Sprint axle in a TR7?

[GrahamFountain]

Hyperthetically, would it be reasonably possible to modify the Sprint axle to fit in a TR7, with the overdriven gearbox, etc. I know Bill Price's team fitted the box in the group 4 rally TR7s, but I belive they used early versions of HD axle, and possibly 4HA axles, not the Sprint's.

It's only hyperthetical, because I'm wondering about whether the TR7 Sprint had to wait for the TR7 5-speed's axle or not, which was derrived from the SD1's, and, presumably, wasn't available untill the production of the SD1's axle had capacity for the TR7 as well. If the sprint's axle would have fitted, then that's not the reason they waited almost three years after the start of TR7 production to even start the TR7 Sprints.

Graham

[Carledo]

Sprint axle is some 2.5" narrower than a TR7 5 speed. Before I managed to get hold of a Sprint axle for the Carledo, I bought a TR7 axle and was measuring and offering it up. It will fit on the trailing arms (with a bit of a stretch) and you can make a hybrid adjustable upper arm that will work but the big stumbling block is that extra width, you would HAVE to open the arches up and fit bubbles to make it work.

So going the other way, you would have the opposite problem, which I guess could be cured with some high offset, deep dish wheels. Plus you would have to weld the TR7 shock mounts to the Sprint axle. Going either way the handbrake cables would probably be a pain too.

But the SD1 axle the TR7 5 speed axle is based on was out with the SD1 in 77 when the TR7 was launched and certainly must have been in development for some years prior to that, so there should have been no need to wait on that account.

Steve

Sorry, my mistake, the TR7 was launched BEFORE the SD1 and only with the 4 speed. But they must have KNOWN the LT77 box and the later design axle was in the pipeline. I think the TR7 Sprint was a half cocked idea to put some more poke in the smog reg smothered US market cars, an idea doomed to failure since the twin carb 16v Sprint motor couldn't pass the California smog checks either! And Triumph had no money to either buy in or build a competitive fuel injection system that would!

[GrahamFountain]

Actually, I don't think BL ever intended to mass produce the TR7 Sprint, precisely for the reasons you mention. Plus I dont think they could have sold it outside the US, because it would have demeaned the 8-valve TR7 in the US, being a model they couldn't have. I also think if they'ed wanted the TR7 to have the 16-valve engine for markets other than the US, they could have found some way to do that well before 1977, and would probably have sold hundreds.


I think they had an entirely different reason for making about 50 cars suitable for "normal sale", but not necessarily to be sold. And specifically, make them in the 12 months upto the end of 1977.

Graham

[Carledo]

I think they had an entirely different reason for making about 50 cars suitable for "normal sale", but not necessarily to be sold. And specifically, make them in the 12 months up to the end of 1977.

Graham

Ah, Homologation!

But the UK and other markets got several models the US couldn't buy, most specifically the Lucas Pi cars, 2500 saloon and the TR5/6. The Yanks got their own gutless, detuned, carbed version of the sports cars at least. The 2.5 Pi never made it, even with carbs. The Tr7 did, eventually get fuel injection for the US market, but far too late to save it's bacon.
American regs and sometimes even the fear of proposed American regs have a lot to answer for. The Tr7s initial appearance as a coupe only is one of them, there was a proposal to outlaw convertibles in the US at the time the TR7 was in planning. Of course, the proposal came to nought, as anyone with half a brain could have predicted. But Triumph at that time saw the US market as its prime customer for sports cars and everywhere else as a bonus, so they did everything with one eye on American regs.

Steve

[dursley92]

Actually, I don't think BL ever intended to mass produce the TR7 Sprint, precisely for the reasons you mention. Plus I dont think they could have sold it outside the US, because it would have demeaned the 8-valve TR7 in the US, being a model they couldn't have. I also think if they'ed wanted the TR7 to have the 16-valve engine for markets other than the US, they could have found some way to do that well before 1977, and would probably have sold hundreds.


I think they had an entirely different reason for making about 50 cars suitable for "normal sale", but not necessarily to be sold. And specifically, make them in the 12 months upto the end of 1977.

