1800: - Cool air for carbs

sleek lemur · Jul 3rd, 2020, 08:06

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 ?

swedishandgerman · Jul 3rd, 2020, 09:31

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!

Bracpan · Jul 3rd, 2020, 23:08

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..

Derek UK · Jul 3rd, 2020, 23:29

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.

Burdekin · Jul 4th, 2020, 00:01

KG trimning has some possible options for the air filter.

sleek lemur · Jul 4th, 2020, 00:53

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.

Jul 3rd, 2020, 09:31	#2
swedishandgerman Premier Member Last Online: Oct 23rd, 2023 21:39 Join Date: Apr 2007 Location: EXETER	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! __________________ 2006 XC70 D5 Manual 1968 Amazon Estate, B18A + Overdrive 2019 V60 D3 Momentum Pro Manual 1970 Amazon 2-Door 1970 142DL

Jul 4th, 2020, 00:01	#5
Burdekin Chief Bodger Last Online: Today 18:30 Join Date: Oct 2009 Location: Aberdeen	KG trimning has some possible options for the air filter. __________________ One day I will get rid of all of the rust.

Jul 3rd, 2020, 23:08	#3
Bracpan Member Last Online: Yesterday 09:43 Join Date: Feb 2020 Location: Wales	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..

Jul 3rd, 2020, 23:29	#4
Derek UK VOC Member Last Online: Today 15:13 Join Date: Jul 2006 Location: Chatham	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.

Jul 4th, 2020, 00:53	#6
sleek lemur Senior Member Last Online: Dec 29th, 2022 11:47 Join Date: Jun 2019 Location: Thorndon, near Eye, Suffolk, England	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.

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