Hello I am new to this form I have a 97 f150 5.4 with a 99 5.4 pi motor I have exhaust leaks at the headers the exhaust manifolds now what I'm thinking is that they are the 97 exhaust manifolds and not the 99 p i exhaust manifolds the 99 have a different part number than the 97's I was wondering if there's anybody in this form that can confirm that they did change the exhaust manifolds in the 99 pi motors form the 97 npi

 

Do you have headers or original exhaust manifolds ?

I'll go with type original. They are basically the same from 97/99 PI /non PI makes no difference. Ford upgraded the body for the 99 F150 and F150 lightning, Expy engines.... Fitment did not change. However, they still suffered the same fate eventually, as they did for the 97/98 models. No advantage over one or the other.

Why do they go bad ? Two reasons, - Corrosion for one. The other reason being a bad transmission mount which can wear down (bushing material) shortly after 150,000 miles along with the Y hanger damper as well. When the mount and damper goes, excessive weight and vibration transfers to the rear of manifold studs. This eventually compromises the seal and shears the rear manifold studs.

 

It's because they're not lining up the exhaust manifold to the Head the p i head is bigger than the 97 exhaust manifold so somebody had to take one of the studs out to get him to fit the way it looks like is the 97 holes the exhaust ports are smaller than a 99 exhaust ports which are bigger

 

Now the fact is that they are different part numbers the 97 exhaust manifold non pi motor 1999 pi motor have two different exhaust manifold part numbers I I went ahead and ordered two brand new OEM exhaust manifold off of 99 pi motor from the Ford house I figured I was onto something because of the two having different part numbers I was looking for a confirmation on that theory

 

BS.

The 97-03 heads are all the same at the exhaust ports. For the 4six and 5four PI/nonPI engines.

 

All I find prefix and suffix's aside, they all cross reference to Z9430 and Z9431. So no, the numbers are the same. You can also get the same part from FoMoCo, Ford Power and Ford Industrial all with different part numbers. One division will also offer parts that the other two don't. Ford Power had headers for the 4.2 but the Ford dealership couldn't get them and knew nothing about them.

 

The intake ports are different.... are you confused?

 

That's what I thought he might be referring too, - but he didn't mention the intake at all. Then went on to say the heads were larger lol.

Well, hope he put his theory to bed and got that confirmation he was looking for.

 

Ok new ? Why do they have different part numbers all I did was change years the top 99 the bottom 97

 

Ford part numbers have a prefix, part number and suffix. Easy enough to look up how they're used. The part number is what you need to look at. If a part is physically changed so it's not interchangeable it will get a different part number. Suffix for example are change codes. If Ford changes who makes or where a part is made it will get a new suffix code. This is just one example of what can effect a change code.

EDIT: prefix = 1, decade, 2, year, 3, model 4, engineering dept.