BlueStag

Ain't no such part to be found on my rig.

You might well be onto it. I did as I described above: cut out a section, replaced with a flex pipe (near where the pipe turns horizontal beside the trans) took off the carbs and heat shield, tightened up the flange before tightening the flex pipe, put the carbs back on, and DAMN! It still leaks. At the back side by the block, a substantial leak. Where there is no stud to tighten.....Kill me now. If I have to take off the whole manifold again I am just going to burn the damned thing down to the ground. Any chance that I can just bung in two gaskets and get a seal? Please?

Pull it out again and test it again. Speak harshly to it. And show it some gasoline. Just show it.

I'm thinking that you are right, that my exhaust is not quite lined up to the manifold. Definitely thinking of fitting in a flex pipe if I can find one.

Got the flexible rubber hangers, but the hole that the exhaust passes thru is pretty tight. I think it is bound up there.

And the dreary tale goes on; I have been fighting a leaky throttle shaft on my front SU, so I purchased from Ztherapy a pair of throttle bodies. While I was wrestling with that, I decided it was time to tackle the leaky manifold to exhaust flange gasket. Of course, I sheared off a stud in backing off the nuts. Wadda surprise. And I decided to clear out the manifold heating and the remnants of primitive emissions hardware. I even got my mitts on an early balance tube to replace the 260 tube that I have been running. I got the broken stud resolved with a helicoil. I set it loosely on the head studs and ran on a few flange nuts just enough to keep it from falling off. And I fought like hell to get the exhaust pipe to fit over the three studs. So much so that I released the manifold from the head and struggled to get the manifold to fit up with the pipe. The gasket had a rough time of it. Eventually I got them tied together and loosely nutted, then the manifold to the head. Got everything tightened up and the carbs on. Fired it up. Damned thing leaks from the manifold to exhaust flange, again. Worse than ever. Kill me now. One element that might illuminate the question: this is all in my Triumph Stag. The Stag has a rear suspension not unlike a ZX: semi trailing arms, which pivot on a subframe. Factory Stags were V8s, and two exhaust pipes passed thru holes in the subframe. My rig has a single pipe passing thru the subframe. I wonder if my exhaust suffers from being too "tight", not having any ability to twist with the engine. I might be looking for some flex pipe. Anyone care to tell me where I am wrong? God knows I am ready to accept being wrong about some damned thing,

Zguy, Thanks. I've already trimmed it and polished it up a bit. It is on the car, even as we speak.

I would dearly like to get an SU balance tube off of a '70 to '72. Ie, one of the less cluttered ones. A euro tube would be great, but I am not fussy. Anything but a 260 tube....

Drilled the damned thing and tapped it for a heli coil. Now I desperately want a balance tube NOT for a 260. I don't need a euro tube, but I'd take one.....but a '70 to '72 tube would be just the ticket. Had the engine running again this evening. Will be a few days before I drive it again.

I am no expert. A '75 280Z engine will have dished pistons. If you put a E88 head on it, I think your CR will drop to absurdly low levels. If you use the P90, I think the same will happen. You might want to spend some time at: http://datsunzgarage.com/heads/ The P90 head has to be the best head that you have on hand to use. It breathes as well as anything Datusn made for the L6. But you will want to put it on a flat topped piston engine. Especially for your modest power ambitions, you will find the SUs very satisfactory. A pair of Hitachi SUs will supply the needs of an engine making 250hp, or so others on this board have shown to be true. You have a shot at making 160hp with what you have, and your minimal goosing plans for the engine makes sense to me. As for MPG, if you want to maximize that, you want fuel injection. SUs are best in that: they are the cheapest carbs that you can use, AND they are idiotically simple to work with. I say that as I am an idiot and would be flummoxed by Webbers etc.

No, no. The damage is not in the head. It is at the other end of the manifold, at the flange, to nut on the exhaust pipe.

No, I got it. There was no shifting this stud. It is the middle one. I'll stuff a new one in until it sicks out the other side of the flange and have it brazed in place. Or get another freaking manifold.

OK, so drilling and tapping is a flaming pain in the butt....... Gonna take this heap to my shop and have them weld a stud in place.

