Hi this is my first post on the forums.

I am looking at replacement engines for a 2008 F350 with a 6.8L V10. Looking at places like NAPA, AutoZone and Advance auto they all list remanufactured engines with either a 12mm or 16mm thread diameter spark plug.

Does it matter? From my research it looks like 2008 is the year that the engines switched from having a sleeve that extends pasts the threads and into the head (16mm) and then to a newer design with 12mm diameter threads with no sleeve.

It looks like the 16mm version is more readily available at the rebuild shops. Could I order a 16mm engine and use it to replace the engine already in the truck if it has 12mm heads?

Yes I'd have to get new spark plugs. But would everything else work? Does anyone know when they switched from the 16mm to the 12mm? The tuck was mafe in May of 2008 according to the door jamb sticker if that helps.
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Thanks,

Matt

 

Subscribed, I have no knowledge of this.

 

Sometime circa 2008 they switched plug designs, the head is going to be different as the plug types are not interchangeable. They switched from the larger longer plug which broke off fairly regularly to a shorter plug. The COP boots are different colors between the two plugs but I don't remember which color is which anymore.

I don't know what else (if any) was changed on the engine but my guess is probably nothing major. If it were me I would want the newer plug design. With a build date of May 2008 I suspect you probably have the new plug design. Pull a plug to make sure.

The new design plug is on the top, you can see the threads are smaller in diameter than the old plug.

 

thanks for the reply. Yes this is the same information I was able to find. There were black coil boots (shorter for the 16mm plugs which are the lower plug in your pic). And brown boots (which are longer for ther 12mm plugs which is the upper plug in your pic)

Yes ideally I'd want the new 12mm design. But the rebuild shops do not have them. I assume probably becaue they are new and still out running in trucks. So no one has had one rebuilt yet so the shops have no cores to rebuild. The block casting and head casting numbers are the same on both types of engine.

So when I go look at the truck that I'm looking to buy I will pull a coil boot and plug and see.

My question really is: if the truck has 12mm plugs could I put a 16mm engine in it? Yes I'd have to put new spark plugs and coils in. But would everything else be tbe same (ecu wold still fire the different plug types, etc)

 

Try Jasper Engines and Transmissions. They should have the correct heads. With all the 3v plug trouble I'd prefer a 12mm engine if my truck had one.