changing liners and pistons

[Lord Flashart]

Hi all,

 

I'm looking at changing the pistons and liners at some point in my TR4.

Is there much of a difference in power from standard when using the bigger liners?

Also what is the displacement in CC of the standard engine when fitted with 89mm liners and pistons. Or how do you work it out?!!

 

Paul

[ianc]

Using measurements in millimetres, the formula is (and I'll use [pi] for the symbol, which has a value of 3.1416 to 4 decimal places):

 

([pi] x bore x bore x stroke)/1000

 

Stroke is 92, so this gives:

1991 for 83mm, 2088 for 85mm (Vanguard), 2138 for 86mm bore, 2238 for 88mm, 2289 for 89mm etc.

 

Ian Cornish

[ianc]

To answer the other part of your query, bigger bore gives greater torque - and torque is what makes a great road car. See my article in TR Action 238, Ocober 2009.

 

Some work on the cylinder head (to improve the shape/breathing) and you'll really notice the benefit!

 

Be aware that increasing the bore (and doing nothing else whatsoever) will increase the compression ratio - see my article in Technicalies CD, Section P2. Note that we didn't have the 88mm and larger liners when I wrote the article in 1972, so you'll have to do the sums for those yourself!

 

Ian Cornish

[ianc]

Just in case someone with a car having other than 4 cylinders should attempt to apply the capacity formula given above, this is the generalised form, where "cylinders" is the number of cylinders:

 

([pi] x bore x bore x stroke x cylinders)/4000

 

As can be seen, for a 4-cylinder engine, this simplifies to the form I gave previously.

 

Ian Cornish

[TR 2100]

Hi all,

 

I'm looking at changing the pistons and liners at some point in my TR4.

Is there much of a difference in power from standard when using the bigger liners?

Also what is the displacement in CC of the standard engine when fitted with 89mm liners and pistons. Or how do you work it out?!!

 

Paul

 

Not a difficult job but more messy than you may think.

There is always so much gunge that builds up between

the liners and the walls of the block and you have to

make sure this does not find its way into the sump.

 

And - if you are doing this job, it would be a wasted

opportunity if you didn't really clean the inside of

the block, including all the oilways.

That leads to an engine out exercise.

 

More torque with larger bore but you would certainly

need to add a 4-branch to make it worthwhile.

The standard manifold restricts the breathing too much.

 

AlanR

[Tr4Tony]

Hi

 

Displacement is 2288mm i.e. 100 more than the standard 'homolgated 87mm plus 40 thou (which is 2188 as per the Works TR4's).

 

If you are going to go down the 89mm route it is worth your while fitting VERY good pistons, something like WISECO or Venolia etc. There are cheaper alternatives but my experience has been troubled. Steve Hall at TR Enterprises has a view on this from his experience of building a lot of 89mm engines for customers, so well worth talking to him. As Ian says the gains are mainly torque which is of most use in pretty much anything but a race car, but you definately go gain some bhp if you like those numbers.

 

Bear in mind with 89mm P&L that the head needs to be appropropriately modified and you will also want to look at the inlet and outlet manifolds to make use of what you are paying for. Moving the fuel air / mix in and exhaust gas out more efficiently is where the real gain is to be made.

 

Regards

 

Tony

[graeme]

Hi Paul,

 

My car is fitted with 89mm P&L and I like the increase in torque they give. However, I have also done work on the head, manifolds and fitted an uprated camshaft.

 

I will be relocating to Vancouver Island later this year with my car (and I think the wife is coming too ). If you are not in a hurry to fit new P&L, we could meet up some time and you could compare my car with yours.

 

Cheers

 

Graeme

[Lord Flashart]

Cheers guys,

Lots to ponder over!

 

Graeme,

 

where about in the North East are you from? I'm from the west end of Newcastle! I'm married to a Canadian which is why I live in BC. I have to say though I hope you've visited Canada lots before you decided to move here. I'd move back home again in a second if finances allowed!!!

 

Paul

[TorontoTim]

I have to say though I hope you've visited Canada lots before you decided to move here. I'd move back home again in a second if finances allowed!!!

 

 

Wow - are you mental? Maybe it's a North East/BC thing - I wouldn't move back to London from Toronto without a lottery-payment bribe!!

[Lord Flashart]

Maybe it is. I'd love to move back to Northumberland! The place I live here is beautiful but very very dull! I'll be home eventually!

 

Paul

[mfperks]

Going back to the original question ----

 

I fitted JE 89mm P&Ls during the engine rebuild, getting the old liners out was "interesting".

Having then removed the rust cake in the block, masses of it came off in big black scabs, I then used one of the intact liners to lap the bottom seal area.

I then machined said liner to use as a step cutter to open out the solid copper gasket and finished with a file.

Gasket for use with the stage 3 alloy head is 2 mm thick. This gives me just over 200psi compression, fine for unleaded and a road car.

Note however that with a modified head, you will also have to relieve an area of liner and gasket to allow the inlets to work, pic attached. Assembly is not a slap it on exercise.

