p90a vs. p79

[Cody 82 ZXT]

LJ, F.Y.I. fluid is not compressable. If it were then things like our brakes would not work.

 

Everyone else, One thing else that I know is that I've had the chance to get some very helpful advise from Lockjaw and it has always been dead on. With his advise my car went form running in the low 14's to the high 12's with minimal money invested. Not that he had some magic formula or anything but, he does know what works and what doesn't. As far as the accuarcy of the Butt dyno I hope any of us know our cars well enough to know when it is running better or faster than it previously was. If you can't then you certainly need some more seat time in the car and less in the computer chair debating issues such as this.

 

My advise if anyone cares, is to run the P-90 if you want a dependable combination that is proven to make power in this type of application.

 

If you want to experiment then try the P90A and see what happens. I'll be glad to see what David thinks when he gets his together. I'll be intreasted to see how his opinion changes as his HP increases. I know that things on the car that I thought would not need to be upgraded at one power level I think are mandatory to upgrade now.

[fl327]

P90 is proven, but the p90a stuff is interesting. Ill stick with the solids, its just the caveman in me.

[SleeperZ]

P90 is proven, but the p90a stuff is interesting. Ill stick with the solids, its just the caveman in me.

 

Yeah, me too. I have too much invested in my solid. LJ is right, the hydraulics will compress some, as the check valve is undoubtedly somewhat springy and leaky on a flow reversal.

[yo2001]

Just add a thought. I don't think the P90A cam was really engineered as a hydro lifter cam. I know 4 deg in advance (which will peak the power earlier than other turbo cam) but other than that the spec is indentical to P90 cam. If the cam is high ramp lift (I don't know the correct term) design after solid rocker lifter cam, then the load is high and the cam will press hydro lifters. At least some. Blah, blah, blah

[Bob_H]

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

 

Sorry Bob' date=' 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.

 

.........

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)

[/quote']

 

First, don't confuse everyone here. Oil for all purposes IS NOT COMPRESSIBLE!. That is a totally different issue from the lifter bleeding down. Two COMPELETELY SEPERATE ISSUES.

I point you to this page that has the following quote:

Incompressibility. For practical purposes, liquids are incompressible. Even under extremely high pressure, a liquid cannot be made smaller. The brake system in a car takes advantage of this physical law. When you push the pedal, the brakes are applied instantly because no time is lost in compressing the liquid. Consider how much longer the brake stroke would be if the master cylinder contained air.

That can be found on the following page:

http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/1-509/Ch1.htm

So lets not confuse the two issues. A worn lifter WILL bleed down and cause a loss of performance. And from your own words showing the lifters on YOUR head were bad, (excessive ticking after driving, etc..), I would also expect a SIGNIFICANT increase in power with changing to ANY other cylinder head with the same camshaft! The devil is in the details here!

I would also expect the same increase with new lifters,(yes, expensive and no longer available), or going through the same process that David and awd92gsx have gone through, i.e. thoroughly cleaning the lifters. But you did neither, you just swapped out your head for a solid head, and now generalize your personal experience with a WORN LIFTER head into all P-90A's. Come on - you are better than that.

I will state ABSOLUTELY that a P-90A head in 100% conditon and a P-90 head will produce the ALMOST IDENTICAL power within the margin of error, or a percent or two, assuming ALL condtions can remain the same.

If it really produced less power, then Datsun would likely have changed the power rating when they came out with the P-90A.... Not saying a manafacturer is perfect, but a 20hp loss is significant...

I get wound up when people generalize their individual experience with a BAD LIFTER head and say all P-90A's are crap for performance. They most certainly are not. Yes, they do require some different,(not more, different), attention than non hydraulic heads. It has been shown by more than two members of this board that they can be cleaned and put back in service. I have personally run a high performance cam with stronger aftermarket springs on a P-90A. And with Sunbelts new line of camshafts that require less spring pressure than stock on a .600 lift/300 duration cam, you can now run any size cam on the P-90A.

Details folks, details...

-Bob

[Lockjaw]

Bob you still neglect to notice what I said, long freeways runs. Guess what, a turbo Z car, with a stock oil cooled turbo, and no oil cooler is going to heat the oil and thin it, hence the ticking. I in no way said the head had bad lifters, but the fact remains, I did not like the racket it made with a stock cam, it should have been silent. Now its ulitimate condition, well who knows, it was a 98k mile engine that was about 10 years old at the time. But hot thin oil means lower oil pressure, so you figure that one out, maybe there was some trash in one of the lifters.

