Hello, recently my 85 decided she didn't want to work.

This Saturday, she ran and drove fine. Parked overnight..was going to Walmart on Sunday, and suddenly it was running like crap. Literally overnight. Running as if a few cylinders weren't firing.

Tore is apart, confirmed timing at the dizzy and cam, nothing changed. New plugs, wires, dizzy cap, and rebuilt my carb, no change. New condenser, made sure point gap was set right.. immediate difference. Point gap was still .019. Now, its running on 7 cylinders. Cyl 1, 3, 5, and 7 all fire strong, timing light has a strong flash.
Cyl 2, 4, and 8 fire but seem weak, the timing light is quite dim. Cyl 6 has no spark. Outside the cyl, I hooked that wire to another plug and grounded it, I got spark, but it was extremely faint yellow. So under compression, no spark. Now..this is strange as hell.

Some info on my motor
355 rebuilt with around 1k miles, stock bottom end, l98 heads, stock early 80s truck cam, weiand speed warrior dual plane, 2" carb spacer, holley 600, ac delco point type dizzy, msd blaster II coil, accel wires. With headers.

I think its most certainly an ignition/electrical issue..
Could this possibly be a bad resistor, or weak coil?
Any help appreciated, this is my DD and having it down bumming rides to work isn't sustainable.

 

Sounds like there's a problem with #6 plug. Have you tried putting a known good plug into that cylinder and trying it?

 

Yes. All new plugs. Was testing the spark outside the cyl with several different wires, and several different plugs. No change.
I changed condenser, not points, could it also perhaps be bad points? This happened seemingly overnight, with no symptoms or issues the previous day. Which is why I'm really stumped.

The condenser I put in was one I had sitting around, and it wasn't new. I tried several diff plugs and wires on #6, in and out of the hole, no difference. Everything yielded a dull yellow spark, so ive mostly eliminated it being the plugs, wires or compression.

 

Sounds like a bad cap or coil to me. Just to be sure, do you have a good ground to the motor?

 

I just replaced the cap yesterday. The old one looked great (dizzy was new 5k miles ago), but I changed anyway. No change. The coil, I didn't change. I do have another known good factory gm coil around, I can try swapping and see what that does.
I also didn't change my rotor, it looked nearly new as well.

And yes I do. I have a 8 gauge cable going from block to frame

 

Usually there is a ground strap from the rear of the cylinder head to the firewall. I had a Dodge work van that would self destruct overnight, turned out to be a loose ground that would intermittently make contact.

 

The coil, condenser, and points are common to all cylinders. In other words, it makes sense (to me, anyway) that, if one one of these go bad, it will affect all cylinders. Electrically, the dizzy cap or rotor might cause this problem. You said you replaced the dizzy cap. What about the rotor? It's possible that the contact that makes with each point on the dizzy cap is pitted or wearing down just enough that it doesn't make contact with #6 on the dizzy cap.

 

True. When the condenser went out, she was only running on 4 cyl. How it was alive, I have no idea.

From just looking at the rotor, it looks good, and is 5k miles new. Doesn't mean its not bad, just that I didn't notice anything.
It can't hurt to change anyway.
I have a spare coil and points to swap out if need be, looks like I'll get a rotor here after work.

And I do have a ground strap, goes from last bolt on my valve cover to the firewall, its tight at least on the valve cover side

 

Move that ground strap to a location on either the intake manifold or better yet the head casting itself. Contact on a valve cover bolt is not good enough. How is your plug wire routing? If you are running factory L98 heads and exhaust manifolds, the wires can be tricky. Be sure you don't have any getting burned or cut against exhaust or sharp edges of metal.

Why points? Why not an HEI. Much stronger spark(unless you're running an add on module) and alot less trouble. Even with the blaster coil, the points cannot generate enough primary voltage, or support enough primary current without burning up real quick, to make any real KV. The HEI makes 40KV stock. Speaking of burning up points and condensers, are you running a dropping resistor? The factory breaker point GMs used a resistor wire to drop engine running voltage to about 9 volts. They also had a bypass from the starter(R terminal) to provide full battery voltage to the points while cranking to help the engine start. To make this work, you need to use an early style starter with the "R" or return terminal. You can also do it using a relay on the start circuit from the ignition switch but the starter is much simpler.

13.5 volts constant, engine running, will fry the points real quick.

 

This is the first thing that came to mind when I read "points/condenser".

 

I'll move it, and my plug wires are routed up and away from the headers/all heat sources and things that could damage em. They're brand new as of 8pm yesterday.

Hei is cursed for me. 10 coils and modules in 2 months with an accel AND delco vacuum advance hei. Switched to points, never had a problem since (till now). Yes I'm running a ballast resistor. 9.3v last time I checked (which was a while ago)

Before this, it started within one turn. My wiring is 100% not factory.
My ignition is wired as such:

BATT + to switch inside, switch to a 10a fuse, fuse to ballast resistor, resistor to coil. Then coil to dizzy. No bypass needed, she starts easier than my FI Mercedes.
Starer is wired straight to 12v from fuse box on its own circuit.
Fuel pump and fan as well.

