NPI & PI cam specs

[Silver95bird]

Looks like mapping the valve with the engine off (collapsed) gives us both the valve mapping, and also the maximum lash adjuster collapse. Then map it again with a solid lifter at the same (max collapsed) height. Then map it again, solid lifter at zero collapse on the base circle. The tough one is trying to get readings for high rpm lifter collapse. With the other mappings already done, the results have to fall between the two of the solid results. Closer to zero than collapsed I'd guess, but how far can only be told by analyzing the lash adjuster travel at rpm.

 

[96blak54]

So much gray area! Thats what we will call it

Ive always said the modulars were the first attemt at veriable valve durations.

We can assume less valve duration and possible lift at lower rpm, while graduating rpm's increase oil pressure in turn, hydraulic actuate the lashers caracter stiffer/resist collapsing.

Well....since we are all out performance nuts....lets focus on max possible cam articulation and figure out the gray area and how it operates.

Now how can we set up a test bench?

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[Silver95bird]

The first thing I'd want is a dial indicator with a loooong arm that could reach the follower as installed. I know it's better to measure the adjuster and valve directly, but logistically this is what we have to work with. It'll at least give us ball park numbers. I'm also thinking the whole NPI pi differences in the adjuster, valve height and pressure will give two separate sets of readings. If the head is on a bench, at least the valve could be measured directly. But it's tough to keep a cam at a setting mid lift that way. Installed may be much easier to work with.

 

[Silver95bird]

I wonder how much preload the lash adjuster is under on the base circle? There must be some to keep the follower from falling out, I can't see zero preload not rattling all the parts to death.

 

[Silver95bird]

I've been looking at pictures of lash adjusters here on break at work, and it sure looks like the oil inlet is smaller than the exit. There's no way significant pressure is building up in there. I'd hazard a guess the hot engine oil, restricted at the inlet, doesn't pump much more oil through under high rpm. It's all about lubricating the follower. Every rotation squeezes oil into the follower under pressure when the cam moves off the base circle. On the base, it refills the adjuster. Hence, spring pressure in the adjuster is King. It's really nifty design. Shimming may be limited by where the inlets and bores line up though. That'd be worth investigating.

 

[Silver95bird]

http://www.modularfords.com/#/topics/173464?page=1

 

[Silver95bird]

This in an 03 04 Cobra section, but the basics still apply. Solid lifter at full extension left the valve .012 off the seat. Assuming a 1.8 ratio, that's roughly .015 compression of the lifter to get to zero lash zero valve lift. Read post 11.

 

[96blak54]

I've been looking at pictures of lash adjusters here on break at work, and it sure looks like the oil inlet is smaller than the exit. There's no way significant pressure is building up in there. I'd hazard a guess the hot engine oil, restricted at the inlet, doesn't pump much more oil through under high rpm. It's all about lubricating the follower. Every rotation squeezes oil into the follower under pressure when the cam moves off the base circle. On the base, it refills the adjuster. Hence, spring pressure in the adjuster is King. It's really nifty design. Shimming may be limited by where the inlets and bores line up though. That'd be worth investigating.

There is a good .030+ for shimming and still be within the bore gap clearances the lasher normally functions within.

The link didnt take me straight to the thread. I dont know why.

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[Silver95bird]

http://www.modularfords.com/threads...usters?highlight=bleeding+down+lash+adjusters

i posted from my phone, maybe there's a problem there. try this.

 

[96blak54]

That was a good read. Especially the guy arguing the opposite of John Mihevits build process.

What I didnt see, why these guys didnt use heat when bleeding the lashers down. The impossible locked up lashers become possible with heat.

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[Silver95bird]

http://forums.tccoa.com/7-engine-4-6l-5-4l/99191-ford-4-6l-2v-specifications.html

I found this, it's rather interesting. Among other things, it lists the rockers as 2.0 ratio. That's odd, as comp's catalog and others list them as 1.8. So, let's dig deeper. It lists cam lift as 7.11mm/7.47mm at the cam, 13.00mm/13.75mm at the valve "theoretical valve lift". But a 2.0 rocker ratio would turn 7.11/7.47mm into 14.22/14.94mm, which converts to .5598/.5881" of lift at the valve! What gives? In both cases, the difference is about .048" between "theoretical" and what the ratio is listed as. Is the collapse of the lash adjuster causing the cam to lose that much lift?

