Took the head off my L28ET last night and see that I have.....flat top pistons?

[dpuma8]

So I am pretty sure that the L28ET engines had dished pistons so I was pretty surprised to see the flats. I have a F54 block and P90A head with a N42 intake manifold. I bought rebuild parts for a L28ET and from what I am reading, the only difference between the F54 block is the pistons inside. So to make mine a true L28ET, what modifications do I need to make?

 

Do I need to upgrade fuel lines, injectors, ECU, and possiblt exhaust or intake manifold? Anything else or am I fine?

 

The pistons have "90" on them.

Edited December 16, 2010 by dpuma8

[MikeBZ]

So I am pretty sure that the L28ET engines had dished pistons so I was pretty surprised to see the flats. I have a F54 block and P90A head with a N42 intake manifold. I bought rebuild parts for a L28ET and from what I am reading, the only difference between the F54 block is the pistons inside. So to make mine a true L28ET, what modifications do I need to make?

 

Do I need to upgrade fuel lines, injectors, ECU, and possiblt exhaust or intake manifold? Anything else or am I fine?

 

 

The F54 block didnt just come in turbo cars. They were in all 81-83 ZX's. The turbo cars got dished pistons and non-turbo got flat-tops.

 

We need a little more info as far as what you need to upgrade. Read through all the sticky's in this forum

http://forums.hybridz.org/index.php/forum/18-turbo-supercharger/

 

If you want to build a L28ET I recommend getting dished pistons.

[Gollum]

If you're going to run less than 300 whp on a stock EFI and dizzy then keep the flat tops. If you're going to run more than that, then switch to dish. But if you're going run a REAL, modern EFI system and use a more controllable spark trigger then just keep the flat tops. You'll still be well under 9:1, and though there's so much talk about this very issue, it's really not that big of a deal.

 

We also need more info though, as it's already been said.

 

1.What color are the injectors?

2.What block code is on the block, does it say F54?

3.Pics of the intake please, I can tell you if it's a turbo one or not.

4.Valve cover hack the big, block style lettering that says turbo?

 

 

Don't be so concerned with having a "L28ET". Any number of L engine combinations can make great turbo cars. So unless you're wanting something that's 100% "accurate" for concourse show reasons then just be concerned about how well what you have will work together. And in all honesty, flat tops with a P90 is a great combo that's been well proven. Keep a nissan head gasket, or felpro if you desire to risk it (I have), and pour your money into EFI and spark control and of course a wideband with laptop to tune it with.

 

You can spend over $500 easily on even a "basic" rebuild. You can do it all yourself, but even the machine work alone will be a couple hundred bucks. You can spend much, much more to have the bottom built by a quality shop that does it all well. But all that being said, you can take a junkyard bottom end and throw a good head on it with your intake and exhaust parts and put over 400hp through it all day long if your tune is good. So forget rebuilding it and just put money into other stuff. I personally wouldn't even worry about building a bottom end until I was 110% sure of my tune and pushing the 600hp crank mark. At those levels the smallest tuning problem will show, where forged pistons will mask it. Get your tune RIGHT, not just mask your tuning issues with a strong bottom end.

[Dusto1002]

ahhhh this sheds some light on what i was thinking, thanks Gollum. not trying to thread jack at all but p90 heads ONLY came on turbos.... right?

[dpuma8]

This is why I am confused. The block says F54 and the head says P90A. When I bought the car from Voltron_Boi, he said it was an L28ET which actually is a L28E with a Turbo. The turbo placement is exactly like real L28ET. I have the Haynes manual and the diagrams look the same.

 

I am rebuilding the engine anyways and will be buying forged pistons. So that I don't have any problems in the future, is there anything I would need to look out for? I see that the L28ET oil pump was stronger in the L28ET so now I know I need to upgrade that. Would there be anything else? Is there a way to check to see if the ECU is NA or T?

 

1) Black injectors

2) Block code is F54

3) I will post the intake pic when I get home tonight

4) Yes it says turbo and the code is P90A

 

I will post pics tonight. Thanks for your help

Edited December 16, 2010 by dpuma8

[Gollum]

Are you sure those injectors are black? They might be brown, covered with a bit of dirt. Scratch one a bit with a flat head screw driver and then check the color with a flashlight on it. The turbo injectors are brown, which is probably what you have. The other common colors where green and white, both much smaller NA injectors.

 

You might have a genuine turbo block that had flat tops put in. Or it could be someone took the NA block from 81-83 and put all the turbo bits on it for the same reason very many people on here do, more compression, more power, etc.

 

Either way, unless you've got low compression during a compression test, or abnormal leakage with a leakdown test, I see a rebuild as a waste of time and money. But if you really want to, go ahead. As we say on hybridz, "there is no best". Therefor there is no "best" way for you to go about this, so take my advice as just that. Advice.

[240zip]

On the flat vs dished issue. You said a 'real' modern EFI. Does the SDS EM-4F with the crank triggered ignition qualify? I'm going to guess a higher (like 9:1 CR) would change the power curve such that you'd get higher HP at lower RPMs but limit yourself (with respect to HP) at higher RPMs.

[Gollum]

SDS is perfectly fine. Garrett on here has put over 400 to the wheels with SDS.

