Lotus Elan

Stromberg Adapter Plates - Federal v UK Spec

PostPost by: terryp » Sun May 13, 2018 12:46 pm

I suppose it?s a case of be careful what you wish for. Basically the last federal engine part on the car is a modified Stromberg adapter plate. Having sourced a UK spec replacement, I now have to ask, would it actually be any better.
The UK spec one I have is the later one with the link pipe at the top.
But the federal one seems to have a link at the top and bottom together with a link between the two. This together with the throttle mount seems to me to be perhaps a better solution?
Are there any technical reasons to suggest which would be better?
I am poised with parts in hand!
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PostPost by: 69S4 » Sun May 13, 2018 1:20 pm

Is your federal link pipe what's left over when you remove the crossover pipes or is it something else?

The UK spec one must be closer to what Lotus intended so I'd be tempted to go with that. It's not as if it's a difficult job to change them. At least it's not one of the low level 'fire risk' ones (as Miles Wilkins refers to them in the twin cam engine book :lol: )
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PostPost by: terryp » Sun May 13, 2018 2:09 pm

Stuart
Yes it?s what?s left after everything is removed and all the holes are plugged.
I was about to change it and noticed the throttle cable!
Then looked at it in another light and thought that it really does the job well.
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PostPost by: 69S4 » Sun May 13, 2018 2:51 pm

The throttle cable fixes to a bracket screwed to tapped holes on the cam cover. I'm not sure about the Weber / Dellorto ones but the Stromberg cam cover has a small section of the casting thick enough to tap into. From photographs it looks like the crossover pipes go straight across that bit of the cover so presumably the federal covers had some other way of anchoring the cable. If you change to the UK spec link pipe locating the cable is going to require a little creative thinking.
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PostPost by: terryp » Sun May 13, 2018 3:09 pm

Stuart, see below, looking very neat. Unless someone says it?s going to give me more power I think I had better leave it!

aff2a232-e708-41cd-a85d-e026f5f3022e.jpeg and


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PostPost by: 69S4 » Sun May 13, 2018 5:06 pm

Looks like you've got the cable bracket mount on the cam cover so that's one headache resolved. You just need some kind of go-faster badge (BRM or something) on the blanking plate to make it look like it's an upgrade :lol:
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PostPost by: USA64 » Sun May 13, 2018 6:48 pm

I would think that all the federal Elans were LHD and the cable passes through the plate in the middle, there's a hole. I could be wrong it's been a couple of years mine has been apart (engine in, body on but still with the body man). As the Stromberg set-up was for the USA it could be that the US set-up was more what Lotus intended, at least for Strombergs. I am using the cross-overs and they seem to solve the mix/lag/plug fouling/crankcase breathing problems I read about here so often. They do get very hot but I drove it year-round with no icing or vapor-lock (knock wood). If you never drove one in snow you're missing a treat!
We are supposed to be having fun, are we not?
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PostPost by: terryp » Mon May 14, 2018 7:20 am

I forgot to say its LHD so perhaps I had better keep with the modified Federal plate for the throttle cable, unless someone can say some technical reason?

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PostPost by: RogerFrench » Mon May 14, 2018 9:49 am

Now that I've interpreted plate as inlet manifold, link pipe as balance pipe, etc., I can comment.
I have a Europa TC which is converted from Federal spec carburation to UK Elan S4 spec. This includes carb changes as well as inlets with high-level balance pipe.
Is it any better than the Federal spec? Yes. Does the manifold make any difference? Hard to tell, but it has fewer holes and disturbances so I'm guessing yes. You do have to find a place to anchor the throttle cable outer, though.
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PostPost by: terryp » Mon May 14, 2018 10:29 am

Ok perhaps I havent explained myself very well.
I have now a UK spec car in all respects apart from having a modified Federal adapter plate and link pipe (all in one) as opposed to the UK spec type which is two pieces and a link pipe.
I just wondered whether anyone knew of any particular technical reason why the UK spec one would be better than a modified federal one.
Just to confirm - I have 3 holes filled in the federal version but a UK version would have two pipe joints!
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PostPost by: RogerFrench » Tue May 15, 2018 7:13 am

Well I understood perfectly, thanks!
The Federal manifold has the secondary throttles, which I guess you have removed, and the associated holes to be plugged. It also has the holes that act as a balance pipe. If it's all clean and no disturbances, I doubt there's much difference in performance to the UK-style arrangement.
I understand the top holes filled, or covered, in the Federal manifold, but don't you have at least 2 more?
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PostPost by: RogerFrench » Tue May 15, 2018 7:58 am

Apologies! Looking at the Parts List I see Lotus call these things Adapter Blocks. I guess my old-fashioned term is just that.

However, seeing that you have the Cam cover with the mounting point for the throttle cable, why not try the UK blocks as well as the Federal? You only need a bit of 5/8" x 1/8" strip with a bent end and 3 holes to fix your cable.
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PostPost by: terryp » Tue May 15, 2018 8:30 am

Roger, the only other holes are the side ones for the throttles, i tapped them and they have a bolt and copper washer, so a pretty good seal.
The throttle cable acts between the adapter block and the carbs , so I would have top fabricate a bracket. Possibly get a new cable as it wouldn't be long enough?
But I am begining to think that the federal casting has more link pipes, so how can that be a bad thing?
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PostPost by: gus » Tue May 15, 2018 12:46 pm

The federal adapter is a POS, it has passages that dip down and can collect fuel, releasing it at inopportune moments or so I am told

No one would ever put use one on purpose.

The late high crossover is the most desirable, though I cannot think of any reason to not use the earlier mid pipe
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PostPost by: CBUEB1771 » Tue May 15, 2018 5:04 pm

terryp wrote:Having sourced a UK spec replacement, I now have to ask, would it actually be any better.
The UK spec one I have is the later one with the link pipe at the top.


Keep in mind that the UK/European market and US market inlet systems for Strombergs serve two different functions. The US market version was intended to route cold mixture to the exhaust manifold for preheating and back to the inlet manifold to reduce hydrocarbon emissions at low engine temperature. The purpose of the UK/European market version was to yield more uniform cylinder filling to resolve an inherent problem in any four cylinder engine with two siamesed carburetors. With the Twincam on Strombergs cylinders 2 and 3 fill a little more slowly than cylinders 1 and 4. The balance tube on UK/European market systems alleviates that problem. Look at the inlet manifold for any BMC product with four cylinders and two SU or Stromberg carburetors. They all have a balance passage cast into the inlet manifold. The US version should have performed the same cylinder balancing function but that design criterion suffered in priority compared to emissions control. If you are not worried about hydrocarbon emissions at low engine temperature then the UK/European system is the better solution. It does not add gobs of power, just makes the power output of each of the four cylinders more uniform.
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