Piston ring gap and replacement rings.

[Nivlek2525]

Hello, I've pulled the pistons from my GTE engine as I'm giving it the once over as part of the restoration. The middle and bottom rings are right on the upper limit in the Haynes manual. The top rig gap is about double the upper limit. About 1.2mm. The bores look ok and the gap distance is equal with the inserted at the top middle and bottom of the bore.  I think I can get away with new rings but the best price I can find is £82 from eBay. Has anyone got a better source they can recommend? It looks like the upper and middle rings from a Chevy 305 would work and are a lot cheaper. Is this just being silly.

 

Finally, the rings are obviously worn but how conservative are the Haynes value? 

Any idea why the top ring has worn so much more than the middle? Is this usually?

As always, all help appreciated.

K.

[Jessopia74]

Top rings need to be kept close to tolerance as possible imo. If your bore us good, definitely new rings would be a good choice.

[Nivlek2525]

22 minutes ago, Jessopia74 said:

Top rings need to be kept close to tolerance as possible imo. If your bore us good, definitely new rings would be a good choice.

Many thanks. I think while I've got it stripped down this far I may as well do it.

Cheers.

[H-400]

The top ring is the one that has got to work the most. The pressure of your "bang" goes into the ringgroove and pushes the compression ring against the cilinder so there is a tight fit and minor loss of compression. Thats why that gap is so important, if it's too big you loose compression and it's an indication the ring is worn. 

 

[Nivlek2525]

15 minutes ago, H-400 said:

The top ring is the one that has got to work the most. The pressure of your "bang" goes into the ringgroove and pushes the compression ring against the cilinder so there is a tight fit and minor loss of compression. Thats why that gap is so important, if it's too big you loose compression and it's an indication the ring is worn. 

 

Brilliant thanks. Much appreciated. K.

[cam.in.head]

just be aware that unless the bore is 100% perfect then there will be an inevitable lip at the top of the bore where the top ring reaches .ive found this to be the case on most cam in head engines above say 50000 miles but obviously depends on how its been treated . 

this used to mean that when you fit a new set of rings to an otherwise standard and untouched bore you would need a top stepped ring so as for it not to break.the ring will have worn in unison to the bore and a new ring will have not and can break if it hits this bore ridge.

if you are fitting standard rings then you would be best to hone the bores and try to get the top ridge smoothed out but dont go too far ! obviously.

this is how i was taught anyway. no offence intended if you already know all this !   sorry.

i  must admit ive rebuilt many a engine and reused the original rings with no ill effects.i have a record of all the cav engines ive ever worked on and recorded the compresion readings.this is with my original gunsons guage and is the same one throughout so my readings are consistent to me ( but may be different to someone elses with a different guage )

hence i know what compressions a good engine of various cc should read and refitted original rings when readings were good.

these engines did have ring gaps that were close to or above the tolerances sometimes but it realy depends on how much you enjoy stripping engines down and how much i needed the engine to be perfect ??

[Nivlek2525]

46 minutes ago, cam.in.head said:

just be aware that unless the bore is 100% perfect then there will be an inevitable lip at the top of the bore where the top ring reaches .ive found this to be the case on most cam in head engines above say 50000 miles but obviously depends on how its been treated . 

this used to mean that when you fit a new set of rings to an otherwise standard and untouched bore you would need a top stepped ring so as for it not to break.the ring will have worn in unison to the bore and a new ring will have not and can break if it hits this bore ridge.

if you are fitting standard rings then you would be best to hone the bores and try to get the top ridge smoothed out but dont go too far ! obviously.

this is how i was taught anyway. no offence intended if you already know all this !   sorry.

i  must admit ive rebuilt many a engine and reused the original rings with no ill effects.i have a record of all the cav engines ive ever worked on and recorded the compresion readings.this is with my original gunsons guage and is the same one throughout so my readings are consistent to me ( but may be different to someone elses with a different guage )

hence i know what compressions a good engine of various cc should read and refitted original rings when readings were good.

these engines did have ring gaps that were close to or above the tolerances sometimes but it realy depends on how much you enjoy stripping engines down and how much i needed the engine to be perfect ??

