302 timing issues

[Guest Anonymous]

Question for you Ford wizards. As I've mentioned on numerous occasions we put that 345 hp crate motor with 5 sp in my bro's ranchero. When I got down here it was a hella dog, I mean my Z would kick its butt big time and I'm giving up almost 100 hp and not much difference weight wise.

I tell him, dude there is something really wrong. Well we look at the timing. Its using a MSD ignition on a duraspark distributor and the vac. advance IS on the ported vacuum on the holley 1850 vac sec carb.

The idle due to the cam (E303 I think it is) needs to be raised, not alot but nearly a grand really especially to keep it from dying with the a/c on. At idle we're seeing almost 10 in of vac at the ported barb on the metering block. I checked for vacuum leaks and found none.

Question, is something screwed up, or is it just the opening of the throttle plates at the faster idle causing it to see vacuum early and if so what do we do? We set the initial to almost 14 deg and disconnected the vacuum advance and the car immediately left a 50 patch of rubber, so it improved alot. It was way retarded (we bumped it nearly 9 degs). But what about the vacuum advance, is it just not going to be operable now or is there a problem in the metering block of the Holley? Any suggestions would be appreciated. I think we can go more initial as long as he's not pinging and that theres more HP left in the motor we're not seeing yet. Thanks in advance (jeez timing pun not intended).

 

Regards,

 

Lone

[DAW]

When you bumped up the initial by 9 degrees you should have been able to then back off the throttle adj screw (close the plates down) and expose less of the ported vacuum slot for the same idle rpm. Before the change, your total advance was too low and it was "distributed" at a suboptimum rpm. I expect he'll see an improvement in mpg as well as performance. DAW

[randy 77zt]

check the TOTAL advance at 3500 rpm or so with the vacuem advance hooked up.should be 35 to 38 be could work dowm to about 32.total is initial+mechanical+ vacuem.you will need about 12 before with the cam.you can change the vacuem can to an adjustable unit.they adjust with an 1/8 allen wrench through the vacuem nipple.if you get a ping on light accel you can make it so it takes more vacuem to get the advance.the vacuem advance is for fuel milage/high way cruising.it helps to have a dial timing light.or find a good shop that knows how to set up distributors but that is becoming a lost art.

[pparaska]

Randy, all the stuff I've read about total timing always references initial plus mechanical advance as total timing at 3000 rpm or so. Vacuum is always on top of that.

[randy 77zt]

depends on if you are getting total amount at a steady throttle (cruise) mode or on a dyno at a wot pull.unless engines are built identical the best advance curve for every engine will be different.a boosted engine usually needs very little advance.an article i read by a honda race engine builder said his total timing under boost was 24 btdc.26 would make a little more hp but blow head gaskits.a na motor has room for error until it is tuned correctly.