H4 float bowls

[cpr1]

Hi all,

I am building a 1275 S with a 276 degree duration, fuelling will be by twin H4 SU's , now the float chambers on these are AUC8402 which on Burlen website they are known as T1 with a diameter of 1" 15/16 , Now the correct AUC 4815 and 4816 which I assume are the correct 30' angle are listed as T2 with a diameter of 2" 5/16 , will I be having fuel starvation if I go with the T1's ? apart from the angle.

Thanks Cpr1.

['S'-type]

AUC 4814 and 4815 are the correct 30° chambers. 4814 being rarer to find second hand. I would suggest running with the T2 size as starvation is possible with T1s. Even on T2s chamber extensions were sometimes fitted to avoid the problem. Bit OTT. Simpler solution to use smaller floats in the T2 chambers.
A T2 holds about 100ml while T1s hold about 55-60 ml (Without floats)
Depends on state of tune and how hard it is driven, you could pootle around on T1s all day no problem.
As mentioned before on this forum, you can run with the more available and cheaper 20° T2 chambers 3495 and 3496.

[cpr1]

Hi,

Thank you very much for your advise.

Cheers Cpr1

[mk1]

Of the two choices mentioned above, the best by a LONG mark is to use 20° T2 Bowls, the T1's are tiny, so not only will they look really weird, but as soon as you put your foot down they will empty & you will get fuel starvation.

[Desmodromic]

I always use T2 bowls with T1 floats, that is the best combination in my experience. 30 degree bowls do crop up from time to time, it's worth setting up an alert on eBay.

[agricola]

anybody a view on the influence of the needle valve size? i.e. how quickly the chamber is refilled?

[cpr1]

Thanks Mark and all those that have shared their knowledge,

cheers Cpr1

[mk1]

The needle valve is the same on both T1 & T2 float chambers.

[agricola]

true mark but you can get larger jets which are allow the float chambers to replenish faster assuming a faster fuel pump there are 3 options 0.096,-0.0125,-0.0156 Just wondered if anybody had any experience?

[mk1]

Have always just used the standard needle valves. I had to use float chamber extensions & small T1 floats on the Hornet as it used to suffer fuel starvation on right hand corners. Larger valves may have helped too.

TBH, I didn't know you could get different sizes

[agricola]

dont be embarrassed just as we have all suspected you are human!!!!
I ask as I have had problems doing road rally tests with HS4 cutting out when I throw it round on the handbrake.
I know some racers put a great loop of extra long fuel pipe around the carbs as an extra reservoir but as that's the wrong side of the float needles didn't make much sense so I bought a larger sets
http://sucarb.co.uk/float-chambers-spar ... tions.html I haven't fitted them so wondered if anybody has.
My old pal who is a Bentley boy recons they used to switch both fuel pumps on?
Though in my case it may just be fuel surging around?

[mk1]

Me? Only Human!

Never

[agricola]

A.I. has arrived at the MK1 forum......................................................