Are the aftermarket carb rubber mountings any good?

[edgyWedgy]

Those mounts look nice i should really get those things too, everyone seems to use them. Did you just buy them, or have them machined at a shop? By the way, a good temporarily solution is something i'd really benefit from. It'd keep the engine from idling/low revving too lean, for as long as i need to make good replacements. But i fail to see how you managed to pull the carbs enought this way to close the air leak. You only pull the top side to the manifold with the tie wraps as far as i see, how did you support the lower side?

I'm curious about another thing too, what is that thing connected to your vacuum cannister if i may ask? I looks different from what i have, and i don't recall newer models having another way of getting vacuum.

[saabfast]

The mounts tend to crack at the top due to the weight of the carbs and the cantilever effect. The zip ties stop the weight of the carbs pulling down and cracking the top of the rubber away. I guess by the same token the ties would close the cracks provided they were not too large.

[Beans]

Those mounts ... Did you just buy them, or have them machined at a shop? ...

They are an own interpretation based on the ones sold by the Dolomite Club.
They were machined to order. More info in my weblog (link is in my signature) use SU as label.

But i fail to see how you managed to pull the carbs enought this way to close the air leak.
You only pull the top side to the manifold with the tie wraps as far as i see, how did you support the lower side? ...

Alan is quite correct there

... what is that thing connected to your vacuum cannister if i may ask? ...

Not sure what you are referring to. if it is the vacuum unit of the dizzy, that is the original pick up pipe connected to it.
In the picture the pipe is disconnected from the carburettor and hanging down.

[sydney.wedgehead]

... a good temporarily solution is something i'd really benefit from.

I got a nearly a year's extra life from some split mounts by coating them with POR15, which seems to stick well to clean rubber, but eventually new splits develop.

I'd rather just fit aluminium o-ring mounts than eff around with a short term fix.

[edgyWedgy]

So did you design and cnc them yourself is because of the availability, price, or quality? The guy i linked to in my first post sells them for $130, it may be a good option. I doubt you can get them cnc'ed for less, but i don't know if he sells outside the US.

@saabfast I get that due to weight the top end starts to crack, but i just didn't expect pulling it back with zipties wouldn't put too much strain on the lower side, while still closing the leaks in the upper side. It's only a great thing though, because it also might be the solution for me.

[edgyWedgy]

I also tried to pull that trick by covering them in sealant, i can't recall which type exactly. Unfortunately, it only solves the problem partially for me. I'll surely try to get my hands on alu mounts, but it'll probably take a week at least. If they're available.

[moodyblue]

Not the best picture but I just ordered some 1/2" flat bar on ebay and made some myself, I fitted using gaskets which give a good surface area seal and a little bit of heat protection compared to O rings. I left the studs long enough to fit spacers but I haven't made my mind up whether to use them or not.

[edgyWedgy]

Nice manifold and mountings. Unfortunately i don't have a router myself. I do have access to a turning bench, but i doubt it's possible to make it without a router. I'll have a talk with the guy that sells them to ask if he also sells outside US.

[moodyblue]

Aluminium is very easy to work, I had access to a well equipped workshop (lathe and milling machine) but I could probably have done it with a hacksaw, a bench drill with correct size hole saw, countersink, and file. I didn't bother with the cutouts for the mounting bolts which is a simpler / neater design and removes a dirt trap, the carbs have to come off in any case if you ever want to remove the mountings. Job satisfaction and you save a few quid

[Beans]

... I left the studs long enough to fit spacers but I haven't made my mind up whether to use them or not ...

My car behaved quite well without the insulation spacers, but after I fitted them the overall performance somehow felt better. Not much but smoother

[sydney.wedgehead]

Not the best picture but I just ordered some 1/2" flat bar on ebay and made some myself...

Great work and thanks for posting... inspires me to do it myself too.

I love the finish you got on the inlet manifold. Is it coated or just blasted?

I like the hex plug you've used on the bottom port. May I ask where you got it and was it difficult to thread the port?

What is the best material to use for phenolic spacers? I've had people tell me to cut up a cheap kitchen cutting board.

[moodyblue]

You should try it, but remember that the measurements have to be spot on, I can't remember them, but I did use the old mountings as a template and guide.
6mm spacers are available on ebay but better ones here:
http://sucarb.co.uk/insulating-manifold ... 11458.html

I blasted it myself with a small hand held DIY thing and sprayed it. I used etch primer before the silver.
The port is blocked for an electric water pump, I just tapped it to M24 (easy job), turned down the head of a stainless bolt to 4mm thickness and fitted it with a dowty seal. I used a woven rubberized gasket material cut to shape for the mountings to the manifold and the stock SU gaskets either side of the spacers.

Thanks for the tip Beans, I probably will use them, it could be to do with the distance increase, fuel/air/velocity etc. improving performance? I'm no expert.

[edgyWedgy]

In think i'll have it machined at a shop, the lathe i can use is a chinese knock-off. I've used it before, and it's usable to make things but it's by far not precise enough for these kind of things. If you happen to still have the measurements somewhere, i'd like to kindly ask you if you can send me them.

By the way, the change in performance is probably because of the different volume of the manifold. The way the engine is taking in air creates a certain resonance(vibration) in the air in the manifold. If the volume and shape of the manifold, and the valve timing are used right for it, it creates a small, minor form of turbocharging. The exhaust pipe can have a comparable effect.
Like a flute's or organ pipe tone changes with the effective length of it, so does the turbocharging effect of the manifold.
The beauty of this, is that it doesn't cost you any engine power, does not require any moving parts or oil, doesn't create heat, and it doesn't have a turbo lag. And it has more advantages.

I didn't expect designers in the 70s to take that effect in account though. At the moment i'm experimenting in SolidWorks' Flow Simulation to find out if there's some gain to achieve with a different airfilter box. If so, i'll surely post my findings here.

[moodyblue]

Sorry I don't have the measurements but I'm sure I saw a CAD drawing online somewhere recently. You make a good point about the airflow in the manifold but I'll have to live with it whatever. I haven't made a decision on air filters yet, K&N flat, deep, classic mini cone or Ramair, there isn't much choice out there, keep us posted on your findings.

[edgyWedgy]

I guess the air filter won't make that of a difference if not restricting too much.(so, unlike the stock filter)
The thing i'm busy with, is a custom designed airbox. I'll build it around a filter of my choice. I have the design of the valve in CAD and i know the valve timing. I still need the cam lobe shape and the shape of inside the cylinder head. Then I can simulate the airflow in SolidWorks to find out the optimal shape for the airbox.