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Twin SU Carbs - Hiff 44 1 3/4"

Any type of technical questions or info

Moderators: KillerRx4, orx626

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DKWW2000
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Twin SU Carbs - Hiff 44 1 3/4"

#1 Post by DKWW2000 » Thu Oct 12, 2017 6:06 am

Just fitted these rare Carbs to my NA S3. Back in the day it was said they give 150bhp.

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The Intakes Growl & Snarl when you floor it :D


Currently Own:- S3 RX7 FB & RX7 FC TII Vert
Previously Owned:- 2 x NSU Ro 80s.....2 x S2 FBs.....DKW W 2000....Suzuki RE5....Norton Commander

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green200b
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Re: Twin SU Carbs - Hiff 44 1 3/4"

#2 Post by green200b » Thu Oct 12, 2017 6:43 am

How do you find they respond compared to a Weber or a standard carbie? I ran SUs on my Datsun years ago and wasn't especially impressed with them but I hope that your setup is better.


green200b, aka Alistair

1981 RX-7 Sport, 12A - daily
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bumpstart
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Re: Twin SU Carbs - Hiff 44 1 3/4"

#3 Post by bumpstart » Thu Oct 12, 2017 12:49 pm

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hif7.. mid 90's// lots of pull from any speed any gear. but slow to react to fast throttle movements . have to play the oil mixture in the bath cup to get response

pretty typical of variable venturi carbs and mixers

i always thought mine where built so much better than anything from weber.

but

. black art


when the going is hard, don't retard, remember your lubrication
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Re: Twin SU Carbs - Hiff 44 1 3/4"

#4 Post by bumpstart » Thu Oct 12, 2017 1:02 pm

twins are always a bastard to keep synchronised

there is expensive dial gauge indicators for piston lift to dial them together

but i found best trick is to make up a manometer on a board of ply . use cordial and clear tube and a few bent nails and an icecream container lid with a 10mm hole poked through ( and a 4mm one with the end of the clear tube poking through, next to it )

use the lid to seal against one of the carbs ( with the throttle stop ) and set a baseline mark on the manometer where it pulls the vacuum to
adjust linkage on the other carb using same test till they match

was using a mix of sewing machine oil and light machine oil in the cups . something you have to feel out for


when the going is hard, don't retard, remember your lubrication
27 years of rotary DIY
tech forum is for tech questions.. private message box is for private messages
paypal : bumpstart13b@hotmail.com

DKWW2000
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Re: Twin SU Carbs - Hiff 44 1 3/4"

#5 Post by DKWW2000 » Fri Oct 13, 2017 6:14 am

green200b wrote:How do you find they respond compared to a Weber or a standard carbie? I ran SUs on my Datsun years ago and wasn't especially impressed with them but I hope that your setup is better.
They respond far better than the Stock Carb , but can not comment on the Webber.
There is far more Torque lower down the Revs & far much better when decelerating. The power is smooth right through the rev range & it feels like it is a lot quicker 0-80 mph.

Bumpstart - Thanks for the helpful advice, I have a bastardised set of MC Carb tuning guages (used them on Ro 80s) that helps to keep them Synced.

Still early days so the novelty factor is still there.


Currently Own:- S3 RX7 FB & RX7 FC TII Vert
Previously Owned:- 2 x NSU Ro 80s.....2 x S2 FBs.....DKW W 2000....Suzuki RE5....Norton Commander

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