Tech spec needed on a B20 gasket...

Gordon Hunter · Aug 6th, 2007, 15:58

Hi folks,

Can any kind soul out there help me?
I need to know the cc of a standard B20 E gasket in order to work out the CR of an engine I am building. Unfortunately I discarded the old one some time ago not thinking I'd need it again.

Many thanks,

Gordon

mike gilbert · Aug 6th, 2007, 18:15

Gordon,
do you mean the thickness? And are they different to the B20B as I have one of those and could measure it - I suspect the E one is thinner.

Gordon Hunter · Aug 6th, 2007, 18:31

Hi Mike,

I'm looking to establish the capacity in CC of the area in the chamber taken up by a compressed gasket. It can be measured by sandwitching the old gasket between two plates of perspex and filling the space with measured parrafin or liquid. Its a bit of a faff to do and as I have allready binned my old gasket, I was hoping to find someone out there who has allready done it.
It sounds like a real anoraks question, but I need to know it to work out what the projected compression ration of a B20 I'm building would be. It'll mean I can do the maths and work out if I can use a particular racing head I have in mind, or if it has been too radically shaved to use with unleaded petrol on a road car.

Cheers,

Gordon

B20F · Aug 6th, 2007, 19:06

The original E headgasket is 0.8mm unloaded and 0.7mm loaded. BUT these original E headgaskets aren't available anymore as far as I know. You have to use either a F gasket (thicker) and plain the head or a B gasket ( the same thickness as an E gasket)

http://volvo1800pictures.com/documen...nual_180_E.pdf

ps:
be aware that if you order a E gasket they probilly sent you a F!

mike gilbert · Aug 6th, 2007, 19:10

Oh I get you now, you need a used item. Sorry, I keep most bits of useless old tat 'just in case', but none of those.

Derek UK · Aug 6th, 2007, 20:43

Here's something to play with http://not2fast.com/turbo/compression/compression.shtml
Standard E head volume is 47cc.
Going from an 0.030 to a 0.050 gasket gives a change in CR of, say, 10.5:1 to a gnats whisker below 10.0:1 so shaving 0.020 off and using the thinner gasket should give 11:1.
Does that sound about right? You need to be able to measure the height of a standard head and compare it to your race one.
Info nicked from the Yahoo 1800 forum so not my own work. Thanks Phil.
Sounds like you're having fun.................

Gordon Hunter · Aug 6th, 2007, 21:05

Hi Derek,

Thanks for your input.
I have managed to measure the cc of the chambers on the head and it works out at 40.7 cc. So I guess this has been seriously shaved.
What I can't manage to work out is the cc of the compressed gasket and the cc of the distance between the top of the piston and the top of the block. After 14 or so unsuccessful attempts, liquid volume measuring seems just impossible in such a tight gap.
If I could only get these figures then I could work out the potential CR of the engine with this modified head and find out if it is going to be a reasonable head for road use.
It is worth checking this out as it has had a lot of expensive looking work done and would give me far better performance over the standard E head I have.
I'll have a look at the link you posted, but I'm no engineer, so If you can help in any way, I'd greatly appreciate it.

Many thanks,

Gordon

Derek UK · Aug 6th, 2007, 22:53

Extrapolating (lovely word, reminds me of Mme Domenique....) from the Vizard Mini tuning book gives some numbers which might be close. Doubling up from a 1000cc engine would give 2cc above the piston and 4cc for the compressed gasket space. Those figures assume a similar bore/stroke ratio. I haven't checked that. It does give you a fixed volume below the head but might not be exact. The piston heights might be different, and all lower than the Mini. 40.7cc would give 11.7:1 using the figures above. If it was 4cc above the pistons it would only be 11.26:1 Probably OK with 100+ octane and a head that flows well, esp the exhausts. Normally, by selectively skimming the pistons and then rebalancing them before decking the block to get rid of the excess, you'd make the most of your CR.

barney paull-edwards · Aug 7th, 2007, 00:06

Not sure if it helps but the head measurement from face to head bolt contact is 88mm, and from head face to overflow pipe is 35mm,if you`re trying to use measurements the old way, use kero in burette, it has less meniscus than water.

Gordon Hunter · Aug 7th, 2007, 09:12

Thanks Derek, I guess an approximate figure might be enough to go the 'suck it and see' route if all else fails.
I was hoping to get more accurate figures and was using the following equation.

Size of engine divided by 4 +total of combined cc in the head/gasket/bore divided by the total number of CC in the head/gasket and bore with piston at TDC = COMPRESSION RATIO.

