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Ok... looks like you need the gasketed spark plugs after all :)
Can you list the production date cast into the heads (as bracketchev70 has requested). It will help with identifying what engine they may have come on... and in selecting the correct spark plugs.
If possible, post a photo of the production date code. See examples below:
398432

398434

The first letter indicates the month, the following two digits show the day of the month, and the last digit indicates the year of the casting. F-12-5 indicates that the head was cast on June 12, 1965, or 1975, or 1985, depending on other clues including the casting number, port shape, chamber type, etc.
 

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Based on the information the OP provided...
The head casting number indicates that they were produced from 1966 thru 1970. From what I have read, GM began to produce the 454 big block engine in 1970. The block casting numbers reference to a 454 big block produced 1971 thru 1979 (or 1972 thru 1978... depending on the different info on the web). I am far from a Chevy big block expert, but it is possible that the heads on your engine may have been swapped from another big block.

GM also started to switch from the gasketed plugs to the tapered/conical plugs around 1970/1971. So to help confirm what type of spark plugs your engine should be using, you may need to remove a couple plugs and take a very close look at the plug seating area on the head.
*Is it flat?... or is there a taper/bevel into the threads?
*Can you tell how deep within the head the threaded portion for the spark plugs are (about 1/2" or 3/4").

If possible, can you take a close-up photo of the spark plug opening on the head and post it.

Example of a tapered/beveled spark plug port.
View attachment 398382

Example of a gasket/flat spark plug port
View attachment 398383

View attachment 398385
I think GM only used spark plugs with gaskets on Aluminum cylinder heads. I am pretty sure in those years the cast iron heads used the tapered seat spark plug design.
 

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I think GM only used spark plugs with gaskets on Aluminum cylinder heads. I am pretty sure in those years the cast iron heads used the tapered seat spark plug design.
I just read a few posts on a Corvette forum, and a lot of members with early model Chevy 427 big blocks with iron heads are using the gasketed & extended length (.750) spark plugs.
Example: AC R44XLS

Some of the Corvette members even stated that the threads on the tapered seat spark plugs did not reach the recessed threads within the heads. The photo that was posted by the OP looks like a flat seat spark plug port with recessed threads.
398446

I also checked on the RockAuto website, and it states that a 1970 Corvette with a 454 used the gasketed & extended length (.750) spark plugs... but the 1971 and later Corvette with a 454 used the tapered seat spark plug (.43 reach).

Hopefully, the OP can post the production date of the heads to help shed some light on this.
P.S. Zander, Thank you for taking the time to post clear and detailed photos (y)
 

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Hi again,
Another problem I hope you guys can help me with.
My engine kills sparkplugs. See the picture .. basicly kills them after 20 of idle . Obviously things are very wrong . Spark plug is the equivalent of the old one I can get in Europe but iam getting new msd iridium plugs. But they new plugs obviously won’t fix the first problem. Engine has new carbouretour and a new distributor and and the leads are all working and tested altought I get new ones in the next days. When I connect my vacuum gauge the the manifold I get zero or almost zero vacuum.. why is that ?? Why’s wrong ? The guy that sold me the car said it was setup for drag racing .. have I got a very different cam to standard?? The engine is a bbc 1978 open up to 468 that’s all I know .. what can I check ? The initial timing is 16 but even likes to go higher and has no problem .. still burns my spark plugs regardless.. has my harmonic balancer slipped ?? So the timing is off ?? Does the cam ( don’t know which it is)in my car cause to have super low vacuum at idle ?
Do I have a leak ? Please give me all you’re input:))
Here’s a good carburetor adjustment
Vacuum gauges only work on small stock cams. Bigger cams are wasteful at low rpms and need extra fuel.

Here is about everything you'll ever need to know about tuning that carb for most applications and weather conditions.

Read and UNDERSTAND all of this..its great info.

1. Be sure the float levels are no more than 25 percent up into the glass (at 50 percent up it will pour raw fuel into the engine).