 

Higher compression doesn't actually change the curve much at all, but it will cause the engine to detonate a bit easier, but the flat tops with a P90 will have more quench. So in the long run this will mean you can run a DIFFERENT timing curve, which means you need programmable spark control. But regarding fuel control, you want to make sure to have GOOD injectors that are decently flow matched, and you want a GOOD EFI system with precise control. Even megasquirt is fine, despite it's very "budget" appeal. Stepping up to the 300ZX is hardly much of an "upgrade" imo unless you're going to add a programmable eprom, which after all that you might as well have MS.

 

Detonation issues generally (not always) show the MOST in HIGH LOAD situations at LOWER rpm. F1 engines could run on pump gas just fine without detonation, because they're literally outrunning it. The combustion process is happening faster at higher RPM, making detonation less likely to show up. So if you run insanely high compression ratio, you're more likely going to have to back the timing out more in the 2k-6k range. If you've got a honda B engine redlining at 10k, you most likely will be running plenty of timing still at redline with 13:1 comp than 11:1.

 

You also want to pull timing with boost, which will help you keeping from blowing up your engine. Timing also needs to get pulled in relation to intake air temperature too. Timing is by far the most complicated part of tuning as it needs to be completely tailored to THAT engine, not just "this engine" with "this head" with "these parts". You need to tune to THAT engine and find out what IT wants with it's timing. Distributors are prone to wandering over time, they can be irregular from unit to unit, etc. They're fine if you understand them and know how to "tune" them in the ways they can be, but they're much like carbs. Older car guys prefer them for their "simplicity" but the modern alternatives can be much better in some ways and almost essential in high performance applications that you still want to be livable on the street. They might still have carbs on top fuel dragsters, but those engines would never be livable on the street. You can make a 1500hp big block chevy that IS drivable on the street, thanks to modern fuel and timing control.

 

 

If you're gonna throw old parts on a car, be ready to deal with rebuilding them. If you want to go fast with old parts, be prepared to know how to engineer them.

[dpuma8]

Well, my car was fine until it started to run really crappy. I did a compression test and some cylinders were at 125 psi and some were 95 psi. I pulled the spark plugs and all of them had oil on them.

 

Interesting point on forged pistons masking problems. I was planning on running those but now I am having second thoughts........

[Gollum]

Get a junkyard flat top block and use that while building a forged piston bottom end. Forged pistons are GOOD, I'm just saying many people end up with too agressive of a tune because the pistons will take it in the moment but then fail over time. Cast pistons break suddenly and overall hold heat very differently. This makes them better to tune with imo because they'll tell you when the piston is getting too hot or you're right at the detonation threshold.

[dpuma8]

Here is the intake manifold

 

 

Edited December 17, 2010 by dpuma8

[BluDestiny]

that's not a stock L28et manifold. That came from a 280z without smog attachments. A lot of people use them over the L28et manifold becasue it looks "cleaner". I'm building my turbo with one.

 

But teh L28et intake has a pop off valve designed to vent excess pressure in the intke. Do you have something like that(a bov, or that thing thats cut off in the last picture)? Also idk what was used to plug the pcv valve hole, but it doesnt look like it will stand up to lot of boost. And where is your pcv valve? and where is the block venting to?

[biohazard53188]

Yeah, its an L28ET for sure... No other revision of the L28 comes with a kitten

[dpuma8]

I am not sure what the pcv valve is. I do have an intercooler and piping with a bov. The car only ran 5 psi.

 

So do I need a different manifold or is mine a desirable one? I want something that won't limit power if I decided to do more boost

[Gollum]

Well the stock wastegate should be getting up to 7-8 psi, so you're down an entire 2 psi somehow. Either the wastegate has been modified or it's sticking open.

 

The manifold you have is desirable to run mostly because it looks cleaner and deletes the EGR (exhaust gas recirculation). I've seen guys make plenty of power on them, so I'd just keep it.

 

Seems like a lot of this engine's setup might be decent, but could also have been done by someone who knew just enough to get himself in trouble. First thing I'd do (if I were you) would be to download a 81-83 280ZX FSM and read up on the stuff pertaining to the turbo engine and do your best to understand how the factory system worked. Read all the stickies you can on this site, and with the knowledge gained go over your car with a fine toothed comb (figuratively) and find out what's working and what isn't. Make sure the things that were done were done RIGHT, otherwise you'll be hunting those problems either until they've forced you to find them or until you get so pissed off you either sell the engine or the car. I've noticed that many times the "problems" a car comes with are due to improper mechanical know-how from previous owners getting in the way.

[ben280zx]

Take gollum advice. As he had got my car running back then. Totally agree with his last comment.

[steve260z]

Uh, oversized piston usually state the oversizing on them. Unless that "90" is a standard Nissan marking, could that block be overbored by .090"?

[dpuma8]

Uh, oversized piston usually state the oversizing on them. Unless that "90" is a standard Nissan marking, could that block be overbored by .090"?

 

 

The pistons said P 90.

[NewZed]

The Picasa photo-editing program from Google is free and will let you export pictures to a smaller size. http://picasa.google.com/#utm_campaign=en&utm_source=en-ha-na-us-bk&utm_medium=ha&utm_term=picasa

 

Import the pictures then export them to a smaller size <1000 x <1000. They will still be of high resolution.

 

This is an interesting thread but the pictures are killing me, both loading-time wise and trying to read the text, then shrink the pictures down so I can see them. They might be the biggest pictures I have ever seen on this forum.

 

Just trying to be helpful...

[HowlerMonkey]

If you found flattops in the engine, you will most likely find the rods lack the oil squirters that cool the pistons down.

 

Depending on your application, this might be important.