engines TR5/TR250

[pfenlon]

apart from the fuel systems what are the differences between the 2 engines.

 

and what is the achillies heel, is it end float crank bearings and rocker oil feed problems.#

 

I am new to this type of vehicle, hope the questions are not letting you all know what a numpty I am!

[Guest ntc]

apart from the fuel systems what are the differences between the 2 engines.

 

and what is the achillies heel, is it end float crank bearings and rocker oil feed problems.#

 

I am new to this type of vehicle, hope the questions are not letting you all know what a numpty I am!

 

Hi Peter and welcome to the numpty club, the main difference is the compression ratio and the camshaft the other problems you mention are common in all

 

Neil

Edited August 8, 2008 by ntc

[Tom Fremont]

Hi Peter,

 

As Neil says plus the TR250 head has different inlet port spacing from any P.I. model, which then standardize on the wide port after 1972 for carb and P.I. Manifolds for triple Webers can be had for either type, but U.K. experts diss the narrow port head for souping purposes, FWIW and of course P.I systems won't retrofit to a '250 head.

[Chris Mountford]

Hi,

 

Apart from the head and cam isues already mentioned, the 250 has a single row timing chain and not the duplex type fitted to the PI cars.

 

The engines, (both) seem to suffer from premature rocker shaft wear and crankshaft thrust washer problems however it is relatively cheap to replace the rocker shaft. However ........The crankshaft thrusts tend to destroy both the crank and the block. The reason for this seems to be sitting with the clutch depressed which in turn puts an end 'thrust' on the crank which forces the washers to wear and ultimately get forced out.

 

I had a dolomite sprint engine do this and I only realised when the oil seals went......on stripping it it had even machined the rear oil seal housing bolts with the flywheel. Total scrap, the only symptom being it stalled on day when changing gear and then restarted when I let the clutch out again (I was still rolling). Most triumph engines of this era seem to have the ability to destroy themselves this way. The 'old' Borg and Beck clutches with really heavy pedal pressure just added to the problem for the 6 cylinder engine. An end float of around 10 thou is OK anything above 20 thou needs immediate attention. If it has an eighth of an inch endfloat then its shot.

Both the 5 and the 250 use the longback crank and these will prove difficult to find nowadays. That will mean a change of flywheel if the crank has to be replaced with a later item...and so it may go on to the point where it is easier to source another complete engine.

If you want to bring a 250 engine upto 5 spec, it may actually be easier to start with an early 2.5 PI saloon engine as a basis. (That is if a 5 or UK 6 engine is not available)

 

Hope the ramble makes sense, and of course others may have different experiences to mine.

[pfenlon]

Hello Neil.Tom and Chris,

 

Interesting info thanks to all of you, I had heard bit but not the nitty gritty, the engine in the car I am buying is Frozen as they say in the USA

 

so until it gets here and I strip it I will have to wait and see if the crank is shot or not.

 

regards

 

Peter.

[jonlar]

The reason for this seems to be sitting with the clutch depressed which in turn puts an end 'thrust' on the crank which forces the washers to wear and ultimately get forced out.

 

Hi Chris, the thrust washers are at the rear end of the crankshaft, so when the clutch is depressed the crank will move forwards.....? It would move back and onto the thrust bearing when clutch is engaged, if heavily worn, one could drop out and into the sump whilst clutch is disengaged?

[marvmul]

In one of his books, Kas Kastner is describing a method to save a block that is damaged in this way. A thicker thrust bearing from a Toyota Supra can be fitted after machining the damaged area. The thicker bearing is compensating for the depth of the machining. The Triumph bearing is only 180°, the Toyota has a 360° bearing, so the main bearing cap must be machined too. The bearing surface now has twice the surface of the original and it can't spin with the crankshaft anymore. This fix can save the block, and the crankshaft too I suppose, when the scoring is not deep.

[jonlar]

I'm not certain, but I think Revingtons do their own conversion.

[Tom Fremont]

A few more things to add:

 

- the single row timing chain was superceded early in the TR250 production by the duplex type. I don't know at which production number.

 

- thrust bearings should last indefinitely if (1) a normal pressure plate is used, i.e. not one requiring tremendous force to release, and (2) if the driver is

careful not to use the pedal except when necessary; i.e. not to keep it in gear when stopped at a light, etc. My current driver has 75,000 miles on its rebuild

with no detectable wear on these. In any case, I thought these were unchanged on the TR6.

 

- the longback crank is fitted with a lighter flywheel than the short ones whose flywheels tend to go on a diet when the engines are modded.

[Bald Rick]

Peter

 

I have an early ex USA TR 6 which has the same engine as the 250. The original camshaft was a 10-50/50-10 with 240 degrees duration. The head is the 516323 head. "Narrow port" I think refers to the inlet port spacing (inlet ports being closer together). I don't think the ports are actually any narrower or smaller in diameter than the other heads. The head was about an eighth of an inch thicker (taller) than the other heads. It has the larger exhaust vaves as in the CP series engine.

