1275GT Group 1 Air Cleaners

[Astro]

This is my question. In the late 70ies, BMC did a lot of homologation for the 1275GT. First, it was one SU HS4, than two HS2 with a special inlet and an air cleaner, later on two HS4 with an inlet but no more air cleaner, at last two HS6 with an inlet but still without air cleaner. As far as I know, the AHT 562 will not fit the HS4 and HS6 carbs. Does anyone know what the 78, 79, 80 group 1 1275GT were looking like? Did they use just trumpets or some K&N cleaners or what else?

[mk1]

By the late 70's ST were offering twin 1 1/2SU & twin 1 3/4 SU kits along with air cleaners for the HS4's but only trumpets for the HS6.

The whole brochure is here http://mk1-performance-conversions.co.uk/leyland_st.pdf

[Astro]

Thank you. These seems to be two pancake cleaners and will fit the HS6 too. They are not mentioned in the homologation papers. However, this list may convince the FIA – hope so. Btw, this paper also lists an intake pipe for the HS4. Does it mean, that this would be accepted too as a group 1 part? Perhaps one have a picture of a contemporary engine bay?

[LMM76C]

Out of interest, what events are you planning to do that run to period FIA Gp1 (not UK Gp1+)?

[Astro]

all the time we do the french historic hill climp championchip. They just changed the regulations. Until now, they collected the results of the periods. Now they count the results of the FIA groups doesn't matter how old. I will not discuss this idea, never the less we want to put our Arden Cooper S into the garage and continue with a 1275GT groupe 1. Maybe a bit slower but more effective to collect points

[steady eddie]

all the time we do the french historic hill climp championchip. They just changed the regulations. Until now, they collected the results of the periods. Now they count the results of the FIA groups doesn't matter how old. I will not discuss this idea, never the less we want to put our Arden Cooper S into the garage and continue with a 1275GT groupe 1. Maybe a bit slower but more effective to collect points

The replica 1275GT built by Swiftune which was such a success at the Goodwood Members Meeting last year was running split webers, is this possible for you.

Regards

Steady Eddie

[Astro]

At all. We have strictly to follow the homologation sheet and the FIA regulations. However, this paper is not so bad. Two HS4 or HS6, 37.6mm inlet valve, big exhaust manifold, big oil cooler, 4.3:1 axe, 630kg - ok in theory, a.s.o. A problem is that I cannot get the GKN rims. Swift got the last ones from Luxembourg and the only possibility now is to use 4.5x12 steel ones. Either, someone will start to produce a reproduction.

[Vegard]

If you look at AppK and the homo papers for a 1275 GT, the carbs are free in gp2. I'd hear with Nick, he seemed to have these rules under control.

[phil82]

@ vegard: yes carbs are free in group 2 but astro is thinking about group 1(b).

@ astro: OT about the wheels. are you just allowed to use the specific silverstone rims? no other 12" rim of the same dimensions?
what about the tires? I once had a discussion with a scrutineer of the german youngtimer trophy and he pointed out that in case of a lack of 12" slicks it would be ok to step up to 13". Of course the YT is ADAC Nordrhein and not France & FIA but maybe it's an idea...

[Astro]

Hello,

we have to follow the App J of the period. That means the homologated carbs, the homologated rims; the tyres are free as long as they fit the rims and even each carpet inside. I still remember the car I used that time - not a mini : oops: but I just could change the shocks, the driver’s seat and the steering wheel.

[phil82]

so if you can't find the rims you might still be able to borrow one, get a 3d scan and the have them made:
http://www.metallgiesserei-gablenz.de/
they aren't far away from you.

[Tulka]

At all. We have strictly to follow the homologation sheet and the FIA regulations. However, this paper is not so bad. Two HS4 or HS6, 37.6mm inlet valve, big exhaust manifold, big oil cooler, 4.3:1 axe, 630kg - ok in theory, a.s.o. A problem is that I cannot get the GKN rims. Swift got the last ones from Luxembourg and the only possibility now is to use 4.5x12 steel ones. Either, someone will start to produce a reproduction.

There are pictures of Longman using 5x12"(i think?) Minilite. It is not what was used at the time?

[Tulka]

I have the type of air cleaner elbows for the twin HS4s used by Longman.

[Astro]

you will sell them or just make a photo? Swift said, that these are not available for there was probably no budget to homologate them.

[Astro]

At all. We have strictly to follow the homologation sheet and the FIA regulations. However, this paper is not so bad. Two HS4 or HS6, 37.6mm inlet valve, big exhaust manifold, big oil cooler, 4.3:1 axe, 630kg - ok in theory, a.s.o. A problem is that I cannot get the GKN rims. Swift got the last ones from Luxembourg and the only possibility now is to use 4.5x12 steel ones. Either, someone will start to produce a reproduction.

There are pictures of Longman using 5x12"(i think?) Minilite. It is not what was used at the time?

It seems to be more difficult. Swift bought the last GKN wheels from Lelong. But when learning that there are no slick tyres to use with, they were allowed to change the wheels. But the FIA on the continent will never permit it.

[Tulka]

I have the type of air cleaner elbows for the twin HS4s used by Longman. Bought at Ripspeed?
Not for sale.

[Tulka]

At all. We have strictly to follow the homologation sheet and the FIA regulations. However, this paper is not so bad. Two HS4 or HS6, 37.6mm inlet valve, big exhaust manifold, big oil cooler, 4.3:1 axe, 630kg - ok in theory, a.s.o. A problem is that I cannot get the GKN rims. Swift got the last ones from Luxembourg and the only possibility now is to use 4.5x12 steel ones. Either, someone will start to produce a reproduction.

There are pictures of Longman using 5x12"(i think?) Minilite. It is not what was used at the time?

It seems to be more difficult. Swift bought the last GKN wheels from Lelong. But when learning that there are no slick tyres to use with, they were allowed to change the wheels. But the FIA on the continent will never permit it.

Be creative; use the original plastic hubcap to hide whatever wheel you use.

[Astro]

mini world once published this picture. Is it really the same one?

[Astro]

Be creative; use the original plastic hubcap to hide whatever wheel you use.

did you ever race under FIA regulations?

[cooper998]

Hello to all from Finland,

I'm allso building a similar 1275GT to group 1 period I (-81) and I have exactly the same problems than Astro. I have not found any information about air cleaner box after 2-3 years...
My GT is going to take part on historic rallying in Finland and we follow FIA rules very strictly. So I'm awere that in group 1 car you can only use homologated parts.
And there is allso other similar problems with homologation papers > not a word what kind exhaust should be, C-ARA 334 can be found from ST data sheet. Is it right one?
Or idler spur gear ratio. Have someone ever heard about straight cut 31 teeth idler gear? or 1.044:1 helical set?
Or page 18/9 V. 16.4cm3 is ok for chamber in head and 27.9cm3 is ok for total chamber, but I cannot get CR to 12:1 how many times I count it
(318.75+27,9) / 27,9= 12,423 and a bit higher with 1293cm..


This might be the answer for the problem if normally means original hs4...
You may not change or modify normally mounted carb. Twin hs4/6 is not normally..

Appendic J -81: Art 258
d) Induction: The carburettor(s) or fuel injector pump(s) normally mounted
on the homologated model and described on the homologation form may not
be changed or modified, except for any part which may control the quantity of
fuel fed to the engine, but not those which control the quantity of air, It is
permitted to remove the filtering element on condition that the original air filter
box is retained.

Tero Gronfors
Finnish champion 2009 with Austin Cooper -65