hello! and LD28 questions

[Guest Anonymous]

hey guys! ive been a regular over on zcars.com for a while now, but just found out about this place recently (incredibly enough).. i see a lot of the same names, the more erudite of the zcar crowd thankfully

 

im in the process of building an engine for my future 240z (i have a 280z n/a driver right now), and while i was at the yard this morning pulling an l28et i glanced to my left to see a deisel maxima! i was thinking i could go back tomorrow to grab the ld28 crank, but then reading some into the archives here and zcars.com i find its a pretty contreversial topic!

 

but what would u guys say if i can get the crank off a junkyard car, and im rebuilding the car bottom-up anyways. worth it or no? what additional rod, piston, head configuration options do i need to take into consideration?

 

also, side question.. this car is going to be built as my replacement driver (giving myself a couple summers to do it though-- im still in school), so i would like decent drivibility, longetivity, mantenance, but i want a good deal extra umph under the hood (300+ hp).. so i was planning going forged pistons, but then read that because of oddball expansion rates, the forged pistons cause accelerated engine wear, and poor street drivibility!? to what extent is this true for those of you using them? and what kind of gas mileage are you getting at ~300 hp?

 

sorry bout the newbie questions but sometimes i just get archived out if you know what i mean heh

 

thanks for taking the time

[Bob_H]

Quick and dirty. First, your subject heading is misleading. That is part of the reason for low response.

First, I will make some assumptions, since you didn't put it out.

I assume you are looking at building a stroker turbo setup for your 240Z.

I am sure you have checked out my webpage, and I will say it again, there is no cheap stroker. And a cheap stroker turbo does not exist. The guys out here who have built good stroker turbos have a bit of money in their engine.

I'd do some more research on the turbo's. Right now, JeffP has a great "stock" turbo setup. He is pushing up near 400 hp to the wheels. It is all in the tuning and setup. His model is a good one to follow that shouldn't break the bank.

Second, I would plan on finding a chassis dyno around you. If you have a turbo setup and are changing it from stock, consider it a must to put it on the dyno and tune it. Budget at least $500-1000 for that. Sure, you won't spend it all at once, but at $1-500 per session, it will add up.

Next, you really don't need forged pistons for the power levels you are looking at. Stock pistons can live up to just over 400hp if taken care of.

If you haven't already, check out my website, the Datsun Workshop. It may answer some of your "other" questions such as rods/heads etc..

Plan on the P-90 or P-90A if you are turbo-ing your motor. It is hard to beat for a turbo.

-Bob

[JoshB 240Z]

I have been itching for this very discussion. I have a 3.1L stroker turbo and have been pretty happy with it. I originally started the project with the idea that I would use a junkyard motor and turbo but quickly found out that the words "stroker" and "turbo" do not go with words like "cheap" and "inexpensive." I would say that my buildup was in the moderate range. I chose to go with the LD28 crank, new Nissan KA24 pistons cut down to fit, Nissan bearings (main and rod) and total seal rings. If I remember correctly the bottom end alone cost around $1500 parts and machine work. I then installed a P90 head with aftermarket turbo cam and 300ZXT EFI. Once this was all done I installed the engine into a 240z and have been very happy. I have only run stock boost at this time and the car is quick. The driveability and gas mileage are good. My only complaint stems from the stock EFI. Currently there are no easy ways to tune the 300ZXT EFI (that I'm aware of) short of having JWT reprogram the ECU. This means that you are forced to run the stock injectors which limits your boost to 10-12psi intercooled. I have been told that this setup should yield 250-275RWHP but don't have any numbers to prove or disprove those numbers.

 

If I were to do it over I probably wouldn't overbore the cylinders to .120" since the large increase in bore doesn't really give you that much horsepower, especially in a turbo application. I can also say that even with the material removed in the overbore and the cut down stock KA24 piston the engine did not self destruct when I over boosted to 20+psi. At this boost level it did detonate and didn't break anything. I was lucky but it goes to show these engines are quite durable.

 

Bob H-What are N/A strokers getting at the rear wheels?

 

Josh

[Lockjaw]

I think NA strokers are putting down 180+ to the wheels, depending on induction, headwork, and camshaft.

 

Bob is right, there is no such thing as a cheap stroker engine. Also, some of the turbo guys have been having problems with the harmonic balancer tearing up when going to the stroker crank.

 

I also think we determined the stroker crank weighs 3 pounds more than a stock crank.

 

The basic buildup uses a 240Z rod, and you want the one's with 9mm rod bolts, which should be replaced with ARP ones, IMO. I think you run the Z24 piston, and have to bore the block out to 89 mm.

 

That is where things get expensive, you have to bore the block, get new pistons, perhaps notch the block, rebalance the assembly because it will be way off, etc. Good machine work is expensive. I had close to 1500 in my shortblock alone, and I did not do anything exotic except go to 1mm over forged pistons. Not even a stroker.

