What rpm is the idle for a gm305?

[sarantis]

Hello everybody
Reading the service manual for a 1978 gm305(mechanical fuel pump-malory distributor) in an effort to adjust the idle-mixture of the 4barrel Rochester carburator,the manual says "with a tachometer adjust idle stop screw to obtain the specified RPM..."What is the specified RPM?I supose it's about 800-900 or at a rate where the engine runs smoothly.IS THERE A SPECIFIED IDLE RPM?

 

[Haut Medoc]

Re: What rpm is the idle for a gm305?

Hello everybody
Reading the service manual for a 1978 gm305(mechanical fuel pump-malory distributor) in an effort to adjust the idle-mixture of the 4barrel Rochester carburator,the manual says "with a tachometer adjust idle stop screw to obtain the specified RPM..."What is the specified RPM?I supose it's about 800-900 or at a rate where the engine runs smoothly.IS THERE A SPECIFIED IDLE RPM?

Generally, 550-600 in the water, in gear......
100-150 more out of gear.......

 

[sarantis]

Re: What rpm is the idle for a gm305?

Thanks for appearing so fast!
With the engine hot or cold?

 

[sarantis]

Re: What rpm is the idle for a gm305?

If so why the advance diagram begins from 800 at 8* btdc?

 

[Haut Medoc]

Re: What rpm is the idle for a gm305?

Warm......
800 rpms in neutral would be the uppermost limit.....
The weights will begin to advance because they need to...
Any more than that & you will have shifting troubles.....​

 

[sarantis]

Re: What rpm is the idle for a gm305?

ok thanks!

 

[Haut Medoc]

Re: What rpm is the idle for a gm305?

I forgot to mention that you want to be below 800....
700 would be better in neutral....
But that 550-600 in water, in gear is the most important.....​

 

[sarantis]

Re: What rpm is the idle for a gm305?

Ok and something last
You adjust the advance with the engine running (as the manual says) or with the boat running? Or they mean the same?

 

[Haut Medoc]

Re: What rpm is the idle for a gm305?

Ok and something last
You adjust the advance with the engine running (as the manual says) or with the boat running? Or they mean the same?

They mean the same
You don't adjust the advance......
You want 8* at idle with the engine running below that 800 rpm threshold, that is when the weights take over the advance......
Like I said, 700 rpms in neutral for the initial setting....