Special tuning H4 carbs

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
AndyPen
Posts: 3125
Joined: Mon Jul 24, 2017 5:55 pm
Location: South Wales

Re: Special tuning H4 carbs

Post by AndyPen »

User avatar
Roadrunner
Posts: 36
Joined: Tue Aug 23, 2022 9:28 am
Location: Oxfordshire

Re: Special tuning H4 carbs

Post by Roadrunner »

Smithmaps wrote: Thu Nov 17, 2022 4:20 pm H4's were the works choice for a very specific reason.
Group 2 Rally regs in the 60's (I think also in racing) allowed the carbs to be changed, but not the inlet manifold, which had to remain standard to the car.
HS4 carbs have a diagonal bolt pattern, as opposed to vertical like the H4, and the 1.5" H4 would be a straight replacement for the 1.25" Hs2 carb fitted as standard to the Cooper S.
In the early days they were in fact straight off the MGA, including the wrong float chambers, necessitating the fitment of extensions to get the float level correct.
Well I though it would be something like that to get around the rules, they used stuff easy at hand that came off the line or was in the stores which would have had the parts
251 ENG
Posts: 1475
Joined: Sun Jun 27, 2010 5:26 pm

Re: Special tuning H4 carbs

Post by 251 ENG »

Also H4 will produce more power and torque on a correctly set up engine compared to HS4,s
User avatar
johnv
Posts: 836
Joined: Sun Dec 18, 2016 1:01 pm
Location: Surrey UK

Re: Special tuning H4 carbs

Post by johnv »

251 ENG wrote: Thu Nov 17, 2022 7:22 pm Also H4 will produce more power and torque on a correctly set up engine compared to HS4,s
I wish you hadn’t said that as I’ve just changed mine for HS4’s 🙄
Mk2 1968 Cooper 998
Mk1 1965 Cooper 1275
Mk3 1971 Cooper S
Mk2 1968 Moke
User avatar
MiNiKiN
Posts: 535
Joined: Tue Oct 10, 2017 3:15 pm
Location: Graz/Austria // NN1 4ST previously

Re: Special tuning H4 carbs

Post by MiNiKiN »

Thank you all, very helpful and informative.
If only I knew the power of the Dark Side...I wouldn't have made contact with an Innocenti :mrgreen:
User avatar
Rolandino
Posts: 477
Joined: Sat Oct 22, 2016 11:37 pm
Location: Wokingham, Berkshire

Re: Special tuning H4 carbs

Post by Rolandino »

H4's have a longer choke tube and the butterflies turn the other way to an HS4. This gives a better mixture. On my S running H4's gave me 12hp more than the HS4's. More revs, and a better torque curve. Only a Weber will give you better figures. I would always recommend H4
mk1
Site Admin
Posts: 18809
Joined: Thu Jun 24, 2010 11:30 am
Location: York-ish
Contact:

Re: Special tuning H4 carbs

Post by mk1 »

Most points have already been covered comprehensively.

The C-AHT-1 & C-AHT-2 brackets will all be available again very soon. I am working with Catmint Gordon to get these sorted.

They will be available through Gordon very shortly.

M
User avatar
MiNiKiN
Posts: 535
Joined: Tue Oct 10, 2017 3:15 pm
Location: Graz/Austria // NN1 4ST previously

Re: Special tuning H4 carbs

Post by MiNiKiN »

Rolandino wrote: Thu Nov 17, 2022 9:50 pm H4's have a longer choke tube and the butterflies turn the other way to an HS4. This gives a better mixture. On my S running H4's gave me 12hp more than the HS4's. More revs, and a better torque curve. Only a Weber will give you better figures. I would always recommend H4
:o :o 12HP is massive
If only I knew the power of the Dark Side...I wouldn't have made contact with an Innocenti :mrgreen:
User avatar
johnv
Posts: 836
Joined: Sun Dec 18, 2016 1:01 pm
Location: Surrey UK

Re: Special tuning H4 carbs

Post by johnv »

mk1 wrote: Fri Nov 18, 2022 9:20 am Most points have already been covered comprehensively.

The C-AHT-1 & C-AHT-2 brackets will all be available again very soon. I am working with Catmint Gordon to get these sorted.

They will be available through Gordon very shortly.

M
Is there a bracket available for the throttle cable / manifold Mark?
Mk2 1968 Cooper 998
Mk1 1965 Cooper 1275
Mk3 1971 Cooper S
Mk2 1968 Moke
User avatar
johnv
Posts: 836
Joined: Sun Dec 18, 2016 1:01 pm
Location: Surrey UK

Re: Special tuning H4 carbs

Post by johnv »

MiNiKiN wrote: Fri Nov 18, 2022 9:25 am
Rolandino wrote: Thu Nov 17, 2022 9:50 pm H4's have a longer choke tube and the butterflies turn the other way to an HS4. This gives a better mixture. On my S running H4's gave me 12hp more than the HS4's. More revs, and a better torque curve. Only a Weber will give you better figures. I would always recommend H4
:o :o 12HP is massive
It is. I had mine on the RR at RACE recently with the H4s, I'll leave the HS4s on when I go again at the beginning of December and see what the difference is. 12HP will persuade me to put them back on! (The only other difference is that I have changed to a 123 distributor)
Mk2 1968 Cooper 998
Mk1 1965 Cooper 1275
Mk3 1971 Cooper S
Mk2 1968 Moke
Post Reply