timing issue or not?

[pjc360]

I am having an off idle stumble problem with my 360 magnum and it is also hard to start when it is warmed up, i gotta crank on it a few times before it will fire up when it is at operating temp, i timed this engine when i first got it running and it was at 8-10 degrees btdc, but i had to re-jet the carb because it was a little rich out of the box, its an edelbrock 600cfm manual choke.
The original jets were .100 on primary side and .098 in the secondary, after some adjustments my engine likes the .092 jets on primary side and .092 jets in secondary, ever since i re-jetted it i have been having this off idle stumble and it is really bad when cold, my question is, do i need to re-time the engine or do something different with the carburetor? i have the acclerator pump set on the richest setting and it seemed to help a little but it did not eliminate the problem totally.

 

[nqkjw]

Couple of things.
Flat spots/stumbles,etc mean lean 99% of the time.
It is actualy very difficult to tune so rich as to cause a flat spot.
In a carter/edelbrock the primary jets should generally always be larger than the secondary jets.The metering rods(used for fine tuning) through the primary jets reduce the area of flow - hence why the larger jet than in the secondaries.
As vacuum decreases(such as WOT) the metering rods(which are stepped in diameter)rise to a smaller step thus increasing the area through the jet alloeing more fuel to flow.
If you insist your jetting is correct there is two ways to improve the stumble.
1. Use a smaller metering rod.Your originals should be 7047s? Try,say,some 6842s or 6537s.7037s could work well too.
2.Change to a lighter stepup spring.Yellow works best in most cases.This will get the metering rod to rise quicker thus riching the mixture quicker.
I assume it's a performer?If so you can't adjust the secondary air door without a lot of trouble.
If it's a thunder you can adjust the secondary air door.

For timing I like to see around 12-16 btdc at idle but check that you don't get too much total.

Hope this helps.

 

[gliderider06]

Sounds like it is too lean to me. Eddy carbs like more initial timing. I set up my 360 with the .100 front with 75x47 metering rods and .95 rear jets. Timing is 18* initial and 34* mechanical, 52* with the vacuum hooked up. Edelbrock has a tuning chart in the owners manual for the carbs, which will help you tune it to the proper setting for the series you are running, weither you want it to run rich for performance or lean for economy. What carb are you running?

 

[moper]

great answers both...