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I am restoring a '62 997 and have quickly realised it's an uphill struggle with regard to the engine.
The most helpful advice received so far is to make a coffee table out of the block and fit a 1275.

But I'm determined to make something special out of the original engine and hence the question.

The block is already at +0.060' and anyway 997 pistons are pretty much not available as far as I can see so I'm going down the old Speedwell route of boring out the block and have obtained a set of Russell Engineering 1100 +0.040' pistons.
I calculate that this will give capacity of 1098cc - a kind of short stroke 1100.

I believe Speedwell used 67mm pistons and sleeved the block. Mine are 65.6mm so should I use liners or will a big over bore work (about +0.130')?
Any one had any experience? No more coffee table advice please!

It depends if you have the early 12A 204 block or the later 12A 497 one .

The later block is the same casting as the 998/1098 so should be good for up to +60 .

997 pistons are available if you know where to look

251 ENG wrote:
997 pistons are available if you know where to look

Nice plugging

No, just good business...

Not the clearest image but it's definitely a 12A 204.

You could also sleeve the block back to stock 997 bore sizes. Good quality 997 NEW Pistons are available in all sizes.

From memory you'd need to take a fair lump off the crown of 1100 pistons so they don't poke their head out, so watch out for too thin a crown thickness or putting the top ring too close to the crown

1098 pistons have a very short compression height .

You need to deck the block about 0.050"

The pistons from OZ that minispares / calver sells are quite good .

Don,t use JP pistons though

251 ENG wrote: Don,t use JP pistons though

Oh, why is that?

251 ENG wrote:


The pistons from OZ that minispares sell

simon

we dont sell these anymore unfortunately, i think keith still has some though

Don,t use JP pistons though.

Never a wiser word has been said

All I will say is I have bored and honed 100,s of A series blocks with no major problems with smoking or oil usage .

Did one engine using JP 1098 and it used more oil than petrol

ace01 may want to to add something to this .

Used quite a few of the piston Calver has and not had any issues with them .

ENG 251, Sorry to hear that you've had that experience from a great piston. Did you look in to why?

I've fitted a lot of brands of pistons over the years and never had a problem with JP's, they are a very good piston. They have a wide choice of rings available too, although, depending on the application, I don't always use their rings, but then, that's true of just about any piston out there. Many of the front running racers in Australia have tried many of the popular brand (and some not so popular) and most use JPs.

Interesting to read the above as I have only used JP's once & had similar problems to the one Simon describes.

It was on an over bored small bore block that ended up smoking like Bill Hicks.

M

Thanks for the replys.

I'm happy with my pistons (which also come from the land Down Under) but am still not sure if the block will take such a big re-bore.
My options as I see them are:
1. Bore the block to suit the pistons then visually check (and hope for the best). If no good then move to option 2...
2. Go for liners with a known wall thickness and material integrity
3. Abandon the block and use a 998/1098 block

It all depends on your budget really.

If I was you I would discuss your options with Simon (251ENG) he has a vast experience of this type of conversion.

M

251 ENG wrote:All I will say is I have bored and honed 100,s of A series blocks with no major problems with smoking or oil usage .

Did one engine using JP 1098 and it used more oil than petrol

ace01 may want to to add something to this .

Used quite a few of the piston Calver has and not had any issues with them .

Thanks Simon, I was keeping my head down there.

I have never seen an engine smoke quite so much. Changed the rings twice and then gave up.

Yes I think the rings were the main issue ,

Would be interested to know which rings other people use on JP,s

It,s not like there cheap , think they cost over £300 a set which is nearly omega money

Going back to boring the early 997 ( 12A 204 ) block out to large size,s , Hepolite used to do a piston to bore 997.s out to 1095cc .

This was something like a 0.120" overbore so there must be a fair bit of metal in the blocks . Did have an engine with them in once but they had used a later thick flange 12A 497 block and fitted liners . I have fitted extra large liners in to 12A 204 blocks before that have had std liners that were damaged . Never gave any trouble .

Thanks Simon et al

I ordered cylinder liners today. I'll post how I get on when it's done.

Lakeland997 wrote:
I'm happy with my pistons (which also come from the land Down Under) but am still not sure if the block will take such a big re-bore.
My options as I see them are:
1. Bore the block to suit the pistons then visually check (and hope for the best). If no good then move to option 2...
2. Go for liners with a known wall thickness and material integrity
3. Abandon the block and use a 998/1098 block

If you bored the block to suit the pistons, you could have the cylinder walls sonic checked for thickness to tell you if you were getting into dangerous territory.....I think anything less than 0.100" is generally considered undesirable.

There are also plenty of piston manufacturers on this side of the pond that could do up a set of custom pistons to any spec you like....they aren't the cheapest option, but they aren't as expensive as most people think. The last person I knew had a set of forged Ross pistons done for his Datsun 1600 roadster for about $500-600. By the time you've sleeved a block, you could be talking 6 of one, and half a dozen of the other.