p90a vs. p79

[Lockjaw]

I would find a p90' date=' I would not use the hydraulic, don't care what anyone says, the solid head will make more power, and you can run a performance cam in it.[/quote']

 

Now we are going to debate which head makes more power again? In no way are you going to notice which head yeilds more power. Unless you are spinning the engine up to 9,000 rpms, the hydraulic lifters will work just great. Look at all the modern 4 cylinder turbo engines making high horsepower for what they are, ie Mitsubishi turbos engines. They use hydraulic lifters, no problems there. End result, not much, or any of a difference, and never have to adjust a lifter again.

 

 

 

No I don't need to debate it with anyone. I took a P90a off my car, put a P90 on it, and it made more power. A good bit more at that, and on a non intercooled application. Thats all I need to know.

 

And the P79, well you can say what you want to say about its ports, but my friend ran 8.40's in the 1/8th mile over 10 years ago will a milled P79 on a stock f54 bottom end in his 240Z, so it must flow pretty well. Actually if memory serves the liners were to help with emissions, and did not have much, if any impact on flow.

 

There are few turbo 6's running 8.40's today on this board, so I don't want to hear about some debate. If you want to test them, you do it, but in my opinion, from my personal experience, go solid, and make more power, and save yourself some headaches.

 

So anyway, you can take advice from someone who has actually swapped the heads on the same car, changing nothing, and picked up power, or you can take the advice of someone who says, theoretically, there should be no difference. There is, and any butt dyno can feel it.

[Lockjaw]

I am with Lockjaw. I talked with several Z gurus and have to say the majority said to use the P90 with mechanical lifters. A Z friend here in town said he ran very identical Z's' date=' different P90's in each. The one with the mechanical lifters made more power and trapped quicker and faster.[/quote']

 

Thats just purity at its best. So many things people say cant be done, and here on hybridz thry have been proven wrong, over and over, time after time.

 

 

So what does your car run?

 

Yeah thats what I thought. Lets ask Sleeper, Cody, James, TimZ, Jeffp, Scottmiz, Jersey, and everyone else in the 12's what head they use, and see.

 

Purism means you think Nissan is the best period, not that you think a nissan solid lifter head is better then a hydraulic.

[yo2001]

Well, this might be one reason why the Mitsu head can turn higher rpm even with hydro. lifters

 

 

Check out the size and it is a roller rocker.

 

Anyway, the lifter failure is common on the earlier 4G63 head. and Mitsubisho did revise the lifters with larger holes. But 4G63 got good oil flow throught the head.

[David K]

No I don't need to debate it with anyone. I took a P90a off my car, put a P90 on it, and it made more power............................................... There is, and any butt dyno can feel it.

 

Thats great and all, but yout ass dyno cannot compare with my hours of research and comparing the solid lifters against hydraulic lifters. Until you get a DYNO SHEET to prove me wrong, i am TELLING you that its not going to make a noticable difference on a street car, period. You can swap heads all day, and of course after all that work, your mind is going to tell you that your car is faster. Same principle as when you wash your car, it feels and runs better

 

hours of research > butt dyno

[Lockjaw]

Yeah I guess your real world experience proves my actual facts wrong. HUH?

 

And it is quite impossible to go back in time, I do know that I raced a car before and after the swap, and he made no changes, I made one, a head swap, and well lets just say the results proved what I say, the P90 is better.

 

And tell me Mr Expert. What have you actually PROVEN with your hours and hours of research? I actually did the swap, you haven't even done that yet.

 

And what does your car run with its hydraulic head? And why is it the fastest turbo Z guys on this board all run the P90?

 

All you have proven is you spend an inordiate amount of time, with a head every one agree's is not as good as a solid lifter head, and you have had to MODIFY it from its stock configuration, and you still haven't proven it EQUAL to the solid lifter head.

 

Argue all you want. The bottom line is, I have run both heads, and the solid head made more power. And I KNOW I can run an aftermarket cam in my solid head, you haven't even PROVEN you can do that in you MODIFIED hydraulic. See I have seen someone run one of the Nissan L9 grinds in a hydraulic head, with the nissan specified retainers, and lash pads, and guess what, it ate it.