 

The main reason this head is not recommended for performance improvement is that you can't fit the later (& saloon type) inlet manifold with twin SU's on it because of the narrow port spacing. This means you are stuck with the original short inlet manifold which is not ideal as you cannot fit SU's to the short manifold. They foul on the steering column! So you are stuck with Strombergs. However there are other options, In addition to Weber inlet manifolds, manifolds for triple SU's or even Triple Strombergs are available from Goodparts in the USA.

 

I have also seen in print that you cannot fit a decent exhaust manifold onto this head. Depending on what you call a decent manifold, the Pheonix 6/3/1 fits perfrectly and should be adequate unless you are looking for every last ounce of power and torque (should that be foot ounces?)

 

My narrow port head is modified to stage 2. I still use the original Strombergs and inlet manifold at present. The engine has a fully balanced bottom end with a lightened flywheel. I have the Pheonix 6/3/1 manifold and single pipe system. The new cam is Vitesse/GT6 with .030" increased inlet lift, and the distributor was custom built by the Doctor!

 

I have no idea what the power output is but it is a lot more than the original 104BHP. I have put in a higher ratio UK diff which slows down the acceleration a bit but the car goes very well. As the engine is loosening up I have started to push it a bit. It will pull 7000 rpm cleanly in 1st 2nd and 3rd although not in overdrive!

 

I hope to get it to a rolling road for a proper set up and test before it goes away for re-juvenation this winter.

 

All of the above is purely based on my personal experience and info found on the net and provided by members of this forum.

 

Good luck with your car and engine

 

Tony

[Guest ntc]

Peter

 

I have an early ex USA TR 6 which has the same engine as the 250. The original camshaft was a 10-50/50-10 with 240 degrees duration. The head is the 516323 head. "Narrow port" I think refers to the inlet port spacing (inlet ports being closer together). I don't think the ports are actually any narrower or smaller in diameter than the other heads. The head was about an eighth of an inch thicker (taller) than the other heads. It has the larger exhaust vaves as in the CP series engine.

 

The main reason this head is not recommended for performance improvement is that you can't fit the later (& saloon type) inlet manifold with twin SU's on it because of the narrow port spacing. This means you are stuck with the original short inlet manifold which is not ideal as you cannot fit SU's to the short manifold. They foul on the steering column! So you are stuck with Strombergs. However there are other options, In addition to Weber inlet manifolds, manifolds for triple SU's or even Triple Strombergs are available from Goodparts in the USA.

 

I have also seen in print that you cannot fit a decent exhaust manifold onto this head. Depending on what you call a decent manifold, the Pheonix 6/3/1 fits perfrectly and should be adequate unless you are looking for every last ounce of power and torque (should that be foot ounces?)

 

My narrow port head is modified to stage 2. I still use the original Strombergs and inlet manifold at present. The engine has a fully balanced bottom end with a lightened flywheel. I have the Pheonix 6/3/1 manifold and single pipe system. The new cam is Vitesse/GT6 with .030" increased inlet lift, and the distributor was custom built by the Doctor!

 

I have no idea what the power output is but it is a lot more than the original 104BHP. I have put in a higher ratio UK diff which slows down the acceleration a bit but the car goes very well. As the engine is loosening up I have started to push it a bit. It will pull 7000 rpm cleanly in 1st 2nd and 3rd although not in overdrive!

 

I hope to get it to a rolling road for a proper set up and test before it goes away for re-juvenation this winter.

 

All of the above is purely based on my personal experience and info found on the net and provided by members of this forum.

 

Good luck with your car and engine

 

Tony

 

Tony

 

(Not 7000 Tony it will go bang how high does your rev counter go?)

Edited August 11, 2008 by ntc

[rpurchon]

The main reason this head is not recommended for performance improvement is that you can't fit the later (& saloon type) inlet manifold with twin SU's on it because of the narrow port spacing. This means you are stuck with the original short inlet manifold which is not ideal as you cannot fit SU's to the short manifold.

 

 

just my 2 pence worth.

the later su manifold or even weber and pi will fit the narrow port heads.

the bolt holes are all the same. the only problem is the inlet ports dont quite match up.

leaving a slight step the shape of a [cresent moon].if that makes sense?

the protuding segement could easly be ground away and smoothed into the port very easly.

its no more than 1/8" at its thickest tapering to nothing.

the other side could be filled with epoxy and smoothed to shape or just left as is.

i bet there are quite a lot of cars out there running with the wrong inlet manifolds.running just fine

with sus id bet they would run better with the saloon manifolds just bolted on?

richard

[Bald Rick]

Tony

 

(Not 7000 Tony it will go bang how high does your rev counter go?)

 

Pic of rev counter attached. It has just been converted to electronic tacho (and calibrated) by Revington. It will go right round to the end of the red section. But as there are no numbers round there I can't be sure. It's probably not even 6,500 but it does sound like it's going to explode at full revs.!

 

 

 

Besides, If I'm the only person to exaggerate slightly on this forum I'll paint my car yellow!

 

Richard

 

Your'e right of course, the later manifold will "bolt on" but I couldn't see the point of having a gas flowed head and putting a mis-matched inlet manifold on it. I would also be concerned about removing enough material from the later inlet manifold to make the ports match up. The PO had fitted an unleaded head from a later saloon to my car and retained the early mis matching narrow port manifold. It went like a dog!

