Engine size ? / piston damage

[westy24]

Hi all , i have a little problem , I'm restoring a minor (Barrie s project ) now ,the problem is I haven't aa clue what size engine it has ,is there any way of knowing bby looking at the engine it's self . The car 1956 split screen ( originally an 803cc ) my grandpa fitted a larger engine and I can't for the life of me remember what he had fitted and sadly he's no longer with us to ask . On the engine there is a large raised 950 would this mean 948 cc ? Iv fully stripped the engine down to rebuild it (taking photos as I go ) !! . Also one of the pistons has damage to it and needs replacing would you recommend replacing all of them or just one ? And finally where is the best place to find pistons and ring sets ? Hope you can help , il upload photo if needed
Thanks baz

[bmcecosse]

Yes - you have A 948 engine there. As long as the bores are ok - just replace the damaged piston, but probably wise to put new rings on ALL the pistons. Perhaps someone on here will have a good secondhand piston to help you out - always worth asking! Best to 'glaze bust' the bores before fitting new rings. Just some emery round your hand (if it will go down the bore) and up down motion to make a 45 degree criss-cross pattern is fine. Remove all traces of emery afterwards, of course....

[daveyl]

I'm fairly sure I have some spare 2nd hand pistons available if you require them. PM me if you need any.

[bmcecosse]

There you go! It's a very friendly and helpful forum we have here!

[westy24]

Thanks for your help guys! On the top of the bores there is a slight lip , On all 4 bores , would a engine bore honer be a good tool to use to remove this . Il post pictures tomorrow of the engine . There is a number stamped on the tops of the pistons are any of these numbers important to me when building the engine or finding a replacement poison ? The number ends in -030 ?

[bmcecosse]

It suggests that the engine has been bored out +30 thou. So for the damaged piston replacement - you will need a 30 thou oversize piston. Any lip is best 'reduced' by rubbing it away with emery paper - or at least taking any sharpness away. It's not perfect of course , but if it's just a 'run around' it should keep you going for a good few thousand miles - and a rebore will need to be to 40 thou overbore - with 4 new pistons to match - not an inexpensive move unfortunately.

[westy24]

i have some photos here of the engine, it was in a bit of a state but now its looking a bit better !![frame][/frame]

[westy24]

its hard to believe this engine was running 2 years ago .[frame][/frame]

[westy24]

[frame][/frame]

[westy24]

looking a lot better[frame][/frame]

[westy24]

this is one of the pistons , with the number on top .[frame][/frame]

[westy24]

the top ring was in 3 pieces . and you can just see that its dented the top part of the ring recess . this was the least damaged piston i think !![frame][/frame]

[bmcecosse]

Well done cleaning up the bores! The general condition suggests severe general wear - and a ROASTING... Looks like it has severely overheated. The pistons are non-original - with that extra ring below the pin. Are the other 3 pistons fit for further use?

[westy24]

Well done cleaning up the bores! The general condition suggests severe general wear - and a ROASTING... Looks like it has severely overheated. The pistons are non-original - with that extra ring below the pin. Are the other 3 pistons fit for further use?

i did wonder if these were original or not as iv seen others with less rings fitted , i am wondering if i should replace the lot and be done with it , what would you do?

[bmcecosse]

Well - that one is no use - and you say it is the 'least damaged' = so based on that - they are all no use! What state is the crankshaft in?

[westy24]

i think il have to replace the lot then !! what is the measurments for the original +30 pistons?, and are these pistons when fitted supposed to be tight ish in the bores or should there be a slight gap for the rings to take up the slack ? as you can tell iv never done an engine rebuild before

[westy24]

Hi again , I have another question for you guys , I have found out the size of plus 30 pistons , the size is 62.32 mm , the pistons that I took out of the engine was 63mm ,is this a plus 40 piston ? Iv also measured the bores ,these was 63 and a half mm , which means a gap of half a mil around the piston ,is this to tight? ( I'm thinking it might be as the old piston rings on some of the pistons was broken and overlapping ) . So if I fit these plus 30 pistons (62.32 mm) they should fit with ease and not be to tight ? What do you guys think ?

[bmcecosse]

They were clearly marked + 30 so I doubt they are +40... Why not measure in inches - just in case there is a conversion error going on.

[les]

What are you using to get your measurements?

[westy24]

Hi there , , a bit of progress has been made , I'm getting the bottom end looked at by a professional to be measured and to advise me on correct piston replacement , the person in question is a good friend of my boss Paul Kynaston ( you tube the name also Dave Kynaston A3) my boss is a keen rally driver and builds rally cars all day long and has offered to help me sort my engine out, he said the plus 30 pistons are the wrong size for the bores and would probably need boring out to plus 40 that way the pistons and the rings will be the perfect fit . I did think that measuring in mm may have baffled me a bit ,as you say inches are the correct terms for measuring older English machinery , thanks for all your help and guidance in this matter ,il post the out come as and when .