PDA

View Full Version : Triumph 6 cylinder engine '67 through '76



arizonamike
05-19-2012, 10:26 AM
Were there any evolutionary changes or upgrades to the engine over the years or are they all the same?

Thanks

Mike

swift6
05-19-2012, 11:17 AM
Aside from the major difference of 2.0 litre and 2.5 litre there were some evolutionary differences in each of the engine sizes. The biggest changes were in the heads. Changes in port spacing primarily on the intake side.

With the 2.5 litres the block slightly changed, mostly increasing the stiffness, not really haringin any compatability issues. The crankshafts changed, around 1970. These crankshafts need a matching flywheel but are otherwise interchangable from early block to late block. The early cylinder heads had a narrow intake port spacing until 1972. Intake manifolds are not really interchangeable early to late (they will bolt on but their flow will be interrupted) but exhasut manifolds are. Camshafts changed in later years and those changes often accompanied compression ratio changes. Heads, as a unit, are interchangeable form new to old/old to new just be sure to use the appropriate head gaskets.

Its really a very wide question. If you had something specific in mind you would get more specific answers.

arizonamike
05-19-2012, 06:58 PM
Thanks Shawn. I was not aware of the 2.0L Vitesse engine until now.

I was just wandering about any 2.5L changes. You answered my question. So, as a general rule. except for heads, replacement parts from the same year engine would be the best way to go ?

Was each flywheel balanced to each crank ?

Would a 1976 TR6 head be higher compression than my 1968 ?

I have not worked on a 2.5L except for maintenance.

Hey I need a set of metric wrenches now. :-)

poolboy
05-19-2012, 08:25 PM
Not metric...
CR dropped to 7.75:1 from 73 on, but just about everyone who had the head reconditioned in the last 35, 40 years must have had the head skimmed at least a tad.

booley
05-20-2012, 07:15 AM
Here's a question, I'm toying with the idea of stuffing a TR6 motor in my GT6. I am somewhat familiar with the oilpan modifications needed with a bfh. What year TR6 cylinder head would match my GT6 head?(I have a set of webers I would like to re-use)

dklawson
05-20-2012, 09:26 AM
The early GT6 heads have pushrod tubes that are aluminum tubing pressed through the head casting. If you have that type of head, you will not be able to use the TR6 heads. If your GT6 head does not have separate pushrod tubes then you can use the TR6 head but you will want/need to modify it.

To keep the compression ratio where they wanted it BL used the same casting in "thick" form for the TR6 and machined it thinner for the GT6. If you put a thick TR6 head on your GT6 short block you will have very low compression.

DNK
05-20-2012, 10:57 AM
The later heads are the same,...are they not.
Pretty sure my head is a GT6 head from Ted


Oh, the GT head is taller ,I do believe

dklawson
05-20-2012, 09:06 PM
The later GT6 head is the same as the TR6 head but it is shorter, not taller. It is the same casting as the TR6 but shaved down in thickness to obtain decent compression.

DNK
05-20-2012, 10:49 PM
Are you sure,Because my new GT6 head is taller than my stock TR6 head

jsfbond
05-21-2012, 06:10 AM
Thanks Shawn. I was not aware of the 2.0L Vitesse engine until now.

I was just wandering about any 2.5L changes. You answered my question. So, as a general rule. except for heads, replacement parts from the same year engine would be the best way to go ?

Was each flywheel balanced to each crank ?

Would a 1976 TR6 head be higher compression than my 1968 ?

I have not worked on a 2.5L except for maintenance.

Hey I need a set of metric wrenches now. :-)

I was under the impression that the GT6 engine was a de-stroked version of the 2.5 block, resulting in the 2.0 for higher revs. designed for more bullit proof racing.

dklawson
05-21-2012, 07:29 AM
The GT6 engine was used first in the Vitesse and that in turn was derived from the 1600cc Vanguard engine. The TR6 engine was derived from the GT6.

Yes, the later GT6 engines that use the same head as the TR6 have shorter/thinner heads than the TR6. I'm not sure why your car's is not. Perhaps a previous owner fit a GT6 head and pushrods to really raise the compression ratio a huge amount.

I'm sure there is more info online about this. A quick Google search this morning found the link below:
https://www.oocities.org/rotoflex/gt6-mod.htm

Quoted from that page...
<span style="color: #FF0000"><span style="font-style: italic">Chris Witor researched several Triumph 6 cylinder heads to gauge their flow characteristics. His conclusion was that the 219016 head flowed best. As the 219016 head was originally fitted to the 2.5 engine, it will require skimming if installed on a 2.0 engine to achieve a reasonable compression ratio. </span></span>

Andrew Mace
05-21-2012, 11:07 AM
The GT6 engine was used first in the Vitesse and that in turn was derived from the 1600cc Vanguard engine. The TR6 engine was derived from the GT6.Right! The six was derived, in fact, from the four-cylinder that started out in 803cc, then 948, 1147 and 1296. All those, and all the sixes except for the 2.5, had the same 76mm stroke. That 2.5L six was stroked rather more (95mm) than was the 1493cc Spitfire (etc.) "1500" engine (87.5mm).

