Big Bore Kit

[Bill Robinson]

Gentlemen, the previous owner seems to think that a Big Boar Kit was installed on this motor. Recently after removing the head I was able to analyze the piston and found the following information stamped on the pistons:

18510 STD

ESF

Can anyone confirm the size of these pistons for me?

Thanks

 

[kob666e]

Check item 52

 

http://www.moss-europe.co.uk/Shop/ViewProd...ateIndexID=2059

[david ferry]

Bill,

 

I would advise you to measure the internal diameter of the liners. That will tell you all you need to know about the size. It will literally take seconds to do, less time than it takes to read this post!

 

Good luck

 

David

[BrianC]

Check item 52

 

http://www.moss-europe.co.uk/Shop/ViewProd...ateIndexID=2059

I assume 89mm is as big as you can go (what capacity does this equate to?) and it's interesting that there are no 'rebore/overbore' sizes (e.g. +0·020", +0·030", +0·040") at this end of the scale. Not that there seems much point having them at any of the more normal (e.g./83mm or 86mm) sizes, as I've been told in the past that it's either not possible or not cost-effective to rebore the liners and fit the next size piston, but to always replace with a piston and liner set. Which begs the question, what does one do with a load of old liners?

 

[Just done a quick fag-packet calculation and 89mm pistons seem to be about 2289.76cc unless the piston height and shape are significantly different. So, if my rusty maths is correct, I assume the really humungous capacities I've seen bandied about require boring/machining of the block to accept larger external diameter liners?]

Edited June 13, 2008 by BrianC

[marvmul]

Gentlemen, the previous owner seems to think that a Big Boar Kit was installed on this motor. Recently after removing the head I was able to analyze the piston and found the following information stamped on the pistons:

18510 STD

ESF

Can anyone confirm the size of these pistons for me?

Thanks

 

Bill, these pistons have 87mm diameter, giving 2186 cc capacity. It's the biggest standard capacity piston in a 4 cylinder TR engine,

though the 'original' standard diameters are 83mm in the TR2-3 and 86mm in the TR4-4A. For some obscure reason you can order 86mm + 0.040" (1mm) overbore or standard 87 mm from AE : it's teh same diameter, yet the standard 87mm is a lot cheaper in the Moss price list than the 86mm+1mm!! AE are very good quality cast pistons.

What is big bore in a 4 cylinder engine? (although 'big bore' is no TR parlée) : 86 and 87 mm are big bore in a TR2-3A, not in a TR4(A).

89mm kits are available and are fitted in the engine without need for machining the block. In a couple of months I will have finished a 92mm bore engine for my TR3 race car :a mr. C. Nuyts from Antwerp has welded steel liners in the block and bored to accept 92mm very light forged JE pistons. The liners are coated with Nicasil. The pistons are a 'standard' JE type, and C. Nuyts made special rods to it (Carrillo type). Standard stroke is 92mm : that will make for 2450cc. I've also a stroked crank for this engine : 94mm instead of

92mm : that would be a real big bore kit with 2550 cc, but the race organisation doesn't allow stroked cranks, so mr. Nuyts made a 92mm crank, with dummy mains, 8 counterweights and small big end bearing pins (in width and diameter).

[BrianC]

Bill, these pistons have 87mm diameter, giving 2186 cc capacity. It's the biggest standard capacity piston in a 4 cylinder TR engine, ...

Yes, I've just realised the 89mm piston set in the Moss catalogue is AE18510X, although the 87mm set is AESA1710KR.

So, what is the difference between Bill's AE18510 and Moss' AESA1710KR?

[marvmul]

I put something wrong in my first post : the 87mm standard piston is more expensive than 86mm+0.040" oversize and the reason is that "87mm standard", the pistons fitted in

Bill's engine, are manufactured by AE, the oversize pistons are not, but they do have AE in their partnumber.

Bill's pistons are definitely 87mm, I've a spare set with the same inscriptions in the piston heads ( except for GUF instead of ESF) .

AESA1710KR is the part number for 1 piston87mm + 1 liner, as fitted in Bill's engine : this is correctly printed in the old Moss catalogue, but in the new catalogues, this number is used for the same piston WITHOUT the liner.

AE18510KR is the part number for the piston in AESA1710KR, without the liner, the number on the piston top is AE 18510 STD (followed by ESF or something else : maybe

this has to do with the actual size of the piston, to get the right clearance with the liner)....

[Alec Pringle]

Hi Brian,

 

from memory, AE18510 was the old 'overbore' designation for the 1991cc TR2 and 3 engine, pistons which came in STD and I think 030 and 040 only ? Liners came only in STD, (2746?) and if necessary they had to be bored out.

 

I can't remember if STD was 86 or 87mm, I think possibly the former, but in any case 18510 was not the same as the 2138cc pistons, rings or liners, which had a different numbering sequence altogether, 15765-8 probably, and came in about 5 different piston diameters.

 

Somewhere I must have a reference to the old numbers, but it might take a bit of hunting out !

 

Hopefully someone with more knowledge of wet liner engines, and a better memory, can offer a more definitive answer.

 

It is, incidentally, possible to rebore liners - they were not, I think, ever avalable in the full range of piston oversizes.

 

 

As for 92mm bore, 94mm stroke, nicasil coatings etc etc - when does 'historic' racing become modsports ?

 

No personal slight towards Marvmul intended, I hasten to add, he's simply making the best of regulations as written.

 

My question is more towards some of the rulemakers, those who seem to extend extraordinary latitude towards what should be 'period' engineering - at least in my view.

 

No doubt this is a debate which could be argued at length !

 

Cheers,

 

Alec