[Healeys] rebuilt HD8s

[Bob Spidell]

Almost certainly a leak at the servo. When you apply brakes, a small slave cylinder in the servo moves a valve which gates atmospheric pressure into the outer part of the large air/vacuum piston (vacuum is held on both sides when brakes are not being applied). If this valve is not sealing completely it could allow atmospheric pressure air into the manifold (there is a check valve on the servo to prevent this and hold some vacuum in the event of engine failure at speed, but it could leak, too). 

Now that you've done the carbs, it's on to the servo! ;) 

Bob 

----- Original Message -----

From: "George Vernau Sr" <gvernau at gmail.com> 
To: "Healey list" <healeys at autox.team.net> 
Sent: Wednesday, June 3, 2015 1:56:17 PM 
Subject: [Healeys] rebuilt HD8s 

I recently rebuilt the HD8 carbs on my 1967 BJ8 and the car runs great again (although the price of carb kits is just crazy these days). However, I notice a slight increase in idle speed whenever I put my foot on the brake, like when sitting at a light. I can't ever remember noticing this before, is there a vacuum leak or is the booster not working properly? Any ideas? 
Thanks for any input, 
George Vernau 
Houston TX 

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