Hi all, I have been offered a 3.4 block that has been machined and line honed and comes with new County brand pistons and rings. I’ve not had any experience with County pistons. Always used Mahler stuff in the past. Does anyone have any experience of County pistons? They are around 40% cheaper than Mahler pistons. I am a great believer in you get what you pay for but if the COunty ones are fine, I’m not adverse to saving some money.
County is a copy of AE Hepolite pistons, but made in Taiwan. There is a lot of experience with them on Triumph, MG and Mini forums.
Thanks Rob. I’ll take a look before I decide
Hi Stephen,
I am also a fan of Mahle pistons and have them in my 52 FHC 3.4 engine. When I was rebuilding my engine I became aware that modern pistons (such as those made by Mahle) have three piece oil control rings that reduce oil consumption so that cars can now go 10,000 miles between oil changes. Mahle was instrumental in the design of oil control rings and has a chart on their website that shows the progression of their design to reduce oil consumption. Engines used to consume a quart of oil in 500-1000 miles (or even less), now virtually nothing. For that reason you might remove a piston and look at its design. My rebuilt engine consumes no noticeable oil between oil changes, a real switch from the old days of checking and adding oil.
Tom Brady
Stephen
I installed County in my 4.2 with 9-1 comp. I did a little research and found they were basically AE.
They seem to be doing the job just fine for over two years now.
Mahle 4-ring pistons were used on my 120’s engine rebuild, and they came complete with rings, but the 2 oil rings are one-piece items.
At first I would get a considerable amount of exhaust smoke (embarrassing!) on start up, which would gradually diminish over a minute or so. I was told by the engine builder that this was because I had the original-style valve guides with no provision for adding valve seals, and it was normal. Now, with a few miles under its belt, there is very little smoke on start up, I’m happy to say.
Hi Chris,
That style piston was used on early 3.4 engines but was later replaced by Jaguar with full skirt pistons without that lower ring. They are still available thru several manufacturers, for the purist I believe. The later design that I used and highly recommend is shown on the right side below.
There has never been a hint of smoke from my engine, even on initial start-up. Regarding valve stem seals, I had them installed on the new bronze intake and exhaust guides.
Tom Brady
The longer skirt would certainly help make the piston more stable as regards rocking movement, and I think the lower oil ring would help in that regard, too. At least, that’s what my very experienced engine builder told me, and he’s built hundreds of XK engines over the decades.
The smoking issue does seem to have abated, now. Next time the head’s off I may well get the valve guides replaced with the type tthat takes seals.