Olgawld Posted September 30, 2019 Share Posted September 30, 2019 As the xflow is coming out, it's done 34000, for a refresh I thought I'd look at the Piston isue. Was weighing up either just new rings, new 1300+90 pistons and rings etc or going for new forged pistons. Keep hearing about the 1300 pistons being a possible issue, and as they were originally for a 55hp car can understand why, but these have done 34000 miles without beaking up so is it worth the extra expense? If so I've seen a set of forged by a company called JE Racing for a fair price,, anybody heard of or used these? Cheers Link to comment Share on other sites More sharing options...
Tazio Posted September 30, 2019 Share Posted September 30, 2019 Have a chat with Dave Gemzoe, he knows just about all there is to know about big power Xflows. Link to comment Share on other sites More sharing options...
Roger King Posted September 30, 2019 Share Posted September 30, 2019 Yes, yes, yes.I have only used Omega, Cosworth and Accralite, but they have several advantages.They don't break like the standard Supersprint 1300 pistons often do (they were after all, originally designed for around 50bhp at 5500rpm max); the rings seal much better and last far longer; they have much lower mass; they run with greatly reduced friction (to the extent that you can feel the difference when installing them by hand - this is largely down to the rings again); you can run higher compression ratios (depending on the engine spec) in safety.Overall, we used to find a gain of around 10bhp on a Supersprint if we did nothing except change the pistons, largely due to the lower friction and better sealing rings. The lower mass did no harm for throttle response either.There is, of course, a downside - cost. Link to comment Share on other sites More sharing options...
Olgawld Posted September 30, 2019 Author Share Posted September 30, 2019 It's been reading some of your previous posts on this subject Roger which has got me thinking about the upgrade. I don't mind spending a few more bob if it's going to be worth it. The engine's the 1700 ax block. That means it'll bore out ok. What size bores nd pistons do you recommend going to now, 1760, which is 85mm pistons, is that right? Thanks Link to comment Share on other sites More sharing options...
Roger King Posted September 30, 2019 Share Posted September 30, 2019 The AX block will generally go to 85.9mm bore (1800ccm) but there is always a risk that you have a bad'un so it is safer (but not guaranteed) to stick with 85mm unless you are prepared to have your block checked for bore wall thickness. I'm not sure you can even get 85.9mm pistons these days.The 83.5mm pistons will give 1700ccm and this is approx .010" bigger bore than a standard Supersprint which means that even worn bores will probably be capable of being cleaned up if you rebore to that size.Whatever you do, please make sure that you use a properly equipped machine shop that can provide you with a plateau honed bore finish. Decades ago, when we went from conventional honed bores to plateau honed, we found that we had 100% eliminated the occasional cases of smoky engine that used to occur. BUT, there are still plenty of machine shops who don't use the plateaued finish. Link to comment Share on other sites More sharing options...
auyt Posted October 2, 2019 Share Posted October 2, 2019 If can add forged pistons like JE use cast piston Clearance due to the material they are made from, so check with the piston manufacturer what they recommend Link to comment Share on other sites More sharing options...
OliverSedlacek Posted October 2, 2019 Share Posted October 2, 2019 Yes, if the engine is coming apart then definitely worth it. The reduced weight makes the engine rev more briskly and reduces frictional losses. This gives you free horsepower (I was sceptical but it was very apparent) and improved fuel consumption. That makes them really goo value for money. Link to comment Share on other sites More sharing options...
Stridey Posted October 2, 2019 Share Posted October 2, 2019 Well I’m driving a Roger King converted AX blocked 7 done 20 years ago at a not inconsiderable cost of circa £3500, commissioned by a previous owner. It seems to have had the works, Raceco exhaust, Alpha 3D mapping at 17,000 miles. It’s now on 57,000.I love this car with a passion, but looking at the wonderful paperwork I have you can really see it is so much more than just forged pistons.Roger, I salute you! Link to comment Share on other sites More sharing options...
robert green Posted October 3, 2019 Share Posted October 3, 2019 Lucky chap. That will be a fab engine!!!! Link to comment Share on other sites More sharing options...
Stridey Posted October 4, 2019 Share Posted October 4, 2019 Robert, it is. I was very lucky as I don't think I paid a premium over a regular Crossflow at the time, 4 years ago. Here is a bit of the paperwork, which included all the test results, running in procedure and servicing guidelines. Link to comment Share on other sites More sharing options...
Roger King Posted October 4, 2019 Share Posted October 4, 2019 Well thanks for the embarrassment of revealing to the world just how dreadful my handwriting is!If only I'd been a doctor. Link to comment Share on other sites More sharing options...
Drumster Posted October 4, 2019 Share Posted October 4, 2019 I recognise that handwriting . Roger did a great job on rebuilding my x/flow at 21k miles. My AX block was bored out to 1800cc and used 85.9mm Accralite forged pistons and had everything in Stridey's post apart from the 3D ignition. IIRC Roger said that the Caterham's figures of 135bhp were a little optimistic and maybe it was nearer to 125bhp. I would have loved to have gone for the 155bhp spec but funds were not unlimited and was a little disappointed to only 'get' 140.....However, the rebuilt built engine revved freely to 7,000 and the car was transformed, the 140 spec was brilliant, That engine was toured, tracked and sprinted until its untimely demise at 59k miles, absolutely nothing to do with Roger's work but a failed piggy back connector lead to a sequence of unfortunate events. Well worth the money if you want to keep the x/flow Link to comment Share on other sites More sharing options...
Olgawld Posted October 4, 2019 Author Share Posted October 4, 2019 Well I'm definitely convinced now to go the forged pistons route. Best price for the accralite 83.5mm ones are Burton's at just shy of £600 for the set. Anyone know anywhere cheaper, or if there's any good second ones about? Am I right in thinking they already have the right cutouts for either the 234 or 244 cam? I've got a 244 sat in my shed so might put that in as well while I'm at it. I shall use the same rods, with new bearings obviously, is that ok too? Thanks Link to comment Share on other sites More sharing options...
Drumster Posted October 4, 2019 Share Posted October 4, 2019 Sorry, I can't answer with any authority but can at least confirm my engine still used the 234cam and the 86.9mm piston looked like this Link to comment Share on other sites More sharing options...
rgrigsby Posted October 5, 2019 Share Posted October 5, 2019 As an ex-Xflow owner another vote for Roger's advice, I had a 155 spec engine for quite a while and it was a lovely thing to drive. Link to comment Share on other sites More sharing options...
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