with a higher lifting and longer duration camshaft that value can get less on starting revs because of bad cylinder filling.I think if the compression ratio gets higher it can help up this a bit or?

I saw a discussion appeared about displacement and if the shaving would decrease it or not.Our engines is on 2316cc but I think that volume only is in the engine block (the volume of the four cylinders gathered), the volume of the combustion chambers isn´t counted into those 2316cc or am I all wrong?Compression relationship = relationship between the volume above the piston at LDP and the volume above the piston at TDP.Like our B230F 2316cc/4=579cc 579cc + 65,79cc = 644,79cc / 65,79cc = 9,8:1 in compression ratio.

So I guess I still have the same volume in the engine block because it is untouched but the volume in my cylinder head has decreased some.

Didn´t mean to make it so long but it concerns important things.I thank all of You again and if someone of You have some thoughts about what I´m writing so please correct me.

Thanks!

Mikael

Sweden

Hey along with shaving the head, if you have access to, I would go for a thin copper head gasket.

I thought the engines were always measured on what they displace, ie--how much water can you put in the spark plug hole with the piston all the way up, multiplied by four in a 4 cyl car.

Displacement is the volume taken up by the pistons moving TDC to BDC. Space at cylinder top is not included in displacement. Don't you think that water would damage rings to say nothing about the possibility of a hydralic lock up. Yikes!

You are right about the displacement not including the head and that its the amount between BDC and TDC, its just funny that any engine can have a differenct cyl head, and in words be the same displacement, but actuallly it can be really different because the head ashpae can totally change how much the engine sucks in. I mean with the cyl heads that have a combustion chamber in the head, that allows more air in since its a bigger volume to fill up, regardless of the written down displacement.

And I guess i just can't visualize it because I thought i could pour like a litre into one cylinder, looks so big, anyhow im wrong your right.

But now, I am not paying any attention to wether an engien is 2.3 litres or 2.4 litres, because hey thats not accurate, the cyl head can totally change everything.

If the cyl head volume is not included, that makes all the specifactions for displacement kind of shoddy, i mean you could get an extra 1/4 of a litre with the cylinder head shaped differently

Hey now I wasn't actaully suggesting you go out and do this, did you just go try it? I'm sorry. It was a visual image, to make ya think about it.

If I took 1 litre milk carton and poured it in one cylinder with the piston down, the complete milk carton could be poured into the cyl adn then some, so i'm not following on a 2 litre engine alowing 1 litre of milk into 1 cylinder.

Unless my eyes are bad, but one cylinder looks deep, and in all the specifications, the stroke is usually about the same as the bore, the piston doesn't move down the amount that the bore is for example 84.4mm stroke, 8.4 cm is the depth that the piston moves down?

like, 2.5 inches?

Thanks for the gentle calibration, Lars. I, agree, you can't change compression without changing volume. Displacement is calculated by volume of cylinder at BDC x number of cylinders. CR is calculated by dividing volume at BDC over volume at TDC. It was fun to figure it all out again in my head. Every now and then you forget these kind of things. At least I do!

Hey but you can change the compression ratio and not the displacement buy changing the cylinder length at the bottom,piston goes down further, longer cylinder, so the engine sucks more air in, sorta like a turbo, same dispalcement but more air!

Thats the only way i can think of changing compression without changing the final displacement!

When a timing belt gets old, it must stretch more than 1 mm, but nobody worries about it affecting the valve timing. I think the change in timing caused by shaving the head 1mm is not great enough to be of concern.

I agree 100% with Chris. 1 mm off the head will not significantly affect valve timing. If you do the math and calculate a 1mm turn counter counter clockwise of the outer circumference of the cam pulley and translate this to a degree it would be a fraction. You may want to check ignition timing but I doubt that it would even be affected much. Curious why you had the head shaved?