Big Valve engine build with 15 thou pistons

[miked]

I have abandoned my quest to do the Zetec elan S4FHC. I am now into a build on a big valve TWINK. Can anyone advise me. I have obtained an engine and am on with rebuild. The bores and piston are in good condition. It looks like a recent build. The pistions are however + 15. I am told that these have got to be original Lotus as this is one on their odd ball sizes and you can not get them. I am wondering if this is the case and if anyboby has a spare set of rings for the pistions. I can give more info' if anybody thinks they can help. I am ok this time as the rings are not worn. Look like someone did a bore but left the head etc.

Thanks Mike

[steveww]

Burton Power / QED / John Wilcox are all good suppliers of engine bits and advice. If +15 is no longer available why not just go to +20?

The block on my twinc is +40 with liners.

[john.p.clegg]

I may be a heathen but what about trying +20 rings,gapped to suite of course???? Is there that much of a difference????
John

[types26/36]

I think you might get away with regapping 20 thou compression rings to 15 thou but I think you would have a problem with the oil rings, I have doubts it would work.
The 15 thou rings were an original Lotus part and was the only oversize Lotus supplied, I remember fitting some several years ago, I presume you have conacted Lotus to see if they can help? if not a 20 thou rebore might be your only option.
Brian

[miked]

John & Brian, the thought had crossed my mind about gapping up and using the 20 thou rings but I am not clued up enough to know. Will take Brian's advice.

I have not tried Lotus yet, but will.

Mike

[types26/36]

Mike,
The lotus part number for a +15 thou compression ring is A026E 0733
and the oil ring is 026E 6004
If I remember correctly the compression rings could be either 1.5mm or 2.00mm thick but the parts book does not show different ones.
Brian

[Hamish Coutts]

Mike,

I've just completed a rebuild of my twink. It's now +40.
The reason for the rebuild was the previous owner bored the block out 7 thou too big when doing an engine overhaul.
When I bought the car it had been lying inactive for three years. It took a while to get it going and when it did the rumbling waterpump bearing drowned out most other engine noise. When I eventually got the car running properly there was a fair amount of piston slap. An engineer pal said I should strip the engine and have a look - thus the rebuild. To cut a long story short I have a set of +20 powermax pistons that have done only around 12,000 miles and still look like new apart from some very minor carbon stains.
If you are interested in these send me an e-mail [email protected]. I don't want much for them.

The block could easily be honed from +15 to +20 and you would need to fit a new set of rings but that would give you a pretty good engine.


Regards,

Hamish

[miked]

Guys, thanks for your help.
Hamish, tried you on emial re the pistons but cant raise you. Looks like Dave has them. Could you please let me know.

thanks Mike