 

You just want to argue, go out and prove it. I don't have to prove it, the facts are, I have seen it first hand, and the fastest turbo cars on the board all run the solid head.

 

You go do research, we will keep running our fast times.

[Bob_H]

And it is quite impossible to go back in time, I do know that I raced a car before and after the swap, and he made no changes, I made one, a head swap, and well lets just say the results proved what I say, the P90 is better.

That was so uncalled for. Not again.

I am getting ready to go on a 6 month deployment so I can't run this topic for 5 pages again.

Lets lay some ground work first.

In pintoz's original post, he was asking about the P-90 vs the P-79 while he was waiting for his new turbo...... So that leads me to believe that this is a turbo car he is asking about. If that is the case - the P-79 is out of the question. With its exhaust liners, they will run very hot, not a desireable trait in a turbo car which already has very hot exhaust. Second, it doesn't really match the turbo exhaust manifold. Turbo = no P-79.

So the discussion is somewhat moot from the original post.

But we went through this last time. All you proved was that for your combination, it was better - and we have no guarunteed that you kept ALL, and I mean ALL condtions exactly the same for the comparision. Therefore it is as good as comparing oranges to wrenches.

And to claim that the hydraulic head made less power leaves so many issues unanswered. Were your lifters even in good shape? Did you have bad oil pressure? How would you even know? Back up your "factual statements" - I know your better than that. For anything under 250hp, I would be my car it is less than a few hp difference at best - if that.

And please don't say " I ran 9.xx with the xx head and 8.xx with the xx head". There are far too many variables in that comparison as well.

Arguing for arguing is pointless which is largely what is going on here. That is my job. Actually, I only argued about the subject. Anyways....

The P-90A can and will make good power up through 7000 rpm as I did on my car. It can be set up to work with an aftermarket cam - you just have to watch a few parameters. And what in the operation of the cylinder head could you possibly point out that would cause a significant power loss, i.e. the hydraulic head requires more power to operate,(to turn things over, etc..)? In some respects it is better, in others worse - it all depends on your application and what shape the lifters are in.

-Bob

P.S. - and oh by the way - I have run an aftermarket cam in my hydraulic head so it most certainly can be done. It ran for about 15k miles before I sold it and it is still going.

[Guest szlash280z]

DON'T MESS WITH ME!!! I'LL ARGUE WITH YOU OVER THE INTERNET!

 

 

sorry, I just had to say it!

 

Bob H, your datsun Z garage page is awesome! I still remember studying it about 2 years ago!

[David K]

I decided not to reply to Lockjaw because anything i say he stomps his foot until he is right.

[Lockjaw]

Well Bob your point is somewhat valid with one exception, when I did all of this, there weren't dynojets in every city, so we tried our best to make valid comparisons using cars and eliminating as many variables as possible. So while not completely scientific, it still does lend credence to the fact that I did in fact run both heads, and did in fact make more power with the solid head.

 

At least I have made a swap and have some basis to comment, rather then doing "research" and saying something is a fact. You can call it what you want to, I call that bench racing, and don't really care for it, and my real world results tend to discredit the "research".

 

You have made an aftermarket cam work, congratulations. I think I could manage that feat myself, but I chose not to play with a head in which I have found less power.

 

As for the P79, well we have been down that road, but none the less, my freind ran 8.40's in the 1/8th mile in his 240 with one, and he was using a square port header, which would be like a turbo exhaust manifold, so it seems the P79 would work in a turbo application, and Yo2001 was using one on his car he just sold, and put down some pretty decent numbers for a 2.6, running moderate boost.

 

Again, I have some factual basis for what I say. I dare say, there are not to many NA guys running 8.40's on this board today, and this was 10 years ago, on a 2.8, not some tricked out 3 liter or larger, and no port work.

 

So I guess it all boils down to those who actually do comparisons in the real world, versus those who just like to crunch numbers. Sorry they did not have dynojets back then, we did have a vericom, and it said my freinds 240Z was making 240 or so hp, wether that is true or not, I don't know, all I know is it ran 8.40's in the 1/8th mile, and would spin well past 7k with little trouble or drama. And he spanked the mess out of a lot of people, including some guy with a souped up stripped out vette with a 454 in it.