I was using parrafin and a burette to measure, however, this proved nigh impossible to get the gasket/bore measured acurately. Hence my original post and questions. However, short of someone else knowing these figures I switched to using a digital vernier caliper to work out the gasket & bore volumes myself using a basic cylinder volume calculation.
My figures are as follows:

B20 individual cylinder displacement = 497.5 cc (1990 / 4)
My modified head chamber (40.7cc)
B20 gasket allowing .1mm for compression on re-assembly (7.236cc)
B20 bore from piston at TDC (4.347cc)

Total = 52.3cc

So, 497.5 + 52.3 divided by 52.3 = 10.5:1 CR!

This figure seems incorrect to me. The original B20 E had a CR of 10.5:1!
This modified head is 83 mm thick. It is not an E head so has either been one of the following:
B20A: 86.7mm
B20B: 86.2 mm
B20F: 87 mm

That's all I know about its history. It looks like some really expensive work has been done to it in the past, so I want to try and use it. Hence the need to work out potential CR. I'd be happy to shave a bit off the pistons if I can only work out an accurate CR first.

My only guess is that somehow I've got the cc of the gasket and/or the cc of the bore from piston at TDC wrong. I have measured as accurately as I can and don't see another way of doing it / checking it unless someone has been there before and knows these figures?

Can anyone please confirm the gasket and piston bore to TDC figures as they should be standard? (the block has only 47K from new and has never been touched)?

Any help greatly appreciated!!!

Gordon

Aug 6th, 2007, 15:58	#1
Gordon Hunter Ex 1800 Register Keeper Last Online: Apr 29th, 2022 17:04 Join Date: Dec 2001 Location: Central Scotland	Tech spec needed on a B20 gasket... Hi folks, Can any kind soul out there help me? I need to know the cc of a standard B20 E gasket in order to work out the CR of an engine I am building. Unfortunately I discarded the old one some time ago not thinking I'd need it again. Many thanks, Gordon

Aug 6th, 2007, 19:06	#4
B20F Master Member Last Online: Jul 7th, 2016 21:43 Join Date: Mar 2007 Location: Zeist View Photos By: B20F	The original E headgasket is 0.8mm unloaded and 0.7mm loaded. BUT these original E headgaskets aren't available anymore as far as I know. You have to use either a F gasket (thicker) and plain the head or a B gasket ( the same thickness as an E gasket) http://volvo1800pictures.com/documen...nual_180_E.pdf ps: be aware that if you order a E gasket they probilly sent you a F! __________________ Last edited by B20F; Aug 6th, 2007 at 19:12.

Aug 7th, 2007, 00:06	#9
barney paull-edwards B.P-E Last Online: Dec 28th, 2007 21:12 Join Date: Jun 2007 Location: new Forrest	gaskets Not sure if it helps but the head measurement from face to head bolt contact is 88mm, and from head face to overflow pipe is 35mm,if you`re trying to use measurements the old way, use kero in burette, it has less meniscus than water.

Aug 7th, 2007, 09:12	#10
Gordon Hunter Ex 1800 Register Keeper Last Online: Apr 29th, 2022 17:04 Join Date: Dec 2001 Location: Central Scotland	Thanks Derek, I guess an approximate figure might be enough to go the 'suck it and see' route if all else fails. I was hoping to get more accurate figures and was using the following equation. Size of engine divided by 4 +total of combined cc in the head/gasket/bore divided by the total number of CC in the head/gasket and bore with piston at TDC = COMPRESSION RATIO. I was using parrafin and a burette to measure, however, this proved nigh impossible to get the gasket/bore measured acurately. Hence my original post and questions. However, short of someone else knowing these figures I switched to using a digital vernier caliper to work out the gasket & bore volumes myself using a basic cylinder volume calculation. My figures are as follows: B20 individual cylinder displacement = 497.5 cc (1990 / 4) My modified head chamber (40.7cc) B20 gasket allowing .1mm for compression on re-assembly (7.236cc) B20 bore from piston at TDC (4.347cc) Total = 52.3cc So, 497.5 + 52.3 divided by 52.3 = 10.5:1 CR! This figure seems incorrect to me. The original B20 E had a CR of 10.5:1! This modified head is 83 mm thick. It is not an E head so has either been one of the following: B20A: 86.7mm B20B: 86.2 mm B20F: 87 mm That's all I know about its history. It looks like some really expensive work has been done to it in the past, so I want to try and use it. Hence the need to work out potential CR. I'd be happy to shave a bit off the pistons if I can only work out an accurate CR first. My only guess is that somehow I've got the cc of the gasket and/or the cc of the bore from piston at TDC wrong. I have measured as accurately as I can and don't see another way of doing it / checking it unless someone has been there before and knows these figures? Can anyone please confirm the gasket and piston bore to TDC figures as they should be standard? (the block has only 47K from new and has never been touched)? Any help greatly appreciated!!! Gordon Last edited by Gordon Hunter; Aug 7th, 2007 at 09:19.

