Pistons

[Hugo]

Is there any consensus on which compression ratio works best with modern fuels? I'm getting stuck in to rebuilding my engine & looking for pistons. Is there a preference for quality? I've found some old-stock Hepolite pistons that are 9:1, otherwise I guess it's going to be Mahle? Anything else out there? It's only for road use, but I want to do the job once only and I do not want to be listening to any mechanical noise when it goes back on the road, so cost is not really a factor.

[Heuer]

Depends which fuel you intend to use. The 9:1 requires Super Unleaded 97+ (BP Ultima, Shell V-Power) although those fuels should be the default for any E-Type owner because they contain less/no ethanol which plays havoc with SU diaphragms. With 8:1 you can get away with 95 Unleaded with some loss of power. My car is running 9.5:1 although with the EDIS/Megajolt I can switch to a different map if I have to fill up with ordinary unleaded. Shell V-Power Nitro+ is my default fuel as it is about 100 octane.

[politeperson]

I used +20 8:1 Mahle pistons. Compressions are (now) 195psi on each cylinder. My head has had one light skim.

Seems good to me. No pinking or other dramas.

[christopher storey]

My cars are 1 with 9:1 , unrebuilt, and 1 completely rebuilt with nominally 7.8: 1 XJ6 pistons, which actually allowing for some refacing probably equate to 8:1. The 8:1 is far and away the nicer engine, although some of that may be due to the fact that I had every component accurately statically and dynamically rebalanced, but also, it is undoubtedly more powerful than the 9:1 engine and does not pink. Frankly, these cars are not really about performance, which irrespective of your specification is still stunning today, so I would always go for the smoothest spec, but if the hepolites are in a size which will fit, I would go for them

The other manufacturer which , certainly a few years ago, did splendid pistons for jaguar, were JE, at that time in Australia

[Hugo]

That chimes with my philosophy. Unfortunately the Hepolite Pistons (eBay item 322575067333) are 9:1. The seller lists them as .3 oversize, which I suppose means +30. The same seller (etypeparts) also has a set with a brand name I've never heard of - 'Covmo' (also made by AE). These are standard bore and unspecified CR.
Barratts are selling Mahle sets for just over £300.
I have bought myself a couple of Chevrolet Corvairs over in Florida. There is much talk about 'Eutectic' pistons for those engines, but also rumours that they can crack under detonation, a problem from which they also appear to suffer along with the E Type.

[christopher storey]

If Mahle sets now are £300 from SNGB , I doubt that you will get better value anywhere

[Hugo]

Yes, I was amazed at the price too - and big end shells are less than £40 a set. I'm still trying to find out what size my bores are - I'm fairly sure the engine hasn't been touched from new, and I measured the bores at a tiny fraction under 3.625". The only markings on the piston are "G" on the right side of the crown; "T 15" on the front of the crown, and "C 28087" at the back of the crown.
I've been trying to look up JE pistons but I find their website utterly impenetrable. Welsh Enterprises sell both Mahle and "County" pistons (whoever they may be). They had a picture of some 3.8 pistons with a lower oil control ring, but no pics of the 4.2 pistons. XKs Unlimited sell pistons which give the manufacturer as "XK Unlimited", which I find highly improbable. Terrys Jaguar spares, just to be different, lists pistons at either 7.8:1 or 8.7:1. Rob Beere lists some exotic-looking pistons which are a bit OTT for my requirements.
The search resumes on Monday when I can do a bit of phoning around (most suppliers very incosiderately close for the weekend!).
Oh, and Rob Beere lists those pesky crankshaft plugs at something like £35 a set. XK's Unlimited want $18 EACH for them. I'm trying to figure out what they're made of - when I drilled the one remaining one out last night it felt like alloy of some sort, but the weight feels like steel. Certainly very soft steel if that's what they are. Does anybody happen to know what they are?

[JagWaugh]

Oh, and Rob Beere lists those pesky crankshaft plugs at something like £35 a set. XK's Unlimited want $18 EACH for them. I'm trying to figure out what they're made of - when I drilled the one remaining one out last night it felt like alloy of some sort, but the weight feels like steel. Certainly very soft steel if that's what they are. Does anybody happen to know what they are?

Probably just a mild free machining steel unhardened. They are staked after installation, and since the crank is hard as nails it's the plug which has to do all the distortion.

[christopher storey]

Hugo : Terry 7.8 pistons are for S2 XJ6 and 8.7 are for the fuel injected S3 XJ6. If you want 8:1 the 7.8s will be the nearest you can get now

The G on some of your pistons will almost certainly be the graded size from the time when the job was done properly and pistons were individually matched to each bore. C28087 is the Jaguar part number

County stuff comes from India. I have used various County bits eg Water Pumps and despite an anecdotally bad reputation ( usually unsupported by any evidence) they have been satisfactory ( famous last words)

[Hugo]

Indian huh? Much as I love the Indians, some of the stuff they turn out is just appalling quality. Most Morris Minor spares are readily available and ridiculously cheap, but of course they're made in India (or Sri Lanka in the case of body panels). I had a Sri Lankan van chassis once that was at least half an inch too narrow. Only two of the cab mounting bolt holes lined up - the rest weren't even visible. It's not a question of easing the holes with a file - they were half or three quarters of an inch from where they should have been. It was as though the whole thing had been put together by eye without any measuring device. And as for the A pillar that the door hinges bolt to, that was at completely the wrong angle & placed the door back by two or three inches! It took longer for my panel beater friends to make them fit than if they had made the panels from scratch!
Mind you, I'm old enough to remember when "Made in Japan" was a joke.
What about COVMO pistons? Have you ever heard of them? I never have. Made by AE according to the seller.
At the moment I'm going to call JE pistons tomorrow and/or Rob Beere to see what they can offer, and it will be a choice between theirs and Mahle from Barratts.