 

You will also need to asses what you want from the car, at 5000rpm we had 110bhp at the wheels and rising rapidly ------ but --- low down punch was only average, so to get a move on you needed to rev the nuts off it, on a road car?

Having chocked down from 36mm to 34mm and re jetting, we now have 106bhp at the wheels at 4750 rpm, but a huge increase in mid range torque. They would not measure the torque on the RR, as the amount of braking to pull the engine down was judged unwise with the risk of clutch damage or similar.

The car now pulls well where you most use it, in the middle band, I do not have a steel or nitrided crank so I am sticking to the 5000 limit, although for "special occasions" we can go higher.

Hope that helps with your deliberations.

 

[Lord Flashart]

All interesting stuff. The parts I'm looking at come from moss and they claim that no machine work is needed. Is this the case or is it the usual moss bovine excrement?

[stuart]

All interesting stuff. The parts I'm looking at come from moss and they claim that no machine work is needed. Is this the case or is it the usual moss bovine excrement?

 

What size did you settle on in the end? and did you get a head gasket to suit them.

Stuart

Edited August 18, 2010 by stuart

[Lord Flashart]

Stuart,

 

Not got any yet. I'm just exploring the concept for a winter project. Machining here is a little difficult to get to and even then I'd be dealing with people to whom a Triumph four cylinder is not exactly familiar!!

 

cheers

Paul

[TR 2100]

All interesting stuff. The parts I'm looking at come from moss and

they claim that no machine work is needed.

Is this the case or is it the usual moss bovine excrement?

 

No - machining is not required.

 

I would think 89mm pistons and liners are a bit more extreme

than you would be looking for anyway, but the solid copper

head gasket can cope with these without further work.

 

In the photo above, the liners have been relieved to match

the head but, unless you fit the largest possible oversize

inlet valves (not really suitable for anything but a race/rally

engine, and even then arguable) and therefore have to open

out the combustion chambers to match, this 'machining'

work isn't necessary.

 

I did something similar on my first TR4 rebuild - I didn't

realise the cons then - but it's just a matter of an electric

drill and grinding wheel (and a lot of care!)

 

AlanR

[mfperks]

No - machining is not required.

 

I would think 89mm pistons and liners are a bit more extreme

than you would be looking for anyway, but the solid copper

head gasket can cope with these without further work."

 

Alan, I agree totally that to fit the pistons and liners in the requires no machining. The heads I have (call me Zaphod) are both modded, the alloy is supposed to be stage 3 and the cast one "looks" the same, so in this instance the gasket interferes with the combustion chamber profile.

 

The solid copper gasket I received was bored with 87mm holes, now perhaps that .040" circumferential protrusion into the combustion area is acceptable, I don't know, BUT I wasn't comfortable with that scenario so opened them up to 89mm.

[Badfrog]

What I'd love to see for real is one of these 2.7L engines made by Kas Kastner with the sideways displaced bores to save wall thickness.

 

Badfrog

[mfperks]

What I'd love to see for real is one of these 2.7L engines made by Kas Kastner with the sideways displaced bores to save wall thickness.

 

Badfrog

 

 

I believe these are Citroen parts? But there would be a "bit" of machining in this instance.

I think I read some years ago that welding the liners in situ was a popular practice.

[TR 2100]

The solid copper gasket I received was bored with 87mm holes, now perhaps that

.040" circumferential protrusion into the combustion area is acceptable, I don't

know, BUT I wasn't comfortable with that scenario so opened them up to 89mm.

 

I would have done the same - you don't want anything protruding

into the combustion chamber. Not so much a matter of gas flow

but any edge is likely to cause a hot spot and pre-detonation.

 

When I did my engine before, solid copper head gaskets weren't

available - I had to use the old steel gasket and even then,

I had to remove some material from the gasket. Quite a bit!

 

Now, solid copper head gaskets are available to suit 89mm liners

without any further work.

 

AlanR

[jellison]

http://www.johnmaherracing.co.uk/enginecalc.htm

 

92x92 - MMmm nice.

 

89 is the best for a cooking road lump though.

[graeme]

Graeme,

 

where about in the North East are you from? I'm from the west end of Newcastle! I'm married to a Canadian which is why I live in BC. I have to say though I hope you've visited Canada lots before you decided to move here. I'd move back home again in a second if finances allowed!!!

 

Paul

 

 

Hi Paul,

 

I live near Middlesbrough, do I need to say more!!! I don't know how long you have been there but this country is going to the dogs.

 

We fell for BC on our first visit in 1980, and have visited many times, its just taken us a while to get there

We have had a house in Nanaimo since 2005.

 

Cheers

 

Graeme

[Lord Flashart]

I guess moving from Middlesbrough makes sense! I lived here for three years, moved back to England for two years, wife got homesick, so we moved back here a year ago. We are in the interior of BC. I've got a couple of mates who are from Vancouver Island and they all say it's the nicest place to live in BC. We'll be here now until my little girl leaves school, she's only three so it'll be a while. Then the plan is to move back to Northumberland. Good luck and drop me a line when you arrive.

 

Paul