Aug 6th, 2007, 18:15	#2
mike gilbert Master Member Last Online: May 2nd, 2024 19:17 Join Date: Dec 2003 Location: Peterborough View Photos By: mike gilbert	Gordon, do you mean the thickness? And are they different to the B20B as I have one of those and could measure it - I suspect the E one is thinner.

Aug 6th, 2007, 18:31	#3
Gordon Hunter Ex 1800 Register Keeper Last Online: Apr 29th, 2022 17:04 Join Date: Dec 2001 Location: Central Scotland	Hi Mike, I'm looking to establish the capacity in CC of the area in the chamber taken up by a compressed gasket. It can be measured by sandwitching the old gasket between two plates of perspex and filling the space with measured parrafin or liquid. Its a bit of a faff to do and as I have allready binned my old gasket, I was hoping to find someone out there who has allready done it. It sounds like a real anoraks question, but I need to know it to work out what the projected compression ration of a B20 I'm building would be. It'll mean I can do the maths and work out if I can use a particular racing head I have in mind, or if it has been too radically shaved to use with unleaded petrol on a road car. Cheers, Gordon

Aug 6th, 2007, 19:10	#5
mike gilbert Master Member Last Online: May 2nd, 2024 19:17 Join Date: Dec 2003 Location: Peterborough View Photos By: mike gilbert	Oh I get you now, you need a used item. Sorry, I keep most bits of useless old tat 'just in case', but none of those.

Aug 6th, 2007, 20:43	#6
Derek UK VOC Member Last Online: Yesterday 14:22 Join Date: Jul 2006 Location: Chatham	Here's something to play with http://not2fast.com/turbo/compression/compression.shtml Standard E head volume is 47cc. Going from an 0.030 to a 0.050 gasket gives a change in CR of, say, 10.5:1 to a gnats whisker below 10.0:1 so shaving 0.020 off and using the thinner gasket should give 11:1. Does that sound about right? You need to be able to measure the height of a standard head and compare it to your race one. Info nicked from the Yahoo 1800 forum so not my own work. Thanks Phil. Sounds like you're having fun.................

Aug 6th, 2007, 21:05	#7
Gordon Hunter Ex 1800 Register Keeper Last Online: Apr 29th, 2022 17:04 Join Date: Dec 2001 Location: Central Scotland	Hi Derek, Thanks for your input. I have managed to measure the cc of the chambers on the head and it works out at 40.7 cc. So I guess this has been seriously shaved. What I can't manage to work out is the cc of the compressed gasket and the cc of the distance between the top of the piston and the top of the block. After 14 or so unsuccessful attempts, liquid volume measuring seems just impossible in such a tight gap. If I could only get these figures then I could work out the potential CR of the engine with this modified head and find out if it is going to be a reasonable head for road use. It is worth checking this out as it has had a lot of expensive looking work done and would give me far better performance over the standard E head I have. I'll have a look at the link you posted, but I'm no engineer, so If you can help in any way, I'd greatly appreciate it. Many thanks, Gordon

Aug 6th, 2007, 22:53	#8
Derek UK VOC Member Last Online: Yesterday 14:22 Join Date: Jul 2006 Location: Chatham	Extrapolating (lovely word, reminds me of Mme Domenique....) from the Vizard Mini tuning book gives some numbers which might be close. Doubling up from a 1000cc engine would give 2cc above the piston and 4cc for the compressed gasket space. Those figures assume a similar bore/stroke ratio. I haven't checked that. It does give you a fixed volume below the head but might not be exact. The piston heights might be different, and all lower than the Mini. 40.7cc would give 11.7:1 using the figures above. If it was 4cc above the pistons it would only be 11.26:1 Probably OK with 100+ octane and a head that flows well, esp the exhausts. Normally, by selectively skimming the pistons and then rebalancing them before decking the block to get rid of the excess, you'd make the most of your CR.

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