Graham

Just out of interest, speaking to Gordon Birtwhistle he told me had a TR7 Sprint auto on injection as a runabout for ages, used to take it home as often as he could. He said that was his favourite of all the TR7 versions he drove.

[GrahamFountain]

Yes, but the 2.5 wasn't primarily aimed at sale in the US for its bread and butter, as the TR7 and 8 were. I take the point about the carbs vrs injection on the 5 & 6; though I have been told the reason was the US dealers didn't want injection, just as they hadn't wanted the IRS on the 4A, etc., but I haven't checked that. Perhaps I should. The solution to the emmissions problem for the 16-valve sprint head involved injection, which, I was also told, was why that development programme got abandoned in 1975 (as I remember). As always, it's probably all much more complicated than that.

But, as we both appear to think, if marketing did want the TR7 Sprint for other markets, engineering could have made it happen. And if marketing didn't want it, for whatever reason, why would they have made as many as they did and only then have it stopped? And that S&M "killed it" is given in Knowles book on the TR7. My speculation as to the reason is just that, because I don't belive the argument S&M killed it after 60 were made, because it's specs were too like the 7's - you don't need to build anything like 60 to work that out, or even to work out how much it costs extra for a CBA.

You did, however, need to build about that many cars to homologate modifications for group 4 cars under the FIA's new rules from 1976, which applied to the TR7 from 31-12-77 on. Ford, GM, and Porsche all built runs of 50 to 60 cars in 77 to 81 to homologate modifications. Toyota and Lancia didn't, and had to give up their multivalve heads before the 78 season. What happened to GM and the HS in Portugal in 1978 is more complicated, but relates to the same rule changes, an article by Graham Robson detailing the differences between the road and rally cars, and, according to GM, some kind of misunderstanding with the FIA/RAC representatives over whether they had till May to make the changes.

Graham

[GrahamFountain]

Just out of interest, speaking to Gordon Birtwhistle he told me had a TR7 Sprint auto on injection as a runabout for ages, used to take it home as often as he could. He said that was his favourite of all the TR7 versions he drove.

Would that be the black "development hack" Knowles reports got disappeared in the late 70s?

[Carledo]

Different car I suspect, but a long time mate and customer has a TR8. Nothing unusual about that, but this one is a works black convertible with RHD and manual steering on a V or W plate (I forget which) It also has bigger brakes, a unique airdam, skirts and a sort of rear splitter and is alleged to be the "last" TR8 development car. Abandoned when the writing was on the wall for Triumph, it was supposedly sold to a couple of the engineers who worked on it and developed further with the motor now producing about 280BHP. Then it disappeared for a few years till my mate got hold of it in about 2004, with a recorded 37000 miles and all original body and paint. I've driven it several times, it's an absolute monster of a car. Shame it got cancelled. (this is the litany of the Triumph enthusiast)
But the point of this ramble is that Triumphs prototypes and development cars were almost always sold off, usually to someone at the factory and then descended into obscurity from there. I suppose we should be grateful because a considerable number of these "might have beens" have beaten the odds and survived when any other manufacturer would have scrapped them. My own theory is that Triumph were too tight fisted to just junk a viable car and offered them around the works in an attempt to at least get something back on their investment!

Steve

[sprint95m]

The TR7 was aimed squarely at the American market, it was introduced there in 1975.

If BL had intended the TR7 Sprint for the US market then the prototypes would have had Stromberg carburettors.
Something that hasn't been mentioned is the cost factor, it was considerably more expensive to produce Sprint engines than TR7 engines.

BL also tested the TR7 with an O-series engine. This option made sense financially given the lower cost of an O -series compared to the slant fours
and their planned use on the incoming Montegos and Maestros (so would have shared development and production costs and these had EFI).



The T2000 was marketed in the USA but withdrawn (due to poor sales) before the 2.5PI entered production.



