I am trying to tune a old 360 in. The truck is a 76 f-150 4x4 with a 4spd, 3:54 gears, 33 tires. So far I have removed all smog crap including the tubes going down into the exhaust ports and put in a straight timing chain, 390gt intake, 4160 holley, long tube headers into 2.5 into a y with 3" to muffler with dual 2.5 out the back. I want to get as much torque out of this old motor before I drop a bigger one in sometime. I have been having a problem with a lean backfire through the carb off-idle since I put it on. So i upped the squirter size to .37 so far and changed the cams to no avail.

Today I checked the timing and base is at 12 with full mech advance never reached. So I tore into the dist and and flipped the advance plate from 15L to 10L. And pulled some orange and purple springs out of a old chevy mallory dual point out put them in. I set the tabs to the spring to have no slack and re-assembled. So now I am running 16 initial, 22 at 1200rpm, 32 full advance at 3000. So far no more lean pop and it runs alot better. Only takes about a 1/2" of pedal travel to hold 60mph on the road now!

Should I leave it at this and adjust the vac advance? Or file down the mech advance stops to get a full 20 and set full mech advance in at 2500with lighter springs ? I use this truck mainly to haul and carry a truckbed camper. I usually cruise around 2000 to 2500rpm.

 

Wow, finally some real-world input on tuning up a 360

I don't know off the top of my head what the timing SHOULD be, but that 360 is low-enough compression that you could probably go even further at lower RPMs... but why mess with success?

I certainly wouldn't file anything because it's not reversible.

What is your intention? Not to have to press 1/2" on the go-pedal to hold 60?

 

If you don't have access to an "OLD" Sun distributor machine you could just stretch both springs a tiny bit, or scrounge up some Ford springs in a bone yard. I think you are very close to ideal. Just get it to advance to a total of about 38* degrees for the best performance and economy. You're on the right track.

 

I was told you want to have full mech advance in at cruise rpms for best economy. So far I have the vacum advance cranked all the way in and still don't have any pinging. I figure if I grind too much out I can always put a weld on it and grind it back down. i was looking around summit racings site, and they have a set of springs for 4 bucks that puts all timing in at 2500rpm. Gas ain't getting cheaper but tunning is free!

 

That is why I suggested 38*degrees at 3,000 is about the ideal. When you have that any minor adjustment can be made in the initial timing, a little less or a little more would not cause a huge difference in performance. If you are happy where it is keep it there and enjoy.