Idle timing, the hunt for the holy grail

[Mike]

It runs so well at that timing number because it is making a lot more heat. It gets hotter and hotter, which means it is capable of burning fuel more efficiently. Run the timing up that high and take some jet away from it. I bet it will run even better. Keep adding timing and taking away fuel until it lifts the top ring lands. Then, after you rebuild it, you'll know how far to not go. :winkn:

 

[Screaming Metal]

It runs so well at that timing number because it is making a lot more heat. It gets hotter and hotter, which means it is capable of burning fuel more efficiently. Run the timing up that high and take some jet away from it. I bet it will run even better. Keep adding timing and taking away fuel until it lifts the top ring lands. Then, after you rebuild it, you'll know how far to not go. :winkn:

:whisper: :wacky:

 

[Mike]

Well, you never know how far you can go until you've gone beyond it. :shrug:

It's the same with torquing fasteners. Go until you strip the threads and then back off an 1/8th turn. :wolf:

 

[PotvinGuy]

I had your same situation with my small block. It ran great at 42 degrees with good street performance. Total advance was well over 50. BUT I worked my way back to near-stock timing with quick centrifugal advance (yellow springs), early secondary (white spring) and short (14 degree) vacuum can. Although it ran great at 42, it is a real rocket now at 18. Both setups run very cool, in fact I don't use my electric fan unless I'm stuck in traffic. No starter drag either.

At 42 it was running silver advance springs, plain secondary spring, and 20 degree can. If you have a mild cam like I do (Comp 252), get your advance all in by 1800 and your secondaries a tiny bit later. This is for a tall rear end! I have a 3.00 Ford, if yours is higher, this may not apply.

Work your way back to near stock. Just because it runs OK highly advanced doesn't mean that's the best setup. Your carb may be a little big for a mild small block, so your secondaries may be coming in late, if at all. If hot starts are a problem, something is wrong. It should fire instantly.

Thanks for the great info. I was hoping someone had been this way this already. I have a new Mallory programmable distributor, so I am going to try lots of different settings. It does start instantly at 20 initial, a little slower at 40. So I think I will try 20 initial plus 20 vacuum, so it will start easy and then idle at 40, hopefully. Then add some speed advance. I think it will tolerate over 50 at cruise. My rear end is 3.0 too. I'm running a small 250 blower right now, but hardly ever get into boost. And the distributor has boost retard if needed.