 

I do know this. My turbo engine was in a 240Z, and thru the 1/8th mile, I could not beat my friend, who owned the 83 ZXT I now own, and his was stock, with a P90 ( and way more mileage). Now it doesn't take much common sense to figure out a 240Z with the same engine and turbo as a ZXT that is loaded, well that should not have been much of a race. But it was, until I swapped the head.

 

I also went from having to run down mustang GT's, at the time, our favorite victims, to pulling them from a dead stop, so the power gain was more then noticeable.

 

David, I really don't care what you have done to your head, the bottom line is you bench race, and have as of yet been able to step up the plate and demonstrate your car runs well. Still no answer to the question of what does your car run? So if you think its name calling to describe what you are doing, so be it, but if I was going to call you a name, I would probably chose something a little more colorful then bench racer. Just so you know.

 

Now Bob I know you don't like car comparisons, but you have to deal with some things that happened over a decade ago, and you know, starving college students won't drive from Auburn Alabama to Birmingham or atlanta to dyno a car. We did not care enough to go that distance. And we would have rather spent the money on some secret mod our friends did not know about.

 

However, you show me an NA guy on this board who runs or ran 8.40's thru the 1/8th mile with a 2.8 that was stock except for a cam, header & exhaust, and sidedrafts. There is no disputing the car ran what I ran, I double checked with my pal, and he has never lied to me. I drove it with SU's, and it was positively brutal above 3500 rpms.

 

Who wants to spend money on a p90a, then spend a bunch of time and money modding the lifters, pay what sunbelt wants for one of their one off cams, and still not be assured the head is going to make as much power as a solid head? Not me. And if by chance you happen to be out messing around and one of those one off lifters takes a dump, then where are you, running like crap as you have already said. Maybe worse, eating a lobe on your expensive one off cam. And I would be curious to see what head sunbelt recommends for their cams too. Maybe JWT as well.

 

No thanks, I will stick with a solid lifter head, and know beyond a shadow of a doubt that my 'lifters" won't go bad, that my valve geometry will be consistent, and that I will always make more power then someone with a hydro head.

[Bob_H]

Bob you still neglect to notice what I said, long freeways runs. Guess what, a turbo Z car, with a stock oil cooled turbo, and no oil cooler is going to heat the oil and thin it, hence the ticking. I in no way said the head had bad lifters, ....... Now its ultimate condition, well who knows, it was a 98k mile engine that was about 10 years old at the time.

I most certainly did read what you wrote. P-90A heads just don't tick after long freeway runs unless they are bad. Hot thin oil does NOT make a lifter tick. Poor oil pressure, inadequate oil pressure/flow, and bad lifters cause lifters to tick. The viscosity on oil doesn't change that much, and that in the end makes little to no difference - oil is still incompressible once the check valve closes - whether it is 10 wt or 80 wt.

Don't assume just because I don't like the way you compare cars that I think everyone MUST dyno a car for any comparison to be valid -for even those are not accurate car to car in different locations.

I am just very against slamming something from one single experience, esp. when you don't know everything about that head, correction, all the condtions about the head. As you said:

But hot thin oil means lower oil pressure, so you figure that one out, maybe there was some trash in one of the lifters.

Maybe? Maybe? Maybe the lifters were trash. Maybe it was perfect - we'll never know. So it is useless to use it as a baseline for all other P-90A's. At NO time did I ever doubt the numbers you put forth. At no time did I say they were crap. At no time did I not think they were GREAT numbers to run for a turbo or a NA car. Never.

What I still have a problem with, and will continue to have a problem with - is there are FAR too many variables to reasonably compare those cars with ones elsewhere, much less with head swaps, etc... But you an I came to an agreement on that last year. That trying to compare your 2.8 experience with say mine is not accurate. Some guys rock at the 1/8 and 1/4 mi. Your friend, Norm, etc.. Others suck.

My bottom line, as it will ALWAYS be - the P-90 is really no different from the P-90A. The sad thing about all this is everyone who has had a bad experience with a P-90A head, assumes they are trash and useless for performance. Bullshit. Your head was trash. You did gain power by switching. You did go faster with a new head. It had nothing to do with the hydraulic head being inherently bad - it had to do with your head being bad. As is the case with nearly every person who had bad experience with the P-90A head.