Drilling and tapping are the easy part. Getting the damned thing out is the rotten bit. I THINK I have loosened all the nuts, yet nothing is moving. I like to back all the nuts to the end of the studs and then break the item lose. I find I don't drop as many nuts that way, and the part does not explode off the surface it is bolted to. I may not have found all the nuts, but damn there sure are a lot of them!

Excellent tip. Got no MIG welder at hand. This stud is well and truly rusted in place.

Sigh. There is not enough of the stud to grab with the vice, I am sure. And I really did not want to change the gasket. There is all that blasted manifold heating plumbing. Good time to get rid of it, I suppose. And while I have the nasty thing apart, I suppose I could get rid of the air injection tubing. What size bung is needed to close those holes? Why can't any of this be easy?

Oh, just kill me now. My exhaust manifold to pipe gasket has been leaking forever. So like an idiot I decided to fix it. I sure fixed it. The middle stud sheared off. There is a short bit protruding, but much release fluid and a vice grip have failed to twist it loose. I could JUST get under there, I suppose, and drill it out and tap it. Grrr. But I am too old for that crap any more. I have already pulled the SUs off. I would have to take off the balance tube, but, is it possible: to back the nuts off holding the manifold to the head without needing to remove the intake manifolds? Once I have the exhaust manifold in the vice I will have no problems drilling it out and tapping a new thread. I hope. Any thoughts? Other than to purchase a header?

Aston Martin, Triumph, Austin Healy, and several others, I am sure. The Brits built lots of pretty good straight sixes after the war. And ran them with SUs.

Hey, Tony. I'm agreeing with you. You say that a pair of Hitachi SU's can supply an engine producing 250hp, I am willing to believe you. Again, had I been forced to guess, I'd have said more like 200hp, but again, as I say, I only have these opinions based on my reading of old Brit cars. You say you have succeeded repeatedly. I utterly take you at your word. I think that I can say two things without fear of contradiction: You will not find cheaper induction for this application. You need to have the carbs utterly rebuilt, no cutting corners. Other than that, I say go for it. Hell, make an engine that produces 300hp on a pair of those carbs. I dig it. Triples don't work well on a Z? OK Jag and Aston used them to effect. I have seen a Triumph TR6 with triples. Me? I think that guy needs to find better ways to spend his money.... Hell, get six tiny SUs from motorcycles.....

So, is it possible for a pair of 1 3/4" SUs to deliver enough fuel and air to maximize the potential of a somewhat "hot" 3.1 (lively cam and medium-high compression ratio)? Apparently. What is the absolute upper potential of this pair of carbs? Apparently on the order of 250hp or there-abouts. If I had had to guess based on my familiarity with Brit cars, I'd have said 200hp, but that would be entirely armchair experience. Consider what sort of power Jaguar and Aston got off some straight sixes with SUs, how many SUs (twins, triplets) and the size. Also assume that your stroker is going to be a few percent more volumetricly efficient than those old Brit engines. Tony says you can do it, so I'd say do it. Lord knows you are not going to find cheaper induction than a pair of SUs. Get them utterly rebuilt. You will get no power out of a carb that sucks air down the wrong path. I'd still like to see SOMEONE ELSE mount three SUs on an L6. Hehehhehehehe.

Good point. But don't forget to speak harshly to it.

Or douse it in gasoline, light it and push it off a cliff. While speaking harshly to it.

It still does not damned crank? Get a jumper cable. First connect to the two bolts to chassis that the two grounding cables attach to. Test. If that does not get the POS cranking, then jump straight from the battery to the starter. Test. No luck there? Push it off a cliff. No. Then do the chassis bolt in the engine bay directly to the battery. No luck? Push it off a cliff. But first go from the starter to the bolt at the end of the cable from the battery. No luck? Douse it in gasoline, light it, and push it off a cliff. Or be prepared to run a cable directly from the battery to the starter. With a link to the chassis. And speak harshly to it. Always works for me.

Indeed. I have a pair of Ztherapy throttle bodies coming and want to do all the work in one hit.

Do I understand you to write that what I am looking for is a 8mm x 1mm? 'Cause I can certainly dash out and grab a few of those!