This is one of those things where it's all relative, the base 5.0 cam is so small in terms of lift and duration that the tighter LSA still delivers decent emissions and a strong vacuum signal, but with more duration both of those things decline if LSA isn't increased significantly. The reason this matters is because these early EFI systems were calibrated to manifold vacuum so that can't be altered too much from factory spec if the goal is correct EFI operation.

 

Nope it doesn't. I don't have Ford's 5.0 book with me, but none of the non HO rollers had a 108*LSA. The F4TE is a 116* You want to argue some more ?

 

This is a plot taken from an actual non HO 5.0 camshaft. It has a 108 lobe sep and that is one of the reasons why these cores are so great to use for regrinding to make into a performance camshaft besides the overall high quality of the core.

 

That's right. What is interesting is how different the HO cam is from the non HO in the previous post. It has quite a bit of duration and to make that work it has the lobe sep spread out to 115. It seems like a better cam for most uses would have been to use less duration on a tighter lobe sep. It would have sacrificed power but it would have probably gained mid range torque and acceleration. These cores have the 351W firing order which doesn't matter but the big wide lobe sep makes these cores less desirable to use for regrinding which is a shame because for some reason they seem to be easier to find than the non HO.

I don't think that I have a plot of a stock 351W camshaft but I assume that it splits the difference in duration but still has a pretty wide lobe sep. GM did this sort of thing too on the EFI engines. Older car engines that had injection had wide lobe seps yet the Vortec 350 engines didn't.

 

Here is a chart I found online many years ago, it is incomplete but evidence collected from other sources seems to indicate these numbers are mostly correct. Some of the choices in cam design you see here are confusing.. take the Lightning cam for example... this is a performance vehicle so why would they use such a mild cam? I can't think of any good reason except emissions which is a major concern for a manufacturer. But to make it even more puzzling, I have used 2 cams in EFI motors.. the Crane 444232 and the Comp 35-349-8 that both passed tailpipe sniffer tests, the Crane easily passed while the Comp was on the limits but then it is from their Extreme line so maybe it's not surprising it pushes the limits.

In this chart I believe the cam listed as the 351 2bbl was the one used in the early 5.8 EFI motors.

 

That chart is very interesting. Just the other day I was talking about how many stock cams are really quite close to one another even though the engines are really different. I had plotted two stock Ford 460 cams that we're going to regrind for a guy who has to make a vacuum rule for a pulling class. They are almost identical duration wise to the cam that came stock in most 350 Chevy engines. You could easily swap the grinds and not tell any difference in the engine. Maybe those designs were actually done by a design or tool shop in Detroit and not the manufacturers, who knows.

 

I don't know how true this is but if you remember Bo Port who ported and installed big valves in a 96/97 F250 460 efi heads. I read on his FB page that he tricked the vacuum signal so the EFI system thought it had good engine vacuum. They had a video of it running and it has a really lumpy idle. I would geuss like a 108* LSA.

If you can trick the vacuum signal (Electric vacuum pump?) into thinking it has a steady vacuum around 16hg-18hg is there any reason why you can't tighten up the LSA?? Just thinking out loud here.

 

Porting heads or even installing heads that flow much better doesn't affect vacuum much though... all else being the same, it and other mods that increase airflow through the motor like exhaust upgrades all work well with SD.. up to the limits of the existing fuel delivery system, then things need to be upgraded and recalibrated. I suspect Boport took it a step too far with the cam change, he probably wanted to maximize gains just to see what was possible but a cam that produced a stronger more stable vacuum signal really wouldn't give up that much power.

As for a way around a poor vacuum signal it would likely be complicated, the signal has to be allowed to vary with engine load.. you can't just peg it at 18in/hg and call it good. The easier solution is to just use a PCM that can be tuned for the lower overall vacuum signal range.

 

Agreed, I don't know how you could get a strong vacuum signal at idle that would vary the vacuum through the RPM curve with a high duration, tight LSA cam. It might have been for just testing as well. I seen it and thought this would be a good place to post it.

Trying to learn about the SD system here... So the stock SD system can handle good heads, intake, & exhaust. With the first three added what about a cam thats has a good vacuum signal like a wider 114* LSA that has a realistic @ .050" duration for truck use?? Or is trying to match the fuel curve demand to much for the SD's PCM capability even if you have enough injector, fuel pressure, & volume??

 

Yes a combo with a less radical cam that produces a stable vacuum signal can work well with SD EFI... just not the factory SD EFI truck computer as it stands. The stock 19lb injectors and PCM become a stumbling point on these trucks pretty quick, they only support around 275-280hp and it's all to easy to blow right past that with a complete heads/cam/exhaust combo. Unlike the MAF system there is no other way to fool the computer into operating with larger injectors it has to be reprogrammed, but the plane jane truck PCMs were never supported by the popular tuners that were available.. those products were developed for the Mustang primarily and later for the Lightning, so a computer from one of those vehicle must be used or you could opt for a PimpX computer now and bypass all of the OEM computers limitations.

 

What year does the 460's EFI system change to use a mass air sensor? I'm almost sure that there are some that do. Was his one of those?

Making the engine larger seems to work ok with the speed density systems for whatever reason from what I've seen. Two different times I built 393 Windsors for people who used them in EFI equipped trucks were they wanted some better torque. Both times I used the Engine Power cam with 190/202@.050 on 108.

 

As far as I know only the California trucks received MAF on the EFI 460's and I think that was 96 & 97 only at that. Boport when he posted on here I am thinking he was using a SD truck.

Thats interesting cam choice for EFI. I take they were MAF trucks??

 

I bet that's right only the California trucks got MAF. The 393's were both speed density as far as I know. I assume that with the extra displacement smooth manifold vacuum was no problem with a duration that short.

I was thinking today and wondering if maybe a reason for the factory cams having a wide lobe sep in many of these engines is simply to allow them to be put into the engine with the intake closing way back. I don't know exactly where they had the cam but let's just say the cam was on 114 sep and in on 120. That would reduce low speed cylinder pressure and N2O emissions.

 

So a truck SD PCM is limited to the stock size injectors only, And is one of the reason why people update to MAF. I forget where i read it on here but someone used a 460 PCM and used 23lb injectors on there 351w. This now makes sense. I know you can get more fuel out of the injectors by adding pressure but that only goes so far. I am sure none of the Mustangs every used a E4OD tranny and trying to find a Lighting PCM is a needle in a haystack for under a grand if you can even find one at all. That leaves MAF conversion with certain PCM's or go to the PimpXshift and ditch the stock stuff. Does this sound about right???

 

Yes there have been some members here that have done that. The mild cam and other factory parts keep HP output within the limits of the stock injectors so they end up with a motor that operates like stock but with a big fat torque curve. One trick I have seen work on a 351 stroker is to substitute a 7.5L SD PCM, it's calibrated for 24lb injectors which technically support upwards of 350hp.