Today I put medium springs in my distributor and set the FBO plate to 10 deg advance. Fired it up and set the initial to 24 degrees. Still has a Top Fueler idle but with 272@.050 I can't say that's a surprise.

Idle vac only about 5" and quite unsteady. I hooked up the can to a Mity-Vac and gave it a squeeze... the timing mark suddenly changed a huge amount and the engine died. Let off the vacuum and it caught again. What I think that's telling me is there's a phasing problem, but not with the rotor to cap (the vac advance moves the pickup plate, not the rotor). Only the centrifugal advance moves the rotor relative to the cap

Just to add to the fun, as the engine was coming to a stop the second time, I let the distributor pickup wires get caught in the alternator belt/pulley and it ripped them up.

But it's not all bad - looking at the mess, I realized that I'd connected the wires backward from the reluctor pickup... which is probably also causing my phasing problem!

Fuel pressure also 4.5 lbs, idle mixtures 1.5 turns out, secondaries cracked... lots of things still to tune. Oh well, enough for one day!

Yes the can moves the plate which does alter rotor to cap alignment when it fires (RP) and centrifugal advance does not. when you pump up the can it changes RP and also greatly increases the reluctor gap & if you are at .008" at rest then that is OK & either one out of whack or a combo of both can cause it to act up. fix the wiring/set the reluctor gap at .008" with a brass gauge or just get it close but not touching & it might be slightly closer at the bottom so eyeball it good. On RP You are at an advantage cuz have the pump at your disposal. turn housing till the magnet is dead even with a tooth & lock it down & make a mark on the metal dist housing outer top perimeter rim just below where the cap seats for where it is clocked (confirm that the springs are retracted all the way which they should be but the slots could be gummed up so twist the rotor back against rotation to confirm) then replace the cap & make another mark on the rim vertically inline with the cap terminal bulge next to the 1st one then remove the cap for easier viewing & see how far they are off then pump it up & see how far it shift away from an acceptable alignment. RP from the can shifts CW on a BB and CCW on a SB & it shifts .024" around the arc for every degree of vac adv (see the # on the bottom of the can arm). the cap terminal width is .214" and the rotor terminal width is .244" & you want them in close proximity & also there is the radial distance from rotor tip to cap terminal and when the combo of RP and radial distance becomes greater than what the available voltage can jump then it will misfire (+ the reluctor gap issue potential). if you need to change RP position or increase rotor tip dimention holler & I will give more info & 3 or 4 options for that.

been there, done that! you would think the car wouldn't start but it will. mine idled pretty well too, it wasn't until i went out on the road did the problem raise it's head. it og coarce didn't occur me because i had been working on something else so of course i was chasing my tail for awhile before i had an 'ah ha' moment!

Yes pick-up coil wires backwards will change the timing. I forgot how much but I think it was at least 12 degrees or maybe more. Ron

the pickup generates its AC voltage when the tooth JUST moves past being dead on with the magnet so a .069" change in distance before reaching that "position" (from switching polarity directions) would change crank timing 12 degrees (& change phasing)

Wires swapped, timing reset. New problem... with my big cam (272@.050) it won't idle properly with up to 24 degrees initial, unless the PCV hose is disconnected allowing more fresh air into the engine. Carb is set to .020 (square) transition slots on pri & sec, and 3/32 holes in the primary throttle blades).

In fact it likes full advance (34-36) at idle. But that will certainly cause a hot starting problem... I do have a dash-mounted retard unit that has 0-15 degree range. So I see three work-arounds:

1) Always remember to turn the dial to -15 degrees when hot starting;
2) Use super-light distributor springs so advance all-in by 1200 (idle);
3) Start cranking then turn on ignition.

I'm thinking about the super-light springs. I already have an FBO limiter plate. That way the cranking timing will be 18 degrees, but when it starts the timing will immediately come up to 34.
Thoughts?

I believe this is the point where you start drilling holes in the throttle blades.

R.

That's what I figured, so as I posted, I already drilled 3/32" (~.100) holes in both plates. Not nearly enough.

If it idles "right" with a foot of PVC hose hanging off the 3/8" baseplate port, that's going to require huge holes in the blades to let in that much air.