DNK
05-21-2012, 11:18 AM
...Yes, the later GT6 engines that use the same head as the TR6 have shorter/thinner heads than the TR6. I'm not sure why your car's is not. Perhaps a previous owner fit a GT6 head and pushrods to really raise the compression ratio a huge amount.

...

Got it straight from Ted.
Now you got me curious and I'm going to recheck just to make sure I'm not talking out my ...SSS.
And my fuzzy memory isn't fuzzier


<span style="font-style: italic">OK, I got my head from Ted, was told it was a GT6 head.
After measuring the volume of one of my cylinders and sending that info to him.
He cut the new head to give it a 9.5:1 ratio.
I just measured the GT6 head and it is 3.58".
Went to my storage loft to measure the stock 71 head.3.53"
Both measured at the spark plug side
</span>

dklawson
05-21-2012, 03:51 PM
I'm not quite following you Don. Are you saying that you have a GT6 head that measures 3.58" thick?

Check out the web page linked below regarding engine spec comparisons. 2/3 down the page you'll reach the section dealing with cylinder heads:
https://www.triumphclub.co.nz/?page_id=653

The only thing I saw with a head thickness over 3.5" was for a TR-250 (and an African? TR6). Most the GT6 heads are around 3.3 to 3.4 depending on the compression ratio. The 2.5Ls all seem to start at 3.48.

DNK
05-21-2012, 04:32 PM
Well, where is the correct place to measure.

Though I measured both heads at the same location ,close anyway and the so called GT6 head is taller even after it has been cut.

Maybe it isn't a GT6 head. Maybe he changed his plan on what head to use

Doug, didn't see my 71 head listed ,307837
https://i123.photobucket.com/albums/o316/donkelly23/TR6/2012-05-14165217.jpg

DNK
05-21-2012, 04:44 PM
Here is my new head info
https://i123.photobucket.com/albums/o316/donkelly23/TR6/2012-05-21143700.jpg

https://i123.photobucket.com/albums/o316/donkelly23/TR6/2012-05-21143644.jpg

And I think it is a Diamond "D" but hard to read inside the diamond

DNK
05-21-2012, 04:52 PM
Better chart
Head Chart (https://www.chriswitor.com/cw_technical/head_applications_chart.pdf)
Looks like it is a TR6

arizonamike
05-21-2012, 11:06 PM
Thanks fellas, very interesting. The way that they were able to successfully continue to modify their current designs making them larger, rather than starting from scratch with a totally new engine design, seems to have worked up until about 1970, when Triumph tried to weld two of their four cylinder engines together for the new STAG.

The Triumph Club NZ has great information. Thanks for that. Found this video there regarding the above.

Hope it does not offend any Stag owners. :-)

https://www.youtube.com/watch?feature=player_embedded&amp;v=TGJty_Rdp1U#!

jsfbond
05-22-2012, 05:31 AM
Thanks fellas, very interesting. The way that they were able to successfully continue to modify their current designs making them larger, rather than starting from scratch with a totally new engine design, seems to have worked up until about 1970, when Triumph tried to weld two of their four cylinder engines together for the new STAG.

The Triumph Club NZ has great information. Thanks for that. Found this video there regarding the above.

Hope it does not offend any Stag owners. :-)

https://www.triumphclub.co.nz/?page_id=88
Even more interesting was that quite literally at the other end of the building, Rover had the aluminum block v8, and would not share. Therby killing any chance the stag might have had.

tdskip
05-22-2012, 08:25 AM
Even more interesting was that quite literally at the other end of the building, Rover had the aluminum block v8, and would not share. Therby killing any chance the stag might have had.

Really? The story as I heard it was that Triumph wanted to go their own way on the Stag engine. Good engine actually, just underdeveloped at time of release and needed more attention than owners were willing to give.

Our Stag contingency will be along shortly to weight in...

Andrew Mace
05-22-2012, 11:51 AM
Even more interesting was that quite literally at the other end of the building, Rover had the aluminum block v8, and would not share. Therby killing any chance the stag might have had.

Really? The story as I heard it was that Triumph wanted to go their own way on the Stag engine. Good engine actually, just underdeveloped at time of release and needed more attention than owners were willing to give....
By the time Rover had scored the V-8 from GM, British Leyland was already one big (un)happy family. I don't think there was any question of sharing or not sharing <span style="font-style: italic">per se</span> with various marques within BLMC; after all, Morgan used the engine in their +8 almost as soon as it appeared in the Rover! If anything, it might have been more a case of a: lingering stubbornness, and b: possibly a lack of manufacturing capacity, as well as the fact that Triumph had already developed the slant-four and, with it, their own V-8.

