NPI & PI cam specs

[Silver95bird]

So its settled! There are more factory cam offerings than we initially thought. Instead of a guess that 2 makes of cams were all that was available, npi and pi, Ford actually helped us out and blessed us diehards with a selection. Thank you Ford!

Now, im still curious if matching cam part #'s are ground equally.
The 2 seperate #'s at the thread beginning were in fact ground the same, but to show consistency, 2 of the same is needed.

Also, with all the cams I have, im uncertain if any were a match from the same engine. Luckily I just aquired an exploder 4.6l and will be pulling both cams for measuring!

Just curious, did you ever get the explorer cams checked out? They should be the same Romeo cams as the 01-04 gt's. I'm also curious if they spec like the truck PI cams or not. I like having choices, but I'm still a bit put off about the Windsor pressed on gears, and the horror stories of them spinning loose. I wonder if the pressed on gears vary as wildly as the bolt ons do, timing wise.

I'm really starting to like the idea of tailoring a cam with either set of lashers. The big question is how much adjustment does that allow? If we're talking 3-4* at .050, that's a pretty big amount. It also means identical cams act smaller dropped into an NPI lashed head.

 

[96blak54]

Ive been super busy lately! I get a little time, you bet your boots ill be mapping! j love discoveries

 

[Silver95bird]

I have a short list of cams to compare to your list as well. It'll be interesting to see what matches and what doesn't. Just need half an hour where the little one and the misses aren't keeping me busy. Lol

 

[96blak54]

Same here!

Quick caliper lift measures of the explorer cam mimics the pi mustang cam. We shall see!

 

[96blak54]

(5months later)

I mapped the exploder cams today!

I believe you guys are going to be very surprised!

Explorer 2002 model 4.6l 2v

Intake / Exhaust
.006" lift
248° / 248°
.050" lift
206° / 208°

LSA 115°

WOW...just....WOW!


Not all pi cams are the same!

Looks like the mustang gt cam is what we want!

I forgot to get the cam part#. Ill look tomorrow and post back!





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[96blak54]

Here is a quick cam speck recap.

Pi cams XL3F-6251-A7C XL3E-6C255-B7B
intake/exhaust at
.006 valve lift 246°/250°
.050 lift 200°/208°
Max lift .480" lsa 116°

*Npi cams F2AE-6250-AA
Intake/exhaust at .006 lift 266°/242°
.050 210°/200°
lsa 113° .450" max lift

F65E-6250-AA(99 vic)
Intake/exhaust
.006 258°/256°
.050 210°/200°
Max lift .450 lsa 116°

*npi 5.4l head F65E-6251-BA
Intake / exhaust
.475" / .460"
.006" 272° / 266°
.050" lift 224° / 210°
114° lsa

*Mustsng pi cam XL3E-6C255-BB (could be B8 or 8B. Light stamping)
Intake / Exhaust .006" lift 244° / 260°
.050" lift 220° / 210°
.495" / .540" max lift
LSA 113°

*Explorer 2002 model 4.6l 2v
Intake / Exhaust
.006" lift 248° / 248°
.050" lift 206° / 208°
.510 / .540
LSA 115°

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[amazingrandy1]

Awesome write-up and information. Thank you for taking the time to do this research, now if I only had the specs for my 05 Vic cams!!

 

[07GtS197]

Well look who came over lol. Maybe Blak would be willing to map out a set if he could get a hold of them. Its pretty interesting how these are either npi or pi cams but they have slightly different grinds.

 

[96blak54]

Awesome write-up and information. Thank you for taking the time to do this research, now if I only had the specs for my 05 Vic cams!!

Your welcome
Pull them out and send them over to me. Ill be happy to map them.

Judging by mustangs duration compared to the others im willing to bet the mustang has the longest intake duration.

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[Silver95bird]

I put all the info in a spreadsheet so I could see it all in one place in a way my mind could try to make sense of it, but it just doesnt add up. The specs seem like they're a bit all over the place.

I am beginning to wonder if a significant part of all of this isn't just a huge case of a lack of QC on the manufacturing end. Definitely I'll be checking what cams I see in the future. The only way to be sure is to get more data. I wonder who made these cams for Ford. The big bummer for me is that the bigger intake lobe cams are all Windsor cams with the Spin-o-matic sprockets on the end of them. I suppose I could weld the sprockets if I really wanted to use them though.

