I have read some things about putting PI heads on a NPI Block to make more power not only from the better designed heads, cam, inake but also from the compression increase caused by the smaller combustion chambers and the non dished pistons.


The compression ratio of my 2002 5.4l is around 9.5:1. And if i put NPI pistons in it im thinking it will raise the compression to 10.4:1.

So how much Crank HP/TQ should a 5.4l engine with Long tube headers, PI intake/cam/head with 10.4:1 compresson and custom tuning and possibly proper port matching and porting of the heads.

If i had to guess it would be getting close to 365hp and 400 ft/lb torque for the engine.

The object is to build a driveable truck that will pull trailers and basically be a fun toy.


Also would 10.4:1 compression be to much for a supercharger setup later. Obviously i wont be able to run a lot of boost but 6-8 psi shoudl still be fine right?


Thanks

 

That PI head swap would net you in excess of 10.5 to 1 compression with flattop pistons. IMO, thats too high for even the premium fuel using the stock PI cams. I've heard of people running high compression like this with a custom tune, but it would involve retarding the timing in the tune to where you would be negating alot of the gains in compression to stay out of detonation territory.You might get away with it running aftermarket cams with a longer duration to bleed off some of that cylinder pressure and a custom tune, but that engine would still be into borderline detonation territory, especially when towing a load. That 10.5 is definately too high for a blower, even at low boost. 9.5 to 1 is about the limit for a streetable combination with a supercharger and pump gas, and alot of the blower specific engines are running only 7.5 to 9:1 compression. If you're serious about running a blower later I'd stick with the NPI heads to keep your compression down and add the headers and other bolt-ons while saving up for the supercharger. I'm no authority on these mod motors, but I have been researching my own build on my 2000 5.4 extensively here lately to figure out what works and what don't. If you decide to do the head swap with mild porting and the stock valves, valvetrain, and cams with a custom tuneand longtubes, I would guess your HP to be in the 315-330 range, with that 400 lb-ft being a fair guess, assuming Premium fuel and that you could tune it out of detonation. Like I said, I'm no expert, but I've talked to alot of engine builders, head porters, tuners, ect lately researching my own build and looked at as many dyno charts as I can find to see how this engine responds to different mods, and this is just my somewhat educated guess as to power/TQ numbers based on what I've seen and heard while researching my own build. Just my .02.

 

NPI shortblocks use a dished piston, NOT a flat-top. They're a smaller dish than the PI heads approx 10cc dish vs 18cc dish,but FAR from a flat-top. CR with PI heads on a NPI shortblock will yield 10.3-10.5:1CR depending on final finish of the combustion chamber and the head gasket used.
105:1 CR and forced induction are not a problem if you setup the system properly,and use the right components. There are many OEM applications that are well over that and SC installs are done regularly on them.
JL

 

In addition to the CR issue, there may very well be a problem with valve relief positioning.

 

2V Modular engine have no valve reliefs in the pistons,and do not need them with OEM cams.
JL

 

My bad on that piston ID. For some reason, I was thinking that the stock NPI used the flat-top. Thanks for the correction there, don't want to pass on bad info. I still don't think I'd want to run too much on the high side of 10:1 on a pump gas motor with the stock cams, though, or over much over 9.5 on a dedicated street blower motor on pump gas. Maybe I'm just too old school on my thinking, but I'd rather err on the safe side when long term reliability is an issue as well as power. Just my opinions, though, as this will be my first buildup on these newer engines, and like I said, I'm no expert with these newer motors.

 

Aluminum heads absorb heat much better than cast iron and you can run higher compression than you can with cast iron. I built a street motor off of a 98 cobra short block and NPI heads that was around 10.2:1 and ran quite a bit of timing with it, 91 oct. fuel, never a problem with detonation.

 

Ya i was thinking that 10.5 would be okay.

 

If you are towing you may need to pull some timing, depends how much you are going to run.

 

You have a good starting point with the stock block that you have.
Why would you want to go backwards with technology and put the
NPI pistons into your block?

My builder told me that the PI heads on a stock block will net 10:1
CR, according to his charts from the manufacturers...not 10.5 CR.
10:1 will be just fine in the modular motors when normally aspirated.
You will never have to run premium in it ever.
If you want more power, it will cost you one way or another.
Start with a complete intake replacement, Gibson headers, SPD
Y-pipe, a Flowmaster 70 series muffler & an SCT custom tune.
All total for about $1,500 and will net you about 40hp/tq.

If you want to take it further and can afford it, get you a set of
Trick Flow Specialties twisted wedge 185 heads. A complete top-
end kit (custom redesigned heads, RV cams & timing chain set) is
about $3,000 and will net you about 60hp/tq above that.
Go to their site to see the gains for your truck.
Dont just take my word for it.

Parts for these engines are not cheap and are sometimes hard to
find for the 5.4 liter Super Duties. But, these are tried and true
pieces that actually net about 100hp/tq over stock at the wheels.
I just recently finished building my truck using all of these parts
with PI pistons and some other pieces also. I have not yet dyno'd
my truck to see the exact numbers due to my time constraints...
Some day soon.

 

bump. I'm planning for a PI head swap for my 99SD 5.4 npi block, very interested in anyone's results here!

Thanks,
Ncon