Idle timing

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

boloboss

Full Access Member
Joined
May 6, 2023
Posts
55
Reaction score
16
Location
Houston Texas
First Name
Shuntel
Truck Year
1984
Truck Model
Chevy C10
Engine Size
v8 350 5.7 liz6er
I have a '84 Chevy C10 with a 350 engine. What should idle timing be set at
 

boloboss

Full Access Member
Joined
May 6, 2023
Posts
55
Reaction score
16
Location
Houston Texas
First Name
Shuntel
Truck Year
1984
Truck Model
Chevy C10
Engine Size
v8 350 5.7 liz6er
Also, I swapped OEM distributor to a HEI distributor deleting the pigtail for (ESC)
With that being said, what should the idle timing be set on my 350 engine?
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,304
Reaction score
8,441
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Like @ali_c20 said you are worried about total,not Idle, total will vary depending on heads,and other variables. Set your timing intentionally too low. Disconnect and plug the vacuum advance. Find 2 land marks approximately 100 yards apart.From a dead stop, accelerate from one,past the other,note your speed .Keep bumping the timing 2 degrees at a time until your trap speed levels off and starts to drop. Go back to lowest setting with highest trap speed. Reconnect your vacuum advance.
 

JD Miller

Full Access Member
Joined
Sep 30, 2024
Posts
76
Reaction score
145
Location
Goober Idaho
First Name
JD
Truck Year
1981
Truck Model
K20 silverado
Engine Size
350
Idle timing, with vacuum advance line to distributor disconnected and plugged, should be 6 degrees . not 12

That is factory spec.
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,236
Reaction score
2,157
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
6 is factory spec, but that was a smog era setting that was very conservative. Most stock engines work better at about 12, or even up to 16 if you have aluminum heads. Still runs fine on 87 octane.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,304
Reaction score
8,441
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
And stock Idle speed timing will change as the engine wears and the timing chain stretches. And dependant on the cam,heads,intake,carbureation and distributor specs,all HEIs are not the same Don't worry about idle,give the engine what it wants.
 

fast 99

Full Access Member
Joined
Dec 31, 2021
Posts
1,982
Reaction score
2,835
Location
Spokane, Washington
First Name
Brian
Truck Year
81,85
Truck Model
K20
Engine Size
350
Vacuum advance units can vary from about 10 - 30 degrees. Centrifugal weights, and springs can be much different as well. Usually, heavier [higher GVW] the truck lower total advance is.

Although total advance may have been conservative back in the emissions days have to remember octane today is much lower and fuel is not designed for carbureted vehicles. Factory specs are a starting point.
 

Forum statistics

Threads
43,939
Posts
946,107
Members
35,983
Latest member
TipTopK20
Top