Possible power increase

[Peter Douglas Winn]

Does anybody know what is the maximum power output for  an early TR6 Carb car. Assuming the head will be kept but SUs and a TR5 cam are used. 

[Andy Moltu]

Is the TR5 cam the best option to fit on a carburettor car?

The PI system will allow some cams to work fine that struggle with SUs.

As for max power thT depends on a lot of factors such as head work, manifold, camshaft. Where in the rev range the power is delivered and what you are doing to the bottom end to cope with the power and higher revs required to deliver that.

Rumours have it that some of the race engines are chucking out north of 250bhp but that will be high in the rev range and likely unpleasant to drive on a road car. 

Obviously that won't be your target on an SU fed road car.

 

[stuart]

Chris Witor does a good cam for carburettor equipped cars https://www.chriswitor.com/

Stuart.

[rogerguzzi]

Hello Peter

                  I fitted a Chris Witor one with the extra inlet lift in the Brother in Laws American TR6 and it worked well(before ti idiot sold it! wife did not like it!! wrong Wife?)

Roger

[matt george]

I've got an ex-US TR6 running a TR5 cam and twin HS6s, it's absolutely brilliant and more than happy running such a cam. Obviously the head has been worked on, higher compression etc, plus long branch inlet manifold, extractor exhaust manifold and 2.25in Phoenix exhaust system, all of which together allow for plenty of extra performance.

The rotating parts of the engine were all balanced during the build process, which also helps, as the car will touch 6k without any complaints, too. It goes very well, certainly a very noticeable improvement over the standard US spec cars that I've driven. I'm yet to get it on a rolling road, but I'd hazard a guess that the power output is now comparable to a UK car.

Matt

Edited October 17, 2023 by matt george
Typo in second para

[A Brit in Bama]

I briefly ran a PI cam on my US-spec 1971 car, using dual Stromberg Carbs, and it ran very well, in combination with a head shave to increase the CR, and some mild exhaust porting.   I imagine that one would run equally well with dual SUs

The engine really came alive when I further increased the CR to around 10:1, changed out the Strombergs and replaced them with triple Weber DCOEs and an extractor manifold though.

While I was considering aftermarket cams, ultimately I decided to stay with the PI cam since it has (a) a longer track record than just about any other cam and (b) a pretty mild lift to duration ratio compared to other higher lift cams, meaning it is likely gentler on the lobes, tappets, and valve gear = longer service life.

 

 

[BlueTR3A-5EKT]

This is an interesting read for a standard car test

http://www.hottr6.com/triumph/index.html

 

Engine dynamo test

http://www.hottr6.com/triumph/tr6dyno.html

 

 

[Peter Douglas Winn]

Quote "I briefly ran a PI cam on my US-spec 1971 car, using dual Stromberg Carbs, and it ran very well" I am trying to find out if you only put a new cam in the motor and leave the head and crabs as they are power output can be achieved.

[matt george]

As has been touched upon, you'll only really get a noticeable increase in power if you modify/upgrade other elements of the system, particularly the cylinder head. If you just put a PI cam in an otherwise standard car, you'll be wasting the cam's potential and/or won't see a huge increase in power. 

Not sure what a PI cam in a standard US-spec engine would do to the drivability either.

Matt

[lee]

Major head skimming is key to this. There’s a fair lump that needs to come off 

[BlueTR3A-5EKT]

The Americans suggest a compression ratio of near 10 to 1 to get a sporty cam to work properly, and stay with petrol station available fuel.

My own TR3 experience was fitting a sporty cam in an engine with a cr of the standard 8.5 to 1,  and the engine was lifeless, lumpy ticker, flat bottom end and requiring lots of revs to get any feeling of performance.  Simply skimming the head to give 10 to 1 brought the thing to life.  This is basic tuning stuff of course.

 

 

 

[Chilliman]

5 hours ago, BlueTR3A-5EKT said:

Simply skimming the head to give 10 to 1 brought the thing to life.  This is basic tuning stuff of course.