2. Set the four small Idle mixture screws in the 1.5-2.5 full turn range is typical.

3. BE SURE the throttle shafts are open a similar amount.

Next, turn the idle mixture screws in evenly until it hesitates when you snap the throttle.

Then turn them back out until the hesitation goes away.

If you are at 1.5 turns or less on the mixture screws at this point, then we need to go up on idle air bleed diameter .010 from current.

As you increase the outer four corner air bleed diameter, it will lean out idle and part throttle operation and improve fuel burning capabilities and idle quality.

Also be sure you are not idling at too low of an RPM as that will cause excessive reversion in the intake manifold and load the cylinders with exhaust. Typically a neutral rpm of 1100-1200 rpm.

Drill the idle air bleeds out (located in the outer four corners) .010 larger at a time until the mixture screws are required to be at 2 turns out as a baseline. Any further in and it will stall or hesitate at the snap of the throttle.

As you drill them out you will be required to turn the idle mixture screws out to regain good idle control.

If after doing these changes it is still rich, possibly it needs a hotter sparkplug or more base ignition timing (typically a MINIMUM of 22 degrees of timing at an idle for most decent sized camshafts).

You'll know you got it right, as when you pull it into gear or put a mild load on it to move it will not drop excessively or require a lot of throttle to move.

If it drops excessively or requires a lot of throttle it is too lean, if it requires you to roll and roll it over to clean the plug up to restart it is too rich.
 

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Discussion Starter #46
Just
I see it is missing some intake manifold bolts. Can you look down inside those holes and see threads? If so you maybe want to remove the intake manifold and install new gaskets and maybe a new intake bolt set.
did that last night .. the outer side bolts were all missing , with a threat available.. always had my thoughts about that gasket anyway so I had a complete set from Edelbrock , with gasket , silicone, gasket glue, new bolts and a with a torque wrench installed last night the intake manifold fresh .. Iam not sooo sure if there was any leaks
 

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Your right. It looks like the gaskets were not damaged. Ok don't flip your carburetor over but see if you can follow the port that you have your vacuum gauge connected to. Look for something blocking the port like silicone sealer or maybe a piece of gasket material. That vacuum port in the baseplate of the carb next to the PCV port should go directly into the intake below the throttle blades. It should be a direct source of vacuum same as the PCV port. Somehow you're getting a bad vacuum reading and it's throwing you off. You definitely have more vacuum than zero and a minor increase when decelerating. You even have a vacuum operated brake booster on that beast. If you had no vacuum I am pretty sure you would be asking the group "How come my brake peddle feels solid but is so difficult to stop the car?". If you have to you may want to rig up a vacuum T in the PCV valve hose. If the T has a 5/16" straight section and a small 1/4" tube coming out 90deg from that, you could connect the gauge to that instead of the small port you're connected to now. The PCV port for sure has manifold vacuum. You can remove the T setup when you're finished.
 

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With your carburetor removed, it would be a good time to check the adjustment of your primary transfer slots. The amount of the transfer slot showing below the throttle blades should look like a square (throttle blades are adjusted by turning the idle speed screw).
398505

Correctly Adjusted Primary Idle Transfer Slots
398507

Only if absolutely needed: Some engines with large camshafts require more air at idle than is provided with this idle speed position. If this is the case, drill a small hole in each of the primary throttle blades (shown below).
398503

To set your secondary throttle blades - First: Completely close them until the blades just touch the throttle bores. > Once the secondary throttle blades are just touching the bores, turn the secondary throttle adjustment screw about an 1/8 of a turn to open the secondaries (shown below). This adjustment keeps the secondaries from binding in the throttle bores.
398506

As Ed D already mentioned... now is also a good time to see if anything is blocking the carb's small "Full Time Vacuum Port". With the carb flipped upside-down, take a small diameter rod (or a 3/32" drill bit) and insert it into the opening of the small Full Time Vacuum Port located in the front portion of the throttle plate. You should be able to see this rod come thru the opening on the bottom side of the throttle plate.
398508

If the rod does not come thru, something is blocking this port... or it was not drilled properly during manufacturing. Repair as needed.
 
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