Question about spark plugs

[Freddo]

Hi everyone,
I did a tuneup on my truck about a year ago. (New plugs, wires, distributor cap, rotor, condenser, points, set timing according to the manual. I think 12 before tdc if I remember correctly.) My truck is a 1967 C10 with a 283 with an oversized Edelbrock 4 bbl carb & Turbo 400. Just an old farm truck. Odometer reads about 15,000 miles which I’m guessing is 115,000 miles. I’ve owned it for 10 years. Odometer was at 7,000 miles when I bought it, so I haven’t put a lot of miles during my ownership. Over most of the 10 years, the engine has ran smoothly and ran exceptionally well for a while after the tuneup.

Over the past few months, it has developed episodes of running very erratically: it misses, loses power and pops, sometimes very loudly. One pop was severe enough to blow a hole in a muffler that was just a few years old. (It has dual exhaust). It is very loud now. These episodes have been fairly random and usually, it would correct itself and run ok. (When it is behaving this way, it sputters and pops, and will barely go down the road. I usually pull over and wait for it to correct itself, and typically it has corrected itself after sputtering along for a while.) At one point, we pulled one plug wire at a time & #8 was not firing. We removed it, cleaned up the plug & it ran pretty good for a couple of errands.
It has gotten progressively worse again and When I pull the plug wires, one at a time, it doesn’t seem to make any difference. It is now running terribly and I can’t take it out of my driveway.
I thought I would try to change the plugs and maybe put in a slightly hotter plug. The plugs that are in the truck are the R45ts plugs and I tried to put in the R45S plugs which I read on this site were a little hotter and should fit. The R45s plugs have the wider base and won't fit into the head. (See picture)
Sorry for the long winded post, but I was hoping to give enough info so that you might be able to offer some suggestions.
Here are a couple of questions:
1. Is there a plug that might be one step hotter than the R45TS that I might try that fits this engine?
2. Any other suggestions that you can offer to get this thing running better?
Thanks in advance for any help or suggestions you can offer. I don't do a lot of posting but I am on here all the time reading everyone's posts and learning.

[Warrens69GMC]

Those are 2 different spark plugs. Do you have tapered seats in the heads or do you have one with a flat face for a gasket?

Or 2 different heads?

Do you have the casting number for the heads?

[Freddo]

Warrens69gmc: Thank you so much for your reply.

I think that the hole for the plugs in the heads must be tapered. I couldn't get the R45S plugs to even start in the threads of my head. The shank on the plug just above the threads is quite a bit larger than the R45TS plugs that are presently in the engine.
I included a picture of the front of one of the heads and included them with this post. (Not thinking it will help much, but thought I would include it.) I don't believe that the heads are different from each other. Unfortunately, I don't have the casting numbers. Not sure where they are at on these heads, but it didn't look like I could get them without removing the head.
Thanks again for your reply. I appreciate your help.

[Warrens69GMC]

Remove the valve covers, they are under them. Standard valve cover gaskets are like 13.99/set, but lets us know exactly what you are working with.

[RustyPile]

While you're removing those valve covers, here's a lesson on what those numbers on AC Delco sparkplugs mean.. R=resistor plug. No "R" prefix= no internal resistor.. 45=heat range.. T=tapered seat.. S=extended tip.. Resistor is self explanatory.. As the heat range number goes up the plug is hotter.. Transversely, as it goes down, the plug is colder.. Taper seated and gasket seated plugs are not interchangeable.. If the center electrode extends beyond the base of the spark plug, it is of the "extended tip" design.. As an example: an R45 plug would have an internal resistor, a gasket type seat, but not an extended tip.

[72SB]

Beyond confirming you have right spark plug type.....the "oversized carb" may be dumping to much fuel causing plugs to fowl if it is to much carb for a 283 or the carb is leakingto much fuel into otor

[HO455]

I recommend doing a careful inspection of the internal parts of the distributor. You may have a crack in the cap causing crossfiring, or the rotor tab could be loose, or the button in the cap could be cracked.
Make sure the ground wire under the points plate isn't broken or has loose strands touch other parts. And make sure the power wire from the coil doesn't have a break under the insulation. Both of these wires have to flex every time the engine RPM goes up and down.

Take a timing light to see how smooth the timing advances. Slowly rev the engine up until the advance stops moving. You can do this on all eight plugs. The advance should be smooth and repeatable if not then something mechanical in the distributor is binding or catching.

