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150BHP v 125BHP


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Hello all ..

 

After quite a few years I am hankering to go back to TR6 motoring .. My previous cars were a 1974 125BHP TR6 and an 1968 American TR250 .. I would very much like to know anyone's opinions of the driving difference between a UK 125 and a UK 150 BHP TR6 and also WHICH year did the detune take place.

I am in the market for a nice restored TR with all the bugs taken care of but I am not sure that some advertisers claims for 150 BHP performance are valid ( not from this forum I hasten to add ) :)

 

Many thanks ..

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Hello 6Pack.....

 

The UK Fuel Injected models changed in late 1972 from the CP Series cars (150 bhp) to the CR series cars (125 bhp).

 

The 150 bhp cars are slightly quicker in standard form but you'll probably find the later 125 bhp cars slightly smoother. The actual difference in performance is marginal and can also depend on how the car has been maintained and set up.

 

The CP & CR letters are the prefix on the chassis and engine number, so your chassis number would have been CRxxxx if it was a genuine UK 125 bhp car.

 

Just to complicate things the American TR6 cars had chassis and engine numbers beginning CF & CC - these cars were de-tuned for emission controls in the US and were about 104 bhp.

 

The best way to check if a car is a genuine UK 150 bhp car is to get the owner to read the engine number from the engine block (not the logbook) as lots of engines have been blown up / changed over the last 30+ years so sometimes although a TR6 should have a CPxxxx engine number it may have been swapped for a saloon car or American type engine. Saloon car engines have engine numbers starting MMxxxx & MGxxxx

 

Clear as mud!!!

 

Just be very careful as all this affects the re-sale values and unsuspecting purchasers do not always do the correct checks, which are vital if you ever want to sell again!

 

Regards

 

Mark

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Triumph's power output figures were always rather optimistic, so in reality you're probably looking at something more like 120bhp versus 105bhp.

I had a '74 CR car for a time and I thought it a more civilised and smoother drive than the CP version. Acceleration and pickup is slightly less aggressive which you may notice, but you will get better fuel economy. Swings and roundabouts as always.

As Marko says, depends on past maintenance and mods as much as original designation.

Jerry

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IMHO the most important to enjoy any TR is a good chassis and a proper suspension setup, rather important on IRS cars ;) . Many 5 and 6s drive like a wet towel :blink:

Ask yourself: Why a lot of HP if you have to brake and stop before engaging a turn.

Go for the best car whatever the HP is. In the mean time 80% of all TR6's on the Continent are U.S. specification cars, with no complains from the owners :)

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And... the '150' and the 125 were not measured the same. The 150 was SAE = no accessories, the 125 was DIN = as installed with accessories. I think I have that the right way round... :unsure: ... anyway the power difference was never 25 bhp.

 

Apart from a slight power bonus, the CP cars also have the benefit of a hatch to cover the heater intake plenum, a prime and costly rot site, whereas the CR cars just had a grid to let the rust in. :angry:

 

All other things being equal a CP car will cost more because of that bogus '150bhp' cachet, so if you buy well you can get more for your money by going for a '125 hp' and as has been said very few cars are really standard by now. My '125' was uprated in the late 70s.

 

Welcome to the forum btw. And as I mention to all new arrivals if I remember, it will facilitate your use of the Forum if you change your View Mode: Towards the top of this thread on the right hand side, there is an Options box. In there, change the Display mode to Standard. That will eliminate the family tree and you will see all posts in chronological order.

 

Ivor

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Hi 6PACK,

just to add some more details to the 125/150hp differences. The CP cars with overdrive used the A type o/d unit which could take more power so had overdrive on 2nd,3rd & top. The later CR cars used the J type (by memory) on which they only allowed 3rd & top to engage but this was balanced by a closer ratio gearbox.

I purchased my TR6 nearly 30 years ago and by shear luck purchased a very late 1972 CP model. I did not know then that his is perhaps the most desirable of 6s because it uses the later gearbox with early overdrive giving the best standard performance of any TR6 with 150hpSAE, close ratio box, 3 speed overdrive.

I subsequently gas flowed the cylinder head and fitted a 6into2 S/S exhaust manifold feeding into a standard S/S silencer and I find this very good, plenty of power with excellent low down torque making it very drivable but with the original TR6 sound. It does tick over a slighty irratic but still below 900RPM.

Suspension is standard except for some polyurathane bushes and spax telescopic conversion to the front & rear. It seems to work very well on the road, great fun when pushed hard.

I hope this is of interest and helps your choices.