You know a lot more than me so I'll never take offence. Its always appreciated when someone takes the time to respond.

Today's development. I found an engine builder/remanucturer about 20 mins from me. He was recommended by a parts shop I use. Been on the same site for 40 years and knew nothing about him. Called him up and he had rings in stock, great. He asked what the bores were like and the condition of the standard rings. I told him the gaps were much bigger than the Haynes manual. He said he wasn't bothered about the gap as long as they were rediculous but wanted to know what the tension was like in them and did they look warn. Anyway, long story he seemed to know about these engines, described it exactly, said the early ones had camshaft bearing problems which were difficult to replace??? After chatting he told be to bring everything along and he'd give me his honest opinion. He checked everything over and said he would sell me new rings but it really didn't need them the gaps were big but the rings were in excellent condition with loads of tension. He looked them over for ages and seems quite happy with them. He said the pistons were fine but needed a really good clean and the only thing he would replace would be the big end bearing, which he didn't have. He said it wasn't a modern engine and he'd have no problems reusing them after cleaning but the bores were too smooth and would probably benefit from a quick home but I could do that myself. So loads of advice, not a penny spend and as I walk out he handed me 2 brand new oil pump gears for a CIH and asked if I wanted them as theyd sat out back for years!

I ordered big end bearings and they come next week. I have to say I'm inclined to clean up the pistons and rings and just put them back in. 

Yes, there is a lip at the top, not too bad but you can feel its there. Not enough to catch a fingernail on.

No, I don't need the engine to be perfect. Its a stop gap until I've checked everything over and I know it all works as everything, gearbox, axle etc are unknown to me. Once I've finished building up the car I'd like to build a really nice 2.4 for it so I just need something that will be ok for a couple of year which will be about 3000 miles.

Any thoughts on what I was told today?

Cheers and have a good weekend.

Kelvin.

[Jessopia74]

48 minutes ago, Nivlek2525 said:

You know a lot more than me so I'll never take offence. Its always appreciated when someone takes the time to respond.

Today's development. I found an engine builder/remanucturer about 20 mins from me. He was recommended by a parts shop I use. Been on the same site for 40 years and knew nothing about him. Called him up and he had rings in stock, great. He asked what the bores were like and the condition of the standard rings. I told him the gaps were much bigger than the Haynes manual. He said he wasn't bothered about the gap as long as they were rediculous but wanted to know what the tension was like in them and did they look warn. Anyway, long story he seemed to know about these engines, described it exactly, said the early ones had camshaft bearing problems which were difficult to replace??? After chatting he told be to bring everything along and he'd give me his honest opinion. He checked everything over and said he would sell me new rings but it really didn't need them the gaps were big but the rings were in excellent condition with loads of tension. He looked them over for ages and seems quite happy with them. He said the pistons were fine but needed a really good clean and the only thing he would replace would be the big end bearing, which he didn't have. He said it wasn't a modern engine and he'd have no problems reusing them after cleaning but the bores were too smooth and would probably benefit from a quick home but I could do that myself. So loads of advice, not a penny spend and as I walk out he handed me 2 brand new oil pump gears for a CIH and asked if I wanted them as theyd sat out back for years!

I ordered big end bearings and they come next week. I have to say I'm inclined to clean up the pistons and rings and just put them back in. 

Yes, there is a lip at the top, not too bad but you can feel its there. Not enough to catch a fingernail on.

No, I don't need the engine to be perfect. Its a stop gap until I've checked everything over and I know it all works as everything, gearbox, axle etc are unknown to me. Once I've finished building up the car I'd like to build a really nice 2.4 for it so I just need something that will be ok for a couple of year which will be about 3000 miles.

Any thoughts on what I was told today?

