Hi
I am working on getting my trials Chummy sorted. At the moment it has a ruby manifold with an SU on it. And with that is goes really very well. However it is the only part of the car which makes it non-eligible for VSCC LCES events. So what I would ideally like is to fit an early exhaust manifold and one of the inlets shown in the attached pictures. It would then potentially be a relatively easy swap between LCES eligible and the SU as and when needed.
It has the additional benefit of being able to be fitted with a standard SWB exhaust pipe.
Does anyone have one of these manifolds they would be willing to part with?
Thanks in advance of any help people may be able to provide.
Locals have had them fabricated by welding based on the updraught alloy housing. The internal dia is no less than the Ruby. One disadvantage is that the carb is closer to bonnet side precluding a filter.
27-01-2022, 10:38 AM (This post was last modified: 27-01-2022, 10:41 AM by Parazine.)
The SU in the photos looks like a type "UBA", as fitted to late Morris Minors and Morris 8's in the thirties. The "OM" has a stub pipe on the inlet side rather than a flange. UBAs are generally stamped "1930" on the side (nothing to do with the date).
I use one of these on my Chummy with a manifold I made from copper pipe, silver soldered together. In the sixties, V W Derrington made a cast aluminium inlet manifold for this job, it has to be very compact to get the SU under the bonnet without a side bulge. I have one of the Derrington manifolds but it's cracked.
I'm waiting to see if I can get it repaired or whether I can find a foundry that could cast a small number, so that they could be reproduced.
BTW, the manifold in the photo is upside down
27-01-2022, 10:57 AM (This post was last modified: 27-01-2022, 11:01 AM by Austin in the Shed.
Edit Reason: add content
)
I made one using an updraught manifold turned upside down,It's on the old forum somewhere.It worked very well with a 1 1/8" SU,Better I thought than the log manifold and 1 1/4" I have on another car.
The modded updraught works on a gravity tank as there is more head of fuel .
Ah - I see the SU isn't part of the spec when VSCC use required...
Two further thoughts. Ian Williams made a lovely little inlet manifold for me from a damaged - then cut down - Ruby manifold. Would this not be another option if you get stuck for the right ally item?
Parazine - does it actually matter which way the thing would be used. The serial numbers do appear to be the right way up on that one though...?
The manifold needs to lower the carb to get a difference in fuel level from the tank. Otherwise there is insufficient head of petrol and you suffer fuel starvation with less than 2 gallons in the tank.
27-01-2022, 11:29 AM (This post was last modified: 27-01-2022, 11:32 AM by Austin in the Shed.
Edit Reason: add content
)
Thinking about it I think you should be able to use the late box / ruby inlet out of a later manifold.Turn it upside down.Only need to adapt the mounting flange to suit. Cost a couple of quid.
After all I won class 1b in vscc four years out of six and third twice using a ruby inlet on a four branch exhaust and 1 1/8 SU.
I think that for LCES the car must be unmodified. A pre 1931 Chummy would have an updraft Zenith. So I think that for an easy swap between carbs you would need to either turn the manifold upside down and have a down draft SU or as you surmise a custom made manifold.
Alternatively you could always “doctor” the Zenith. I believe Robert Forman described this somewhere on the forum. I’ve got a “doctored” carb following his description ready to fit on my RK. It involves a wider Venturi, thinner butterfly, jet alterations and a bored out manifold. I’m not sure if this mod would be allowed under LCES rules but it would be hard to detect .
The pictures don't show my actual carb which is slightly earlier.
The plan is to revert back to the early exhaust manifold then just swap the inlet manifold and carb in and out.
With the current set up, with the Ruby manifold, the SWB exhaust pipe has been cut and shut to fit the slightly different exhaust exit position. This modified pipe clashes with the standard flitch panels I have installed so going back to the standard pipe would be neater.
The craziness of changing one thing and it effects half a dozen others.
I friend has offered me a welded up "updraft manifold modified into a side draft" one, and my Dad has a early manifold tucked away somewhere so I think I should have all of the bits.
I couldn't possibly comment on whether I would modify the updraft Zenith which would be used on Light car events.
.