liners in v8 250 block

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TWF
Posts: 34
Joined: Wed Mar 09, 2016 7:10 pm

liners in v8 250 block

Post by TWF » Fri May 18, 2018 1:03 am

Hi, I have recently purchased a v8250 block with the pistons ,on inspection I realised that it has liners installed which looked to be in excellent condition and my first thought was to re ring the pistons and reassemble it, however on closer inspection the pistons are quite sloppy in the bores and I have been told that the liners are slightly oversize by .003" to .005". my question is, would it be ok to bore the liners and fit + .010" or + .020" pistons , Regards ,Terry.

Ian Slade
Posts: 384
Joined: Sat Feb 13, 2016 9:54 am
Location: Akrotiri Cyprus

Re: liners in v8 250 block

Post by Ian Slade » Fri May 18, 2018 6:18 am

Before you do anything, measure the pistons and the bore and check against recommended sizes, the pistons are not that tight in the bore when cold. With a 20thou oversize bore you are removing 10thou / side of the liner, you would need at least a liner thickness of 20 thou after a rebore probably 40thou for reliability.
Owner since the 70's, Genghis is slightly to my left.

tjt77
Posts: 371
Joined: Wed Mar 23, 2016 7:01 pm

Re: liners in v8 250 block

Post by tjt77 » Sat May 26, 2018 10:32 pm

Liners were fitted at factory in some blocks..common reason was the original boring went 'over' tolerance.. ALL the 3.8 jaguar blocks had liners fitted in order to ensure minimal 'issues' with what was considered a large overbore on a block designed for 3.4 litres.... and the material in liner used is much harder and more durable than cast iron.. so I'd say you have a 'better than average' block..
Yes you can rebore it.. up to +.060" is fine.. you could likely take it out +.080" quite safely.. ( the wall thickness of factory fitted liners is well over .100"... a +.080" rebore would only take .040" out of the liner wall.. leaving the liner wall thickness +/- .060".. close to 1.5mm )
I'm just in process of building one up here ..aquired 2 dismantled engines with all parts cleaned up recently so I could see exactly what I was purchasing....one of which had a linered block.. both were standard on all dimensions with OEM pistons and bearings .. but bores between .003 and .004 oversize after honing and some pitting from corrosion present.. so both will end up bored oversize.. I have the first one back from machinists as of thursday..

TWF
Posts: 34
Joined: Wed Mar 09, 2016 7:10 pm

Re: liners in v8 250 block

Post by TWF » Wed May 30, 2018 9:10 pm

Hi ,thanks for your replies ,I am not looking for any extra cc so am only going up to +.010",the first cylinder was bored today and looks good . Regards ,Terry.

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