[Healeys] Still stalling at idle

warthodson at aol.com warthodson at aol.com
Fri Aug 3 14:53:09 MDT 2018


Ira,
The first thing I would want to know if I were assisting you in person would be "what non-original 'improvements' have you made to your engine, carbs, fuel, electrical, cooling, etc. system?" For example: Do you have the original style air cleaners & crankcase breathing system? Is the vacuum advance working correctly & smoothly? What is the timing set at & how was it measured? What plugs are you using & what are they gapped at? What cam are you using & what is the engine compression? What are the valve lash settings for your cam and have they been checked recently?


I would want to inspect the HD8 choke mechanism to determine if it is fully released when the engine is warmed up. Just pushing the choke knob in is no assurance the mechanism has fully released.
I would like to verify the idle mixture by "pushing the lift pin up about 1/32" after the free pay has been taken up"-see shop manual. This is almost impossible to correctly do on a hot engine with a pair of HD8's! 
Up to this point I have assumed that the carbs are in very good repair & set-up correctly. Including: correctly synchronized, all the interconnecting linkage is set correctly including the appropriate free play in the various forks, pins & screws. 


There are 2 schools of thought on adjusting HD8 idle. 
One contends that the "slow run screws" should be completely closed & the idle set with the "fast Idle" screw. The debate occurs over the definition of the "fast Idle" screw vs. the "throttle adjusting" screws.



The other school contends that the HD8's as fitted to Austin Healeys, only have "fast idle" screws & were not ever fitted with "throttle adjusting" screws. Note that the manual says "Whenever the throttle adjusting screws are fitted...……….".


Many people think that "fast idle" screw & "throttle adjusting" screw are interchangeable terms, but they are not. 


If you close the "slow run screws" then, on the HD8's as fitted to Healeys, you will have no choice but to try to set the idle with the fast idle screws which are intended to be part of the choke mechanism & intended to be completely disengaged when the car is at operating temperature. 
This means that you will not have a dedicated idle circuit & will be depending on the carb throttle butterfly (which will be almost closed) to control the idle speed. The affect is that the smallest change in the throttle butterfly position will have a large affect on the idle speed. If you have a "hotter" that standard BJ8 cam the challenge is accentuated.


Gary Hodson




-----Original Message-----
From: i erbs <eyera3000 at gmail.com>
To: Dave Porter <frogeye at porterscustom.com>
Cc: Ahealey help <healeys at autox.team.net>
Sent: Fri, Aug 3, 2018 2:00 pm
Subject: Re: [Healeys] Still stalling at idle



Floats and needles where checked by mechanic. Plus are clean.


Ira Erbs
Portland, OR
typos and artifacts are the fault of my phone


On Fri, Aug 3, 2018, 8:41 AM David P <frogeye at porterscustom.com> wrote:

          
    
Ira, to follow up on Kees note.. when it stalls pull and examine      the condition of the spark plugs. They should tell you what is      happening..though not why .. Dave
    
    
    
On 8/3/2018 1:37 AM, Kees Oudesluijs      wrote:
    
    
            
What is the CO content of the exhaust gasses when idling? The        mixture could be way to rich. Look at float height, wrong carb        needles/jet, leaking float valves, mixture adjustment, sticking        pistons etc.
      
Kees Oudesluijs
      
      
Op 3-8-2018 om 01:14 schreef i erbs:
      
      
                
Still have idle issues when engine is at running          temp. Have replaced needle and seat, floats, fuel pump.          Checked timing. Idles at 1000rpm. Then slowly drops and then          stalls unless I pull choke out or rev the engine. Idles fine          until engine gets hot. Hd8 carbs on BT7 engine with hot cam          and bored +40.
          
          
Ira Erbs
            Portland, OR
            typos and artifacts are the fault of my phone
        
        
        
        
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