+1

[Nigel Triumph]

On 10/17/2023 at 12:52 PM, stuart said:

Chris Witor does a good cam for carburettor equipped cars https://www.chriswitor.com/

Stuart.

+1 for Chris Witor.

I fitted his CW3201 cam to my 2.5 litre GT6, which also has mildly ported head, skimmed for CR of 9.5:1, and is fuelled by twin SU HS6s. Chris rates this set up at around 135bhp. The cam has the same timing as the later CR series TR6 PI with extra inlet valve lift.

It preserves the low rpm manners of the Triumph six pot, with extra mid range torque and top end power. The original 2500S saloon engine I fitted in the GT6 was rated at only 105bhp.

Nigel

[JJohn]

When I bought my ex-US TR6 it arrived with a TR5 head, twin Strombergs and all the anti-emission gear.  Threw the carbs and emission stuff away and fitted HD6 SU's, a CP1 cam and a tubular exhaust manifold.  It ran very well, until it developed cracks across nos 1 & 6 valve seats.  I then fitted a 2500S head after shaving 80 thou off it and on the rolling road, it gave 154 bhp.  Since then, as the result of the reduction in fuel quality, the power has decreased.  12 months ago, it was tested at 138 bhp.  It is very flexible and torquey.  It pulls away smoothly in O/D top from 1,000 rpm.  Driving up to the speed limits will return up to 33 mpg, A delight to drive.

[North London Mike]

On 10/17/2023 at 12:52 PM, stuart said:

Chris Witor does a good cam for carburettor equipped cars https://www.chriswitor.com/

Stuart.

+1 for Stuart's comment. Moby, my RBRR/10CR saloon has a TR6 block +40, with the 2500S head (with extra gas flow and valve work) and the CW Cam. HS6 carbs. Very nice road car, drive away from a standard PI set up IMHO 

[DRD]

51 minutes ago, JJohn said:

When I bought my ex-US TR6 it arrived with a TR5 head, twin Strombergs and all the anti-emission gear.  Threw the carbs and emission stuff away and fitted HD6 SU's, a CP1 cam and a tubular exhaust manifold.  It ran very well, until it developed cracks across nos 1 & 6 valve seats.  I then fitted a 2500S head after shaving 80 thou off it and on the rolling road, it gave 154 bhp.  Since then, as the result of the reduction in fuel quality, the power has decreased.  12 months ago, it was tested at 138 bhp.  It is very flexible and torquey.  It pulls away smoothly in O/D top from 1,000 rpm.  Driving up to the speed limits will return up to 33 mpg, A delight to drive.

John, what petrol were you using for the recent RR test?

[JJohn]

Shell V-Power with Valvemaster Plus additive.

[DRD]

1 hour ago, JJohn said:

Shell V-Power with Valvemaster Plus additive.

That's still high octane fuel so sounds surprising, maybe other factors at play?

[Tim D.]

5 hours ago, North London Mike said:

+1 for Stuart's comment. Moby, my RBRR/10CR saloon has a TR6 block +40, with the 2500S head (with extra gas flow and valve work) and the CW Cam. HS6 carbs. Very nice road car, drive away from a standard PI set up IMHO 

Can attest to moby's poke. She chased us up the gross glokner pass in the 10CR  and acquitted herself well. For the record we were in my supercharged tr6. We didn't have to change down below 4th on the climb. Great torque. But then we also destroyed a set of ujs on the driveshafts. 

Tim

[astontr6]

On 10/17/2023 at 10:34 AM, Andy Moltu said:

Is the TR5 cam the best option to fit on a carburettor car?

The PI system will allow some cams to work fine that struggle with SUs.

As for max power thT depends on a lot of factors such as head work, manifold, camshaft. Where in the rev range the power is delivered and what you are doing to the bottom end to cope with the power and higher revs required to deliver that.

