How to adjust idle

[K10-Kansas]

I've driven my truck for about 10 minutes after having a crate engine put in. It's a blueprint 350 carbureted small block. Is near as I can tell I would simply loosen these 2 screws and slide the accelerator cable bracket forward correct?

[RustyPile]

No, that's incorrect.. Leave the bracket alone.. The curb idle is adjusted by turning a screw on the carburetor.. Located on the driver side of the carburetor body, near where the throttle shaft passes through.. The screw is hidden from view of the camera in your pic...

Idle adjustment is made only after the engine is thoroughly warmed up and choke is fully open. Last "item" on the adjustment list.. (1) timing, (2) idle speed, (3) idle mixture, (4) final idle adjustment.

[K10-Kansas]

Originally Posted by RustyPile

No, that's incorrect.. Leave the bracket alone.. The curb idle is adjusted by turning a screw on the carburetor.. Located on the driver side of the carburetor body, near where the throttle shaft passes through.. The screw is hidden from view of the camera in your pic...

Idle adjustment is made only after the engine is thoroughly warmed up and choke is fully open. Last "item" on the adjustment list.. (1) timing, (2) idle speed, (3) idle mixture, (4) final idle adjustment.

Great, thanks

[Chevy nutcase]

Idle screw location

[K10-Kansas]

Originally Posted by Chevy nutcase

Idle screw location

Oh thanks. I really appreciate that. I'm going to go look up some videos on the steps mentioned also.

[Ironangel]

What Rusty said...After you get the timing close, put a vacuum gauge on the manifold vacuum port. Some carbs have two mixture screws some have four, Count the turns in until lightly seated so you have a reference point. I have mine at one turn out on the Holley 4-corner, 2-1/2 turns out on one of the Quadrajets. Use that vacuum gauge to set your mixture screws, one at a time, making small adjustments on the mixture screw will raise or lower the vacuum. Adjust each screw to max vacuum, making small adjustments to the idle speed screw as you go to hold the recommended idle speed. Also making timing corrections as you go. Those Blueprint motors are broke in and ran before leaving the shop. They have perfected the art of what works and what don't. I havent read one bad review on their motors, they seem to hold together well. What I meant to say is, follow what Blueprint recommended for that motor. "Cheers!"

[K10-Kansas]

Originally Posted by RustyPile

No, that's incorrect.. Leave the bracket alone.. The curb idle is adjusted by turning a screw on the carburetor.. Located on the driver side of the carburetor body, near where the throttle shaft passes through.. The screw is hidden from view of the camera in your pic...

Idle adjustment is made only after the engine is thoroughly warmed up and choke is fully open. Last "item" on the adjustment list.. (1) timing, (2) idle speed, (3) idle mixture, (4) final idle adjustment.

When you say choke open, is that what happens when warmed up? I don't have a choke knob on my dash.

[K10-Kansas]

Originally Posted by Ironangel

What Rusty said...After you get the timing close, put a vacuum gauge on the manifold vacuum port. Some carbs have two mixture screws some have four, Count the turns in until lightly seated so you have a reference point. I have mine at one turn out on the Holley 4-corner, 2-1/2 turns out on one of the Quadrajets. Use that vacuum gauge to set your mixture screws, one at a time, making small adjustments on the mixture screw will raise or lower the vacuum. Adjust each screw to max vacuum, making small adjustments to the idle speed screw as you go to hold the recommended idle speed. Also making timing corrections as you go. Those Blueprint motors are broke in and ran before leaving the shop. They have perfected the art of what works and what don't. I havent read one bad review on their motors, they seem to hold together well. What I meant to say is, follow what Blueprint recommended for that motor. "Cheers!"

I know my Blueprint documents said to adjust timing to 35 degrees advanced but I don't remember seeing and idle RPM value. Is 1,000 a good number to adjust to or should I email Blueprint?

[MySons68C20]

1000 rpm will be fine....just make sure your vac advance is disconnected and plugged when setting you mechanical total timing.

[K10-Kansas]

Originally Posted by MySons68C20

1000 rpm will be fine....just make sure your vac advance is disconnected and plugged when setting you mechanical total timing.

Yup, absolutely, thanks!

[RustyPile]

Originally Posted by K10-Kansas

When you say choke open, is that what happens when warmed up? I don't have a choke knob on my dash.

Sorry for the delayed reply, K10-Kansas.. I've been 180 miles from home and away from my computer since June 25..

