Don't got to do anything with vacuum right? Just get timing gun,  clip it to number 1 wire and set?

GT, after 25 years of building racing engines, dyno tuning them along with competing, I have NEVER seen colliding flame fronts (detonation) bend or close a spark plug ground strap. Now destruction of the porcelain insulator is a no brainer. Everything else that I read on this subject is true and common sense, so no disrespect and I do know WTF I’m talking about. This person faced with this problem will find the cause, and it most likely will be a mechanical interference issue. . Perhaps as detonation was occurring pieces of the porcelain insulator broke apart, and that’s what caused the ground strap to be hit and close down.

Oh well that kinda worries me back some more haha. I was hoping it was something simple as detonation.  I'm also hoping it's a possibility that when I had my heads off, that when I set them on the ground or when the shop had my heads they maybe set them down little too hard and closed up the gaps. Cus these heads are some heavy suckers. but I put some other plugs in there and we'll see what happens when I turn it on. Hopefully all is fine

You left the spark plugs in the cylinder heads when they were removed for machining and pressure checking?I would have no doubt that the physical damage was caused by that if that is the case.


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Well when I gave them the heads, I gave them the heads with plugs still on. When I got them back they where still on. I'm not sure if they took them off before doing work and put them back on when returning them

GT, after 25 years of building racing engines, dyno tuning them along with competing, I have NEVER seen colliding flame fronts (detonation) bend or close a spark plug ground strap. Now destruction of the porcelain insulator is a no brainer. Everything else that I read on this subject is true and common sense, so no disrespect and I do know WTF I’m talking about. This person faced with this problem will find the cause, and it most likely will be a mechanical interference issue. . Perhaps as detonation was occurring pieces of the porcelain insulator broke apart, and that’s what caused the ground strap to be hit and close down.

The ground electrodes can get very hot when the engine runs extremely retarded ignition timing. Then it could have likely run extreme advanced, causing the damage to the insulator.

In light of the new and left out information by the OP, I apologize for the rum induced comment, yet stand by the intended fact that detonation can totally close the gap on a spark plug without ANY physical contact whatsoever.

Had it happen numerous times on pump gas restricted race engines. Seen it several times on others rigs.

Race fuel burns too slow to do it I suspect.

No harm no foul.

GT

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Your killing me.

Consider the spark plug a highly tuned precision instrument vital to the survival of your engine.

Quick story and I won't beat you up any more.

Working on a Chrysler New Yorker about 1994, 3.0l V6. Customer complaining of a rough idle and intermittant hard start.

Car had been to four different shops,  none of which could fix it.

I worked at a Chrysler dealer and was the drive ability tech.

After driving the car. It warmed up and drive like a pile of crap.
Brought it into the bay and hooked it to an oscilloscope,  Bam.. three cylinders spiking like a big dog.
Pulled the plugs, they were brand new proper number plugs, the gaps were all over the place. From .024" to.040".

Regapped and reinstalled. Car ran perfect.

Customer had her car tuned up at a Precision Auto just three weeks prior to my getting it.

Always put in a fresh, properly gapped plug. Otherwise you will find yourself chasing your own butt.

Lecture over.

GT

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Haha. Okay. I will do all that. Do it right do It once.  New plugs going in

As we get more information from the owner, it's all starting to make sense, leaving the sparks plugs installed in the head is a big no, no. First rule to go by is, spark plugs are the first to be removed and the last to go back in. I said it before, and I'll say it again, it's going to wind up being something simple and stupid. The plugs being left in the heads while being carted all over the place is the reason for the ground straps being damaged or closed. We all know how destructive detonation and or pre-ignition can be for any engine, but this was most likely never the "real" cause of smashed plug tips. It was just a simple mistake made by the owner of not removing the plugs from the heads when removing them and who knows where they went and how they were handled, then re-installing the heads without even looking at the condition of the plugs. Hey, were human and we learn from our mistakes. Throw a pair GM R43TS plugs in with a gap of .035-.040 and set your timing properly and hit the water and don't look back....Cheers, ,

Are those aldelco plugs shorter than the auto lite 26?

Just picking then up as we speak haha

You should be just fine with that plug, and 145 is a normal heat range, with an HEI ignition system I would bump up the gap to .045. People seem to make a bigger deal with plugs and gaps than needs to be on stock or slightly modified engines. There is no rocket science behind plugs, higher compression and all around higher cylinder pressures = heat, you need to start running a cooler plug heat range so the tip can dissiapate heat quicker into the head material in between power strokes. Lower cylinder temp's & pressures need a warmer plug to keep the tip dry and free from impurities of combustion and not fuel foul. As far as gap, high cylinder pressures we close down the gap, so it's easier for the ign system to bridge the gap against all that compression pressure and flow the amperage, that's what lights the fire.

Rear cam plug rusted through?

 

Could it be those valve covers I put?  I capped them and had to breather on them.  Straight shut

You need to have good crank case evacuation or, at the minimum, good free flowing breathers.  It is the nature of a reciprocating piston engine to build crank case pressure with just the rotation of the crank (not considering blow-by at this point).

A V-configuration is the worst at this, but let’s consider the best possible design, a horizontally opposed boxer configuration with both connecting rods on a common crank throw.  In the boxer configuration, while one piston is approaching TDC, the other is approaching BDC.  Sounds good so far, however the geometry of the connecting rods dictate that the pistons move at different rates relative to TDC and BDC.  That means that the volume of the crankcase changes as the crankshaft rotates, thus building crankcase pressure with nothing more than rotation of the crank assembly.  Then compound that with blow-by.  All piston engines will have some degree of blow-by.  The weaker the piston ring seal, the more blow-by that engine will have.  You need some way to vent this pressure or better yet, evacuate that pressure or gaskets and seals can become overwhelmed and leak.  Ideally, a slight vacuum pulled on the crank case to just below atmospheric pressure would virtually eliminate any leaking seals and gaskets as well as reducing pumping losses.

Too much vacuum can also be detrimental.  First, a vacuum pump can produce so much vacuum that gaskets can be pushed into the engine by atmospheric pressure.  Then the necessity to reverse the crank seals to withstand atmospheric pressure acting against negative crank case pressure becomes apparent.  You can also run into issues with components requiring splash lubrication, such as wrist pins, when the cloud of oil (windage) slinging around with the crankshaft is pulled out of suspension.

Bottom line; make sure that you have good crank case ventilation.

Good luck,

Joe

You need some big 'ol hillbilly breathers in those badboys... 

But do you see how my old covers have that breather type or whatever thing those are sticking up high. And the new ones just have for the cap^breathers.  You think since I capped them with the caps, it built pressure and blew the rear main?

I don't rightly know, you haven't shown the breathers yet... 

GT

Well I only turned it on for less than a minute and it puked at least a qrt