5.0L (1979-1995) MustangTechnical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.
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I recently bought a 1990 LX Notchback that I was told was stock. When trying to do a tune up they stock Autolite copper plugs (#25) would not thread into the head. Looking at the existing Autolite copper plugs (#605) the are different. I pulled the valve cover on the passenger side looking for indentification markings. The numbers i found are not making any sense to me. The numbers i found are 8E7 and a round stamp with 97531. There is a FORD stamp twords the front and a CP stamp near the FORD stamp. On the coners of the head at the front is an S and the back corner has an 18. Can anyone help me identify these heads?
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I'm not the most knowledgeable here but I'd say those are E7 heads, and you've got the right plugs in the 25's. They should work ???
One a side note, those are not stock headers.
Someone will chime in and give you the right answer.
306 with all bolt ons, letter cam, ported E7's, T5 swap, full exhaust, 3:55's, 2" drop, and the worst paint you'll ever see or feel.
Dyno'd 300/316, 2745lbs-track scale
Best ET………12.4@108, 1.66 60ft on 8" ET Drags.
24 mpg (combined)
Those are stock heads. The two plugs have the same thread pitch so the correct 25s should work unless they've been cross threaded. The 605s are a little colder plug and also have longer reach in the cylinder. They are normally used on the 3.8 and 4.0 v6s.
I spent 10 minutes trying to install one plug before i realized that the plugs where different. It would not even grab any threads I kept thinking I was just at a bad angle. Will it hurt it to run it with the 605's? Are they better or worse than the 25's?
I took a couple of pics of the front drivers side under AC compresser.
I could not see any ridges so they are not GT40 heads. But the block
and heads are painted blue which to my knowledge is not factory. Headers
are MAC even flow shortys.
25's should be the right plugs for pedastal mount heads........headers may be making it tough to get a straight shot with the correct plug..meaning 25's not 605's
When I put the 605 back in and it went straight in with no problem. Tried with the 25 for 10 minutes and could not even get it started. According to auto lite's website both plugs are threaded the same but yet the 25 will not thread in. I'm wondering if it has something to do with the threads being shorter? Maybe it is bottoming out before it gets to the threads?
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