Up till this last Sunday, she ran like a champ, then suddenly stopped running like a champ. I'm happy with points.

 

Changed the ground so that its head to firewall. No change.
New (used, but known good) coil, no change.
New rotor, no change.
New resistor, no change.
Wired + resistor straight to batt to eliminate wiring issue, no change.

Via process of elimination, its something in the dizzy..

 

Stupid questions:

What's the distributor cam look like?

Did you lube the distributor cam when you installed the points?
Did you put a dollop of lube on the rubbing block of the points?

ACDelco P/N U1904
GM P/N 12338672

 

Can't visibly see any wear,
It came greased.

Just got a new dizzy, now I'm getting strong fire on all 8.
Didn't lube the new one..

Sounds like I have a pretty large vacuum leak now, I have to turn my mixture screws all the way in and even then, rpm still flutters a little and occasionally dies. That's easier to chase down though, probably in my carb.

 

Mixture screws in? I'm pretty sure that's full lean. Some of the Holleys did go the other way but I'm pretty sure that the 600 vac secondary is not one of those. In fact I just installed a 600 Street Avenger on this 69 Mustang Mach 1 sitting in my shop and I know for a fact that this one is in for lean, out for rich. Are you sure it's running lean? How is your timing?

 

I'm sure that it runs like crap, and that before this whole ordeal, she ran fine, no leaks. Night one, to rule out the carb I rebuilt it, at midnight, tired and with work in the morning. So not 100% that it was done right. Its not a main or spacer gasket, I just threw a random baseplate gasket on though, that may be it.

My fuel pressure is at 8psi running.

 

Yeah, could be a leak at the base plate, if it's really lean. Try a little brake cleaner or propane around the base of the carb. If it gets worse with the screws out more, be sure you're not just dumping fuel. Look for soot at the tail pipes. Do you have a cat installed? That can make it harder to judge exhaust. This is dumb thing to bring up but be sure you got all your hoses right, like the PCV, fuel line, and brake booster in the right place. Check you float level to be sure the float bowls are getting fuel.

 

That's the first thing I tried, no noticeable difference, so I think its inside the carb or the base plate. Not the PV either..
And no cat, I'm running true dual straight pipes with stacks. Theyve always had soot at the tip, since the original motor blew as much black smoke as a diesel lol.

All vacuum connections are good, floats checked and good, not sunk, .100 needles are new and not dumping fuel, no pcv (breathers on both covers). Dizzy stabbed at 8* advance base.
no suction where the pcv would be, so not intake (both intake and heads were machined, and test fitted to make sure they fit). Drivers side breather actually has a little smoke coming out.

No black smoke other than at very High Rpm, even then its just a small puff out both banks.

 

Its sounding like its indeed getting too much fuel, I was wrong. Won't even run unless the idle screws are full lean.

I have an electric pump, if I fill up the float bowls, shut it off and start the car, if runs but like crap for a min, then starts to sound better till it runs out of fuel.
Not blowing black smoke, doesn't smell like gas, not dumping fuel while running. Though if I leave my pump turned on, the motor will die after a minute or so of running, and blow gas out the front.

 

Have you pulled a plug to see what it looks like? Possible that the plugs may have taken a dump as well.

 

New from a couple days ago, but I'd guess they've got some soot build up.

 

Check float level. You may have gotten something out of whack in the front fuel bowl. That's what it sounds like.

I mentioned checking your hoses because I had a newly built chevy come to me one time for a similar issue and found that the builder had mixed up the PCV and fuel hoses on the Edelbrock (Carter AFB)carb. You can imagine what that ran like. Funny thing is, it took me a minute to catch it. I was trying to understand what the problem was and my buddy says "is that where the fuel line goes?" I hate smart asses. I don't know how the guy ever drove that thing to my shop. Must have been fun.

EDIT: I agree too that once plugs get fuel fouled, they can make getting the engine to start and run a challenge. If you can get them to fire and clear up, you can usually save them. More KV helps there.

 

I lowered both of em considerably, she doesn't flood out anymore, just runs like crap at idle. As of recent, I noticed both of my pcv breathers smoke some, I'm wondering if I lost a cyl (overnight?) Somehow.. will do a compression test later. or if its just a junk carb.
It was new back in, oh, the 70s?

And..wow.. I'm surprised that would even run with those two switched. Unless he got some serious blowby and had some pretty fuel dense crank case vapors..
But yeah, my booster, fuel line and vav advance are right, and where they'he always been. Vac advance on the metering block.

She fires up quite easy, just the same as before the issue.
Key ON, pump ON, IGN ON, pump once, and within one turn she's alive. Except in the cold (no choke).
I can put her in gear and she stays alive, the idle is just..completely erratic though. I'll see if I can get a video after work.
By the way, I really appreciate your help, my fine sirs.

 

Plot twist! Compression test revealed I have 0 compression on cyl 4. 0. Nada. I just dropped the pan yesterday, it didn't smell of fuel, so I don't think I have a gaping Hole in the piston. I dont think cams just go flat in a day with no metal shavings.. so betting I have a stuck valve/bent valve/push rod/valve train issue.
My lovely new plugs are covered in soot as well.
Bottom right is cyl 1, left is 2..etc