AK260

Modified fully radiused Webber velocity stacks to fit my SUs. On the test drive the car sprinted into the rev limiter in first and second without me intending to! So they are adding value. The quality is 500% better than the MSA horns and they cost 1/3 in England. Can’t recommend these highly enough for an aftermarket air box.

Interesting, thank you!

To echo Steve, great post! [emoji106] What motor did you go for? (Year / model number)

I’ve been on the back of a GSX-R600 and MY GOD that thing could accelerate. Cant imagine what it must have felt like in yours full throttle aiming for the horizon!

Agreed chap! My buddy did go with his SUs and we got them tuned right pretty quickly. It produced excellent power below the 4k rev limiter ceiling on the first drive, so he's going to use them for the first 1000 miles and send the car with the triples to the RR once the run-in period is completed. With the AFR sensor / gauge installed, we should be able to find a needle in my collection that is rich enough to fuel it sufficiently further up the rev range. On that note, to prove that the SUs can deliver enough fuel for over 230bhp to 6.6Krpm, I dropped in super rich KV needles into mine and the carbs can hit high 10s on the AFR at 6K rpm on a third gear pull - clearly over-rich, but point made! With that argument out of the way, there is only the question of flow, which his OERs will clearly address in good time. The beauty of going this way is that he will now have a direct comparison for SUs v DCOE (for the sake of scientific research 😛 and my personal curiosity). This way he will not wonder if he should have just kept the SUs, he will know through real-world driving experiences, where the SUs work best and where the DCOEs bring the engine to life even more. I'm personally a die-hard SU man for a road car, but with this nearly 3.0 engine being something quite special, even I have to concede that it needs the extra flow and sound track of the triples. But equally, I want to see what they do to the engine's current scintillating pull between 2-4Krpm - where we spend a lot of time in 2nd /3rd around the UK's fun twisty country roads - and it's still not "on cam" at that point!!! Can't wait to see what it will do between 4-7K. I've seen too many dyno charts of triples showing a rise in torque at 2/2.5k only to drop off quite noticeably until 4K where they come to life and produce great power / fuel atomisation. I'm hoping with some proper tuning and choke sizing, he can have the best of all worlds. Either way, that engine needs triples or Efi to give its full potential.

Yeah, I was wondering about that too!

You know, I have a dropbox folder full of little gems I discover over time on the net - this was in that folder and I have to agree with you. I was looking at it on my phone screen so didn't spot it. I also have no idea what it's supposed to be or where it came from 😉 Sorry for causing confusion / mis-info.

The first one is looking from the top down, the third one is looking from the underside up. I think ;)

I did mine as per the diagram on the right for exactly the reasons you mentioned - namely to provide more surface area at the top against the insulator.

Does this help?

Ps. Mine arrived just now and it is indeed glass! This came in too! When the wife asks, I’m blaming Cliff!!

Yep! That’s exactly it. Been thinking about It for 3 years and finally ordered it. I saw installed it in a friend’s car at the weekend and it looks period correct in any classic car. The “glass” though is plastic - which is a good thing if you think about it. Hope the Site-mister gets his pump sorted out! Oh and his fuelling too.

I’m about to do the same set up with a big filter / regulator and a facet silver top in tandem with my mechanical pump. My internet research has found that most aftermarket inertia switches can trip too easily, especially on track days. But the modern Mini’s switch is very reliable and doesn’t trip with pot holes etc. Also placement is important. Vertically inside the car on the firewall appears to be ideal. https://www.hubauer-shop.de/en/fuel-pump-emergency-off-switch-07131068856.html Part no. 07131068856

Also LHD v RHD makes a big difference on brake lines routing. Tell us more about the car.

Fair point, I guess I was looking for max flow at 6K RPM where the engine "should" be thirstiest.

I have to agree with you there! [emoji106] I like keeping the mech pump - i may also look into a bypass set up on the elec pump in case it ever fails. The problem is never fitting these things, it’s the stuff we put around them like not using the wiring loom supply and adding inertia cut off relays etc ;)

Thanks sir, I will look into it! [emoji106] Interestingly, the online fuel flow calculators all converge on around 18-20 gph (imperial) for 240bhp, so the silver top at 30 should be OK I think. [emoji848]

Does anyone know the actual flow rate of the mechanical pump? I am tempted to support mine with an electric pump. - a facet silver top as it’s not too juicy on pressure for my SUs (with a regulator of course) but their literature says it’s good for up to 200bhp - mine makes anywhere from 230-245 depending on whose dyno it’s on! ;) But the difference between a silver top and a red top is only 10% more flow for the red top. Yet the red top is quoted as 200+ applications. But what does the “+” mean if it’s only 10% more flow? 10% more power or infinity!? ;) But foremost I’m interested to know the flow of the mech pump - can’t seem to find it in the FSM I have.

Well I’ve just been sent the builder’s pamphlet / notes on their recommended running in procedure and it’s quite the opposite of what I had been told before (or misunderstood). Frankly I’m horrified as it goes against every grain of what I’ve been taught, BUT he builds engines so he knows what is best for his engines. The procedure is to fire up and let it idle for 20-30 mins, then baby it along at constant revs for 200-300 miles. I’ve always been told that you need to get the rings to expand under acceleration and seat under deceleration but NEVER to be left idling or steady state as it’s just polishing the bores. I know I didn’t want to get into this but there, I’ve done it myself! :p

When I googled it, I was served up some “wife pleasers”!!!! https://www.redbubble.com/i/throw-blanket/1975-Datsun-280Z-by-FromThe8Tees/66717202.16D0B

The good news is my friend has decided to use his SUs for all the reasons mentioned until the initial running in period is complete. Thanks all for the advice and an interesting discussion - so far ;)

At the risk of starting a heated debate, please help me understand this - why can carbs be better than ITB / injection? Except for the obvious other points, I had always understood that DCOE carbs suffer with reversion / standoff when the air pulses back and forth past the jet. Not forgetting low air velocity atomisation issues (read below 4k rpm) if not choked right down - which in turn takes away the benefit of better breathing up top. But an injector isn’t affected by how many times the air passes it back and forth or by the shockwaves in the same way as a carb jet. It just injects fuel once, at the ideal time and with great atomisation. So what am I missing? I’m not questioning factual experience but I’m keen to learn.

I have to agree with that - but never having set up a set of triples, I wasn't sure if I was being pessimistic 😉

I like the way you think!!!! 👍 And there speaketh the voice of experience!

Hello wise ones. I have a friend who is about to install his triple OERs onto a brand new high-end engine for his first start up and initial run-in. But given what a critical time those first 20-30 mins are, there isn’t much latitude for messing about to get them dialled in. So, I have advised he starts with his good known SUs set a little richer (say 3 turns down) than previously to account for a more thirsty engine and then once initial run-in is complete, he can swap them out. Also easy to get the adjustment right quickly with his afr guage. However, what if? What if he threw on the OERs and kept them there from the very beginning? How do you set them up so that the engine starts and is able to rev out to say 4k rpm without being overly lean or rich? Has anyone set a “base tune” on these carbs either off the car or with the engine off and is there any advice for my buddy? My assumption is that you can turn all mix screws out equally from closed to a ball park / best practice first setting, balance the throttles to “nearly there” using a feeler gauge. Or is it just a bad idea to start the engine and run-in with the OERs? I know there are different / opposing religiously held views on how to run-in an engine but that’s almost irrelevant as the engine builder has recommended the start it and hold it at xK rpm for y minutes. (My personal church preached a different method but let’s not get into that as it will divert us from our purpose). Or indeed, am I asking a question asked many times before and can be pointed to a previous thread?