L28ET Build Idea, verification of hold?

[Ryu_Z32]

Ok after months and months of research. and hunting for a Datsun. I have found one, and preparing for a simple yet effective build. What do you guys think of this? This is my motor stuff, i also will be doing fuel mods and all that fun stuff!

 

L28 Block (280z)

L28 Crank (280z)

L28 Rods (280Z)

L28 Pistons (280z)

P90 Head (280zx)

2mm Head Gasket

 

Full rebuild, bearings, gaskets, seals, and rings.

 

 

stock compression on the 280z is 8.3:1, so with the thick (2mm) head gasket, Would it drop me to 8:1 CR?

 

Can the stock 280Z rods handle 20 pounds? Thats my max, and i cant find where anything has stated the bottom end strength of the 280z.

Edited August 7, 2010 by Ryu_Z32

[emeraldlion]

So here's the thing about boost and why you can't just ask "can it handle xpsi of boost" It's not the boost that kills the engine it's the power level and the presence of detonation that will kill your engine. If you build a solid 8:1 CR engine and have excellent tuning with an intercooler and a quality turbo you should be able to make more than enough horsepower reliably

 

 

I edited this post to remove a statement that as stated was inaccurate(sorry everyone)

Edited August 9, 2010 by emeraldlion

[letitsnow]

The 280z and 280zxt pistons are largely the same(look in the sticky ^^^ for exact details)so the cylinder head will dictate your compression. Using a p90 head on any l28 with dished pistons will result in ~7.4:1(depending on head gasket). Seeing this, I'd go with a 1mm gasket because there's no need for any less compression.

[Ryu_Z32]

emeraldlion - thanks buddy. that makes sense, i was just more concerned on reliability of internals really. Like i know a VG30DETT stock injectors cant take more than 17 reliable, and how the 2.2 Ecotec in SS Cobalts have forged internals stock and cant take more than 420 hp, and the wrist pins in VQ35DE's cant handle more than 450hp on daily consistence. Thats more or less what i was trying to get at.

 

 

 

letitsnow - sorry i should have clarified that i would run the stock 280z pistons. At 7.9:1 compression, you NEED boost to keep the motor running more or less lol

[Tony D]

pistons will let go in every case due to detonation before the rods will...

 

sigh...

[B00STDZ]

pretty sure hp limit is around 350whp on a stock motor with daily beatings.

[Tony D]

pretty sure hp limit is around 350whp on a stock motor with daily beatings.

 

Define that limit. 20 years durability? I've been at that threshold since 1985 and still have no issues with my NA Turbo Conversion. Probably 50K plus miles on it in that time. 26K of it driving daily as a commuter from Corona to OC.

 

The limit is based on detonation, NOT HORSEPOWER! 200HP will kill the engine if it detonates. STOCK 180HP will kill the engine if it detonates. The horsepower is basically irrelevant. You don't detonate, things won't break. Show me someone making 400 HP that doesn't detonate, and you will be amazed how long a stock engine will last.

 

But like all things, people using a stock bottom end tend to be trying to get a lot for nothing. And cheaping out tends to make things break. Usually (I'd almost say always) from detonation.

 

I would say 350HP will deliver stock engine longevity. I have no oil consumption, full compression after all this time. I don't detonate, either. I don't think 350HP is by ANY means any sort of a 'limit' on the engine.

 

It is if you want 100% engine reliability for 100K+ miles. Hell, who knows, maybe 200K miles.

[letitsnow]

letitsnow - sorry i should have clarified that i would run the stock 280z pistons. At 7.9:1 compression, you NEED boost to keep the motor running more or less lol

 

Yeah, stock 280z pistons have the same dish, with those and a p90 you'll have ~7.4:1 with a 1mm head gasket. That's the same as the stock L28ET, no need to lower it with a thicker gasket.

Edited August 8, 2010 by letitsnow

[Ryu_Z32]

Tony D - "But like all things, people using a stock bottom end tend to be trying to get a lot for nothing. And cheaping out tends to make things break. Usually (I'd almost say always) from detonation." I dont see how im being cheap, by using the bottom end....that makes no sense to me... Im only changing the head for better flow, and a turbo set up.

 

 

letitsnow - wow. was the 280zx CR 7.4:1? Thats insane! So, With the P90 head, and a cosmetic head gasket, id be looking at that CR? So then cramming 20 pounds of boost would be needed...now to research a turbo...lol thanks for that info, i really had no idea the CR would drop that far.

[johnc]

i really had no idea the CR would drop that far.

 

You should spend the next few days searching and reading. All of this information has been posted here during the last 10 years by hundreds of members who have already done what you're trying to do. Its all here free for the reading.

[Tony D]

Tony D - "But like all things, people using a stock bottom end tend to be trying to get a lot for nothing. And cheaping out tends to make things break. Usually (I'd almost say always) from detonation." I dont see how im being cheap, by using the bottom end....that makes no sense to me... Im only changing the head for better flow, and a turbo set up.