I'm also surprised that the lifts vary sometimes as much as the durations do. The ramp angles between the adv. and .050 seem to vary a bunch too. THis sure would explain a bit more of the whole factory dud/factory freak thing, especially added to the crappy +6/-6 variance in the cam gears. I was looking for a pattern, a trend, but it just looks like a roulette wheel. Kind of sad really.

 

[96blak54]

Take these ^ thoughts and then integrate veriable valve lift......or I should say verible lash resistance and they start to make sense.

Let me explain. Lasher collapse time is affected by the hydraulic oil psi. Low rpm the lashers collapse fast and as rpm rise and so does the oil psi, the lashers collapse time changes or becomes stiffer.

The lashers technically are hydraulic lifting mechanisms and the follower is not a cantilever like a pushrod rocker, meaning its purpose follows the cam lobe but floats between lasher rate and spring rate. One of the two gives in before actuating the valve and the motion is like a water flowing wave untill higher psi comes into play. Verible lash rate affecting cam lift, cam lobe articulation.

I find it a thing of beauty!

Its the only way it makes sense.

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[96blak54]

For anyone curious!

Take a pumped up lasher and attempt to collapse it with pliers. Like squeeze the oil out.

Next
Take another lasher, do the same, but this time get it to 220° before attempting to squeeze it.

Here is what youll discover.

The affects of oil at higher temperature. And its sort of amazing!

Where the cold lasher was next to impossible to squeeze down cold, the hot lasher literally takes no effort to squeeze using the same method.



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[Silver95bird]

Makes me wonder if I wasn't crazy running a little thicker grade of oil in it. I bet it makes a difference, especially with NPI lifters!

 

[Silver95bird]

Here's a thought. Can a pi lash adjuster be shimmed from the bottom for more spring preload without screwing up the oil flow or keeping the valve off the seat?

 

[lwarrior1016]

Here's a thought. Can a pi lash adjuster be shimmed from the bottom for more spring preload without screwing up the oil flow or keeping the valve off the seat?

If you do that, the valve will never close when oil pressure comes up high enough to overcome spring pressure.

 

[96blak54]

Here is what got me thinking the lasher adjusts preload.

My comp cams exhaust base circle is .050" smaller than the intake which is by stock standards. If lift values were hard meaused from base circle to max lobe lift add in the follower ratio....my exhaust valve would lift .610". Simply put.....the npi valves can not lift that much. Retainer to valve seal interference would happen, but it dont. Only explanation is the lasher collapse rates and a lock point the lasher has.

Im certain the big cam companys have this figured out. Also suggest taking note to some cam grinds having .570"+ lifts.

Next question....

What is lasher lock point?

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[Silver95bird]

If the oil pressure alone were enough to offset the spring preload, Ford wouldn't have been able to add a full spring to the lasher and reduce the seat pressure on the pi heads without keeping the valve off the seat, no? To me this indicates the oil pressure alone isn't turning the lifter into a "solid" lifter at high oil pressure. It retains some give even in the pi cars. This ties directly to Black's question of what the lasher lockup point is.

 

[96blak54]

Also to add, the pi lashers bleed different than npi. Pi lashers are tougher to bleed down

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[Silver95bird]

I was reading threads elsewhere, when similar topics came up. A few thoughts. Base circle smaller than stock won't change max lift. Only when the cam goes above oem base circle will it lift the valve off the seat. It's the geometry and the lash adjuster not hitting it's lock point. Also add in apparently the cam does not always touch the roller in the same exact place along the follower as it rotates. This affects rocker ratio and ramp rates at the valve vs the cam. As the cam moves the follower also moves, and so does the geometry. So mapping the cam vs mapping the valve events may not be identical.

 

[96blak54]

Right...one needs to map the valve articulation. Not the cam lobes.

Now how do you suppose we can figure out how much the lasher compresses before over coming the valve spring?

How much oil psi do they take to maintain a low compressed state and high compressed state? Or does the oil psi have a hydraulic affect at all?

The heads are orficed and my discovery showed 15psi oil pressure at high rpm.



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