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Hemi keeps breaking spark plugs
#662407
04/06/10 03:08 PM
04/06/10 03:08 PM
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Joined: Aug 2005
Posts: 403
30 miles west of EuroDisney
fbernard
OP
mopar
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OP
mopar
Joined: Aug 2005
Posts: 403
30 miles west of EuroDisney
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Hi all,
Long story short, a friend of mine bought a concours-restored 68 Hemi Charger. He's working through the hassles of driving a car which was never driven since it was rebuilt (that was 4 or 5 years ago). Among the worst things, the K-member was unscrewed almost 2 inches (oil pan on the steering link), there was no transmission mount.
I was checking out the engine with my friend's mechanic last week, and we found 3 plugs dead (pulling out the plug wire while the engine was idling did not change the idle speed one bit), I ended up installing 8 new plugs (Bosch, I don't remember the reference, the same as what was in the engine when bought)
Today, the owner calls me, and says the mechanic found the same 3 plugs dead (2 and 4, and 1 or 3). So, 3 of the 4 front plugs.
Plugs look OK from the outside, but they are short-circuited and give no spark.
I believe the carbs may need to be rebuilt again (the idle mixture screws did not have much effect when I tried to tune the carbs).
Has anybody here ever seen plugs go out like this? Was it due to a rich condition?
Thanks.
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Re: Hemi keeps breaking spark plugs
[Re: fbernard]
#662411
04/06/10 04:57 PM
04/06/10 04:57 PM
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Joined: Jan 2003
Posts: 5,106
Chicago Blackhawks
hemicar1971
master
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master
Joined: Jan 2003
Posts: 5,106
Chicago Blackhawks
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If you would like a quicker fix, get your camera, take close up pictures of your plug ends so we can all see what the plugs are doing. When you tested the motor after the plug changes,how did you run the motor. Underload, at idle,etc. Take pictures and post all the plugs even the ones you changed.
1971 HEMI E BODY REGISTRY
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Re: Hemi keeps breaking spark plugs
[Re: fbernard]
#662412
04/06/10 07:52 PM
04/06/10 07:52 PM
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Joined: Jun 2004
Posts: 3,319
Chicago Burbs
sthemi
master
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master
Joined: Jun 2004
Posts: 3,319
Chicago Burbs
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The Bosch heat range cross reference may not be exact.. Try one or two steps hotter or switch to Autolite plugs if they are available... I tried some Bosch in my small block and they did not last for two weeks before they fouled. Other things to look at may be bad plug wires, or carb problems (dirt or jetting). The plugs numbers should be the same number as 1969 340 HP engine. 
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Re: Hemi keeps breaking spark plugs
[Re: attaboy]
#662414
04/06/10 10:43 PM
04/06/10 10:43 PM
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Joined: Jan 2003
Posts: 21,065
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,065
Niles , Ohio
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One big problem was the Bosch plugs.Ive been a pro for 40 yeras and Ive replaced thousands of those pieces of junk because they dont work.Buy some good plugs and check the compression and spark to those cylinders.Rocky
Chrysler Firepower
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Re: Hemi keeps breaking spark plugs
[Re: therocks]
#662415
04/06/10 11:57 PM
04/06/10 11:57 PM
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Joined: Feb 2003
Posts: 10,201
Someplace you aren't
SomeCarGuy
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 10,201
Someplace you aren't
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Bosch plugs suck. Get rid of them. Check the timing. It may be retarded a bit, that may have the carbs idle speed set wrong. Might not be on the idle circuit. That would explain why the idle screws have no effect. From what you have said, this car has no telling what kind of mismatched mess of parts. At least you have Moparts to bail your buddy out. 
I want my fair share
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Re: Hemi keeps breaking spark plugs
[Re: BuBbABFP]
#662417
04/07/10 09:23 AM
04/07/10 09:23 AM
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Joined: Jan 2003
Posts: 21,065
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,065
Niles , Ohio
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I always ran Autolites.Just put NGKs in my built 440.Idles better and seems throttle is a lot snappier.Rocky
Chrysler Firepower
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Re: Hemi keeps breaking spark plugs
[Re: DAYCLONA]
#662420
04/07/10 10:04 AM
04/07/10 10:04 AM
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Joined: Aug 2005
Posts: 403
30 miles west of EuroDisney
fbernard
OP
mopar
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OP
mopar
Joined: Aug 2005
Posts: 403
30 miles west of EuroDisney
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Thanks for all the answers. To go a bit further : - The compressions were checked and are excellent (all at 12.5 bar, which should be around 150 psi). - I did check the timing, it was around 15° at idle (around 850 RPM) at first, with 35° all in at 3000. I set it at 8° idle later, because the engine did start easier with that (also because the FSM I had said initial timing 5° BTDC with + or - 2.5°). I tried to stay around the OEM advance setting since I suppose the engine was rebuilt to factory specs (although I don't even know if the camshaft is hydraulic or solid, it should be solid for 1968 I think). The car had problems idling, so the owner installed a brand-new MSD ready-to run billet distributor and Blaster coil (after a mechanic told him the points ignition xas probably toasted. Same mechanic told him the engine leaked oil after he pulled one plug!!) I gapped the plugs at .035 when I installed them, the previous plugs were around .030. Quote:
concourse restored? how does a k frame unscrew 2"?