And the name calling - trash talking whatever you call it, is really not good for hybridz. No matter how much you disagree. There is nothing inherently wrong or inaccurate with David's statements. But you don't agree with his statements, so he is benchracing in your mind, or whatever you want to label it. What crap. Fundamentally, some of the things you said are inaccurate - had he countered them, as did I. They were the basis of your stand/arguement. Even with the record set straight on how lifters bleed down or why, you will still not like the P-90A or think it is good for performance. But your reasoning was wrong initially. My guess is you just have different reasoning now - and that is fine.

I'm not sure why I am even covering this. I guess it is because I have respect for both of you. And I see this as only eroding that - and that is not good. Just me though... We can all agree to disagree - nicely.

-Bob

[yo2001]

But technically the cam out of P90A having 4 deg advance from the factory, would it not peak power earlier than P90 head with P90 cam? (stock to stock)which mean less power?

[Bob_H]

Possibly. But we don't know what "effective" lash of the hydraulic heads was compared to the non-hydraulic heads. I do know the grinds are different when ordering aftermarket cams - but I can't remember the difference they told me. It is also possible that the 4 degree advance was an overall change for the turbo's and was in Datsuns mind, a change for more performance? Who really knows. But a valid point you brought up earlier as well.

-Bob

[Guest Boyd]

I like a solid lifter head simply because there is less to break. It either works or it doesn't. With my P90, I don't have to wonder about the hydraulic lifters and their condition. I cannot make an arguement either way as to which head produces more power or if a P90A can produce at the least the same amount of power. Within a couple of months, I will be able to say just how much power I am making with the P90 setup on stock '77 block.

 

Plus, there's just something about a 30 minute Saturday afternoon drive, followed up with a 6 pack and feeler gauges to set the lash.

[Lockjaw]

Well all I can say is you won't ever convince me the P90a is as good as a P90, much the same as you won't ever convince me a N42 is better then a p79.

 

And you are correct, I don't have hard numbers to always back up my claims, but I don't need them I was as big a skeptic as anyone about the relative merits of a p79, until I got to look at the back end of a car running one, and watch it continue to pull away.

 

I mean when you have the king Z car, and it followed all the comon logic of the hotrod Nissan books of the day, and someone comes in, tells you their smog head is the way to go, we laughed. We talked about that for months while the guy was working on his car. Junkyard 2.8 with a P79 milled 45 thous. He left me for dead, and my car wasn't slow.

 

I don't need hard numbers when someone is whipping my butt. You know what I am saying too.

 

Bottom line is, the solid lifters don't have problems, ever. To me, you need no other reason to run a solid head then that. Whatever series you want, if it makes you all warm and fuzzy to use an N42 have at it, personally, there won't ever be one on my car. But then I can handle setting up a P series to deal with the timing chain slack and all that from milling, others cannot.

 

In fact, on my turbo engine, there would be a P79 there long before an N42. Thats how much I believe. When someone comes up with some hard numbers I can look at, then I may change my mind.

 

Oh and my friends NA car, every bit a match for my pals turbo car, which ran 13.1's @109 or so, if memory serves. So it wasn't just an 1/8th mile wonder. I am telling you, I have never ridden in an NA datsun that ran like that one. It pulled to 8k and sounded like it was turning 6k.

 

Of course it was really cool when he went to a 3 inch exhaust and flowmaster. Now that baby would talk to ya. Turbo's are fast, there is no dening that, but to me, there is something about a high compression L6 with a big cam, header and exhaust. If there is a finer sound on this earth, I haven't heard it.

[SleeperZ]

Of course it was really cool when he went to a 3 inch exhaust and flowmaster. Now that baby would talk to ya. Turbo's are fast' date=' there is no dening that, but to me, there is something about a high compression L6 with a big cam, header and exhaust. If there is a finer sound on this earth, I haven't heard it. [/quote']

 

I'm with you 100% on that one LJ. --> n/a L6

[yo2001]

Yeah, 2 chamber flowmaster, 10.3:1, cam and 7000rpm+ on a N/A car, can't get much better.

[cygnusx1]

The only trouble I have with my P90A is that my injectors are too loud!