 

I didn't think the mis matched ports could make much difference. But when I tried a set of restored SU's and 2500S manifold from Andrew Turner on the early narrow port head, the car did not go well at all. It is better with the original Strombergs and the matching manifold.

 

But this is just my experience of playing about. I've got two different heads to try out yet, and different cams. I'm also thinking about triple (not Weber) carbs. If we all did the same things, and agreed on the preferred route to performance this would be a pretty boring forum.

 

Tony

[rpurchon]

i have su on my car with a late head and it goes v good see my rolling road post.

is there room for 3 strombergs/su on a rhd car.

i wouldnt go down the weber route seems like theyre as much bother as pi.

i wouldnt go mad re cam shafts. i liked my early us cam shaft.

the torque started at 1000 revs, ok might not give top end perfomance,but you cant have both.

 

richard

[pfenlon]

Thanks to everyone for their comments, its a minefield for the new starter, and so many have their own ideas and stages of tune.

 

I would like my 250 to produce 150 bhp. but it wont on carbs. I dont like the Lucas injection system, I know it works well when set up but it isnt for me.

 

The TR6 which I had with EFI was quite amazing, mike Pumford did a wonderful job when he made the system. but in TR6 circles the system didnt catch on,

 

probably due to cost. but I dont wish to race the car just enjoy it with almost as much power as the 5.

 

My next question has to be is the 6 engine the same as the 5.

[jonlar]

Chris and Tom, unless I've got a totally erroneous idea of where the thrust washers are located (at the rear of the crankshaft, but on the inner side of the rear crank bearing) and would not be under any pressure at all when the clutch is disengaged (pedal fully down) as the crank will be pushed away from the thrust bearing. Also the fore and aft movement of the crankshaft can actually be measured by levering the crank/pulley fully back, and then depressing clutch to see what forward movement there is and how worn/non-existent the thrust washer is? Am I completely off course on this, and got things arse about face ............?

[rpurchon]

Chris and Tom, unless I've got a totally erroneous idea of where the thrust washers are located (at the rear of the crankshaft, but on the inner side of the rear crank bearing) and would not be under any pressure at all when the clutch is disengaged (pedal fully down) as the crank will be pushed away from the thrust bearing. Also the fore and aft movement of the crankshaft can actually be measured by levering the crank/pulley fully back, and then depressing clutch to see what forward movement there is and how worn/non-existent the thrust washer is? Am I completely off course on this, and got things arse about face ............?

 

there are 2 thrust washers front and rear of the back main bearing.

the rear one wears away.and after a lots and lots of wear it can turn

and fall out.

richard

[johnny250]

Thanks to everyone for their comments, its a minefield for the new starter, and so many have their own ideas and stages of tune.

 

I would like my 250 to produce 150 bhp. but it wont on carbs. I dont like the Lucas injection system, I know it works well when set up but it isnt for me.

 

The TR6 which I had with EFI was quite amazing, mike Pumford did a wonderful job when he made the system. but in TR6 circles the system didnt catch on,

 

probably due to cost. but I dont wish to race the car just enjoy it with almost as much power as the 5.

 

My next question has to be is the 6 engine the same as the 5.

 

One easy way to drastically increase the performance is to fit a supercharger.... I believe that the original 250 head is ideal for that with the lower compression ratio..... (pity I sent mine for scrap before I realised that it might be useful to someone!)

For what it's worth my 250 with later head, fast road cam, tubular manifold and twin SU's goes like stink... and with good economy, but not having driven a car with PI I don't know how much better it would be. I am seriously considering the Megasquirt EFI option (low cost) as I have now got some of the old Lucas PI bits.....

 

john

PS see Megasquirt post if interested

Edited August 12, 2008 by johnny250

[jonlar]

there are 2 thrust washers front and rear of the back main bearing.

the rear one wears away.and after a lots and lots of wear it can turn

and fall out.

richard

 

Thanks Richard, I thought there was only the one on the sump side - your explanation makes sense of Chris' and Tom's comments.

[Red 6]

I would like my 250 to produce 150 bhp. but it wont on carbs. I dont like the Lucas injection system, I know it works well when set up but it isnt for me.

 

Yes it will and a lot more to boot, well mine does anyway. The existing head can be ported and flowed just like any other head, yes the inlet spacings are different which means for simplicity it has to stay but su will bolt on in place.

 

I have kept mine LHD so there are no problems with fouling the steering colum (which is a new one on me).

 

Fit a single pipe big bore exhaust and an uprated cam (say 270deg for fast road) and a large rear view mirror so that you have a full view of a tr5 fading into the distance as you whizz off.

 

My next question has to be is the 6 engine the same as the 5.

 

As a rule of thumb, Yes, and No. Yes the 5 and 6 had same spec CP engine no as later 6 had CR spec engine.

 

There will be an anorach along in a moment to debate crankshafts and cylinder heads and most importantly the design of rubber hose used to link the plenum to the inlet. and then theres the..............