I have a 98 f150 4.6. After having alot of issues with cylinder 8 and not being able to fix the code. I went through plugs wires coils. After a compression test it was releaved that we have some internal problems. Probably a cracked valve as the spark plug was found damaged in orginal troubleshooting.



The truck has 1992-1998 standard heads. Can I replace those with the 1999-up Performance Improved (PI) Heads, without changing pistions?

 

HI!... Your truck currently has the "97" - 98" non P.I heads on it. You can install a set of "99" to "03' (04 Heritage) P.I heads but it will raise your compression ratio to about 10:1. You will need a tune after the head install. Also your NON P.I intake manifold will need to be changed out for a P.I intake manifold. If you can try to finds a set of P.I heads from 2002 to 03. They have more spark plugs threads and prevent plug blow out. Or you can buy some of the older P.I heads and have time serts installed in the plug holes.

 

What is the downfall of higher compression? And why is there a need for a tune after install of PI heads?

 

HI!... Well it's strongly suggested due to the full point in compression increase. The engine will be more prone to detonation with the higher compression and the factory tune. Or you can run 94 octane all the time...... Plus the P.I heads have a different cam profile than the non P.I heads.

 

Just performed this upgrade a few weeks ago on my 97 as have several of my friends in the last couple of years. Neal is right about the compression increase. I have heard anywhere from 9.7:1 to 10:1. I have around 800 miles on mine so far using regular fuel I have not experienced any detonation at all even at expressway driving and hard acceleration. The other people I know who have done this have noticed none to very little detonation as well. One guy only noticed a lttle while crossing the Big Mac bridge pulling a trailer with snowmobiles. None of us have had a tune performed but as Neal mentioned its always available if you need it. It's cold here in Michigan so I may notice some in the hot summer but maybe not. You will gain around 30 hp max. I feel more power while driving but it's not huge by any means. Once you get past the rusted exhaust bolts and other rusted on parts etc. its not a bad job and my truck runs better than it has in years. Make sure you clean all the EGR and vacum ports in the throttle body while you have it down. Good luck

 

HI!... Just remember there is "SILENT" detonation as well. Just because you can't hear or feel it, that doesn't mean it's not there. The proper way is to data log the truck and see what the knock sensor and other parameters are doing.

 

Your right Neal. I don't tow anything so I'm not to concerned about it in my situation but some of the others I know have logged theirs with minimal effects only while towing. If I was to tow I would run premium on those occasions. A tune as you suggest would be good insurance no doubt. Take care.

 

HI!... Ya I've heard of guys doing this swap and getting detonation if their running 87 octane or lower poor quality fuel. If you run 93-94 octane, I don't forese a problem, but it's always good to double check and data log just to make sure. These engines are not cheap to repair. lol!

 

thanks guys
I'm just gonna swap engines I found one that didn't kill my wallet. Now I'm just trying to make sure the wiring harnesses will match

Thanks again