Cheers and have a good weekend.

Kelvin.

Seems he knows the CIH engine👍 It's great he was check tension of spring too, but you would usually notice this if you tried to measure gap in the bore (they slide or drop down bore when knackered) As Cam.in.head described about compression and the lipped bores, if it's checked and is fine then great. Agree about hone the bores, as I mentioned before new rings & hone go together. You are correct that can be done yourself, just follow the guides that can be found on YouTube for best technique .

Check pump gear housing wear, especially on the bypass cover. These are available though if it's heavily worn - ask if not sure.

as with everything a pair of eyes up close is never better than the poorer substituted picture, but feel free to post pictures up of anything you not sure about as plenty of people on this forum who are really experienced with these Engines.

As for parts 'out if spec'. Agree completely with the advice you gave already had; This comes with experience as and when you can get away with slightly out of spec parts. An example is I like a slightly slack bore and background piston rings, is great to aid a modded engine, but it sounds like a bag of spanner's when cold 😬😂 

 

Edited October 30, 2020 by Jessopia74

[Nivlek2525]

30 minutes ago, Jessopia74 said:

Seems he knows the CIH engine👍 It's great he was check tension of spring too, but you would usually notice this if you tried to measure gap in the bore (they slide or drop down bore when knackered) As Cam.in.head described about compression and the lipped bores, if it's checked and is fine then great. Agree about hone the bores, as I mentioned before new rings & hone go together. You are correct that can be done yourself, just follow the guides that can be found on YouTube for best technique .

Check pump gear housing wear, especially on the bypass cover. These are available though if it's heavily worn - ask if not sure.

as with everything a pair of eyes up close is never better than the poorer substituted picture, but feel free to post pictures up of anything you not sure about as plenty of people on this forum who are really experienced with these Engines.

As for parts 'out if spec'. Agree completely with the advice you gave already had; This comes with experience as and when you can get away with slightly out of spec parts. An example is I like a slightly slack bore and background piston rings, is great to aid a modded engine, but it sounds like a bag of spanner's when cold 😬😂 

 

Yes, instead of installing new piston rings I could install a turbo and a 100 shot if Nitro's and take advantage of the extra bit of gap????

The new big end bearings come on Thursday. Unless I have a change of heart by then the old pistons and rings are going back in for now.i asked the guys advise and he gave it for free so it's worth a gamble. If the compression is shocking then I know I was wrong.

I still need a few bits and pieces for the bodywork. I need a bottom front panel and I need to order more 2k primer etc so I'm not short of things to spend money on!!

Thanks again 👍

[Jessopia74]

How about £45 for a full set? 
https://www.ebay.co.uk/itm/PISTON-RING-FOR-VAUXHALL-CAVALIER-OPEL-ASCONA-B-BEDFORD-KADETT-C-20-E-S-N-2-0/392451709969

[Nivlek2525]

5 minutes ago, Jessopia74 said:

How about £45 for a full set? 
https://www.ebay.co.uk/itm/PISTON-RING-FOR-VAUXHALL-CAVALIER-OPEL-ASCONA-B-BEDFORD-KADETT-C-20-E-S-N-2-0/392451709969

I saw these earlier but could work out if there was another £20 quid postage on top of that. Still cheap really. I've sent a message because I think the extra postage is express delivery. If they are only 45 I'll have them ( and put the turbo and Nitro's on hold for now😬)

[cam.in.head]

personally i would just reassemble with the original rings ( all in their original locations) and do a very light hone.

did you run the engine or drive the car before dismantling ? 

[611]

and start saving that money if you are going for the 2.4! That's going to cost you for pistons!!

When you get around to the 2.4, make sure you have saved up a few quid as that will need a re-bore and ideally Woosner pistons, both sets of bearings (if your talking about the CIH 2.4?) and save the pump gears for the 2.4 if they are brand new? as they cost an arm and a leg, you don't want to waste them on the old engine as you will need them for the 2.4 to get the best oil pressure you can.