If you have an automatic choke, it should be temperature responsive.. When the engine is cold and not running, the choke should be completely closed. "Patting" the throttle pedal before starting allows the choke to close. Upon start up, the choke will open slightly -- 1/4" to 3/16".. As the engine temperature comes up, the choke will slowly move to the fully open position.

Curb idle, engine fully warmed up, for a basically stock engine should be about 650 RPM - 750 RPM, depending on transmission type. That 35* timing setting recommended by Blue Print is total advancement. Connect a timing light and with engine running, slowly open the throttle until the timing stops advancing.. That's the rpm to use to set the timing at 35*. This is done with the vacuum advance hose disconnected and plugged. 1,000 rpm will not be fast enough to reach full advance..

[K10-Kansas]

Originally Posted by RustyPile

Sorry for the delayed reply, K10-Kansas.. I've been 180 miles from home and away from my computer since June 25..

If you have an automatic choke, it should be temperature responsive.. When the engine is cold and not running, the choke should be completely closed. "Patting" the throttle pedal before starting allows the choke to close. Upon start up, the choke will open slightly -- 1/4" to 3/16".. As the engine temperature comes up, the choke will slowly move to the fully open position.

Curb idle, engine fully warmed up, for a basically stock engine should be about 650 RPM - 750 RPM, depending on transmission type. That 35* timing setting recommended by Blue Print is total advancement. Connect a timing light and with engine running, slowly open the throttle until the timing stops advancing.. That's the rpm to use to set the timing at 35*. This is done with the vacuum advance hose disconnected and plugged. 1,000 rpm will not be fast enough to reach full advance..

Thanks. I definitely did this wrong a few months ago. I'll redo it.

[K10-Kansas]

Originally Posted by RustyPile

Sorry for the delayed reply, K10-Kansas.. I've been 180 miles from home and away from my computer since June 25..

If you have an automatic choke, it should be temperature responsive.. When the engine is cold and not running, the choke should be completely closed. "Patting" the throttle pedal before starting allows the choke to close. Upon start up, the choke will open slightly -- 1/4" to 3/16".. As the engine temperature comes up, the choke will slowly move to the fully open position.

Curb idle, engine fully warmed up, for a basically stock engine should be about 650 RPM - 750 RPM, depending on transmission type. That 35* timing setting recommended by Blue Print is total advancement. Connect a timing light and with engine running, slowly open the throttle until the timing stops advancing.. That's the rpm to use to set the timing at 35*. This is done with the vacuum advance hose disconnected and plugged. 1,000 rpm will not be fast enough to reach full advance..

Any guesses on at what RPM timing would no longer advance? I was guessing it would be 2,750 from what I've seen on videos but I don't know if I'm understanding that correctly

[RustyPile]

Originally Posted by K10-Kansas

Any guesses on at what RPM timing would no longer advance? I was guessing it would be 2,750 from what I've seen on videos but I don't know if I'm understanding that correctly

The amount and RPM of the total advance it totally dependent on the distributor "set up".. These figures are arrived by selecting springs and weights.. Stops in the distributor establish the total amount of advance, typically around 20* - 25*.. Base timing is added to arrive at the 35* number.. Springs and weights determine the curve of the advance. Heavier weights and lighter springs give a faster (sooner) curve.. Lighter weights and stiffer springs slow down the advance...

Typically, you want all the advance in around 2500 - 3,000 RPM.. If the advance is "brought in" too fast or too soon, pre-ignition can occur.

[K10-Kansas]

Originally Posted by RustyPile

The amount and RPM of the total advance it totally dependent on the distributor "set up".. These figures are arrived by selecting springs and weights.. Stops in the distributor establish the total amount of advance, typically around 20* - 25*.. Base timing is added to arrive at the 35* number.. Springs and weights determine the curve of the advance. Heavier weights and lighter springs give a faster (sooner) curve.. Lighter weights and stiffer springs slow down the advance...

Typically, you want all the advance in around 2500 - 3,000 RPM.. If the advance is "brought in" too fast or too soon, pre-ignition can occur.

Great info. I really appreciate it.

[Ironangel]

Originally Posted by K10-Kansas

I know my Blueprint documents said to adjust timing to 35 degrees advanced but I don't remember seeing and idle RPM value. Is 1,000 a good number to adjust to or should I email Blueprint?

Im thinking 800 for a nominal pump gas build...And yes find out what their recommended idle rpm for that build is.