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How 'bout some info on the relative weights? U.S. cars fattened up considerably over the years, gaining circa 250 lbs. The '69 TR6 was actually 9 lbs lighter than the TR250 but the next year was over 100 lbs heavier. What about the RoW cars? :huh:

 

 

Hi Tom,

 

I'm sure I read somewhere that the UK TR6 of 1969 was actually heavier than the outgoing TR5, which blunted acceleration a little!

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I dont see the the TR6 as the kind of classic that needs to be kept original, original in overall appearance yes, but not mechanically. I like the injection system, but there is nothing wrong with Webers for those who like the look and sound.They could have been fitted in period, in fact most of the available upgrades are nothing out of the ordinary, except perhaps electronic fuel injection which I feel is not right, as out of period. With sensible upgrades therefore the 6 can be a very useable sportscar. As such for me it must have performance,modern performance. not be left standing by warmed up hatches. The 125 and 150, though they have reasonable torque, are not in my view powerful enough, if you attempt to overtake somebody who puts there foot down, or are harrassed by a boy racer, the power is deficient. The necessary torque can be added by boring out, improving the cam, and head work to stage two, with increased compression. Add electronic ignition and a free flowing exhaust. Balance and lighten.With care an engine that is still smooth and tractable can be produced. This in my view makes it a sports car that befits the name, and still able to keep up 40 years later. To sum up then I would by either 125 or 150 but make sure I set aside the funds 3 to 3.5K to get a good engine. Personal view only. David Johnson.

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Hello all ..

 

After quite a few years I am hankering to go back to TR6 motoring .. My previous cars were a 1974 125BHP TR6 and an 1968 American TR250 .. I would very much like to know anyone's opinions of the driving difference between a UK 125 and a UK 150 BHP TR6 and also WHICH year did the detune take place.

I am in the market for a nice restored TR with all the bugs taken care of but I am not sure that some advertisers claims for 150 BHP performance are valid ( not from this forum I hasten to add ) :)

 

Many thanks ..

 

I would also guess that the driving difference felt by someone driving the CP TR6 is that it costs less to keep on the road due the the fact that they do not

have to pay road tax as they were all manufactured before 1st Jan 1973. Making them a happier driver than those driving the CR (post 1st Jan 1973) TR6. :lol:

Edited by simon iregbu
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  • 7 years later...

I own a CP and CR tr6. The CP is quick off the mark but a little flighty, the CR is smooth and cruises really well. I like driving both cars for different reasons and at the end of the day although one is "150bhp" and the other "125bhp" there is very little difference between the two. More often than not its not about speed but about image. I like to hear the burble of my 6 when I trundle down a high street or through a small village and the appreciating looks that either of the cars receive. Both are injection and if I am honest I found the CR injection system the easiest to set up. I find prices slightly differ with The CP commanding more, but then the condition of the actual car overall is what to look at not how powerful it may or may not be. Remember when buying a TR6, it's not just about engine size but about buying the car in the best condition, underneath as well as no top!

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They have different cams as the most significant difference.

256 degrees CR versus 280 degrees CP.

 

Well set engines will rev up to 6000 when CP and die at 4500 when CR.

The metering unit must be different, the CR has three springs, the CP only two.

The compression ratio is different.

 

The manifolds are different, the CR has one more line to connect the manifolds.

Wilder cams do not like that manifold that much, it has also a D-shape said to

improve the torque what I did not find out.

 

Later CR heads have smaller exhaust valves 30mm against 32 at the CP version.

Some say these heads flow better, I do not think so and make the bigger valves fit.

 

Anyway: Like posted above the setup of the engine plays a bigger role than being

CP or CR but with no doubt a fast setup CP is a very sweet thing that can not be

compared to the carb versions being a bit lazy and dont want to rev.....

 

With a good setup of suspension and the stock brakes in good order there is no need

to worry about too much engine power. Anyway a lot can be done to improve brakes and

suspension, too. Thats the fun with the TRs

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Have owned both and the cp is definitely the one to go for in my opinion

Much more of a sports car to drive and more fun

The cp seemed to run out of breath in top gear overdrive,didnt have as much grunt

As said just my opinion on the 2 cars that i had

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Hello all ..

 

After quite a few years I am hankering to go back to TR6 motoring .. My previous cars were a 1974 125BHP TR6 and an 1968 American TR250 .. I would very much like to know anyone's opinions of the driving difference between a UK 125 and a UK 150 BHP TR6 and also WHICH year did the detune take place.