From what I understand, the previous owner (or the restorer) was afraid to kink the air cleaner lid when the hood was lowered, so he unscrewed all four bolts a great deal.
In fact, there is enough clearance to shut the hood with the K-member bolted in (no kidding!).
With the brand new hood insulation, someone probably thought there was not enough clearance.
Quote:
If you would like a quicker fix, get your camera, take close up pictures of your plug ends
I'm not there anymore, but the plugs I took out had a small shiny ring around the top (probably around the part protruding from the head into the chamber) and were lightly fouled black.
Quote:
Hemi plugs don't need the sealing ring, as the spark plug tubes do the same thing.
Should the sealing ring be removed from the plug then? Or should the ring/seat be conical?
The O-ring goes between the tube and valve cover, right? Only the spark plug pressure on the tube seals the tube from the head itself?
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Re: Hemi keeps breaking spark plugs
[Re: fbernard]
#662421
04/07/10 10:18 AM
04/07/10 10:18 AM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
I Live Here
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I Live Here
Joined: May 2003
Posts: 15,487
Florida
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no help here but... how can someone think unscrewing the 4 k member bolts will let the hood close with out hitting the air cleaner lid????  it would still sit on the frame and hold the engine at the hieght its gonna sit when on the tires and at ride hieght  it would let the k frame move around and drop when jacked up I would think that has to be the most crazyest thing I have ever heard or seen  what am I missing on that idea????? 
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Re: Hemi keeps breaking spark plugs
[Re: scratchnfotraction]
#662422
04/07/10 11:35 AM
04/07/10 11:35 AM
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Joined: Jan 2003
Posts: 6,840
The Swamp
Sixpak
master
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master
Joined: Jan 2003
Posts: 6,840
The Swamp
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Quote:
no help here but...
how can someone think unscrewing the 4 k member bolts will let the hood close with out hitting the air cleaner lid????
it would still sit on the frame and hold the engine at the hieght its gonna sit when on the tires and at ride hieght
it would let the k frame move around and drop when jacked up I would think
that has to be the most crazyest thing I have ever heard or seen
what am I missing on that idea?????
Better tell your friend to get the car re-aligned after the K frame is tightened up. Obviously the idiot that 'restored' that Charger had zero idea of what they were doing. The only time I've heard of any sort of spacing done on a Chrysler K frame was on the 68 Hemi A bodies, and there they added shims between the K and the frame rails.
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Re: Hemi keeps breaking spark plugs
[Re: Sixpak]
#662424
04/07/10 12:18 PM
04/07/10 12:18 PM
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Joined: Jan 2003
Posts: 21,065
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,065
Niles , Ohio
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If you have Boschs that run good you better play the Lotto.Ive only seen 1 car that they actually ran in.Like Ive said Ive pulled probally thousands because they are crap.Thats with new Ignition systems which can just about fire anything.Spend 10 bucks each on Bosch when you can buy a set of NGK race plugs for 15 bucks.Makes sense.Rocky
Chrysler Firepower
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Re: Hemi keeps breaking spark plugs
[Re: DAYCLONA]
#662425
04/07/10 12:21 PM
04/07/10 12:21 PM
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Joined: Feb 2003
Posts: 10,201
Someplace you aren't
SomeCarGuy
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 10,201
Someplace you aren't
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Quote:
Bosch plugs, Platniums can't be beat, esp dual or quad tipped Platniums,......If you don't have the ignition to utilize them, then they will foul, the majority of Mopar stock point/electionic set ups can't handle a "standard" Bosch plug, you'll need to downgrade to a NKG or Autolite,.....I would start by correcting the carbs and ignition system rather than blameing the plugs
I had a set of those that didn't work worth a crap in a late model car I bought. I swapped them for some NGK iridium and life was good.
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Re: Hemi keeps breaking spark plugs
[Re: SomeCarGuy]
#662426
04/07/10 12:26 PM
04/07/10 12:26 PM
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Joined: Aug 2003
Posts: 8,827
Houston, Tx
hemi68charger
master
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master
Joined: Aug 2003
Posts: 8,827
Houston, Tx
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If the centerlink is hitting the oil pan, it could be installed upside down. Yes, there is a proper orientation it needs to be in. When I got my Daytona, the centerlink was touching the oil pan. Found out that the centerlink was installed incorrectly. Also, are you sure you're getting spark to these "bad" plugs? Could be a distribtor or cap issue........ Maybe even wire.
Troy
TroyHouston Mopar Connection Club'69 Charger Daytona 440 - auto - 4.10 Dana (now with 426 hemi) '69 Charger 500 440 - 4speed - 3.54 Dana '70 Road Runner 383 - 4speed - a/c (now with 440)
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