70 olds 350 timing Help!

[Richie84cutlass]

I built a 1970 olds 350 motor 10 to 1 compression MSD ignition need help setting proper timing... what should my initial and total timing be?

 

[Richie84cutlass]

 

[Richie84cutlass]

 

[olds307 and 403]

Run a good amount of initial, like 18 to 20 degrees and another 14 to 18 degrees max mechanical, 34 yo 38 total. You will have to limit vacuum advance to around 10 degrees. What cam? Olds like a lot of timing but your high compression will greatly limit what your motor will tolerate.

 

[Richie84cutlass]

Bored 30 over forged flat top pistons Howard's 4/7 cam swap hydraulic rollers Manley hardened pushrods Comp Cam rolling rocker Comp Cam Springs slightly port and polish 6A heads I believe the cam is the biggest Howard's makes for the 4/7 swap MSD Pro Billet distributor msd6al 2 box Holley 750 HP carb still have stock stall converter and stock rear end and still need to get a set of headers

 

[Richie84cutlass]

Stock 307 was 24 degrees initial timing I was just wondering if the 350 was going to be different

 

[Richie84cutlass]

 

[fleming442]

What was done to the heads to accommodate the lift of the cam?
Why 4/7 swap? That's questionable old school thinking for a Chevrolet.

 

[olds307 and 403]

I assume at least W31 valves and the bowls opened? My understanding Olds heads will accommodate that lift, you just need roller rockers with them. Yeah, the low compression Olds V8's will tolerate a lot of timing, the swirl port 307's ran timing over 60 degrees. I have personally ran close to 60 degrees on non swirl port, low compression Olds V8's. I am over that on my 260. You will want 20+ base with 230+ duration and around 36 total. You will have to experiment with vacuum advance and see what it will tolerate. I assume you have at least a 2500 stall and 3.73 gears with this motor?

 

[bracketchev1221]

Short answer, put as much initial as the car can handle to start. Then cut down on the advance and set your total to about 36. Without going to the track or having a dyno, you really won't know if more or less timing makes a difference. On my 565 the difference from 36-40 was 4 hp loss. Not enough to matter, but no point putting more advance than it needed. As you already know, get that converter changed it MAY give you headaches trying to idle in gear.