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5/25/2019 11:12 PM  #1


Which Spark plugs for a 302 EFI

I am fitting a 302 EFI into my 66 and foolishly removed the plugs and threw them away without noting the numbers.
Please can anyone recommend a decent plug to run in this engine. I'm not sure what year the engine is as it was a crate engine which came out of an 83 Fox body car.
Thanks for any help.

 

5/26/2019 4:10 AM  #2


Re: Which Spark plugs for a 302 EFI

Autolite 3924.  Gap based on the ignition system.  In a typical TFI EFI engine I would start at 0.045", and could go as high as 0.060" depending on what coil you are running.

 

5/26/2019 12:15 PM  #3


Re: Which Spark plugs for a 302 EFI

Do those plugs have a flat seat as the heads accept tapered plugs. Im not 100% sure of the year as the engine may be newer than the car that it was in as I don't even know if Fox body Mustangs had EFI in 1983.
Looking at Autolite site, for an 86 engine it reccommends 2545 plugs which are tapered.

 

Last edited by gkm24 (5/26/2019 12:17 PM)

     Thread Starter
 

5/26/2019 5:54 PM  #4


Re: Which Spark plugs for a 302 EFI

Good to hear that you are still hammering away on it, Graham.  The Fox in '83 was not injected...and the 5.0 designation came out with the change to roller cam in '85.  Another thing...if you are using an 83 engine I'm not sure about the firing order as I don't know when they went to the 137xxxxx FO from the older 154xxxxx order.  If you are going with the Ford EEC-IV you'll need to wire the dizzy for the cam FO but leave the injectors wired to run the 137XXXXX FO.  Otherwise the the HEGO's will be sending bad into the the PCM and things will go downhill from there. 
From what I've read having this FO miss match may cause a slightly rough idle but will not affect normal driving.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

5/27/2019 5:16 AM  #5


Re: Which Spark plugs for a 302 EFI

No Fords had EFI in '83.  I'm assuming the car the engine came from had a later engine swapped in.  Not sure the seat style on the plugs, but they need to match the heads.  I would pop a valve cover and check the casting number on the heads.  If they are an E7TE the 3924s are correct.  If not, they may be an earlier head and require a different plug.  The E7TEs started in '87, before that I believe they were an E5xx number, but not sure if they used the same style plug. 

The HO designation and the firing order swap were at the same time ('85).  This was one year before they started EFI.  The first EFI was SD; they went to MA in '89. 

 

6/04/2019 10:15 AM  #6


Re: Which Spark plugs for a 302 EFI

Thanks for your help so far and Hi to you Bob.
The engine came out of the Fox body Mustang running beautifully but I had to swap the sump and decided to strip the engine to check it out. It looks brand new inside. I will check the casting numbers on the heads to see if I can get a rough idea of the engine date. There is a label on the valve cover. I will try to get a photo of it on here to see if it tells anything too.

     Thread Starter
 

6/04/2019 10:17 AM  #7


Re: Which Spark plugs for a 302 EFI

Just to say also that the engine is a Roller cam engine so must be after 1985 then. Just in case this helps.
Thanks everyone.

     Thread Starter
 

6/04/2019 1:16 PM  #8


Re: Which Spark plugs for a 302 EFI

I Have looked on the valve cover of the engine and there is not much writing left.
there is a big AL078623 505
another code ending in 36AA
and a date 06/19/91.
I can definitely make out the AL, the 36AA, the 505 and the date. The other numbers are to the best that I can see/guess as they are very faint.
Does this help any?

     Thread Starter
 

6/04/2019 6:54 PM  #9


Re: Which Spark plugs for a 302 EFI

Pull a valve cover.  There will be a number cast into the head that will start with an "E"  That's the number we need.

 

6/05/2019 10:14 AM  #10


Re: Which Spark plugs for a 302 EFI

Took a look on the heads and there is a cast in plate with 1F 6 on one head and 1F 7 on the other.
That doesn't sound right does it?

     Thread Starter
 

6/05/2019 10:41 AM  #11


Re: Which Spark plugs for a 302 EFI

gkm24 wrote:

Took a look on the heads and there is a cast in plate with 1F 6 on one head and 1F 7 on the other.
That doesn't sound right does it?

Dates are:

June 6, 1991
June 7, 1991

 

6/05/2019 10:48 AM  #12


Re: Which Spark plugs for a 302 EFI

Fantastic! Thanks very much. So which spark plugs would you recommend for this? it is only normal use in my 66 Mustang.

     Thread Starter
 

6/05/2019 11:15 AM  #13


Re: Which Spark plugs for a 302 EFI

Go to rockauto.com for reference. It'll list copper core and platinum plugs for your application.....bob's your uncle on preference, but at least you'll have plug numbers

 

6/05/2019 2:33 PM  #14


Re: Which Spark plugs for a 302 EFI

Unfortunately that's not the number you need to tell you which plugs to run.  With the engine of unknown origin you can't say for absolute certain that just because the heads were cast during the E7TE production run that they are definitely E7TE heads.  You have an EFI engine from an '83 Fox Mustang; a car that never had EFI from the factory.  Maybe the engine is from a later year Mustang, but its just as likely that its from a '91 truck, van, Crown Vic, etc.  Some of those other vehicles used E6SE heads up to '91, and those two heads do not use the same plugs. 

It occurs to me that the casting number is actually on the bottom of the head on the exhaust side, below one of the two middle ports.  I don't know if you can see it with the heads installed, but maybe with a mirror, etc. 

 

6/11/2019 1:55 PM  #15


Re: Which Spark plugs for a 302 EFI

I got the numbers eventually and got the correct plugs which have a tapered seat 14mm short reach. I got Bosch plugs HR10BCY. The heads are with the machine shop at the moment so I will put the numbers on here when I get them back so as to just complete the thread. thanks for all your help.

     Thread Starter
 

Board footera


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