TR6 with Stag V8 engine

[garyf]

Wow this looks interesting
cheap at £15k I think

https://www.carandclassic.co.uk/car/C991294

[Scar]

The question is... Why? Wasn't the straight 6 with fuel injection as powerful as the v8?

[jakesmig]

With a 4L Stag and a 1.8L Midget I'm up for modifying cars, if I was doing another it would be a TR6 because they look cool, however it would be one I would leave as standard.

[Phil S]

from memory the later tr6 was 125 bhp.. but the Lucas injection was never perfect.
Phil

[I am Groot]

The question is... Why? Wasn't the straight 6 with fuel injection as powerful as the v8?

Straight 6 was capable 150 Bhp in some forms on the tr6. It was originally going to be the Stag power unit but Triumph decided the wanted the TV8 because it had for more torque and was a lighter unit. Can only think this is a very fast tr6 that revs, drives and sounds much better than a standard car. Cheap though isnt it?

[DJT]

Straight 6 was capable 150 Bhp in some forms on the tr6. It was originally going to be the Stag power unit but Triumph decided the wanted the TV8 because it had for more torque and was a lighter unit.

Don’t know where you heard that. The Stag was always going to have the V8, not the 6. Originally the V8 was intended to be a 2.5 litre PI, but problems getting it clean enough for the USA led to it being bored to 3 litres and fitted with Strombergs.

With hindsight, it may have been better if they did launch the Stag with the 2.5 straight 6 in either TC or PI form, until the V8 was fully sorted, when they could have added it to the range. But, as stated, Triumph management were determined it was going to have their own V8 from day one.

[I am Groot]

Don’t know where you heard that. The Stag was always going to have the V8, not the 6. Originally the V8 was intended to be a 2.5 litre PI, but problems getting it clean enough for the USA led to it being bored to 3 litres and fitted with Strombergs.

With hindsight, it may have been better if they did launch the Stag with the 2.5 straight 6 in either TC or PI form, until the V8 was fully sorted, when they could have added it to the range. But, as stated, Triumph management were determined it was going to have their own V8 from day one.

It's in Mathew Vales Stag Entusiasts guide Dave and documented elsewhere. The Straight six was biggest engine triumph had in 67 and it was originally proposed and actually was in some prototypes. However it was decided the Stag was the flag ship product and needed a V8. Your correct this was originally developed as a 2.5v8 also but later for the reasons you have given increased to 3.0.
rgds
nigel

[Guest]

Straight 6 was capable 150 Bhp in some forms on the tr6.

This is wrong.
I have never ever seen a TR5 or TR6 that ever even comes close to 150bhp!

The best I have seen on measurement in perfect condition made 99bhp at the wheels at nothing like the revs they claimed.
That's 117-118bhp at the engine folks!
Like most stuff from the 60s, there were lies, damn lies and statistics.

The Stag was claimed to make roughly 145bhp.
In reality it makes about 125 on a good day, with all the high compression pistons, the Mk2 heads and decent working carbs and all the other stuff in perfect nick.

The difference between 117bhp & 125bhp is scarcely detectable, but the Stag having a very short stroke crank, while the TR6 having a massive long stroke and a smaller engine, makes the "hot cammed" early engines with their Lucas pi, have a massive hole in the torque curve below 3500rpm.
There's literally nothing down there.

The end result, because it's in a lower state of tune with milder cams,- the Stag has a much broader torque range and can stretch to over 6000rpm, which is suicide on a TR6, while pick up from 1000rpm on a lazy OHC V8 is effortless.

[DJT]

It's in Mathew Vales Stag Entusiasts guide Dave and documented elsewhere. The Straight six was biggest engine triumph had in 67 and it was originally proposed and actually was in some prototypes. However it was decided the Stag was the flag ship product and needed a V8. Your correct this was originally developed as a 2.5v8 also but later for the reasons you have given increased to 3.0.
rgds
nigel

I’ve got that book. Plenty of inaccuracies in it that aren’t borne out elsewhere.

There is an excellent article available on the SOC website of a transcript of an interview with Brian Bayliss on the development of the Stag: http://www.stag.org.uk/members-area/...e-bayliss-talk Some of the information has been incorporated into this article, also on the SOC website: http://www.stag.org.uk/the-car/a-history-of-the-stag

[flying farmer]

The question is... Why? Wasn't the straight 6 with fuel injection as powerful as the v8?

The 150 bhp TR engines never put out that amount,, the best standard car I saw at the 1st TR national day rolling road put out 122bhp+, and all the modified ones were worse, though a lot have got better over the last 15 years or so!
My Stag engined TR with a Holley put out 165bhp that same day.
Wonder when it was built and if it was effectively a copy of mine? My car got a Stag engine back in about 1995, appeared in Triumph World magazine back in 1997 (I think), and also appeared in a book about modifying TR5s and TR6s a year or too later. (I have a copy somewhere in the house).
It is a shame Triumph never got round to building one themselves as the engine runs far cooler in the TR bodyshell which would have got the engine a less bad reputation.

If all the performance tuning mods that have been applied to the straight six engines over the years had been directed at the Stag engine instead then the TR range would have been quite spectacular!
Hopefully I will get the new engine in my TR running in the next week or so. Must get round to updating the thread.
Neil

[I am Groot]

Neal, did you get 160 Bhp with standard storms and tubular manifold on your stag?
Just wondering because I am making this modification. Wondering what to expect
Rgds
Nigel

[flying farmer]

I got 162bhp with the engine that is currently in the estate with strombergs and the regular Stag tubular manifolds. It has had some porting work done though, and straight through silencer boxes.
Below is a picture of the latest engine installed in the TR, hopefully I will get it running within the next week.