Rumours have it that some of the race engines are chucking out north of 250bhp but that will be high in the rev range and likely unpleasant to drive on a road car. 

Obviously that won't be your target on an SU fed road car.

 

Based on another TR owner's experience. He did the following: Gas flowed head with larger inlet valves, compression increased to 10 to 1, cam Newman PH2 as old SAH profile, better than a TR5 cam, extractor exhaust manifold, single pipe open exhaust Phoenix. Once set up on a rolling road it ran very well with power from 1200 RPM to 6000 RPM, But I suspect that it would go better with DCOEs?

Bruce.

[Andy Moltu]

I didn't say you can't get the TR5 cam to work with SUs, just there might be better options.

[TRTOM2498PI]

On 10/21/2023 at 12:13 PM, astontr6 said:

Based on another TR owner's experience. He did the following: Gas flowed head with larger inlet valves, compression increased to 10 to 1, cam Newman PH2 as old SAH profile, better than a TR5 cam, extractor exhaust manifold, single pipe open exhaust Phoenix. Once set up on a rolling road it ran very well with power from 1200 RPM to 6000 RPM, But I suspect that it would go better with DCOEs?

Bruce.

I think it could be a close call.  If you start talking about a Newman PH3 or PH5 cam, then I certainly believe webers would be my choice to exploit the additional power.  I know someone with a PH3 and webers, and it is a great package.  I plan on combining my PH5 cam with EFI (plus other mods), so I hope that should prove interesting.

[astontr6]

22 hours ago, TRTOM2498PI said:

I think it could be a close call.  If you start talking about a Newman PH3 or PH5 cam, then I certainly believe webers would be my choice to exploit the additional power.  I know someone with a PH3 and webers, and it is a great package.  I plan on combining my PH5 cam with EFI (plus other mods), so I hope that should prove interesting.

I see the PH5 as a race cam? I was looking for  good mid range power so I went for a PH2 which gives very good mid range power and makes the car vey good at hill climbing and a motorway cruiser with good fuel consumption.

Bruce.

[TRTOM2498PI]

1 hour ago, astontr6 said:

I see the PH5 as a race cam? I was looking for  good mid range power so I went for a PH2 which gives very good mid range power and makes the car vey good at hill climbing and a motorway cruiser with good fuel consumption.

Bruce.

Hi Bruce,

Yes, the PH2 is ok.  I have the Newman PH2/PH3 Hybrid cam, complete with their steel EN40 followers.  Been using this cam since the engine was built in 2011. A fantastic cam, when on Lucas PI.  Has all the road manners of a CP cam, but just makes more power everywhere.  Totally user friendly, in any environment (road or track). A PH3 is perhaps a step too far with Lucas PI, or some compromises in fueling. 

 

I know someone who uses a PH5 with webers, with excellent results & road manners.  With EFI, I am think it will be even better. If there are power gains to be had, the Emerald K6 ECU will find it.

 

Cheers.

[rogerguzzi]

1 hour ago, TRTOM2498PI said:

Bruce,

Yes, the PH2 is ok.  I have the Newman PH2/PH3 Hybrid cam, complete with their steel EN40 followers.  Been using this cam since the engine was built in 2011. A fantastic cam, when on Lucas PI.  Has all the road manners of a CP cam, but just makes more power everywhere.  Totally user friendly, in any environment (road or track). A PH3 is perhaps a step too far with Lucas PI, or some compromises in fueling. 

I have a Newman PH2 in my Lowy 1500 Spitfire but with ITB's EFI and with the EN40 followers

I think it is a great cam I can still use the bottom end for normal driving but at 2,500/3,000 RPM it comes alive!

I can be on the motorway in O/Drive(28%)at 70MPH = 3,000RPM and put my foot down and it just goes!!

Plus being only a 1500 and on ITB's EFI I average 45MPG so a winner all around

Plus Newman use NEW blanks not regrinds of old ones(another plus to me!)

Roger