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How to identify manifold/carb?
Posted: Mon Oct 12, 2020 3:43 pm
by Andymoor94
Hi guys,
So since I got the car, I've always been perplexed by this odd-looking, poorly done adapter on my carb. It tells me that SOMETHING isn't correct.
Now I've done some research with the numbers stamped on my carb and can confidently say that I'm sure it's the H1, which is standard for the 803cc engine. That leaves me with the question of the manifold. How can I identify the manifold? and more importantly, what's the part number for the original?
Cheers
PS apologies for the poor photo, I did what I could with what I have at work. I will get a better picture soon!
Re: How to identify manifold/carb?
Posted: Mon Oct 12, 2020 3:56 pm
by Murrayminor
It looks like a modified manifold, maybe the inventor wanted to take the carb away from the heat of the exhaust manifold.
Although the long inlet throat could cause issues itself.
Re: How to identify manifold/carb?
Posted: Mon Oct 12, 2020 4:06 pm
by philthehill
The part number of the standard 803cc inlet manifold is 2A540. Fitted with H1 carb AUC738 (can be found on the float chamber tag).
The part number for the 948cc standard inlet manifold is 2A718. Fitted with H2 carb AUC833 (can be found on the float chamber tag).
Between the inlet manifold and the carb is a home made adapter (non factory issue).
I would suggest that the carb fitted is in fact a H2 and the adapter allows the fitment of the larger bore carb. The type and size of carb can be confirmed by reading the letters/numbers on the float chamber tag.
Re: How to identify manifold/carb?
Posted: Mon Oct 12, 2020 4:14 pm
by Andymoor94
philthehill wrote: ↑Mon Oct 12, 2020 4:06 pm
The part number of the standard 803cc inlet manifold is 2A540. Fitted with H1 carb AUC738 (can be found on the float chamber tag).
The part number for the 948cc standard inlet manifold is 2A718. Fitted with H2 carb AUC833 (can be found on the float chamber tag).
Between the inlet manifold and the carb is a home made adapter (non factory issue).
I would suggest that the carb fitted is in fact a H2 and the adapter allows the fitment of the larger bore carb. The type and size of carb can be confirmed by reading the letters/numbers on the float chamber tag.
As ever, thanks for the detailed answer, will have a look when I'm home.
What are the benefits/let downs of a H2 on an 803cc engine?
Murrayminor wrote: ↑Mon Oct 12, 2020 3:56 pm
It looks like a modified manifold, maybe the inventor wanted to take the carb away from the heat of the exhaust manifold.
Although the long inlet throat could cause issues itself.
What you can't see on the photo is the braising has holes in it! I imagine that can cause grief in itself
Re: How to identify manifold/carb?
Posted: Mon Oct 12, 2020 4:48 pm
by philthehill
The H1 carb is quite restrictive in air flow and fitting a H2 will improve the airflow to some degree providing that the internals of the adapter and original manifold have been opened out to match.
Provided that the holes in the braze do not go fully through to the inlet tract there should be no effect on the fuel/air mixture.
My original 948 was fitted with a H2 carb. I replace it with a H4 on a Janspeed fabricated inlet manifold to increase the air flow. The manifold/inlet tract was matched to the carb and gas flowed and it did make a noticeable improvement in performance.
Re: How to identify manifold/carb?
Posted: Mon Oct 12, 2020 6:20 pm
by Andymoor94
philthehill wrote: ↑Mon Oct 12, 2020 4:48 pm
The H1 carb is quite restrictive in air flow and fitting a H2 will improve the airflow to some degree providing that the internals of the adapter and original manifold have been opened out to match.
Provided that the holes in the braze do not go fully through to the inlet tract there should be no effect on the fuel/air mixture.
My original 948 was fitted with a H2 carb. I replace it with a H4 on a Janspeed fabricated inlet manifold to increase the air flow. The manifold/inlet tract was matched to the carb and gas flowed and it did make a noticeable improvement in performance.
Not much performance to be gained on an 803. Not without damage!
Anyway, checked the number and... Well.... They would suggest H1 and correct manifold... But clearly not the case
Re: How to identify manifold/carb?
Posted: Mon Oct 12, 2020 7:01 pm
by philthehill
The manifold is correct 2A540.The float chamber tag may be AUC738 but to further confirm as to whether the carb is correct or not remove the air filter and measure the size of the bore through the carb. As the inlet tract has that home made extension anything could have been done including changing the float chamber/float chamber tag.