To answer the original question, I think no, using the SD1 axle was surely intended from the start, not only for the TR7 Sprint but also the TR7 itself.
If the Dolomite and TR7 ranges had continued into mark 2 versions I reckon the O series, LT77 five speed and SD1 axles would have fitted.




Ian.

[GrahamFountain]

If BL had intended the TR7 Sprint for the US market then the prototypes would have had Stromberg carburettors.

Even with Strombergs, they couldn't sell the 16-valve engine in the US because it still couldn't take the emission control equimpent like the 8-valve.

BL also tested the TR7 with an O-series engine.

Bet they didn't make anything like 60 of them. Or have 30 at the press garage. But then they didn't rally an O-series engined TR7.

The point is, did they wait till 77 to build a significant number of TR7 Sprints because they couldn't have built any before, or because they didn't want any till they realized they were going to have to re-homologate the 16-valve TR7 because the TR8 might not be ready for the start of 78? Which it wasn't. Robson says, at the time Davenport didn't know when it would be ready. Implying, I think, that was because he didn't know if or when they could get the RAC to belive they'd made 400, when they hadn't come anywhere close.

Graham

[sprint95m]

If BL had intended the TR7 Sprint for the US market then the prototypes would have had Stromberg carburettors.

Even with Strombergs, they couldn't sell the 16-valve engine in the US because it still couldn't take the emission control equimpent like the 8-valve.

Why not?
Saab managed to do that (on their 900 16 valve 2 litre engine), didn't they?

The TR7 wasn't the only car to be trialled with a Sprint engine. The 2000 was also tested
but this was unsuccessful because the car was too hard on fuel and not fast enough.
I have seen a Stag V8 engined T2000 prototype (displayed a Ingliston some years ago).
Canley Classics owner Dave Pearson has a collection of T2000 prototypes, maybe including a Sprint engined one?

The O-series engined TR7 project was c. 1980.
There was a lengthened wheelbase body shell also.




Just out of curiousity,
does a TR7 Sprint have the curiously shaped engine mounts like those on a Dolomite Sprint?


thanks,

Ian.

[xvivalve]

I scrapped a (aftermarket) Sprint engined '7 a few years ago; it had most peculiar support structure for the engine, but one that looked to be original? From memory, a cranked cast bracket was bolted to one side of the subframe, passed under the upper part of the sump and supported the other side of the block!

[Carledo]

The Saab engine is a red herring, the 900 head is 16v true, but it is Saabs own with 2 camshafts and was designed and built much later, probably with the designers eye pointed squarely at emission regs. In fact, by the time of the 900, only the block bore a passing resemblance to the Triumph original, Saab had developed and improved all the rest, notably including a belt driven water pump.

Steve

[sprint95m]

The Saab engine is a red herring, the 900 head is 16v true, but it is Saabs own with 2 camshafts and was designed and built much later, probably with the designers eye pointed squarely at emission regs.

That doesn't satisfy my curiosity I'm afraid, as I already knew that,
it was the equipment added to allow the use of Strombergs that intrigued me.




Ian.

[Carledo]

The Saab engine is a red herring, the 900 head is 16v true, but it is Saabs own with 2 camshafts and was designed and built much later, probably with the designers eye pointed squarely at emission regs.

That doesn't satisfy my curiosity I'm afraid, as I already knew that,
it was the equipment added to allow the use of Strombergs that intrigued me.
Ian.

Sorry Ian, shouldn't try teaching my Grandma to suck eggs!
I'm not sure about the US market cars, but I had a 1975 Saab 99 2.0 that ran on a single Stromberg carb. This was only an 8v engine but still had a large and wide rocker box,similar to a Sprint one. From direct experience with American cars of the 70s and 80s, I can tell you that most were fitted with a large and bulky air pump driven by a V belt which was part of early EGR tech (my UK car didn't have this) but the problem with the Sprint and TR7 may have been purely one of space, there not being enough room under the bonnet to get the necessary stuff in! Saabs had a much more generous engine bay. Add the crippling power losses induced by early Cat tech and that may have been considered sufficient reason not to bother! But it's only a theory!

Steve