Bought Autolites and they wont thread in.

[Jekyl]

So I pulled out NGKs outta my engine and I tried to replace them with Autolite 25s and THEY WONT THREAD IN. They are shorter too by a 3rd of an inch. Pisses me off. Why wont they fit? And yes I tried for almost 20 mins hand threading them in and trying to thread it in with the socket and everything. They wouldnt catch at all like they are too big.

 

[Mustang5L5]

What heads do you have??

 

[RYC CUKR]

What he said. I believe that GT40 and GT40P heads require the longer reach lugs. I found that out when I swapped over to the P heads and tried to thread the stock plugs in. had to get longer plugs went with autolite 104s

 

[5spd GT]

I have had problems before to get the plugs to catch in the threads. You have to get that right angle on them. If you have stock heads you shouldn't have a problem. I'm guessing you do (unlisted in sig.) and the level of visible mods you have shows that even the previous owner probably didn't install heads...but hey, you never know

 

[Mustang5L5]

If they are GT-40P's or GT-40's, you want to run Autolite 764's.

Go buy one and see if it fits properly. I beleive they are a longer plug than the 25's.

 

[HISSIN50]

um, how did the thread pitches compare (old one you removed compared to the new ones)?

 

[Jekyl]

um, how did the thread pitches compare (old one you removed compared to the new ones)?

Threads are exact same. I will pull the plugs out that are in it later today and post what kind they are. I know the plugs that are in the heads right now are atleast a half inch longer than the autolite 25s.

Is there anyway to visually see what kind of heads I have? I am not sure what all is on my car becuase I just bought it. The stuff listed in my sig are the only mods I have recognized so far.

 

[04sleeper]

What is the brand and number of the old plugs?