 

And in a purely mechanical sense, the hydraulic lifter is supported by oil pressure, and oil is compressable, a solid rocker shaft is not, and I will go even further and say the seat pressure on the valve spring is indeed higer then the oil pressure on most Z engines, so it would seem, at least to me, that the place of give in the valvetrain of a P90a would be the lifter itself, which could not be a performance benefit, if you ask me.

 

But again, what do I know? I am just some guy who counts money for a living, and has spent the last 16 years fooling with Z cars. I think the fact that none of the fast turbo guys run a P90A speaks volumes about what the consensus is on the head.

[Lockjaw]

I decided not to reply to Lockjaw because anything i say he stomps his foot until he is right.

 

 

I just don't like bench racing, which is what you are doing. You don't have to like my opinion, I don't have to like yours, but I have a basis for mine, where is yours?

 

Oh and what does your car run? I missed that somewhere.

[JMortensen]

I have to say something here, because it seems that this is getting nasty. David - I'd be reluctant to believe you if I had EXPERIENCED the opposite too. I think Bob has it right that LJ is comparing apples to oranges, but there is some merit to "been there done that" experience too. I am much less likely to purchase Pirelli tires now that I've owned 2 sets and they both went out of round and constantly needed to be balanced. You might tell me all day long that Pirelli makes the best tire on the planet (and I had a friend who did this for months), but I still won't believe you (or him).

 

Also, all of your contentions are based on the reseach that you've done. I could reseach the shape of our lovely planet at the Flat Earth Society http://www.flat-earth.org/ website for hours and still come to an incorrect conclusion. Not saying that your research is wrong, just that research alone has limitations.

 

Yo has the best contribution I think. Just look at the rockers between the Mitsu motor and the L series. That speaks volumes to me.

 

Really, though, when you get to this situation it's best to just drop it. You build your hydraulic head, LJ can build his solid lifter head, and no one is the worse for wear. Someone needs to be open minded for the argument to be worthwhile. Apparently neither of you are.

 

Jon

[yo2001]

I can tell you what I made. As much if not more power out of P79/L26 combo than P90/F54. First, on 8:1 compression made 208RHP@8-9psi before it went too lean on Stock N/A ECU with turbo injectors and BTM. (on stock turbo) Then, made 253RHP on 12psi on 60-1. the compression was 7.8:1 after HKS headgascket. So that's close to stock turbo motor compression.

[Bob_H]

And in a purely mechanical sense, the hydraulic lifter is supported by oil pressure, and oil is compressable, a solid rocker shaft is not, and I will go even further and say the seat pressure on the valve spring is indeed higer then the oil pressure on most Z engines, so it would seem, at least to me, that the place of give in the valvetrain of a P90a would be the lifter itself, which could not be a performance benefit, if you ask me.

I'll address this tomorrow, but in essence, your assumption is completely wrong. Fluid is not compressible any more than a solid metal is compressible,(i.e. they will all "give" a little, but for all purposes they are incompressible). And the pressure of the oil has nothing to do with what the lifter sees. Once the check valve seats, the pressure is significantly higher,(an order of magnitude) than the seat pressure or it wouldn't stay pressurized - but that gets into the theory of how it works.

There is a lot more to this....but I will have more time tomorrow afternoon.

-Bob

[Bob_H]

And Jon, I haven't forgotten about you - I will respond to your last e-mail when I get back up in Norfolk tomorrow.

-Bob

[Bob_H]

I'm somewhat afraid to respond again as this topic has finally quieted down.

But a quick referesher on the "how to" of the hyd. lifters:

First, they are pressurized into the "up" position by oil pressure. This end supports the end of the follower or 'rocker' as commonly called that is not touching the valve. As the camshaft comes around and begins to exert pressure on the follower, an internal check valve in the lifter seats and doesn't allow any further oil to escape the lifter. In essence, since a fluid is incompressible, it is the same as a solid lifter. The advantage is the oil pressure sets your "lash" for you and keeps the cam from hitting the follower abruptly each revolution.

