Holley carb, power brake connection

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Aug 16, 2020 | 05:09 PM

'81 Vette

Thread Starter

Heel & Toe

Joined: Aug 2020

Posts: 17

Likes: 2

Holley carb, power brake connection

Hi all,
First post!!
I've just fitted a Holley 4175 carb to my Vette while I have the Qjet rebuilt.
I was hoping this was going to be a direct, plug and play replacement but both the fuel line and the brake booster line require modification. The fuel line isn't a problem but the brake booster line is being a bit of a pain.
I'm in the UK so sourcing these little parts can be a bit of a pain.
Does anyone know what size and type adapter I need to screw into the base of the Holley to fit my original brake line to it.?
The qjet has an adapter but it is bigger than the Holley.
Thanks in advance.

Aug 17, 2020 | 08:21 AM

speedreed8

Melting Slicks

Joined: Oct 2006

Posts: 2,417

Likes: 336

From: Texas

I installed a Holley 4175 on my 79 and had to order this fitting. 3/8 tubing x 1/8” npt. For the power brake fitting

Last edited by speedreed8; Aug 17, 2020 at 08:21 AM.

Aug 17, 2020 | 08:26 AM

'81 Vette

Thread Starter

Heel & Toe

Joined: Aug 2020

Posts: 17

Likes: 2

Thanks for that! Now to try to source one locally.

Aug 17, 2020 | 08:48 AM

jb78L-82

Le Mans Master

Joined: Oct 2007

Posts: 7,462

Likes: 985

From: RI, Now Franklin/Nashville TN

My 4175 has been on my car since 1985 and I probs cut the line back then, spliced in a piece of rubber hose, and connected it to the vacuum nipple off the back of the Holley....see below. I suspect the 4175 you have has a different connection.

Aug 17, 2020 | 08:58 AM

'81 Vette

Thread Starter

Heel & Toe

Joined: Aug 2020

Posts: 17

Likes: 2

yes, the new base plate has a threaded port instead of a nipple.

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