You can also test for misfires using a test light. Hook the alligator clamp to a good ground and then while the engine is running follow each wire with the probe looking for sparks. Don't forget to check the coil wire and cap too. See video at 3 minute mark.

If you don't find anything you can take a spray bottle and mist water on the wires and check again. Sometimes just misting the water and looking in the dark (Safety first not pitch black dark just low light.) will let you see sparks coming from the wires.

Remember just because parts are new doesn't mean they are good.

Good luck and put what you find.

https://youtu.be/u2Qy3ocTvdU

[Freddo]

Warrens69GMC wrote: Remove the valve covers, they are under them. Standard valve cover gaskets are like 13.99/set, but lets us know exactly what you are working with.
I am including a picture of the head with the valve cover removed. One shows what looks like 482824. Thanks for your help!

RustyPile: Thanks for the detailed info about the AC plug numbers. Sounds like if I wanted a hotter plug, I would need to consider going up a number.(?) and my engine will need the T in the designation for the tapered plugs. Sounds like I need to do more research on that one.

72SB, I would agree with you on the carb dumping gas. I will dig into that as well. Thanks for the suggestion.

HO455: Thanks for the tips on the ignition items. It's a direction I hadn't gone at all because they are new. Sounds like I need to take a hard look at these items as well. I appreciate your suggestion.

Thanks for your help. I will follow up with what I learn.

[Warrens69GMC]

R45ts is the correct plug if both heads are the same, your carburetor seems to be giving too much fuel.

[1967GMCC20]

My 67 Truck 283 turned out to be 307. Few if any 283s had tapered seats. Check head casting number, block casting. REFER to MORTEC casting identification.

#8 the infamous #8.... hello. That's a vacuum leak 9 out of 10 times. Trans line, modulator connected to #8 runner. Modulators can leak putting oil in #8 runner.

[kwmech]

You're not dealing with a 283 with that color head and drilled accessory holes in it and that casting mark-- Maybe a 305

[geezer#99]

I read that head as 462624 which is a 350 head with 76 cc’s.
On a 283 that makes a 7 to 1 compression slug.
You need to post a pic of the engine casting number. It’s found behind the drivers side head on the bellhousing flange.

[cj847]

Originally Posted by Freddo

Hi everyone,
I did a tuneup on my truck about a year ago. (New plugs, wires, distributor cap, rotor, condenser, points, set timing according to the manual. I think 12 before tdc if I remember correctly.) My truck is a 1967 C10 with a 283 with an oversized Edelbrock 4 bbl carb & Turbo 400. Just an old farm truck. Odometer reads about 15,000 miles which I’m guessing is 115,000 miles. I’ve owned it for 10 years. Odometer was at 7,000 miles when I bought it, so I haven’t put a lot of miles during my ownership. Over most of the 10 years, the engine has ran smoothly and ran exceptionally well for a while after the tuneup.
.

Based on this part of your post, I don't see an issue with carb size or plug selection. I would be looking for what has changed (ie, vacuum leak, points worn, bad condenser, cracked cap, etc).

[Freddo]

I am including 3 pictures of the driver's side rear flange. I know the numbers aren't too legible, but they appear to be 3849852. I think this checks out to a 1957 through 1966 283, but I'm not certain. I assumed that the engine was mostly original, but with a 50+ year old truck, I guess it could be anything. What are your thoughts?
I won't have a chance to check the ignition components as well as vacuum leaks until next weekend, but they are excellent suggestions and I appreciate them.
Thanks again for your help!

[tdangle]

You have a later engine in your truck as the TS plugs were used in mid 70's engines that have different heads. I once had the same type of issue with a 350 in a 78 Camaro. It ended up being the center button in the cap of the HEI ignition was shot. New cap and rotor and no more problems. You could have a a problem with the needle and seat in the carb, but I suspect ignition issues first. And by the way it's only too much carb if you have it wide open throttle. The factory put Quadrajets on everything from 305 and up and they flowed around 750 or so. Also too much fuel will usually make it very sluggish not miss.

[1967GMCC20]

3834812....283...62-63...2
3837739....283...58-62...2
3849852....283...57-66...2. Yours is 283 block.
3849935....283...65-67...2

[1967GMCC20]

Now that right angle symbol in your heads is an 040 casting which night indicate you have 2 different heads. Verify head castings.