[formulabird428]

Hoping I can get a direction from the PY forum:

Symptom:
Starts right up, idles nice when cold (have to feather it until about 140F). I drive it around and it runs great. One thing I do notice is that the A/F ratio is a little higher than normal -- maybe 0.5-1.0 points higher. Where it used to idle at 14.5 to 15.5, it's now from 15.5 to 16.5. Coming off of a cruise and stopping to idle, it goes above 18.0. I get it a little throttle, and then let it rest to idle again, and it returns to 14.5 to 15.5. Again, car has always done this, but it just "seems" to be a little leaner. In light throttle, it's about 12.5, which is pretty much where its always been for the last 5 or 6 years.

After about 25 minutes, it breaks up bad. Pops through the exhaust once or twice. I pulled it in the driveway, very hard to start. Backfires a few times. I actually had to pull it back in the garage today, since it wouldn't start at all afterward. Pulled Cylinder 1 plug and it was dirty, threads were wet, but tip was black-brown.


It has an HP 830 Holley with a new baseplate. Jets are something like 79 / 84 or something like that. I do have the back blades cracked open to allow for more air at idle. The T-slot is .030" showing.


Some components are old, but I don't drive the car more than 200 miles per year.


MSD 6AL ignition w/blaster 2 (coil is about 5 years old, 6AL is about 8 years old)
NGK plugs (about 4 years old, 1500 miles)
Holley regulator (this thing is all over the place, could be a problem here). I can't seem to set it and have it stick to a number. It will idle at 10, then drop to 4, up to 7, etc. Any recommendations for a better regulator?
Recently set the lash @ 0.020 / 0.022 per Reed Cam Card, but it is smooth as glass up through 5k rpm (when cooler - 160 or 170, not 190F hot).
Not that this matters, but oil pressure is good.

Any thoughts? Fuel delivery? Carb? Regulator? Ignition?

Thanks in advance.

[STEELCITYFIREBIRD]

Take regulator apart. Bet its corroded bad.

[66bonne]

I would first look at the regulator. And my guess is that there is an o-ring or regulator pump gasket in there that has malfunctioned due to the effects of today's fuel. The fuel could also cause the O-rings in your needle seat assemblies to go bad. {Been there, done that.} I say this due to your car sitting a lot.
I use an aeromotive regulator but I still have to check the O-rings and gaskets.
Good luck.

Jim

[66bonne]

The second thing I would check is the coil as it is acting like it is overheating. Due an ohms test on it.

Jim

[dmac]

Check plug wires and dist cap, along with coil, and coil wire connections and condition.. Wet plug sounds like fuel may not be igniting, then igniting in exhaust. And since you recently reset lash, double check settings. If set when cold, lash will decrease when hot, potentially hanging open too long

[CROCIE JR]

Check to see if the coil is hot to the touch 180-190. I dont run canister coils anymore. They always seem to go south lately. Same sym. you are getting.

[steve25]

Put a timing light on it when it acts up to prove out failing spark or not.
When its acting up kill the spark and then crank it over, does it crank smooth (even), or sound like its speeding up and skipping over a cylinder or two? If so a valve may be adjusted too tight for normal engine temp!

[68 Firebird]

Had a similar issue last year. Ran the GM HEI for years with no issues.
Car was great for an hour or so and then would miss.
Fine on a highway run though, just acted up when HOT outside and just cruising around.
Would usually show up at a light and go away once cooled again.
Water temps were in the 180's the entire time.
Put a light on it when acting up and saw erratic flashes that were coinciding with occasional miss.
Always had a strong, steady flash when cold.
Put in a new DUI HEI and has been fine since.

Gerry

[shaker455]

Originally Posted by formulabird428

Hoping I can get a direction from the PY forum:

Symptom:
Starts right up, idles nice when cold (have to feather it until about 140F). I drive it around and it runs great. One thing I do notice is that the A/F ratio is a little higher than normal -- maybe 0.5-1.0 points higher. Where it used to idle at 14.5 to 15.5, it's now from 15.5 to 16.5. Coming off of a cruise and stopping to idle, it goes above 18.0. I get it a little throttle, and then let it rest to idle again, and it returns to 14.5 to 15.5. Again, car has always done this, but it just "seems" to be a little leaner. In light throttle, it's about 12.5, which is pretty much where its always been for the last 5 or 6 years.

After about 25 minutes, it breaks up bad. Pops through the exhaust once or twice. I pulled it in the driveway, very hard to start. Backfires a few times. I actually had to pull it back in the garage today, since it wouldn't start at all afterward. Pulled Cylinder 1 plug and it was dirty, threads were wet, but tip was black-brown.


It has an HP 830 Holley with a new baseplate. Jets are something like 79 / 84 or something like that. I do have the back blades cracked open to allow for more air at idle. The T-slot is .030" showing.


Some components are old, but I don't drive the car more than 200 miles per year.


MSD 6AL ignition w/blaster 2 (coil is about 5 years old, 6AL is about 8 years old)
NGK plugs (about 4 years old, 1500 miles)
Holley regulator (this thing is all over the place, could be a problem here). I can't seem to set it and have it stick to a number. It will idle at 10, then drop to 4, up to 7, etc. Any recommendations for a better regulator?
Recently set the lash @ 0.020 / 0.022 per Reed Cam Card, but it is smooth as glass up through 5k rpm (when cooler - 160 or 170, not 190F hot).
Not that this matters, but oil pressure is good.

Any thoughts? Fuel delivery? Carb? Regulator? Ignition?

Thanks in advance.

You have a very long history of your combo not running right.
Bring it here & well help you!

[ta man]

What fuel pump?

[formulabird428]

Update:

In addition to the original post, I did try and take the timing. I thought it was because the light was hitting the water pump at first, but come to think of it, I had a hard time reading the timing. It did seem to bounce around 12 to 16. Maybe another sign of ignition.

The weather was much cooler when I started it up the next day. Up to that point, I hadn't changed anything yet. Only checked the lash (no problems) and took apart the regulator (appeared to be fine). It fired right up, ran perfect as it has for the last several years. Assuming the problem was the coil, I tried to heat it up by driving around town. Water never got above 180 but oil was a nice and hot 235. Despite my attempts to get it to repeat the severe miss, I could not. It did break apart a little, but nothing like the previous day. I changed the coil anyway and there didn't seem to be any change. I had to put the car away and get ready for another event, so I could not continue testing.

I think my next steps will be to get a better regulator. This one goes from 7 to 11 to 2 all in one cruise. Fuel pump is Holley Blue. About 7 years old. 1/2 line to #8 to 2 x #6 out of regulator to carb. Also, coil is very close to distributor, but consequently above the driver header (they're not coated). Therefore, everything is hot to the touch. 6AL box is inside the car. Lastly, the car is still running lean(er) than normal.

I'm going to attack the fuel regulator. May look at the pump too. And give the carb a cleaning.