Picture the engine layout. The cam/follower would look like a teeter totter. As the cam increases in lift, one (or both) sides has to give. If one gives but not the other, you get exactly a teeter totter. If both the adjuster and the valve move, it's more like a teeter totter with a spring under the pivot in the middle. The give in the adjuster is causing give in the valve motion as well.

I'm beginning to suspect shimming the adjusters would be noticeably different in the valve events. I don't think they should be shimmed the full .048, you need slack for production differences and to retain the oil squirting feature of the adjuster. I'd suspect anything up to a .025 or .030 would work though. Don't forget, it's like changing 1.5 rockers to 1.6 rockers on a sbc. It doesn't change just the lift, it also changes the advertised and .050" cam events - even if that's subtly done. I'd suspect mapping the stock cam lobe, and then mapping the same lobe again with a .030" shim would be most interesting. The mapping needs to be done on the valve though.

If the Cobra adjusters were collapsing .012 ish on the base circle, and we're losing another .048" in collapse, that's .060" of total collapse in the adjusters. That's a lot!

Now imagine different shims under intakes and exhausts. You could tailor any cam to anything you'd want that way.

Neat, huh?

 

[96blak54]

DANG!

Now that was one heck of an explanation! Good detail sir!

I may need to revert to all the followers I have hanging around, measure for differences.

We really should never assume any of these parts are the same

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[96blak54]

All the mapping I have done is locked lasher(welded) and shimmed to be 100% sure the lobe and follower are not scewed by a squishy lash adjuster. The valve does not make contact to the seat and both mating lobes and valve movement are simultaneously measured. This way I can be sure all components are direct with each other

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[96blak54]

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!

So im getting ready to do that. My 5.4l 2v npi build this go-a-round got 5w-30 with fairly new PI lashers on the intake valves and 4v lashers on the exhaust. Its got a collapse lasher on the passenger side that clunks at idle and low rpm. Im wondering if I make the switch to 10w-30 their will be a change. I haven't reconnected the oil psi gauge on to the head yet, but before with the last build when it was hooked up, the most oil pressure the head seen was 15psi at 5000rpm. im wondering if psi will raise and also wondering how the lashers will react. Better yet how the whole package will respond.

 

[Silver95bird]

Are each type of lifters the same height when collapsed? If they are, then I'd argue changing the lifters is mainly a change in the ramp angle at the lower end of the cam. It'll be interesting to see what kind of a change you get out of it.

 

[96blak54]

When collapsed, yes they are the same height. I agree with you about lower ramp change. And when thought about, it totally makes sense! The open and closing points are normally whats characterizes the cam.

 

[96blak54]

Coming up soon!

2002 5.4l cam specs

 

[96blak54]

2002 5.4l 2v pi
XL3E 6C255 B8B

Int/Ex
.006 256/254
.050 206/204
Max Lift .504"/.535"
LSA 113
46 overlap measured at the lobes

I added overlap on this one. I didnt think about it on the others. Guess this thread needs a revision!

 

[Silver95bird]

I've been looking over all these specs, and it occurred to me: Are all of the OEM base circles the same? do they vary, and if so, how much? I know this is a bigger issue with the aftermarket cams, but judging from the similarities/differences I'm beginning to wonder about the OEM tolerances here as well.

Keep in mind the factory lash spec is pretty wide, so small variances will get absorbed by the lash adjusters. Measuring with a solid adjuster is like rolling a highlighter over those variances, so it might be worth a look.

 

[96blak54]

Im getting ready to re-map all these cams. Confirm the specs and add in overlap amount. I like the idea adding in lobe base circle size for each lobe mapped. Doing this will show any variation.