BN1 - Question about cold air box

[matt78]

Hello.

My BN1 seems to be equipped with 2 cabs H6 (I think - couldn't find a number), with separate filters from later versions (AH 6 cyl.).
I intend to install a cold air box (100M type) that I saw on pictures, but when looking under the bonnet, I wonder how it could be fitted, because there is a very short distance left between the front carb's filter and the bodywork...
Maybe I'm wrong, and the 2 SU carbs aren't H6 ones and their intake ducts are too much long ?
If not, how did you manage to get the air box fitted ?

Matt

 

[Bob_Spidell]

The factory 100Ms had the bracket that supports the shroud bent outwards a couple inches so the cold air box would fit (it's one of the ways to identify a 'factory' 100M). I have a 100M and, if it wasn't for 'authenticity,' I'd remove the CAB--it was missing when we bought the car--and install some good aftermarket air filters. The CAB is a PITA to get on and off, and you pretty much have to remove it to do any work on the carbs. I corresponded with a guy who raced a 100 way back when, and he claimed the car developed more power with velocity stacks than the CAB.

BTW, you can determine the carb type/size by measuring the opening; the carb number designates the diameter of the throats in quarter-inches. So, an H6, or HS6, has a one-and-a-half-inch throat diameter, HD8s have a two-inch diameter, etc.

 

[red57]

Bob, Slight correction - the numbers are the multiples of 1/8" plus 1". Examples:
H4 = 4 x .125 + 1 = 1.5"
H6 = 6 x .125 + 1 = 1.75"
HD8 = 8 x .125 + 1 = 2.0"

Dave

 

[Bob_Spidell]

Bob, Slight correction - the numbers are the multiples of 1/8" plus 1". Examples:
H4 = 4 x .125 + 1 = 1.5"
H6 = 6 x .125 + 1 = 1.75"
HD8 = 8 x .125 + 1 = 2.0"

Dave

Thanks for the correction. I was wondering how an H4 could have a one-inch dia. throat.

 

[matt78]

OK, I better understand the trick !
Your comment about efficiency combined with this packaging constraint - Idon't want to modify anything on the body - are going to help me saving money...
I'll check the carbs' type following your indication.
Thank you for your information.

Matt

 

[CraigC]

Matt, the quickest way to determine if you have the standard 100's H4 or the 100M's H6 is to look at the mounting flanges. The H4 has 2 mounting holes, top center and bottom center. The H6 has four, one at each corner. They cannot be interchanged on the same manifold.

 

[matt78]

Matt, the quickest way to determine if you have the standard 100's H4 or the 100M's H6 is to look at the mounting flanges. The H4 has 2 mounting holes, top center and bottom center. The H6 has four, one at each corner. They cannot be interchanged on the same manifold.

Yes, you are right. Mine have 4 mounting holes, so for sure are not 100's, but I wondered if they were H6, HD6 or HD8... especially regarding their overall size, due to my potential packaging issue with a cold air box. At the moment, following the advices I got, this is no more an issue :joyous:

Matt