<VV> Turbo Motor Cycling

[Hugo Miller]

I wonder if this might be a vacuum issue to the distributor, causing 
the timing to fluctuate. I once had something similar on an old British 
car, as the distributor base plate moved, the wire to the points was 
periodically touching ground where the insulation had chafed, making it 
'hunt' like an old diesel engine. Just a thought?

On 2019-10-31 02:56, kevin nash via VirtualVairs wrote:
> From: Brian via VirtualVairs
> Sent: Wednesday, October 30, 2019 10:11 AM
> To: VirtualVairs at corvair.org
> Subject:  Turbo Motor Cycling
>
> I am finishing up a project for a fellow club member to get his 1965 
> Turbo
> convertible back on the road.  He dropped the valve seat which cause
> significant damage so a total engine rebuild was necessary.  Using 
> all stock
> parts I rebuilt the engine.  I then ran it on the run stand that we 
> have
> here in our club.  I ran it with two carburetors while both the Turbo 
> and
> the carburetor were out for professional rebuilding.
>
> While on the engine stand it ran flawlessly.  Now that is installed 
> in the
> car and the Turbo with his carburetor is installed there is a cycling
> problem.  The engine fires instantly and with the choke disconnected 
> idles
> but the idle fluctuates from about 690 RPM to about 920 RPM.  The 
> cycling is
> slow in other words it will run for a couple of seconds may be as 
> much as 30
> seconds and then the idle will jump either up or down.
>
> As mentioned all the parts are stock to include the camshaft.  Timing 
> is set
> at 24? as per the shop manual.  Not being a Turbo guru I am stumped.  
> Is it
> possible that this cycling is caused by an improper setting of the 
> idle
> mixture or is there some other issue?  Any help would be much 
> appreciated.
> Thanks in advance.
>
>
>  It sounds like a air leak- a really common one on stock Turbo's is
> that thick fiber gasket between the carb and throttle plate. The 
> other
> cause might be a linkage/idle adjustment and or idle mixture
> adjustment. Idle on Turbos is supposed to be 850, and the manifold
> vacuum should be around 13" hg. Just for kicks and giggles, try
> richening the idle mixture screw 1/8th of a turn, and see if anything
> changes.
> Kevin Nash
> 63 Turbo EFI daily driver, Baddest cooling fan on the planet!!
>
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