And to say that "none" of the fast turbo guys run the P-90A is a misnomer as we only know a few that post here.... There is nothing inherent in the P-90A head that keeps it from performing well on a high horsepower motor - I did it for 3+ years and it is still going. The key is good lifters - without them the head sucks. That is the most common reason people don't use the P-90A. The second most common reason is they think that a performance cam cannot be used with it - which it can. And with Sunbelts new camshaft designs that utilize less spring pressures than stock, any size cam can now be run with the P-90A.

There is merit to racing and putting down actual numbers - but to completely discredit something else purely on your own experience is limiting at best. My experience points completely opposite. But we both succeded.

You already know how I feel about comparing your cars with other cars we know nothing about - that was covered well in the first P-90 vs P-79 thread. Lets please not go there again - it doesn't help our arguements. Bottom line - this is all worth what we paid for it - nothing. apples to oranges.

-Bob

[Jersey]

Hopefully, when i get my cousins '78's turbo swap done with the P90A head, she'll be in the 12's or better. If not, i'm coming after you Bob!!! LOL. J/K.

 

Bob - on a side note, are you active with the Navy? I was just down in Norfolk with the family a few months back. A family friend, Master Chief Bob Conklin, took me out on the USS Reagan for "family day" i believe it was called. Awesome.

[JMortensen]

So what's the deal with KA24's and VG30's ticking really bad after an autox run? I know its the lifters, but that doesn't make any sense if the lifters pump to a particular pressure then hold it. Maybe the lifters lose their pressure when they slow down for a corner and rpms drop??? Just curious, not trying to keep the argument going...

 

Jon

[Bob_H]

First, yes, I am on Active duty - leaving for a 6 month deployment next Tuesday. And Family day cruises are awesome. It is the one time the rest of you can see exactly what goes on around an Aircraft Carrier - the launching, landing, and an airshow with no rules!

As far as ticking lifters after autox runs? The problem in my BMW M Coupe, and other E36 M3's had to do with oil - specifically not enough. With just a normal fill of oil, coupled with hard driving, the oil would foam a bit, and the pickup would be uncovered, or be drawing from aerated oil. When you can't supply oil to the lifter when it is not under pressure from the camshaft/follower, it bleeds down. You then get the ticking.

I can't say that is the case with the KA24's and VG30's, but was with the BMW S52's. Or possibly with a poorly designed system,(talking general here, not specific motors), the oil pump just can't keep up with the requirements, or the lifters are poorly designed to refresh the pressure in the lifter. If you start up a hydraulic head car, and then pop the valve cover, the lifters are pumped up. They take anywhere from 2-5 min to bleed back down. So to properly check the cam timing of a hydraulic head, you must start the car,(or at least turn it over and build oil pressure), then shut it off and quickly remove the valve cover. Makes for a fun time....

-Bob

[Lockjaw]

So what you are saying is oil is not any more or less compressable then metal?

 

Sorry Bob, but there is not any way you can convince me that the hydraulic lifter doesn't compress some. I mean I have worked on V-8's and you can surely compress the hydraulic lifter with a pushrod.

 

I hated my head when I had it to. Long runs on the interstate and then coming into city traffic always resulted in lifter tick at idle, which I despise. I considered replacing them all with new ones, which I could get at the time, but they we 36 bucks each, at cost , which works out to 432 bucks, versus the 250 I paid for a solid head.

 

And it certainly seems to me that if there was no performance advantage of solid over hydraulic, that all the cam manufacturers would have somehow managed to figure that out by now, and quit offering solid lifters, since a hydraulic is obviously easier to deal with. (sarcasm added)

 

 

The bottom line is no one has stepped up with a hydraulic and run good numbers, you are pretty limited with the stock cam to a powerband that keels over about 5500, and I guarantee you the solid head is way more forgiving as far as setting up with an aftermarket cam.

 

 

The bottom line is you can spend a bunch of time and effort and money one a haed that might make as much power as a solid, or you can just get the solid head and be done with it. Seems like common sense to me.

[David K]

im a bench racer!!!! look out, the name calling is starting! I didnt know bench racing was hands on experience!!!

 

MAYBE YOU MISSED THIS

http://hybridz.org/phpBB2/viewtopic.php?t=26904&highlight=hydraulic+lifters

 

Lock, i guarantee you, your head (hydraulic) that you did not like, wasnt in as good as condition as the solid head.