Carb & Ignition use

[Jack21]

Motor has 2500 street miles on it now. 351W, TFS 2.02/1.60 heads, Comp hyd roller 224/224, Ede Performer RPM, Holley 700 DP (4778), MSD distributor, Accel 300+ CD box & coil. Autolite 3924 plugs gapped at .045. FMS plug wires. Initial lead 14deg. Cent 20 deg @ 2500RPM. Vacuum 8 deg at part throttle cruise. Idle vacuum 16" @ 800 RPM.

Running too rich. Ignition or carburetion?

Took it to emissions test sta. If it's close to State emissions spec, then the motor is dialed in (for street use anyway). It isn't! CO around 3 % (ehh), HC 3000 - 4000 (way too high). Emissions tech suspects ignition problem, thinks motor is misfiring.

Carb. Not my first Holley. Some of you hate Holleys, and some of you love 'em. One of the advantages of a Holley is it can be tuned. One of the disadvantages is, it must be tuned. But once dialed in, it should need nothing except occasional cleaning. At least that's been my experience.

New carb. Box primaries were #69's. Now down to #64's. PV is 65. Engine seemed like PV open at cruise and some acc pump fuel getting into motor thru vacuum chamber. How? Throttle body - metering block surface is dead flat (these warp sometimes and have to be filed or milled flat), and not a cold casting (no casting porosity). Gasket embossed pattern gives no indication of improper sealing. Drilled & installed brass tube & O-ring in acc pump xfer channel to seal (not that it needed it from the gasket pattern, but to eliminate the variable). Replace PV again.

If it doesn't sort out, anybody using BG Speed Demon 650? Complaints? Praises? Anybody using Holley Pro-Jection? Complaints? Praises?

Ignition. Verified TDC actual vs pointer. It's off 3 deg. Checked dist rotor phasing and it's centered on #1 when plug fires. All plugs appear to be firing but dark & sooty. Checked coil output. Plug fires with a "Bzzzzt" rather than the healthy "Snap" I'm used to. This is the Accel setup. Checked with spare Crane HI6 & PS91 coil. Same bzzzt. Doesn't seem like a healthy enough spark to me???

Default ignition around here seems to be MSD6A. Does it snap or bzzt at plug? Should I scrap the Accel and get the MSD?

Thanks.

[JAM1775]

Running rich can be effected by jets, high float levels, high fuel pressure, too small an air filter or air bleeds. Larger idle air bleeds will effect the AF on the low end. The higher end or WOT are effected by 4 other air bleeds. On my BG Race Demon the air bleeds are accessable around the top of the throttle body.
Just a thought to throw out there. It sounds like your timing is okay. My FMS crate 351W is initial at 12-14 and max at 36 around 2500. But I am thinking carb A/F tuning as it seems your timing is not really retarded.

[dalola]

Jack,
This may sound overly simple, but usually it's the simplest of things that totally throw everything off.
Check your distributor for the correct cap and rotor application. I've seen cases of the wrong rotor applied(ie: big gap with contacts), and with todays powerful ignitions, it will usually run, but the spark is very weak by the time it gets to the plug. Also, check your plug wires for cracks. Same scenario...spark will get to the plug, but be very weak. Also ensure a tight fit at both ends of the wire. Are these premade wires, or the DIY kit?
My thinking behind this is your sooty plugs. Again, with the type of ignition you have, if it's functioning properly, even in a somewhat rich condition, it should be burning the plugs much cleaner. Based on your description, I can't believe you are running that rich with your combination of parts. I think the problem may be lots of resistance somewhere in your spark path.
Just a thought.
Dave

[mikiec]

Here in AZ we have emissions testing. I used to work for those folks for about 12 years.

What we found out is that high hydrocarbon (HHC) numbers usually were a function of ignition. Ie: bad wire, timing off, engine problems, etc....

High CO numbers will cause the HHC to climb. However the CO numbers must be real rich to have any effect on HHC. In the order of 6 to 8%.

Carb idle circuits, air fuel mixture scews, being out of balance could also cause high HHC readings. This applies at idle only.

Mike

[Coloradocobra]

What compression ratio are you running? As compression increases, plug gap must go down. .045 at 9:1 may require 0.35 at 10:1. Notice I said MAY. I would drop it down to 32 to 35 and try - nothing to lose. I was trying to run a wide gap on my car and it just didn't run right. It is much better at .035. Can you wire the coil directly to the dist. and eliminate your spark box temporarily? Also, do you run through a ballast resistor in your setup? Should you be?

Just a few thoughts,

Gary

[Jack21]

Thanks fellas. Figured if I provided enough details, some of you would point out what I may have overlooked. You have.

Distributor. It's an off the shelf MSD. MSD cap & rotor. But it's the same size as the pre HEI. Considered adding a brass extention to the rotor tip. Crank in mechanical + vacuum and the tip could get slightly out of phase. This should not effect idle, & off idle richness.

No ballast resistor. Everything runs on 12 volts.

Wires are out-of-the-box and bolt 'em on to the motor Ford Motorsport wires.

Switched to a set of Autolite platinum pro plugs, APP3924 (TFS heads). That seemed to make a world of difference. A bargan at $3.50 - $4 bucks each. Gapped at .045 for the Accel ignition & coil. Compression only 9.6:1 so it would run on pump gas. Will try dropping the gap incrementally down.

Anybody ever try another CD box and go back to an MSD?

One change at a time.

Got the Holley manual out. Anyone ever try drilling small holes in the primary butterflies to lean out the idle air? This is a 700 DP which typically goes on motors with low idle vacuum. This Comp Cams hydraulic roller cam really inhales the air with the vacuum it pulls at idle. Would have expected 11" - 12", not 16".

Thanks