You will also need a few other bits for the 2.4 that are specific to the 2.4. Thermostat housing, inlet manifolds (if you are going carbs) etc..

[Nivlek2525]

12 hours ago, cam.in.head said:

personally i would just reassemble with the original rings ( all in their original locations) and do a very light hone.

did you run the engine or drive the car before dismantling ? 

No, the engine was out of the car before I got it. The lad I bought it off just wanted the shell so he never ran it as far as I know either buy he was under the impression it was a later engine than it is so there really is no history. The engine lad I spoke to yesterday seemed pretty confident they would be ok and I'm not convinced I can get rid of the ridge so I might just end up smashing the new rings.

 

[Nivlek2525]

12 hours ago, 611 said:

and start saving that money if you are going for the 2.4! That's going to cost you for pistons!!

When you get around to the 2.4, make sure you have saved up a few quid as that will need a re-bore and ideally Woosner pistons, both sets of bearings (if your talking about the CIH 2.4?) and save the pump gears for the 2.4 if they are brand new? as they cost an arm and a leg, you don't want to waste them on the old engine as you will need them for the 2.4 to get the best oil pressure you can.

You will also need a few other bits for the 2.4 that are specific to the 2.4. Thermostat housing, inlet manifolds (if you are going carbs) etc..

I've no fixed plans at the moment, that's why I'm trying to get the GTE engine together. Structurally the car is not sound and the body work is coming along slowly. But everything is unknown mechanically on the car and although I'm replacing obvious things as I go there's probably lots to do that I don't know about yet. So I want to get it up and running on the GTE engine and get some miles on it, hopefully buy the end of next year as I want to take it to a local show in September. Then as a separate project I'd like to look at an engine swap. The 2.4s do come up in the frontera forum occasionally on not failures etc. Not often but they do exist. I also like the 3 litre, again, thin on the ground. But it I wait to do a 2.4 or similar now the car might not be ready for a lot longer. That's the plan anyway.

Cheers for the heads up on the things to think about.

[Nivlek2525]

https://photos.app.goo.gl/p5UKr6vG6gnVeAqE6

Random engine photographs. In the engines defence the bores look and feel better than these photos suggest. Clearly not brand new though...

[Jessopia74]

9 minutes ago, Nivlek2525 said:

https://photos.app.goo.gl/p5UKr6vG6gnVeAqE6

Random engine photographs. In the engines defence the bores look and feel better than these photos suggest. Clearly not brand new though...

Indeed, looks very good for a CIH. Pistons have very little wear markings

[cam.in.head]

2.4 engines / fronteras pop up now and again on eBay as you say as either cheap runaround so or mot failures. 

Also if you are lucky a low mileage example may be found as I did a few years ago that didn't need anything doing to its engine apart from a basic overhaul. New front and rear crank oil seals and valve stem seals so engine didn't need dismantling. Although low mileage examples are getting harder to find !

reassemble your 2 litre and any advice you need is here on the forum to get it all up and running. That's what we're here for !

[Nivlek2525]

1 hour ago, cam.in.head said:

2.4 engines / fronteras pop up now and again on eBay as you say as either cheap runaround so or mot failures. 

Also if you are lucky a low mileage example may be found as I did a few years ago that didn't need anything doing to its engine apart from a basic overhaul. New front and rear crank oil seals and valve stem seals so engine didn't need dismantling. Although low mileage examples are getting harder to find !

reassemble your 2 litre and any advice you need is here on the forum to get it all up and running. That's what we're here for !

Thanks. I generally keep an eye on prices and I've seen a couple lately for sub £1k. Both running and driving. I've read 2.4 bores wear on anything over 40k miles but if a low-ish mileage one could be found I'm sure there would be some life left in it.

Could a 2.4 crank and pistons be put in a standard 2.0 block or are the blocks different? 2.0 blocks are more plentiful and might be cheaper than a rebore. Just thinking allowed.

