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 Post subject: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 3:43 pm 
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1098cc
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Location: Bundanoon nsw
Is anyone out there using twin 1.5" su's on an 1100 engine ?

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 Post subject: Re: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 4:29 pm 
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1275cc
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I Don't know of anyone.

But I am looking for a specific type of 1 1/2's and have a spare set 1 1/4's :)

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 Post subject: Re: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 5:22 pm 
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1360cc
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I'm thinking you should maybe do some work on your engine to match the carbies :!: :idea: 8)

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 Post subject: Re: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 5:47 pm 
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If a std 998 can run an 1&1/2 quite well,
then an 1100 can run twins with no problems at all... true

each piston inside the 998 sees a single 1&1/2 (one at a time)

so a set of twins is simply better because of less restriction in the manifold
& far better (more even) distribution across all 4 cyls

they work extreamly well if set-up well for the intended purpose

so even with twin 1&1/2 carbs,,, each piston is still only seeing a single, just a far straighter , more direct, less restrictive path

same-same , just less restriction & more even distribution
no more inner 2 running slightly rich & outer 2 running slightly lean

simples

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 Post subject: Re: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 6:13 pm 
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Yay For Hay!
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Location: Wodonga - Vic/NSW border
TheMiniMan wrote:
If a std 998 can run an 1&1/2 quite well,
then an 1100 can run twins with no problems at all... true

each piston inside the 998 sees a single 1&1/2 (one at a time)

so a set of twins is simply better because of less restriction in the manifold
& far better (more even) distribution across all 4 cyls

they work extreamly well if set-up well for the intended purpose

so even with twin 1&1/2 carbs,,, each piston is still only seeing a single, just a far straighter , more direct, less restrictive path

same-same , just less restriction & more even distribution
no more inner 2 running slightly rich & outer 2 running slightly lean

simples


except for the stop-start of the air flow down each throat because of the 2-1--3-4 firing pattern

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 Post subject: Re: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 9:09 pm 
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religious status
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Location: near Baulkham Hills, NSW
simon k wrote:
TheMiniMan wrote:
If a std 998 can run an 1&1/2 quite well,
then an 1100 can run twins with no problems at all... true

each piston inside the 998 sees a single 1&1/2 (one at a time)

so a set of twins is simply better because of less restriction in the manifold
& far better (more even) distribution across all 4 cyls

they work extreamly well if set-up well for the intended purpose

so even with twin 1&1/2 carbs,,, each piston is still only seeing a single, just a far straighter , more direct, less restrictive path

same-same , just less restriction & more even distribution
no more inner 2 running slightly rich & outer 2 running slightly lean

simples


except for the stop-start of the air flow down each throat because of the 2-1--3-4 firing pattern


That effect is minimised by the balance tube, usually pretty big on twin SU setups.

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 Post subject: Re: twin 1.5" su's
PostPosted: Fri Jul 17, 2015 10:36 pm 
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848cc
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AWOODY wrote:
Is anyone out there using twin 1.5" su's on an 1100 engine ?

Yes I am.


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 Post subject: Re: twin 1.5" su's
PostPosted: Sun Jul 19, 2015 5:20 pm 
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1098cc
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Location: Bundanoon nsw
What is your engine spec , needles and springs.

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 Post subject: Re: twin 1.5" su's
PostPosted: Sun Jul 19, 2015 8:42 pm 
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Location: near Baulkham Hills, NSW
I ran twin HS4s on a 1098 back in 1967. It was bored to 1218cc (68mm Imp pistons), ran a ported 1100S head with stock valves, a C-AEA544 cam and stock 1275 rockers. Exhaust was a Sonic LCB.
It ran mid 16s at Castlerealgh drags, blew my mate's 1275S away. :)

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:


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 Post subject: Re: twin 1.5" su's
PostPosted: Sun Jul 19, 2015 9:57 pm 
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848cc
848cc

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AWOODY wrote:
What is your engine spec , needles and springs.

Motor was build in the mid 1990's so memory of exact details is vague.
It's an 1100 plus 60 thou
Modded 202 head with a lot (I now think to much) decked of it as I struggle to get head gaskets to seal.
Russell engineering cam (I can't remember what he was doing back then, 1993 or 4 or what it was called)
LCB exhaust with single RC40
Twin H4 SU's (I will check the needles and springs and let you know)

and it pulls really well and was a great replacement for my tired 1360.


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 Post subject: Re: twin 1.5" su's
PostPosted: Mon Jul 20, 2015 4:23 pm 
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1098cc
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Thanks for that , yes my engine was built a long time ago (2 owners) and the guy who built it could not remember the exact details !

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 Post subject: Re: twin 1.5" su's
PostPosted: Mon Jul 20, 2015 6:36 pm 
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848cc
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I think the springs are blue and the needles are E3.

I will pull one out and have a look when I get a chance (may not be till the weekend).


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 Post subject: Re: twin 1.5" su's
PostPosted: Tue Jul 21, 2015 3:06 pm 
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1098cc
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Location: Bundanoon nsw
that will be interesting, thanks

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