TR3A increasing cylinder bore

[OllieK]

Hi. I have now reached the stage where I need to rebuild my engine. I will need new pistons and liners. If I increase the bore will I need to change other items like the camshaft, timing and carburettor jets? I was thinking of using the 86mm kit from the TR shop. Apparently these are County pistons. Are these an ok make? An advice appreciated. Thanks

[John Morrison]

Not much to change, Crank and Cam - no.

Carb needles - maybe.

County stuff been around years and is fine for road going Tr's, perhaps a re-think if you 

were going Hard Racing.

John.

[Hamish]

If I was doing the change you are proposing I would consider 87mm. I had this on my last engine that was done in the ‘80 and was great for the OP and me.

H6 carbs just rejetted 

[Kiwifrog]

Been running the 86mm county  liners and pistons in my engine for over 10 years with no problems, the carbs did need their needles to be changed though, standard cam and standard crank.

cheers

Alan

 

 

[Ian Vincent]

I agree with the replies above. For everyday motoring County pistons and liners (87mm bore) have worked fine for me since 2014. 

Rgds Ian

[Andy Moltu]

The currently available 89mm pistons & liners are used as the standard build by the TR specialists.

The supplied pistons are decent quality and the package gives improved low end torque with the other items left standard. The pistons are significantly lighter than standard 86mm offerings.

[Lebro]

You will need a special head gasket though, not the case with 87mm

Bob

[Andy Moltu]

Not that special.

I use the composite head gasket as supplied by TR Shop, TRGB and others.

The problem with these engines and head gaskets is rarely the liner size (unless you go 90+) but the heads themselves. To aid flow some of the head tuners get overly aggressive with grinding away the shrouding around the inlet valve. Leaving not much to compress the fire rings.

[OllieK]

Hi guys, just received my 87mm pistons and liners. Thanks for your advice! I have H6 SUs. What do I need to do regarding the jets/needles? 
 

also I’ve been trying to find Vandervell bearings, standard size. King bearings are available. Has anyone used these? Are they any good? 
 

thanks, Ollie

[Lebro]

KIng seems to be the standard offering these days for new shells. I managed to find som NOS Vanderville ones but they were not in mint condition, being rather old.

Still working ok though.

Bob

[Ian Vincent]

On 6/19/2025 at 6:07 PM, OllieK said:

also I’ve been trying to find Vandervell bearings, standard size. King bearings are available. Has anyone used these? Are they any good? 
 

thanks, Ollie

King bearings seem to be all that are available nowadays.  They work for me. 

Rgds Ian

Edited June 20 by Ian Vincent

[iain]

34 minutes ago, Ian Vincent said:

King bearings seem to be all that are available nowadays.  They work for me. 

Rgds Ian

+1

[RAHTR4]

Ollie,

You have a P.M.

Richard

[Rob Salisbury]

Hi Ollie,

             For Vandervell shells Google Basil Adams, a College Prof in the States, he set about buying up the entire Universe supply of Vandervell shells some time ago and,at a price, may have what you want, I've had several NOS sets from him in the past.

Cheers Rob