 

You will definitely need a cam and header if NA to make any kind of decent power, and SU's work, although side drafts would be a better choice.

[Guest Anonymous]

yea, sorry about the misleading topic.. "ld28 _crank_ questions" was supposed to be it. anyways thanks for the responses..

 

i could have been a little more clear about establishing that the l28et i was getting while i spotted the deisel maxima is the engine i am planning to rebuild for dropping into a 240z, but you guessed right and it is.. hence i have a f54/p90a combo ready for bottom-up rebuild. the p90a looks to be in great shape (no gunk whatsoever) but im still trying to decide whether im gonna go with it or get a p90 instead.

 

that said, let me clear some things up a little.. i am not trying to build a "cheap" motor. by no means is this a 'get it done as fast and cheap as possible' project. hm let me simplify the question a bit..

 

what/how much are the gains of using the stroker crank with 89mm pistons, vs using stock bore/stroke. i can get this crank really easily, plus i was planning to put a load of money into the rebuild even without a stroker. (was planning on new pistons and rods in the first place)

 

"I'd do some more research on the turbo's" - been doing it, plus just ordered 'maximum boost - corky bell' the other night.

 

lockjaw, this is to be a turbo engine. t3/t4 hybrid, sds programmable fi, one of the junkyard intercoolers (or better) are current plans. (btw what is hp potential of a setup like this..?)

 

thanks guys

[Lockjaw]

Well Jeffp's setup is a stroker with an 88mm bore I believe. His last dyno run netted 415hp to the wheels and 473 ft=lbs. His engine is pretty thoroughly massaged though.

 

I don't know what the difference would be between stroked vs stock stroke. I would suspect the major difference would be in the torque output.

 

I would go with the P90 head. I am not a fan of those hydraulic lifters, and they are expensive to replace.

 

I would also recommend a good intercooler and skipping the stock one route. Stock intercoolers just are not up to the task of handling the boost that a modified engine puts out, and a good spearco is not to expensive.

[Cody 82 ZXT]

One thing that I think people forget is that to really take advantage of the added volume of the engine you need to have the head worked. That is one reason that Jeffp's car is running so well. It flows air very well. In some of the other post he mentioned that his car is making the same power at lower boost levels than some of the other cars with similar configurations. Yes the added stroke and bore help but, if it dosn't flow right it won't make the power your looking for.

[fl327]

i came up on a built motor, but i would go stroker i were building one from scratch, if you are gonna go the cheap route, i would just go the junkyard and pull the engine, get the crank balanced and get all the bearings replaced, hone the block and re-ring the pistons. money that could have been used on a stroker

could go some head porting, port and polish,an o-ring, and a steel headgasket, you should be ready for the world after that, granted you dont try to shoot 20psi on the stock efi system.

 

hey josh b.- i can get chipped z31 ecu's custom tailored if youre interested, with increased inj. duty cycle, redline delete, you name it, i can probably get it done cheaper than a jwt.

[SleeperZ]

Originally posted by Lockjaw:

I would go with the P90 head. I am not a fan of those hydraulic lifters, and they are expensive to replace.

Hoodwink - if your P90A has adjustable pivots, just use it, it will not be different than a P90. On the other hand, if the pivots are hydraulic, I agree with Lockjaw, go with the P90 or non-hydraulic P90A, as if one goes bad they are difficult to find.

[jeffp]

Hi there hoodwink, I dont know for the life of me why people say the stroker engine is not good. I did my engine to 3.0 I could not justify the 89mm bore for a turbo application. I wanted a little more meat there. I did things different from most on my engine. I increased the rod/stroke ratio of the engine and increased the stroke as well the bore. I am making the same power at 20psi as a stock L28 bottom end at 25-26psi,, so you can see there are advantages to the increased swept volume.

I wanted an engine that would last a good long time so that is the reason for the 88mm bore, andI wanted to be sure I could run the boost levels high and not break parts. I did not oring the block, but used ARP studs and a metal head gasket and have had zero problems with it.

My cylinder head is ported and somewhat polished. I did not go with a full race setup because again I wanted it to last a good long time. I did port match the intake, and the exhaust as best as possible without taking to much meat out of the head. I am speaking mostly of the exhaust, the intake is port matched perfectly with the intake.

I built the bottom bullet proof for the most part, so I would not have to worry about it.

I paid 5400.00 for the bottom end parts and assembly, and I provided the crank. I went with clevite 77 bearings, larger premium wrist pins and total seal rings. Je forged pistons, and somewhat of a mirror image of the combustion chamber on the top of the piston to inhibit detonation.

