Something screwed into the exhaust ports of a Sprint head

[GrahamFountain]

I've got some close-up photos of the head on the injected Sprint engine in the SD2 engineering development car at the British Motor Museum in Gaydon. Unfortunately, I can't post them here without paying a fee - not sure how much even.

Anyway, these show some additional parts screwed into the head above each of the exhaust ports. They appear to be a threaded insert about 3/8" dia. sticking out of each of these is about 3/4" of about 1/4" round bar, flattened from, more or less, where it comes out of the insert.

Has anybody got a suggestion what these might be for? I wonder if they're to measure the exhaust gas temperatures remotely - though there's nothing connected to any of them.

The other question is, would anybody know how to identify a 16-valve version of the cost-reduced Triumph slant-four engine being developed for SD2 upto about 1975 or so?

Graham

[matt of the vivas]

Air injectors to meet US smog regs? Was a common way to do it back then, air pump driven off the front pulley pumping air into the exhaust manifold to get more complete combustion and cleaner emissions.

[Galileo]

A charge? Surely that would only be if you publish the photo for profit? There are a few pictures of the SD2 floating around but they always seem to just show the injection side.

[GrahamFountain]

A charge? Surely that would only be if you publish the photo for profit? There are a few pictures of the SD2 floating around but they always seem to just show the injection side.

It's because I had them take the pictures for me, so they retain copyright. If I went and got them to lift the lid and I took pictures I could do as a would, but between the petrol and the cost of a new ear after the wife'd had her say, it was just easier.

None of the other photos showed what I wanted to see - the exhaust manifold.

Graham

[GrahamFountain]

Air injectors to meet US smog regs? Was a common way to do it back then, air pump driven off the front pulley pumping air into the exhaust manifold to get more complete combustion and cleaner emissions.

That would make sense, as the SD2 was supposed to be able to meet US emissions requirements. In which case, the bits of round bar would be just plugging up the holes?
Graham

[GrahamFountain]

Air injectors to meet US smog regs? Was a common way to do it back then, air pump driven off the front pulley pumping air into the exhaust manifold to get more complete combustion and cleaner emissions.

Also, it seems that air injection wasn't enough on its own because, according to David Knowles' TR7 the untold story, the carbed version couldn't meet reqs, and the injection system was also needed.
Graham

[Carledo]

Air injectors to meet US smog regs? Was a common way to do it back then, air pump driven off the front pulley pumping air into the exhaust manifold to get more complete combustion and cleaner emissions.

This sounds like a very likely explanation to me! Ive had a couple of 80s American cars and this featured on them. they had holes in the head above each exhaust port with a threaded adaptor screwed into it and a metal pipe leading off which eventually wound up at the affectionately named "smog pump" I'm not sure that carbs in general couldn't meet US emission standards, my 85 Oldsmobile Custom Cruiser station wagon had the full smog pump kit, electronic ignition and a hulking 4 barrel Rochester carb on its 305 cu in V8, all of it OE. Not sure why they bothered, the rotten thing only produced about 140bhp and did around 8mpg, I didn't keep it long! A later Cadillac Seville that I inherited from my father in law had a fuel injected but smaller V8 that was positively eco friendly by comparison, according to it's trip computer, it could do 26 miles per (US) gallon at 65mph cruise. This car also had the full emission gear fitted and working. But the results it produced on British MOT testing equipment were not all that good!

Steve

[GrahamFountain]

Once again, I'm going off what David Knowles says about the carb version of the Sprint not being able to meet US requirements.

As I remember, and I'm not certain I've got this right, the California Spec TR8 had to be injected because of the higher requirements there, and still only made 135 hp. I think it gives a bit better than 8 mpg. Maybe ever twice that.

Graham

[Carledo]

Well I guess you can understand the 8 mpg when you consider the roughly 2.5 tonne weight of a "full size" US wagon and total absence of anything resembling aerodynamics. So a TR8 would be at an instant advantage. But there's NO excuse for only getting 140 BHP from a 5+ litre V8!

Maybe there's somthing inherent in the SU design that kept them outside the US specs (or just bloody mindedness by US legislators)

Steve

[GrahamFountain]

I've been back and looked at the pictures from the BMM of these things screwed into the head. And it does look like they are fairly thin walled tubes that have just been cut off and hammered flat. So I think they must be inserts for a smog pump, as suggested by matt of the vivas.

As to whether there's a problem with the SUs specifically, I don't know.

But while the UK spec TR7 Sprint compares very well with (arguably is better than) a US spec V8 in a TR8 (slightly lower max power, but peak torque given at a higher percentage of maximum rpm), presumably, by the time this smog pump's sapped its power, the 135 hp V8 is a clear winner - even with its asthmatic top end.

BTW, anybody know what power one of these air pumps uses up?

Graham