When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My take: dwell usually goes from 30 to 35-50 as the rubbing block wears. It doesn't go to 12 degrees unless something is loose. Or defective. I would very carefully check the points breaker plate and the rest of the distributor, and if ok, install a NEW set of points and condenser. Fix what's broken before chasing ghosts in carburetion, etc. All due respect, Powershift is incorrect. A dwell of 12 degrees will advance the timing, not retard it. Bigger dwell angle = less /retarded timing.
Listen to GTO guy and check the internals of the distributor. Everyone likes to blame malfunctioning on carburetion but it is usually the ignition which is the issue. Check for looseness on the breaker plate, slop in the shaft, itself, and do what he suggests. It will save you a lot of time and it is easier to diagnose.
Last edited by Dan Hampton; 07-28-2020 at 04:01 PM.
My 396 all of a sudden stopped idling. Found a broken valve spring.
Just a thought.
Man, I would check that. Only seven bolts on each valve cover, if even just for peace of mind....... If it is a broken intake spring, at some point the spring height collapses, the piston hits the valve as it is chasing it up, knocks the keepers out of the retainer and then the valve starts to fall into the cylinder...... Wham, bam, you get one of these......
Man, I would check that. Only seven bolts on each valve cover, if even just for peace of mind....... If it is a broken intake spring, at some point the spring height collapses, the piston hits the valve as it is chasing it up, knocks the keepers out of the retainer and then the valve starts to fall into the cylinder...... Wham, bam, you get one of these......
Look like a "bone stock" valve out of a late model Kia.
I installed a new set of points and condenser. Set the dwell and checked the timing. No change in the poor running condition. Engine was surging at 1000+ RPM.
I checked the vacuum can as suggested above by Powershift. It starts pulling at 3" and stops at 13" breaker plate moves smooth, and the can holds vacuum until bled off with the valve on the Mity Vac.
Plan to switch out the coil with one of the spares I have sitting around here, and check the spark plugs.
Gotta do some storm prep as well. Looks like Isaias will be here Monday based on the current track.
Sure wish we could get a season without a storm (or two. Or three) around here...
Carter
Also, haven't forgotten about the valve spring comment made above (426 Hemi).
I would change the condensor. My 65 would all the sudden start running rough ,popping...I went thru the carb,timing.valve lash...Then changed the condensor. Didn't
think it was the cause but it worked. I always kept a spare in the dash.
Carter - Here's the steps I took to find my missing under load problem:
1. Cleaned the points and checked the dwell - it was 35 degrees, I adjusted it to 30. Should be 28 to 32 for my 350CI motor
2. Reset timing to 8 degrees initial and 36 full advance
3. Then checked the manifold vacuum. At idle it was at the bottom of the green. I think 17". Rev it up and it goes to 25". Real steady - it did not jump around which would signal a broken valve spring.
4. I checked the float level on my Holley. Primary level was good. Secondary level was too high. Adjusted it down to where it should be.
5. Adjusted the idle mixture screws to get the most vacuum.
6. I had all the ignition shields off... Checked for arcing in the wires. Nothing noted. They are fairly new.
7. Finally, I pulled all 8 spark plugs and that's where I found the problem. #1 was a mess. The rest were pretty good. So the #1 plug was the cause of my misfire. Bought 8 new plugs since I had them all out anyway. Gapped to .035. The plugs I used were AC R43S. It had these in the car when I bought it. It's a built motor so I'm hesitant to use a hotter plug like a 45S. I don't know what the build entailed so I'm going to be conservative here.
Car runs great now. The plugs I removed were installed 2 years and about 3,000 miles ago. I've got extras so for now I'll just change #1 plug periodically until I pull the heads for a rebuild. I suspect a bad valve seal. I've attached a picture of the plug. I'm surprised it fired at all.
I don't understand #3 above at all...Intake manifold vacuum should be at maximum with throttle plates closed and I've never seen over 22" of vacuum at sea level.
Personally I would run a hotter plug, at least try it for a few hundred miles then recheck them - but its your car.
Last edited by Frankie the Fink; 11-30-2020 at 06:31 AM.
I don't understand #3 above at all...Intake manifold vacuum should be at maximum with throttle plates closed and I've never seen over 22" of vacuum at sea level.
Personally I would run a hotter plug, at least try it for a few hundred miles then recheck them - but its your car.
Thanks... I'll have to revisit this again. Not an expert on manifold vacuum by any means.
I don't understand #3 above at all...Intake manifold vacuum should be at maximum with throttle plates closed and I've never seen over 22" of vacuum at sea level.
Personally I would run a hotter plug, at least try it for a few hundred miles then recheck them - but its your car.
He meant it went up as he increased the RPM gently to cruise....which is normal until more throttle is applied and then it goes back down. Closer to 21" would be the norm at about 1200 RPM or so. I would do a leakdown test on the above post's fouled-plug cylinder to determine if the oil fouling is a bad valve guide seal, guide, or possibly a piston ring issue. If it is simply a worn guide/seal, what FTF said....run a hotter plug in that cylinder, or an old time anti-fouler.
If the miss is at idle also, pull each plug wire one at a time while running and see which cylinder is effected and go from there. That will confirm a problem with one cylinder or a spring issue.
07-28-2020, 04:01 PM
