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Bizarre 302 spark plug problems

chuck1022

Contributor
Sr. Member
Joined
Feb 25, 2017
Messages
562
Went to parts store and bought new spark plugs. Got home and couldn't install them. The new plugs dont have enough thread to reach into my heads. The plugs i pulled out were champion 7981. They have a thread reach .9 inches. The oem plugs have a reach of .45 or something. I swapped them out to the 7981 plug and these are used for 4cyl fords...not 302. Anyone seen this before
 

Timmy390

Bronco Guru
Joined
Jan 1, 2011
Messages
5,609
Loc.
Conway, AR
What heads are you running? For example, plugs that fit E7 heads will not fit GT40P heads. The 40P's need a longer threaded section

Tim
 
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chuck1022

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Feb 25, 2017
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What is the year model and history on the motor?

1977 . Wss told the motor was "rebuilt". I will try and upload a picture of where the spark plug goes. Any specfic areas that i could take a picture of to help figure out wtf is going on
 

blubuckaroo

Grease Monkey
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Jun 11, 2007
Messages
11,795
Loc.
Ridgefield WA
The thread size and tapered seat are correct for that motor, but the reach is way long.
I wonder if someone has bored out part of the threads in the head, or installed some sort of sleeve?
 
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chuck1022

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Feb 25, 2017
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Do these pictures help at all
 

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chuck1022

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Feb 25, 2017
Messages
562
runs great, no problems there. 14-15 mpg, starts at a tap of the key.... i have driven the truck more in the last 2 months then the last 2 owners in 25-30 years...just sat in their garage holding down the concrete..........any help would be great
 

73azbronco

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Nov 11, 2007
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7,796
Put back whats in there. Don't mess with success. :)Not sure but that 7981 part number comes up as an Explorer motor, P head maybe?
 

Timmy390

Bronco Guru
Joined
Jan 1, 2011
Messages
5,609
Loc.
Conway, AR
That big "S" cast in the corner of the head points to E6SE heads

R = E5AE
S = E6SE
T = E7TE

Think they came out in 1986?? One you only on the Stang but stayed longer in the Vic's T-birds etc. Replaced with the E7 heads which were still around in 1996 on 351W's

Tim
 
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chuck1022

Contributor
Sr. Member
Joined
Feb 25, 2017
Messages
562
That big "S" cast in the corner of the head points to E6SE heads

R = E5AE
S = E6SE
T = E7TE

Think they came out in 1986?? One you only on the Stang but stayed longer in the Vic's T-birds etc. Replaced with the E7 heads which were still around in 1996 on 351W's

Tim

BINGO Tim. I checked the plugs for a 1986 mustang and they are the 7981!!!!!! not sure what that all means other than I am gonna put the plugs back in and keep driving it
 
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chuck1022

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Feb 25, 2017
Messages
562
quick google search of e6 heads showed less than favorable opinions of this head. THat being said it works fine on my truck and I am not going to upset the universe by swapping them out of a perfectly good running motor. In the future, what are the heads I should be looking for when I rebuild this motor? my truck is a stocker, so i do not need big horsepower or rockcrawling stuff.
 

Timmy390

Bronco Guru
Joined
Jan 1, 2011
Messages
5,609
Loc.
Conway, AR
E7's are an upgrade. GT40 is even better and GT40P is even a touch better than the 40 non P. Then you get in to aluminium

P heads have unique spark plug angles so standard headers and exhaust manifolds do not fit. Some will fit with modifications. I'm running P heads and run Bronco Hut shorty headers. Fit great with no modification needed.

Tim
 
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chuck1022

Contributor
Sr. Member
Joined
Feb 25, 2017
Messages
562
E7's are an upgrade. GT40 is even better and GT40P is even a touch better than the 40 non P. Then you get in to aluminium

P heads have unique spark plug angles so standard headers and exhaust manifolds do not fit. Some will fit with modifications. I'm running P heads and run Bronco Hut shorty headers. Fit great with no modification needed.

Tim

I wanna keep stock exhaust manifolds, so i will look for e7 or gt40 non p.. rhanks
 
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