Ring gaps

Sam1275 · Nov 20th, 2018, 08:26

Does anyone know the maximum ring gap for a b230? Or where to get oversized pistons from in the uk that aren't rediculous money.

I have a ring gap of 0.030 at the top of the bore and 0.018 in the center so i think im at the maximum limit of bore wear.

The car didnt smoke and pulled well before i removed the engine. Its going in a project car and i would like it to last

Thanks

Laird Scooby · Nov 20th, 2018, 10:09

Are you talking about mm or thou? There's a big difference!

Have a look at Pg14 of this pdf, it should tell you all you need to know but if you have that much variation in ring gap in the normal swept area of the cylinder wall, i think a rebore would be a good idea. Volvo might be surprisingly cheap on pistons, alternatively try Rock Auto in the USA.

http://www.myvolvolibrary.info/Tech_...DataPocket.pdf

https://www.rockauto.com/

Good luck with it!

mjk164 · Nov 20th, 2018, 10:18

Minimum ring gap tolerances should be observed in order to prevent the ring ends from butting together as the ring expands when the engine approaches operating temperature. The ring makers recommend a minimum of .0035" gap per inch of cylinder diameter. So for the red block b230, 3.7" (bore) x .0035 = .013" minimum gap. To check ring gap, the rings should be placed at the lowest possible part of the cylinder (below ring travel area) as this is the portion of the cylinder that is unworn and which the ring is sized for. Checking ring gap in the worn portion of the cylinder will show a gap increase in direct relation to the amount of cylinder wear present.
If the pistons have not seized in the past, you may find that the pistons are OK but only the rings need renewal. The usual recommendation is a maximum wear of about .003" per inch of cylinder diameter so for your b230 that would be about 0.013 plus about .012 = .025"...measured at the bottom of the cylinder bore. Yours is .030" at the top and it will be get less as you measure down the cylinder. Parts of the cylinder and rings are about on the limits of wear but, as you say, it pulls well and doesn't smoke.
You could leave it as it is. But if the engine is coming out for another use and your pockets are deep, you will end up with a re-bore, new pistons and rings, check the crankshaft bearings etc etc etc.
The choice is yours.

Clan · Nov 20th, 2018, 11:11

Quote:

Originally Posted by Sam1275

Does anyone know the maximum ring gap for a b230? Or where to get oversized pistons from in the uk that aren't rediculous money.

I have a ring gap of 0.030 at the top of the bore and 0.018 in the center so i think im at the maximum limit of bore wear.

The car didnt smoke and pulled well before i removed the engine. Its going in a project car and i would like it to last

Thanks

I would be inclined to leave the pistons they are the very highest quality Mahle and don't really wear fit new rings if you like .. it was ok before so leave well alone .. you cant determine any bore wear without measuring them properly ..

Jimsiss · Nov 20th, 2018, 13:09

Quote:

Originally Posted by Clan

I would be inclined to leave the pistons they are the very highest quality Mahle and don't really wear fit new rings if you like .. it was ok before so leave well alone .. you cant determine any bore wear without measuring them properly ..

Very true, you need the proper tools and know how to correctly use them. Telescopic bore gauges and a quality set of external micrometers (not vernier/digital calipers) will do the job, there are far more sophisticated measuring techniques out there but this is the way most machinists still do bore measurements today.

Sam1275 · Nov 21st, 2018, 19:47

Quote:

Originally Posted by Clan

I would be inclined to leave the pistons they are the very highest quality Mahle and don't really wear fit new rings if you like .. it was ok before so leave well alone .. you cant determine any bore wear without measuring them properly ..

I meant where can i get oversized pistons from that aren't rediculously expencive not std ones the bore was measured with new rings from Hastings and is the quickest and easiest way of determining bore taper i have found

Jebus · Nov 21st, 2018, 20:40

Classic Sweede would be a good guy to speak to

classicswede · Nov 21st, 2018, 21:30

As far as I know the only person to stock new pistons!

https://www.classicswede.co.uk/B230_..._18275842.aspx

Other sizes available

Nov 20th, 2018, 08:26	#1
Sam1275 New Member Last Online: Nov 21st, 2018 19:47 Join Date: Nov 2018 Location: Poole	Ring gaps Does anyone know the maximum ring gap for a b230? Or where to get oversized pistons from in the uk that aren't rediculous money. I have a ring gap of 0.030 at the top of the bore and 0.018 in the center so i think im at the maximum limit of bore wear. The car didnt smoke and pulled well before i removed the engine. Its going in a project car and i would like it to last Thanks

Nov 20th, 2018, 10:09	#2
Laird Scooby Premier Member Last Online: Today 12:22 Join Date: May 2012 Location: Lakenheath	Are you talking about mm or thou? There's a big difference! Have a look at Pg14 of this pdf, it should tell you all you need to know but if you have that much variation in ring gap in the normal swept area of the cylinder wall, i think a rebore would be a good idea. Volvo might be surprisingly cheap on pistons, alternatively try Rock Auto in the USA. http://www.myvolvolibrary.info/Tech_...DataPocket.pdf https://www.rockauto.com/ Good luck with it! __________________ Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........

Nov 21st, 2018, 20:40	#7
Jebus VOC Member Last Online: Aug 13th, 2023 17:49 Join Date: Aug 2016 Location: Aberdeen	Classic Sweede would be a good guy to speak to __________________ 1992 2.0 SE Turbo Wentworth, now with b230ft & M90 2005 S60 2.0T the baby T5

Nov 21st, 2018, 21:30	#8
classicswede Trader Volvo in my veins Last Online: Today 17:58 Join Date: Dec 2004 Location: Anglesey	As far as I know the only person to stock new pistons! https://www.classicswede.co.uk/B230_..._18275842.aspx Other sizes available __________________ http://www.classicswede.org www.classicswede.co.uk

Nov 20th, 2018, 10:18	#3
mjk164 VOC Member Last Online: Apr 12th, 2024 13:08 Join Date: Aug 2006 Location: Hounslow West London	Minimum ring gap tolerances should be observed in order to prevent the ring ends from butting together as the ring expands when the engine approaches operating temperature. The ring makers recommend a minimum of .0035" gap per inch of cylinder diameter. So for the red block b230, 3.7" (bore) x .0035 = .013" minimum gap. To check ring gap, the rings should be placed at the lowest possible part of the cylinder (below ring travel area) as this is the portion of the cylinder that is unworn and which the ring is sized for. Checking ring gap in the worn portion of the cylinder will show a gap increase in direct relation to the amount of cylinder wear present. If the pistons have not seized in the past, you may find that the pistons are OK but only the rings need renewal. The usual recommendation is a maximum wear of about .003" per inch of cylinder diameter so for your b230 that would be about 0.013 plus about .012 = .025"...measured at the bottom of the cylinder bore. Yours is .030" at the top and it will be get less as you measure down the cylinder. Parts of the cylinder and rings are about on the limits of wear but, as you say, it pulls well and doesn't smoke. You could leave it as it is. But if the engine is coming out for another use and your pockets are deep, you will end up with a re-bore, new pistons and rings, check the crankshaft bearings etc etc etc. The choice is yours.

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