I have a 84 f150 with a 88+ 4.9 FI 300 straight six, that was converted to carb with the old 84 parts and put In It. Im not sure what year the engine Is so to get plugs for It Im going by what was previously In them which was a motorcraft bsf44c. The guy at oriely said that the autolite 5125 plugs are a cross reference for that because they didnt have motorcraft, he said he wouldnt reccommend autolite but thats what he had. The guy said he wasnt sure what plugs to give me because he wasnt sure If the people switched the head and put the 84 on or left the 88 head on, so that would matter which plugs I got, but he gave me the one that crossreferenced to the one that was In the truck so If anything Im putting the same plug In as was previously In.I also called fleet farm to see If they had motorcraft bsf44c they also crossreferenced me to the 5125 autolite plugs. I have read thing online about how autolite plugs are crap so I dont want to run them, but are there any and put the 84 on the 88 I got them. other plugs compatiable/the same as the motorcraft bsf44c plugs. I dont know what year the engine Is I know Its fuel Injected so Its atleast a 88, thats why Im going by what plug It had not the year. I think the gap for the 88 Is like a .044. Could I get a different brand thats reliable, but Idk what year the engine Is.

 

All years of the inline use the same plugs bro.

 

They don't on the 302 and 351 depending on the year the heads were made. No idea on the 300.

Adrianspeeder

 

I'm 99% sure they are the same.
and if all else fails get them for whatever year the head is.. 84 correct op?

 

It was a 84 motor, they took a FI motor so that would mean Its atleast 87 and put that In the truck and converted that to carb using the 84 parts, If they put the 84 head on or left the 87+ one on I dont know. I dont know the year of the engine either thats why I cant get spark plugs, I gave the number to the ones that were In It and the only thing that came up to work was autolite 5125 but autolite Is crap so I wanna return them and figure out what year this engine Is so I can get plugs, but Idk what I would tell the sales clerk If Its a 87+ that was converted to carb, what would the engine be considered. Idk. But first I would have to find out If they put the 84 head on or left the 87 one Idk how to though.

 

They are the same plugs. Just get em for a carb'd year.

 

The FI and carb plugs are different though arnt they. They are two different heads. Thats why I have to know what head first though.

 

The threads are the same, the plugs burn range or heat range or whatever may be different from the carbd to fi.
Get some carbd year plugs and try em, plugs are cheap.

 

The Autolite 5125 is the plug for all 300 EFI engines and they do fit the carb head with out any issues. I don't know what you read but I have used Autolites on most of my Fords and Mopars for twenty odd years with only one failure when the ceramic seperated from the shell. On my 300 the plugs last at least 30k miles.
regards
rikard

 

If the plugs in it now are crap and autolites are all you can get, go for it. Usually O'Rielly's can get parts ordered for next day pickup. Personally i prefer the Motorcraft plug over anything else for these trucks. Good luck.

 

Non-platinum Autolites are fine in a 300. It's the platinums in a Triton that have issues.

 

I run Autolite copper core plug's in my '68 Ranchero (289) and in my '94 Gen. 1 Lightning (351W-R) with zero issues. Motorcraft copper core plug's are also a good choice for your 300 ci.