CR to CP

[Louis58]

What are all modifications and different components needed to upgrade my tr6 from a 125bhp to a 150bhp? Thank you 

[Nigel Triumph]

The biggest difference is the camshaft, though there are many details to consider, for example the metering unit calibration, throttle bodies/linkage, overdrive...

But the real question is why do it? In reality the CP series cars never made 150bhp, and performance difference vs the CR cars is marginal.

Merely the opinion of CP series owner!

Nigel

 

[astontr6]

12 minutes ago, Louis58 said:

What are all modifications and different components needed to upgrade my tr6 from a 125bhp to a 150bhp? Thank you 

First thing there was never a production line 150bhp? It was only in in BL brochure. I bought a 125 CR type in 1973 and I spoke to SAH who were the Ace tuners for Triumph cars and they had the status of being approved by BL for Special Tuning. This meant that if they fitted one of their tuning kits you sill kept the BL Warranty. This is what they did to my car: Modified cylinder head, all gas flowed and compression raised to 9.75, a cam change to their 375 type, which is a bit more powerful than the original CP cam. Today Newman's PH2 is basically the same spec. Lastly their wheel barrow exhaust with extractor manifold. On a local Dyno at the time, I was quoted 160 bhp! My car certainly goes. Extra power is felt in the mid range when hill climbing or overtaking.

Bruce.

[Louis58]

11 minutes ago, Nigel Triumph said:

The biggest difference is the camshaft, though there are many details to consider, for example the metering unit calibration, throttle bodies/linkage, overdrive...

But the real question is why do it? In reality the CP series cars never made 150bhp, and performance difference vs the CR cars is marginal.

Merely the opinion of CP series owner!

Nigel

 

Thank you. Do you do you know if you actually need the different throttle bodies and linkages to get it to run right? 

[astontr6]

1 hour ago, Louis58 said:

Thank you. Do you do you know if you actually need the different throttle bodies and linkages to get it to run right? 

I still have the original throttle bodies which were modified by Prestige 5 years ago as the throttle spindle bores were badly worn and I had a very variable tick over.

[astontr6]

12 hours ago, astontr6 said:

First thing there was never a production line 150bhp? It was only in in BL brochure. I bought a 125 CR type in 1973 and I spoke to SAH who were the Ace tuners for Triumph cars and they had the status of being approved by BL for Special Tuning. This meant that if they fitted one of their tuning kits you sill kept the BL Warranty. This is what they did to my car: Modified cylinder head, all gas flowed and compression raised to 9.75, a cam change to their 375 type, which is a bit more powerful than the original CP cam. Today Newman's PH2 is basically the same spec. Lastly their wheel barrow exhaust with extractor manifold. On a local Dyno at the time, I was quoted 160 bhp! My car certainly goes. Extra power is felt in the mid range when hill climbing or overtaking.

Bruce.

I did a typo the cam number should read 357 and not 375?

Bruce.

[John McCormack]

Having driven a few CR and CP cars I would say the difference in performance is more than marginal.

Yes the CP 150bhp SAE is nearer 140 bhp DIN. However this is still 15 more than the CR, or a bit more than 10%. The CP torque is also more than the CR.

Each CP car I have driven had noticeably more get up and go than the CR cars. I've driven 3-4 of each and taking into account different condition, final drive ratios and state of tune, the CP has better performance.

I also drove a couple of ex US cars with Strombergs. These TR6s were noticeably lower in performance and not much, if any, better than my slightly modified TR2s. Nearly 200kg heavier and similar power.

 

[astontr6]

26 minutes ago, John McCormack said:

Having driven a few CR and CP cars I would say the difference in performance is more than marginal.

Yes the CP 150bhp SAE is nearer 140 bhp DIN. However this is still 15 more than the CR, or a bit more than 10%. The CP torque is also more than the CR.

Each CP car I have driven had noticeably more get up and go than the CR cars. I've driven 3-4 of each and taking into account different condition, final drive ratios and state of tune, the CP has better performance.

I also drove a couple of ex US cars with Strombergs. These TR6s were noticeably lower in performance and not much, if any, better than my slightly modified TR2s. Nearly 200kg heavier and similar power.

 

BL's in house unpublished figure in the DIN standard was 137bhp for a CP engine. The CP engine had a more revs than the CR. The SAH cam 357 which was a copy of BL's own S2 cam for street use, sold in the USA only, along with the S4 another BL cam a racing profile. The Americans could make the street TR's really go even with Stromberg carbs.

Bruce.

[DRD]

19 hours ago, astontr6 said:

BL's in house unpublished figure in the DIN standard was 137bhp for a CP engine. The CP engine had a more revs than the CR. The SAH cam 357 which was a copy of BL's own S2 cam for street use, sold in the USA only, along with the S4 another BL cam a racing profile. The Americans could make the street TR's really go even with Stromberg carbs.

Bruce.

Bruce, do you know what the duration and lift is of the 357 cam?

Cheers Darren

[astontr6]

3 minutes ago, DRD said:

Bruce, do you know what the duration and lift is of the 357 cam?

Cheers Darren

the lift was .405", duration around 282, timing  inlet opens 31 BTDC/exhaust  opens 71 BBDC figures same for closing 31 closes / inlet closes 71. No mod needed for MU. BL recommends 10.0-1 compression ratio.

Bruce.

[TRTOM2498PI]

23 hours ago, astontr6 said:

the lift was .405", duration around 282, timing  inlet opens 31 BTDC/exhaust  opens 71 BBDC figures same for closing 31 closes / inlet closes 71. No mod needed for MU. BL recommends 10.0-1 compression ratio.

Bruce.

Hi Bruce,

 

PM sent.

 

Cheers.

[cp25616]

Have to endorse John's observations with regard to the differences between CP and CR cars, the difference IS marked indeed. My first 2 TR6pi's were CR cars and if I am being blunt, were breathless devils. Tame to use another word.

I have owned another 5 TR6pi's and 1 TR5 since, all CP ones and there is no comparison. Far greater gutteral urge throughout the rev range and they don't get anything like as breathless higher up in the rev/speed range either.

Yes there will be people out there who differ with my opinion but hey I am only telling it like it is.

Alan

[ntc]

2 hours ago, cp25616 said:

Have to endorse John's observations with regard to the differences between CP and CR cars, the difference IS marked indeed. My first 2 TR6pi's were CR cars and if I am being blunt, were breathless devils. Tame to use another word.

I have owned another 5 TR6pi's and 1 TR5 since, all CP ones and there is no comparison. Far greater gutteral urge throughout the rev range and they don't get anything like as breathless higher up in the rev/speed range either.

Yes there will be people out there who differ with my opinion but hey I am only telling it like it is.

Alan

+1 the difference is there in the drive