blakep82
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| posted on 27/1/08 at 12:08 PM |
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rubber intake manifold runners?
can anyone see any problems with making a manifold flange and welding on, say 3/4" of tube as a runner, and then using rubber (petrol
resistant) hose as the main runner.
it would save too much trouble with
1, bending (or cutting and re welding) of tubes,
2, getting the angles all right, as the rubber will sort any misalignment
3, calculating runner lengths, as they could be changed really easily by shortening the rubber or putting longer pieces in
obviously the carbs would be supported on their own brackets, the alternator bracket has a handy provision for this on the ecotec engine
any thoughts?
this is for bike carbs on a vauxhall engine btw.
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thomas4age
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| posted on 27/1/08 at 12:17 PM |
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Bad idea,
rubber will deflect or even collapse completly when the throttle is shut the vacuum created in that event is enomous,
you could cut up the rubber tube into socks and fit as much alloy tube in between as you can, flow-wise... it's not all that good.
regarding lentgh,
are you going hemholtz? or have you got a RPM prefference for when the peak torque should be there? cams? exhaust?
grt Thomas
If Lucas made guns, Wars wouldn't start either.
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blakep82
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| posted on 27/1/08 at 12:29 PM |
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hmm, hadn't thought of the deflection... can't you get reinforced tube with spiral steel running through it?
at the moment, the idea is to get it running... i can think about the rest later
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saigonij
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| posted on 27/1/08 at 01:04 PM |
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i tried that with silicon hose, even the 90 deg bend collasped under the vacuum.
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jacko
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| posted on 27/1/08 at 05:22 PM |
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What engine and carb are you using?
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blakep82
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| posted on 27/1/08 at 05:58 PM |
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2.0 ecotec 16v etc, and zzr1100 carbs
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zetec7
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| posted on 27/1/08 at 06:40 PM |
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Motorcyles use rubber intakes without collapsing...at least, my Kawasaki GTR1000 doesn't seem to have a problem with this. How about visiting a
motorcycle breaker's, and getting the appropriate rubber ones for your carbs?
http://www.freewebs.com/zetec7/
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blakep82
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| posted on 27/1/08 at 06:45 PM |
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^ thats the reason i was thinking it, but bikes only seem to use short peices (lik an inch long) to clamp over the manifold and carb to make the
join...
what about nylon (plumbing) tube with rubber bends at both ends?
edit: i'm thinking mylon isn't resistand to petrol is it...
ally tube then with rubber at both ends? 
[Edited on 27/1/08 by blakep82]
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coozer
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| posted on 27/1/08 at 09:19 PM |
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I made a manifold out of 5mm thick steel with 45mm tubes. I used these because they were free from work
In order to match my carbs to the tubes (ZX9R) I simply made a couple of plates from the offcuts of the manifold plate and welded them onto the tubes.
I then used the original bike inlet rubbers that bolt to the engine as a template for the holes.
The inlet holes were smaller than the 45mm tube behind so no matching required.
 
inlet
 
inlet2
The thing sits and ticks over smoothly at 700rpm but I've still to set them up and use it in anger over the whole rev range.
Steve
1972 V8 Jago
1980 Z750
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blakep82
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| posted on 27/1/08 at 09:41 PM |
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^ thats quite a nice idea 
any idea on a starting point for the runner length?
i understand that the lengths have effects on how the engine performs, but how long is average?
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coozer
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| posted on 27/1/08 at 10:08 PM |
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Ha! no idea. I just made mine after looking through the photo archive and seeing some of the bespoke jobbies. Also the length of weber manifolds so
fingers crossed they will be OK!!
Steve
1972 V8 Jago
1980 Z750
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blakep82
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| posted on 27/1/08 at 10:24 PM |
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what length are yours?
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