I wouldn't want locked out advance for the street. I'm wondering if we are missing something related to the AF ratio (which is what we are trying to figure out) OR if it needs a more race orientated carb to go along with that cam

What is the PCV hose plugged into when it is not "idling right"?

The PCV valve in the valve cover. It's brand new and functional.

What's interesting is if I just stick the open hose inside the valve cover hole, the engine also starts missing and slowing down. Yes, there's a breather on the other valve cover. Removing it didn't change anything.

I always thought that there would be mostly fresh air in there... doesn't look smoky or smell gassy. Could it be that the new rings aren't seated yet, since they haven't been under load?

Odd, I was thinking the PCV might be too small not allowing enough air flow, but then you did the hose trick in the cover and that ruled that out. Unless you are somehow kinking the hose or blocking flow someway? Maybe the hose if bad internally?

I changed the oil, now Brad Penn 10W-40 "With High Levels of Zinc and Phosphorus!" Says so right on the bottle

The break-in oil did smell a bit gassy but no obvious metal particles. Only a very small amount stuck to the magnetic oil pan plug. Don't have a filter cutting tool at the moment but I saved the filter.

With the timing set at 34 initial, the idle is acceptable at 1000-1100 rpm and 6-7" vacuum and the PCV connected. Wideband showing mostly 13.5:1 although it does wander some between 13 and 14.

It does fight the starter a bit after several minutes shut down, but dialing out some timing from the dash took care of that. Guess I will have to lock out the distributor...

Disconnecting the PCV hose at the valve now causes too fast an idle (1600 and 9" vac). I can control the idle speed with my thumb partially plugging the hose. Hard to drive that way though.

Perhaps R. Dogdays had the right idea - drill the throttle blade holes somewhat larger, maybe to 1/8"...

At some point (soon) I'm going to quit tearing my hair out and send it to Thumperdart!

Don't tell me you have vacuum advance hooked to manifold vacuum.

Questions:
1. Have you drilled all 4 throttle blades, or only the primaries?

2. Why are you trying to run a PCV valve on an engine like this? You really don't want that recurculated sh!t getting sucked back into your induction system...

3. Where is your vacuum advance connected (direct manifold vacuum or a carb port that only pulls vacuum at higher RPM, but not at idle)?

4. Stick car or automatic, and what stall if an auto?

Doesn't matter where I hook it, there's not enough vacuum at idle to activate the can! Right now I don't have it hooked to anything.



OK, in the order you asked:

1) only the primaries with 3/32" holes so far.

2) to get the "recurculated sh!t" ventilated out of the crankcase, I don't like sludge and acid formation... although I have considered just installing a second breather.

3) see above. Doesn't matter at 6-7" of idle vacuum.

4) stick.

What do you think?

My last combination with a 266 at .050 SFT cam worked with...
- 1200 RPM idle
- 25* initial
- 35* total
- full advance around 3000
- carb had all four plates drilled with ~ .110" holes
- no vacuum advance, although it would have probably been helpful at my 3500 highway cruise RPM

I have a loose converter, but a stick car is going to be more prone to low-RPM detonation under a load. Otherwise, your option of locking out the distributor and dialing back the timing when starting sounded reasonable.

Thanks for the data! Those are quite similar parameters to my initial try (1200, 24/34 in by 3000), except that I didn't have .110 holes in all four plates. With 3.91 gears and 295/50R15 tires, I will also be cruising at 3000+.

I have noticed that this cam idles smoothest at 1200 also, although it will tolerate 1000 but a fair bit lumpier.

Would you recommend the four smaller holes over two larger ones?
I'm thinking that if I screw up, I only have to repair or replace two blades

Start with 4 x . 093 or .100 and see if that gives you enough bypass air. Throttle blades are cheap and you can buy pre-drilled sets, too.

Oh, dump the PCV and run at least 2 breathers.

I'd be curious as to what the cranking compression is.

I can tell I've gotten older....... The 272deg cam and "street" duty no longer seem like a good idea to me, whereas 25 years ago I would have been up for trying it(maybe).