Cool air for carbs
 

My 1800E now runs twin Webers. Am looking into heat shield above the exhaust manifold and also the possibility of an airbox over the carb trumpets, fed by a pipe from the front of the car, through the hole where the original air source for the EFI came.

Anyone with any experience in this area ?

A friend of mine on this forum Khe Sanh rightly pointed out to me all the sound insulation on the inside of the bonnet lid of P1800 which will add the heat insulation. I never thought of that when I owned my car, but on reflection, it was quite obvious!

You might have to get a general airbox and cut the inlets for the carbs out to fit...
I also think you might have to fit shorter trumpets to get clearance and fit an air filter either as part of the airbox or in the feed from the front..
Those gauze filters not only filter nothing but also sap power.
When i first fitted a K&N filter on a car years ago the rolling road chap said they are worth thousands, I asked why ? because running car without filters drags in so much dirt and dust the damage can be considerable in no time at all...
But i bet they sounds great like that..:regular_smile:

It's possible that the B20 SU filter box could be used by using an adaptor plate for the Webers. No filter inside and slightly shorter trumpets with rolled ends inside the box. Air intake could be routed to the hole and an ES type filter used. A cone or barrel type of aftermarket filter would also fit but they are more for looks than effective as a proper filter. Paper filters are pretty consistent over their normal service life whereas oiled K&N types gradually get clogged due to the oil and dust combining to reduce the flow.

KG trimning has some possible options for the air filter.

Thanks everyone. Wise words, Bracpan, the option of K&N filters means I need to invest in shorter trumpets to allow a minimum 25mm clearance. Even then, it's touch and go whether the K&N filter will fit.

The power loss on the rolling road was 2bhp (160 without, 158 with).

A friend with a racing MGB has simply trunking pointing at the carbs. Feels that an airbox can give cooler air to the front carb, thus disturbing the balance.

Definitely going to fabricate some sort of exhaust shield.

MGB man could put a deflector in the airbox and adjust it to balance the cold air feed.

K&N can be cleaned easy and have a no quibble 1,000,000 mile guarantee. So once bought you have them for life plus they come out test after test as one of the best filters on the market, they can still flow more when dirty than a paper filter, and seeing the dirt they collect gives you a good indication of how much would have gone into your nice clean engine !....I've used them on road and race cars since 1985 "never" had a problem.
But i agree looking at the gap there is not much room to fit on the carbs...
Possible Air box and pipe with a remote filter mounted low to collect cold air ? It would not be a very big filter for the power the engine puts out..
Unfortunately the area where the carbs are does collect warm air, especially the rear carb, we did a few experiments on a turbo competition car to find where good exit vents would disperse the hot air from under the bonnet (from the rad and intercoolers) and its nearly always back on the side edges of the bonnet. if you look at a lot of rally WRC cars they have exits in those ares... on some cars you cars you can actually feel the heat on that part of the bonnet..... do a test after a run..
The best way to lose heat from the exhaust manifold is to ceramic coat it but its not cheap and you will still get the heat from the rad..
Have a look at the link below, its probably not the right size but it gives you an idea of whats you could do, then run a flexy pipe to a filter...what ever you do don't fit a sponge cone filter they are cr*p...
https://www.efihardware.com/products...or-Carburettor

Thank you, Bracpan. I really appreciate you taking the time. I'll definitely follow through on your suggestions.

In real terms how much does a power loss of 2bhp equate to the driving experience? I take it that you are not thinking of trying for a formula1 test.