I can run 91 octane fuel @ 11psi of boost without any problems. I know this sounds like it is not much, but when you stop to consider the stock compression of an L28 is 7.4:1 and I am running 8.5:1 there is quite a significant difference onder all conditions boost and non boost conditions. I tried to taylor the engine and the compression in such a way that I could get the hp numbers I wanted without getting a totally monster turbo to give me the required air flow and cylinder pressures to get some good power from the engine. I have often times wondered what the engine would be like if I had set the static compression to 9:1 very good off boost response in that case and the turbo could be a little smaller still to get good power. I like having good power off boost and really like the power increase under boost when I want it.

so that is about it for me.

I say go for it and build it beefy, overkill is not going to hurt you at all, and just may prove to be a saving factor for you one day.

have a good one, jeff

[Bob_H]

Hey all, time to weigh in again.

JeffP and others, noone said the turbo stroker is not good. I said, and was backed up for the next three posts that it was not cheap

And JoshB said:

but quickly found out that the words "stroker" and "turbo" do not go with words like "cheap" and "inexpensive."

Josh, that is awesome! BTW, I did not quote this to prove my above point, I just loved the comment. But regardless, you backed it up with your bottom end cost. I love the stroker, but it is most certainly not a cheap route. And for the hp goal that hoodwink was looking for, (300 hp), I cannot reccommend a stroker unless he just wants to spend extra money,(you are welcome to be my sugar daddy ). That is an easily atainable power level with the stock type turbo setup and a decent intercooler.

And Josh, Lockjaw was right on for his power estimates at the wheels. I have seen strokers from 160 to 255 at the wheels. The 160 was a poorly tuned SU setup. Most are in the 170-190 range. It cost quite a bit of money and tuning time to get over 200 at the wheels in a NA setup. I am sitting at 180. When I get a heat shield on the car and stop boiling over the rear carb, I should be about 185-190, and about 200-205 on torque. That is pretty normal, about 20-30 lb-ft and about 15-20 more hp than an equal 2.8L.

As for the P-90A with hydrualic pivots. I have run mine for 15k miles on my stroker with an aftermarket cam and many trips to 7k with 0 problems. I love how quiet the head is and that it requires NO adjustment. I'm lazy, what can I say! If they are in good shape, I say go for it. Post and find awd92gsx. He has a tech bulliten for Mitsubishi's and their hydrualic lifters. He can tell you how to check if they are good, and how to "fix" them if they are questionable, (by "fix" I mean soaking in diesel and testing).

-Bob

[Guest Anonymous]

thanks again for the responses guys! jeff definitely knows what im talking about.. id rather put more money into (go overkill) something than save and be doubtful. one of my main goals for this engine is for it to last! its going to be an everyday driver for probably quite a while once i get it done.

 

heres some more stuff.. i said "300+ hp" but i mean 300 is about the baseline of what i expect to make.. i am not so much aiming for a hp goal, as i am aiming to make as much as possible without making the car non-practical (ie having to use race gas and getting 8mpg etc). i want to use pump gas, get reasonable gas mileage, but also have a heckuva sports car on my hands, not so much minding how much money it is going to cost.

 

jeff what kinda gas mileage do you get with your setup? and also those forged pistons.. they require intermittent engine breakdowns or anything?

 

as of right now i am planning on going the stroker route. im liking what im seeing from jeffp.. ill probably follow him as much as i can.

[Guest Anonymous]

ok ive heard of "o-ringing" a couple times, then i found out to "o-ring" a block is to put a copper gasket around grooves at the top of the cylinders? if thats right, what exactly is the purpose?

[JoshB 240Z]

Hoodwink, you're almost there. O-ringing the block is where a groove is cut into the deck of the block so that a piece of steel wire can be crushed (for lack of a better word) between the deck and head. This helps to seal the cylinders by isolating the combustion process to the cylinders and away from the paper gasket. I'm sure someone else on this forum can give you a better description of the process.

 

Len168-Thanks for the offer but I will be going to an Accel DFI soon. I have been building my wire harness for the past ten months and almost have it finished. Once it's done tuning shouldn't be a problem.

[Guest Cusp]

You've seen how on a head gasket around the combustion chamber there's a copper o-ring, that helps control the combustion. Just having the fibrous part of a gasket all the way up to the combustion chamber wouldn't cut it. You'd blow a gasket in seconds.

 

Oringing takes this copper gasket idea one step further. You have your machinist notch a small groove around the combustion chamber on both the head and the block, and an o-ring (think piston ring) is crushed in the groove. It seals very well and allows for much increase in boost levels. However, unless you're gonna go very high with boost levels, this is a bit expensive and a little overkill. I would use a felpro to about 16psi, if you're going higher than 16, o-ring that lil pup.

[Lockjaw]

I am not sure O-ringing is necessary. I am using the stock nissan head gasket, I have flat top pistons and I have been running lots of boost with no problems.

 

My block is decked though, and the head was given a clean up pass with the milling machine.

 

But I would not tell someone not to get it done either.