I am in the market for a nice restored TR with all the bugs taken care of but I am not sure that some advertisers claims for 150 BHP performance are valid ( not from this forum I hasten to add ) smile.gif

 

Many thanks ..

As a continuous owner of a UK CP Pi car for 44 years I enjoyed reading all the posts in answer to your sensible questions.

The HP rating thing is academic really, as the TR6 as the last of the old school traditional British US dollar earning Sports cars is totally outclassed on the roads today in all aspects of performance and handling...so just enjoy it for what it is and the smile it puts on your face, and the looks it still gets, oh and that great 6 cylinder burbble it makes.

 

The CR car was a response to the CP car being too 'Cammy' and fiddly to drive in commuter traffic..that's about it really. But if you can find a good condition UK CP Pi car it'll give you that classic period feel.

As far as performance goes when my totally standard 1969 CP Pi car was 6 years old I entered it in a Sprint event, as my Racing Car wasn't ready and I didn't want to scratch...on the Standing start quarter mile my best time was 15.37 at 84mph and 0 - 60mph in 7.6 seconds. I'm not sure what a stock CR car could do, but I doubt it's too far off.

 

Just check out the chassis for rot, the diff mountings (as torque rips the bolts free) and stick a screwdriver behind the Crank Pulley as the Thrust Washer is the weak link of the Triumph Six.

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Contrary to what's stated before the CR shouldn't struggle to rev over 4500rpm.

The cam is the biggest mechanical difference - being less peaky then the CP. The metering units were calibrated differently to suit and the inlet manifolds (linked by 2 balance pipes rather than one) and linkages were different. The linkage of the CR being a pig to set up but is best overcome with an after market linkage.

 

There were minor differences to cranks and heads but these were probably not hugely significant for performance (not at all as far as the crank) - indeed the best head was fitted to the 2.5S saloon.

 

The blocks do differ in that there is a groove around the cylinders on the CRs which wasn't present on the CP - but this really just affects the type of head gasket and not performance. (Triumph also made his modification to the Spitfires at the same time)

 

Instruments also changed - a voltmeter instead on an ammeter and the number plate lamps moved from the bumper to the rear panel.

 

150 or 125 BHP - well 2 different measuring standards (SAE and DIN) and nowhere near the 25bhp the numbers might be assumed to imply.

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Forget the figures being bandied about there really is a notieable power difference between the CR and CP models. I know I have had 2 x CR models and 4 CP models in 36 years of TRing and the CP revs more freely and is quite a bit quicker to boot. The standard CR TR is a little breathless and the earlier A type overdrive is also better than the J type on the CR cars as well.

There are a few little things on a CR car that are better than a CP car but overall my advice would be to drive both and assess for yourself.

BTW the very early CR cars used the A type overdrive up to circa CR 567.

Alan G

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Hi Andy

The later CP engines also have the recessed block.

Nope

Forget the figures being bandied about there really is a notieable power difference between the CR and CP models. I know I have had 2 x CR models and 4 CP models in 36 years of TRing and the CP revs more freely and is quite a bit quicker to boot. The standard CR TR is a little breathless and the earlier A type overdrive is also better than the J type on the CR cars as well.

There are a few little things on a CR car that are better than a CP car but overall my advice would be to drive both and assess for yourself.

BTW the very early CR cars used the A type overdrive up to circa CR 567.

Alan G

+1 the difference is in the drive.

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As to whether the A type OD is better than the J type I think that's very much a personal preference. Having had both I prefer the J type for it's smoother operation, no less positive in engagement but more civilised. It's also a more modern design dating from the 60s rather than the 40s design of the A type. They're different for sure but as for one being better than the other, personally I don't think so in normal use. If better means stronger then yes, the J type gear teeth are smaller and it's wired so as to not be available in 2nd gear presumably to limit the torque load. I can't recall the last time I used OD on 2nd so whether it's a limitation is moot.

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As to whether the A type OD is better than the J type I think that's very much a personal preference. Having had both I prefer the J type for it's smoother operation, no less positive in engagement but more civilised. It's also a more modern design dating from the 60s rather than the 40s design of the A type. They're different for sure but as for one being better than the other, personally I don't think so in normal use. If better means stronger then yes, the J type gear teeth are smaller and it's wired so as to not be available in 2nd gear presumably to limit the torque load. I can't recall the last time I used OD on 2nd so whether it's a limitation is moot.

The only place I've ever used O/D in 2nd is between the hairpin and Barn corner at Cadwell park.

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