Jump to content

cronoz78

Engine Rebuild Preparation

Recommended Posts

I have been told that the most experienced engine builders are on this forum so I thought I might get some help and direction.

I am considering doing an engine rebuild on the 78 280z this May.  It is only a street car, I drive in traffic and highway.  It is mostly stock except for Headers, Fujitsubo exhaust, ZX distributor.  I have had it for 8-9 yrs. 
The goal is a cost effective, reliable, healthy bump in power and fix leaking oil seals as the ODO says 27k. Now is that 127 or 227 miles??? 
I've done everything else myself but left the engine work to the last, now that I have time and space to mess around with it.


Reason: leaks from here and there, need fixing so why not just get it over with...
This will be my first engine rebuild (it doesn't look to difficult) 
Yes, I have the shop manual and the 2 books.


Does anyone have any suggestions on things I should change while I'm in there? (N47 head)

My loose plan:

- Do a leakdown, compression and dyno test so I can have a baseline.
- All Gaskets (Felpro full kit)

- Block to be decked/faced, honed and head to be decked/faced
- Cast Pistons - Flat tops any recommendations?
- Head rebuild?  decked/faced, ISKY 718147 Stage 1, ********What should I change here to accept the new cam? Springs?, lash pads?, retainers?, rockers?, shorter valve seals***** Recommendations?
- New bearings, rod bolts, frost plugs, timing chain kit.
- Ignition plan to keep the OEM (any benefit to a new ignition system?)
- ZX Turbo oil pump
- Adjustable fuel pressure regulator (suggestions?)
- While I'm at it... flywheel faced and new clutch OEM or Exedy OEM Replacement Clutch Kit 06009.  No lightwieght flywheel as I dont want a "blippy" thottle response.

Any info would be helpful if you have done this before 
Where should I buy these parts because there are good parts and CHEAP parts
If you don't feel like typing I can call you just PM me.

Thank you in advance.
D.

20180619_215853.jpg

Edited by cronoz78
  • Like 1

Share this post


Link to post
Share on other sites

Get new Nissan head bolts (turbo if you find them),  OEM for front & rear seals, ITM pistons have a good reputation for your application,  new water pump, & liberal use  of assembly lube.  Zcar Depot is a good source for many of the needed parts.   Japan parts are always best vs china. 

Since you are in Canada, one of the northern experienced guys might be able to point you in the right direction for sourcing parts.

Nice looking 280 ....

  • Like 2

Share this post


Link to post
Share on other sites

...and if you are going with a different cam you'll need an adjustable (program-able) fuel management system.

Edited by rcb280z

Share this post


Link to post
Share on other sites

Tom Monroe's "How to rebuild your L series motor".  I'd never built a car motor, read that book about 4 times and now have a great running healthy 2.8 in my '77 280Z.  Easy to understand and everything is explained in simple terms which was great for me. :beer:

https://www.amazon.com/Rebuild-Your-Nissan-Datsun-Engine-ebook/dp/B006VUICHG

Image result for Tom Monroe's "How to rebuild your L series motor

  • Like 2

Share this post


Link to post
Share on other sites

I’m looking forward to this thread. I’m about to do a full L-28 engine rebuild (my first ), so I’m interested in the same considerations. I’ve done some preliminary research and have read the first book “How To Rebuild Your Datsun Nissan OHC Engine”. Just bought the other book, “How to Modify Your Nissan Datsun OHC Engine”.

My thoughts here...BTW I’m no expert. Why waste time doing a leak down test before teardown. Compression test makes some sense but your be pulling the head anyway and you’ll find out quickly if you had a bad valve or leaking head gasket. Leak down would be if you hadn’t decided you were going to or needed a rebuild. Sounds like your moving forward regardless.
So my thoughts what’s the best bang for the buck after deciding what is the “End State”. You said a good street driver. With that in mind why would your replace the pistons to forged? That’s not going to make a performance difference unless you plan on boosting or really trying to make the engine high performance. Cams while able to increase power, reduce daily drivability and will require a change to the EFI to compensate.
From what I’ve read on the interweb here are some good options.
1. increase displacement. If you’re set on getting new pistons then bore out the cylinders. I’ve decided not to go this route. A good honing is my plan.
2. Porting the intake and head to smooth out airflow.
3. Header and exhaust. (You’ve done that)
4. Upgraded ignition.

Basics should do:
-rings, bearings, valves, all seals and gaskets, timing chain kit, new hardware. (Head bolts etc..).
-Good idea with turbo oil pump

Shaving the head to increase compression is good option but like any mod like that needs to be done with care. If you overdo the CR upwards to 10:1 your begin to experience possible pre-ignition which will not be healthy for your engine. Unless you live near an airport and want to use 100LL aviation gas. Be prepared to pay ~$8 a gallon.

For a basic rebuild, I priced all the parts and it was around $730.
This included all the items I put above in “basics should do” to include new freeze plugs, complete new engine hardware, and water pump.
I look forward to people who have more expertise to chime in and you’re in luck because this is where the L28 experts live.




Sent from my iPhone using Tapatalk

  • Like 1

Share this post


Link to post
Share on other sites
17 minutes ago, Av8ferg said:

The place I'm getting the dyno test I will get them to do the compression test and while I'm at it the leakdown I guess - that was my thinking
I will get cast 280zx flattop pistons to increase the compression. No need for forged as I will never turbo this car.
Regarding the cam. I have been in contact with a Z shop up here and they recommend the Isky Stage 1 as it enhances the existing power-band.  Nothing is drastic about it. This is their experience and I trust their input.
I don't plan on boring out the cylinders ect... I am trying to keep everything close to original so that the OEM ignition system can still be used. Basically, from what I understand the flattops and the new cam are the only things being changed from OEM and the adjustable fuel pressure regulator is the only thing that is needed to "keep-up."