 

Follow John C's suggestion.

Second, are you running or planning on running a full on WBO2 controlled Standalone EFI system with proper compressor bypass valve and full fuel system? You only mention hardware, nothing about the most important item on the engine: The fuel and spark control system.

 

The HARDWARE is not the issue. Fuel and spark control is. You can have a $15,000 bottom end, it's still going to blow when you try to run 8 psi on a stock N/A fuel pump and stock N/A injectors without an intercooler on a 110F day up a long hill...

 

You're spending money to spend money because you haven't a clue where to spend the money. It sounds good because this is what all the books tell you to do. But in the real world anybody who has been aroudn turbo-L's for any time will tell you it's everything OUTSIDE THE LONGBLOCK that makes the horsepower reliable. Bolting on a head for 'flow' is laughable---unless you are spending $2400 for a fully worked head with ports polished and matched. The different head won't make enough of a difference to be worth the effort (flow-wise).

 

Take this bit of advice: Save the money you intend to spend on 'bottom end improvements' and just leave it alone. What you put in there likely will be worse than what Nissan Assembled the engine with in the first place, and won't last as long.

 

Instead, take that money and put it all toward fueling and spark control, and learning how to tune it, on a bone-stock bottom end. You, like so many are obsessed with a PSI rating of the engine---which is totally irrelevant. HORSEPOWER GOAL will dictate what you need eventually. And from experience 400HP will be doable on a bone stock bottom end with nothing special done. The longevity of that build will be ENTIRELY dependent on what sophistication you placed into the anti-detonation spark/fueling delivery control system.

 

I have seen big dollar engines wasted from a clogged fuel filter. It gets expensive when you skimp on fuel control, and put money into the strongest link in the equation.

 

L-Engines don't need internal reinforcement, they need SUPPORT SYSTEMS appropriate for the horsepower level desired.

 

As this is rarely understood, people will spend money 'fixing what isn't broke' and then with no money left in the coffers, buy some cheap system, or band-aid their stock system trying to make horsepower. And things go boom. Like I said, you have obsessed on hardware, the most durable part of the equation, and mention nothing about the MOST CRITICAL OF THE SYSTEMS. You need to read. You're approaching this bass-ackwards. You want 20psi on a stock bottom end. To me, 20psi is something in the area of 600HP. To use a stock bottom end at this power level is astoundingly cheap, bordering on insanity of the delusional.

 

And that's exactly what I mean by "trying to get a lot for nothing, and cheaping out."

[Nigel]

20 psi of boost on a small turbo inefficient at pushing that level will be less damaging than a large turbo very efficient at pushing 20psi.

 

 

I'm confused. How is a small turbo running outside of it's efficiency range and thereby doing little more than generating heat and promoting detonation going to be less damaging than a large, efficient, and therefore cooler running turbo at the same boot level? That's like saying vented brake rotors are more likely to cause brake fade that solid rotors.

 

Nigel

'73 240ZT

[Tony D]

It isn't, it's a grossly incorrect statement. You are correct Nigel. You are not insane.

[ktm]

Tool shed anyone? There is quite a bit of misinformation in this thread that it is not worth saving. Purge it from the search database if you will.

[letitsnow]

Tool shed anyone? There is quite a bit of misinformation in this thread that it is not worth saving. Purge it from the search database if you will.

 

Tool shed still shows up in a general search, just not in a sectional search. But yeah, the OP does need to spend a few hours searching and reading.

Edited August 8, 2010 by letitsnow

[emeraldlion]

Sorry it was kinda worded poorly. I was referring to the fact that the power created by the same 20psi is going to differ and the strain on the physical engine from power levels will be less. At the time my mind wasn't even thinking about the heat generated by the turbo when it should be the biggest consideration.

 

Sorry

Edited August 8, 2010 by emeraldlion

[Tony D]

Sorry it was kinda worded poorly. I was referring to the fact that the power created by the same 20psi is going to differ and the strain on the physical engine from power levels will be less. At the time my mind wasn't even thinking about the heat generated by the turbo when it should be the biggest consideration.

 

Sorry

 

OMFG, I agree with KTM, this is getting deep...

 

BMEP is BMEP

[emeraldlion]

alright I guess I just don't understand what I'm saying that is so off charts. I have always understood that a larger turbo pushing 20psi will create more power than a small turbo pushing 20 psi. I have also been brought to understand that more power creates more strain or wear on engine parts and that's what I was referring to. If that's incorrect I apologize. I didn't think about the heat issue. Again I'm SORRY if this has caused any misinformation.

[Tony D]

clarifing is not as effective as editing out...

[emeraldlion]

I agree and as such I should have started there. Going to go try and get my head screwed on right, will be back tomorrow hopefully slightly more on course.