['71SB409]

My '71 is a street driven car that i'd like to take to the track once i get everything done on it. Im assuming im better off setting initial timing instead of total timing (but im not sure if that would be the best for my application or not). I have an old tune up book that lists what timing should be set to for a stock car w/the stock motor but lets face it, mine isnt close to being stock. Heres all my info, hopefully it helps.

-SB 400 bored 40 over right around 10:1 c.r.
-D.U.I. distributor w/vacuum advance
- Holley street avenger 770 carb w/vac. secondaries
-Trick flow 23* 420 hp top end kit
- Cam 228/234 @ .050
- .480/.494 lift
- TH350 2800-3000 stall torque converter
- Hooker comp headers w/2.5" exhaust through FM 40 series and 2.5" tail pipes
- 3.73 gears

Thanks for all the help guys, hope this is enough information to get things rolling. I have been running this set up for a while w/the timing set from that book, but i think it could have run better. I took the dist. out and had it checked and just put it back in and want to set the timing for good!! Thanks again guys!!!

~Paul

 

[Jerry70]

When you set initial you are also setting total (and everything in between). Because there's no load at idle, most engines will tolerate a wide range of initial (but usually idle better with more than less). Once you take it above idle in gear there is a load on the engine and the amount of advance becomes much more critical. For this reason I'd start with total. If the proper amount of total results in too little/too much initial the distributor will need to be recurved to allow both best initial and best total.

 

[d1_bradley]

A pretty common starting point is 36 total, all in before 3000. (This with vacuum advance plugged). If you don't have a dial back timing light, get one. They are NEEDED with a performance engine.

 

[Dave Hopkins]

I agree on the dail back feature! You can spend a ton of money on an engine and never allow it to approach its potential by not having the advance curve right!
My goals
1: Absolutly zero movement out of the centrificle at idle or up to 1000 RPM.
2: Full advance from centrificle about 2800 and that should get to abt 36 degrees
3: Vac should get you into the 50s. Then take it on the road and listen with care! I was running high 50's earlier, then listened on the highway, pulled it back a couple and realized it sounded better, got rid of a very light jingle at 2800, then tried a small amount of mid grade gas, jingle came back, topped up with supreme, jingle gone so I think I have it where I like, have not put the dial back on to check the final but I am guessing its abt 56 (mine is a big block with Edlebrock heads so we are not equal)
4: Then we want vacuum to pull back when it dips 2 inches of vac below idle.
The base can be what it is IF you have a modern starter, old GM starter may object but forget factory numbers like 4 to 6, its going to be in the teens.

 

['71SB409]

Alright guys thanks for all the help!! Now, where can i find one of the afore mentioned "dial back timing lights?" And will they be labeled as such or what do i need to look for?? Thanks a lot!!

~Paul

 

[Jerry70]

Most auto parts stores have them, as well as Jeg's, Summit, and Sears. A lot of guys use the Sears Craftsman one and like it. They are also referred to as "adjustable" lights.

 

[zeke67]

16 to 18 degrees of initial timing with another 18 to 20 of mechanical advance to give 36 to 38 total timing. With any sort of performance cam, that amount of initial timing will help keep your idle clean and improve throttle response. The add in vac advance as already mentioned, connected to manifold vacuum to further improve idle and part throttle driveability.

 

[SWHEATON]

ZEKE,nailed it,do exactly what he saysy and your motorshould run well .

Scott

 

['71SB409]

Thanks for all the help guys. I appreciate it!! I did end up calliong the manufacturer of my distributor to see if they had any tips for me, plus i had to ask them a few questions about my newly re-built distributor. They said the same thing around 16* initial and i should be pretty good. As soon as i get it going (a lot going on the next few weeks) ill report back on if i feel its running better!! Thanks again!!!

~Paul

 

[zeke67]

I still think you need 2 to 4 degrees more. But don't take my word for it. Search on SWEATON's posts. He has very detailed descriptions on timing and why you need more.