Amazon: Head Gasket

[Bracpan]

Simple question, does any body know the thickness of the standard cylinder head gasket for the B18 engine.
I believe you can get thicker versions but i just need the standard one to work out the compression ratio

[Clan]

Originally Posted by Bracpan

Simple question, does any body know the thickness of the standard cylinder head gasket for the B18 engine.
I believe you can get thicker versions but i just need the standard one to work out the compression ratio

There were 3 thicknesses from volvo I believe ,
thin for the B20E
in between for the B20B
thick for the B20A


similarly the B18 i would think . have you tried volvo ?

[142 Guy]

The information I have lists it as 0.85 mm for all the B18 engines. I don't know whether that is the compressed or uncompressed thickness. The difference in compression seems to come from different head thicknesses listed for the different engines.

[Army]

If you look on the skandix site there is a bit of additional blurb about head gaskets and their thicknesses in the product descriptions...

...for a specific spec'd engine I think you need to find a part number in a parts book. Take that number to a manufacturer's parts catalogue (also available on-line) where more often than not the thickness is specified in the technical descrption.

As said above, however, the gasket does get compressed when fitted so you will need to guestimate that.

If you have an engine in bits measuring the thickness of a removed gasket would probably give a better idea.

[Bracpan]

Many thanks its much appreciated
Its a spare head ive bought so i can rebuild it for unleaded..
I will get all the work done then probably leave any skimming until I take the old one off.
I think the .85 is the standard h/gasket and 1.2mm and 1.6mm are available so I have a good range to play with.
I would like to get the compression ratio around 9:1

[Army]

Originally Posted by Bracpan

Many thanks its much appreciated
Its a spare head ive bought so i can rebuild it for unleaded..
I will get all the work done then probably leave any skimming until I take the old one off.
I think the .85 is the standard h/gasket and 1.2mm and 1.6mm are available so I have a good range to play with.
I would like to get the compression ratio around 9:1

I'm sure that every decent machine shop would be able to tell you which head gasket (thickness or perhaps other important information) to use.

I'd ask for advice from the machine shop (assuming you can find a decent one)

In my experience with refurbishing heads there is usually a whole load of unexpected additional work. Don't want to bring you down but valve guides could be worn - you might have to replace valves and have valve seats re-cut which would then mean skimming.

Here in NL the bill at a decent machine shop would be about 500 to 700 euros. I don't know if it would / will cost that much in Wales but keep an eye on the cost of buying a pre-done unleaded head from one of the Scandinavian suppliers...

[142 Guy]

The 140 came equipped with the B18 A / B in the first year of production. My 140 parts manual indicates that the same head gasket was used for both engines - part # 418990 and the OEM thickness is 0.85mm.

If at all possible stay away from thick head gaskets. 0.85mm is already pretty thick and at or beyond the limit in terms of establishing an effective quench zone to prevent detonation. Go to an even thicker head gasket and you should probably plan to keep your compression ratio in the low 8 range.

When I rebuilt my B20E, I measured after re assembly of the block and the piston crowns were sitting 0.018 - 0.020" below the deck of the block. At that point, I should have taken everything apart and sent the block back to the machine shop to have it decked so that the crowns were sitting about 0.002" below the deck. With the standard E head gasket (0.028" compressed) that would have given me a quench depth of 0.030". Right now my quench depth is 0.048". Anything much past 0.035" becomes less effective rapidly. I didn't deck the block and with my stock 10.5:1 compression ratio I still need to retard ignition timing around 2500 RPM to avoid detonation running 91 octane fuel (R+M)/2.

Since the head is on the work bench, you can measure the volume of the combustion chambers (if the valves seal). When the old head is off the engine you can measure the clearance of the piston crown to the deck block. With that data and a little bit of arithmetic you can calculate your compression ratio for the different head gaskets. If you are striving for a compression ratio in the 9.?:1 range and the 0.85 mm head gasket end up with a CR that is too high, I think you would be better off having the machine shop open up the combustion chambers a little bit to reduce the CR rather than install a fat head gasket.

Some people have claimed that if you get the quench depth in to the 0.030" range you can run a 10:1 compression ratio with regular unleaded fuel with no detonation. I have no experience with that so I cannot verify that claim.

[Bracpan]

It looks like I have the same low compression head as the one on the car at the moment but will measure the original one when I swap over and only then machine the head to suit using the.85 gasket if needed.
The head will be needing new valves and probably guides as well. As i only paid £40 for the head and have had work done by the same chap for many years on race engines i built. its going to be by far the cheapest alternative. Plus i know and trust his work over anybody else ive used and he is local and old school.
A while back in time I used a very well know UK company to work on a multi valve head and they miss read the valve clearances mixing thous for metric...never again I now go to who i know and trust.