As I recall, it took an outsider making MGB V-8 conversions to finally shame MG/BLMC into doing it themselves!

TR3driver
05-22-2012, 12:20 PM
Also, there was supposedly a report from the Triumph engineers that the so-called Rover V8 (actually a General Motors design sold to Rover after GM had too many problems with it) would not fit into the Stag. From what I have heard, that may have had some truth to it, as Rover had not yet developed the modified components that would allow it to fit in the Stag's rather cramped engine compartment. ("reverse" Oil pan and shortened water pump IIRC)

Also, it's my understanding that the original plan was for a "modular" V8 that could also be manufactured as a 4-cylinder. Not quite the same thing as "welding two 4-cylinders together". The original development was actually a joint venture with SAAB. (SAAB paid for much of the development, in return for training and rights to use the resulting design in their own cars.) The TR7 motor was actually a further development of the 4 pot version, and of course SAAB continued using the design for many years, making their own changes until it was quite successful for them.

The marketing folk may have had some input as well. Back then, a SOHC V8 was much sexier than a pushrod motor.

jsfbond
05-22-2012, 01:47 PM
A freind of mine installed that same Buick (215)V8 into a 1960 MG Midget. What was commonly refered to as a Chinese car after completion.

martx-5
05-22-2012, 02:49 PM
... The TR7 motor was actually a further development of the 4 pot version, and of course SAAB continued using the design for many years, making their own changes until it was quite successful for them.

I was working as a mechanic at a Saab dealer shortly after the first 99's started appearing with the Triumph engine. Huge number of warranty problems with it, mostly with the head. Actually, Saab didn't use it very long, by 1972, after four years, they <span style="font-weight: bold">substantially</span> redesigned the engine and began producing it themselves. It was know as the Saab B engine. (https://en.wikipedia.org/wiki/Saab_B_engine) We just called it the King Kong. It was pretty much bullet proof after the changes.

swift6
05-23-2012, 08:08 AM
I was under the impression that the GT6 engine was a de-stroked version of the 2.5 block, resulting in the 2.0 for higher revs. designed for more bullit proof racing.

The 2.0 is essenntially a de-stroked version of the the 2.5 but the 2.0 came before the the 2.5, it wasn't developed from it. So in historical terms, the 2.5 litre version is a stroked version of the 2.0 litre. As Andy pointed out, the vitesse series started as an 803cc(?) 4 cylinder and kept getting bigger. The first 6 cylinder vitesse engine being 1.6 litre, bore size was increased to get to 2.0 litre and then stroked to get to 2.5 litre. The 2.5 litre was also the basis for the DOHC 2.3 litre and 2.6 litre I-6 used in the Rover SD1's. By the time that DOHC engine had finished development so many changes had been made that it had lost any real sense of lineage back to the vitesse series engines.

Andrew Mace
05-23-2012, 10:05 AM
Right again, Shawn. Actually, I'm pretty sure the first six was a 2.0, as used in the Standard Vanguard Six models, circa 1960-61. It was then "sleeved down" to 1.6L for the Vitesse 6, and I vaguely recall that a 1.5L version was considered for some applications but never put into production. Similarly, there had been some plans to use (I think) the 1.6L version as a "base" engine in the big Triumph saloon introduced in 1963; we know that car as the 2000 and later the 2500 and 2.5, but that "base" model never came to be.

jsfbond
05-23-2012, 02:26 PM
So being a carpenter type, I ask the question "If the short stroke of the race born design is great for higher revs, then why go to a longer stroked engine? Is displacement a just trade off for throwing more mass? Is the TR6 engine really that more powerfull?

Andrew Mace
05-23-2012, 03:33 PM
Keep in mind that none of these engines was designed for racing! The wet-liner four was developed to give reasonably good power and long service and also to be easily "field-serviced" around the world, first in the Standard Vanguard and soon after in the Ferguson tractor. It was only after much "redevelopment" that the engine also became a decent powerplant for sporting cars. Similarly, the "SC" 803cc four-cylinder was also developed for a basic, economical car, and it was only much development and redesign that it became bigger, more powerful, etc., etc. Both engines dated from a time when long(ish)-stroke engines were still favored, in some part for tax reasons but also for basic power at lower revs! Thinking of any of these engines as short-stroke is really not accurate. Some came closer to being "square" but that was about it. The original 803cc four had (as previously noted) a 76mm stroke and a cylinder bore of only 58mm, only a bit larger in diameter than your typical Smiths/Jaeger fuel or temp. gauge!

swift6
05-26-2012, 08:48 AM
Andy alluded to it in his above post, when he metioned the tax implications. The tax on the vehicle used to be based on the bore displacement. So the easy way to increase power without increasing the tax was to increase the stroke of the engine. If you look through the design of many British engines there is a historical trend of long stroke low revving engines. Even after the basis for taxation changed, the trend continued.

Toque was the key to power over horsepower with stroking the engines.