 

[Jessopia74]

38 minutes ago, Nivlek2525 said:

Thanks. I generally keep an eye on prices and I've seen a couple lately for sub £1k. Both running and driving. I've read 2.4 bores wear on anything over 40k miles but if a low-ish mileage one could be found I'm sure there would be some life left in it.

Could a 2.4 crank and pistons be put in a standard 2.0 block or are the blocks different? 2.0 blocks are more plentiful and might be cheaper than a rebore. Just thinking allowed.

 

Yes, you can re-crank the 2.0 block, but some slight modifications for the throw is needed, a little due grinding, very minimal stuff.

The 2.3D crank can also be used, but the journals are wider/larger so a bit of modification needed. 
I read a thread ages ago on a forum, will find my link and add it as it has some great info as the guys over the pond have issues with parts they need to find alternative solutions .

edit to add link, although thier forum seems to be down atm, usually us up.

https://www.opelgt.com/threads/modern-2-5-2-7l-engine-build-thread.101865/page-6

😎

Edited October 31, 2020 by Jessopia74
Add link

[611]

6 hours ago, Nivlek2525 said:

Thanks. I generally keep an eye on prices and I've seen a couple lately for sub £1k. Both running and driving. I've read 2.4 bores wear on anything over 40k miles but if a low-ish mileage one could be found I'm sure there would be some life left in it.

Could a 2.4 crank and pistons be put in a standard 2.0 block or are the blocks different? 2.0 blocks are more plentiful and might be cheaper than a rebore. Just thinking allowed.

 

Its probably not worth spending the money on modifying the 2.0 block, better off just getting a high mileage 2.4 and having the rebore, as you would need to buy the pistons and rods to fit the 2.4 crank in the 2.0 block and there are the expensive part and you will need to go 95.5 i expect even on the 2.0 unless that is very low mileage and you can get away with the standard 95 pistons. Just worth keeping an eye out for a cheap 2.4 and if one comes along buy it and keep it and work on it while you have the 2.0 in the car and running.

Loads of 2.4 engine talk on the Opel GT forum (https://www.opelgt.com/) (best to sign up so you can see it all and ask questions) there are some real CIH experts over in the US but that's probably because they can get anything machined and quite cheap over there.

Got a bit of info on my blog http://www.theopelproject.com/ that might help.

and as Jessopia74, says. Just ask on here if you need any info.

 

Andy

[Nivlek2525]

Update. I decided just to put the old rings back in and see how I get on.  I cleaned everything up in particular the groves in the pistons and put everything back exactly where it was.  It certainly looks nicer.

 

 

 

I then decided to fill the bores with white spirit (it's what I had to hand) to see how fast it run through. Nothing did. I waited about 10 mins and not a drop. I would have expected it to work its way through the gaps in the rings pretty quickly. So that feels like a bit of a win??? I know theres no pressure but it must have a some sort of seal. 

 

 

Edited November 7, 2020 by Nivlek2525
Edit photo

[IanMc]

You still have a little bit of carbon you could remove on the piston crowns. Every little helps!  

[Jessopia74]

Sounds like a very respectable seal

[Nivlek2525]

1 hour ago, IanMc said:

You still have a little bit of carbon you could remove on the piston crowns. Every little helps!  

Excuses time. 4, 3 and 2 are pretty much as clean as I could get them. 1 was the last one I did and I was rushing to pick the kids up yesterday. The piston side and ring grooves are spot on but the crown could be better on that last one. I found I couldn't clean it off and had to polish them with metal polish. If I'm honest I was getting a bit fed up as I'm half expecting all this not to work.  Hence I was quite pleased when solvent didn't just pour straight through.

I shall be out there tomorrow Ian with the autosol to touch up the last piston😜 

26 minutes ago, Jessopia74 said:

Sounds like a very respectable seal

Time will tell. I'm off next Friday so might be able to get the head on and get a feel for seal when I turn it over.