 

 

 

I’m looking forward to this thread. I’m about to do a full L-28 engine rebuild (my first ), so I’m interested in the same considerations. I’ve done some preliminary research and have read the first book “How To Rebuild Your Datsun Nissan OHC Engine”. Just bought the other book, “How to Modify Your Nissan Datsun OHC Engine”.

My thoughts here...BTW I’m no expert. Why waste time doing a leak down test before teardown. Compression test makes some sense but your be pulling the head anyway and you’ll find out quickly if you had a bad valve or leaking head gasket. Leak down would be if you hadn’t decided you were going to or needed a rebuild. Sounds like your moving forward regardless.
So my thoughts what’s the best bang for the buck after deciding what is the “End State”. You said a good street driver. With that in mind why would your replace the pistons to forged? That’s not going to make a performance difference unless you plan on boosting or really trying to make the engine high performance. Cams while able to increase power, reduce daily drivability and will require a change to the EFI to compensate.
From what I’ve read on the interweb here are some good options.
1. increase displacement. If you’re set on getting new pistons then bore out the cylinders. I’ve decided not to go this route. A good honing is my plan.
2. Porting the intake and head to smooth out airflow.
3. Header and exhaust. (You’ve done that)
4. Upgraded ignition.

Basics should do:
-rings, bearings, valves, all seals and gaskets, timing chain kit, new hardware. (Head bolts etc..).
-Good idea with turbo oil pump

Shaving the head to increase compression is good option but like any mod like that needs to be done with care. If you overdo the CR upwards to 10:1 your begin to experience possible pre-ignition which will not be healthy for your engine. Unless you live near an airport and want to use 100LL aviation gas. Be prepared to pay ~$8 a gallon.

For a basic rebuild, I priced all the parts and it was around $730.
This included all the items I put above in “basics should do” to include new freeze plugs, complete new engine hardware, and water pump.
I look forward to people who have more expertise to chime in and you’re in luck because this is where the L28 experts live.




Sent from my iPhone using Tapatalk

 

Share this post


Link to post
Share on other sites

Do you know the compression ratio you’re going to get with an N47 head and flattop pistons, I’m just not sure what it would be? Looks like right now with dished pistons you would be 8.29:1.
I’m going to go with the P 79 head and flat top pistons.

Your chamber will be 9cc smaller than with the P79 and flat tops and that head has 8.82:1 CR.

1914c57a235842f6262781214c53e453.jpg


Sent from my iPhone using Tapatalk

Share this post


Link to post
Share on other sites

The ignition system can be used on anything.  It's the EFI system that will give problems.  You might be fine with your power increases, or you might find that it runs a little rich at the low end, or it pings at the high end.  Or it won't pass emissions.

The adjustable FPR is a crude way to add fuel at the higher RPM so that the cam has what it needs to make power.  But then you'll have to make adjustments to other parts at low RPM or you'll have a gassy smelling car.  That's the basic dilemma.  The EFI system has no O2 sensors so does not self-correct anything at all.  It's designed to produce a certain amount of power at each RPM range.  But it actually runs pretty rich at WOT, 27% extra fuel, so there's a little room there without doing too much.

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Av8ferg said:

Do you know the compression ratio you’re going to get with an N47 head and flattop pistons, I’m just not sure what it would be? Looks like right now with dished pistons you would be 8.29:1.
I’m going to go with the P 79 head and flat top pistons.
Your chamber will be 9cc smaller than with the P79 and flat tops and that head has 8.82:1 CR.
 

Should be about  9.7 : 1  CR with the stock gasket thickness.   

Share this post


Link to post
Share on other sites

Does the bottom end need rebuilt, or you are just wanting to try it?!The bottom ends are about bullet proof unless it’s been neglected . Should be able to tell that by how clean the inside of the valve cover looks. Does it use or blow smoke? You might pull the head off and still see the cross hatch marks in the cylinders. I’ve seen it on a  motor with 100k +

You could save $$ and time and aggravation and less down time with your car by not touching the short block except gaskets . You could improve CR with a smaller combustion chamber head .  Instead of rebuilding that head you could put money towards a different head .

Facing the block? Probably won’t need decked either. 

Now the head should be resurfaced if it has any defects or just for the HG longevity.

Shorter valve seals or different valve springs for anything more then 460 lift cam. Probably get away with stock seals up to 480. 

Just throwing it out there

 

  • Like 2

Share this post


Link to post
Share on other sites

I see you are in Kanata area?  I am in NS but work for a telecomcompany HQ'd there.  I may be able to stop by every now and then to lend a hand.   Having a good set of tools is important.

 

Below (attached) is a software tool for doing initial engine configurations. It is a zipped  html file. 

 

image.png

 

 

 

S30 Engine Modeller V4.zip

Share this post


Link to post
Share on other sites
21 hours ago, cronoz78 said:

I have been told that the most experienced engine builders are on this forum so I thought I might get some help and direction.

Like I said, these guys are the best.  That s30 engine calculator above that 240260280 posted is not only a great tool but lots of fun mixing and matching, swapping heads and pistons to see how much potential power you can squeeze out.  I know you are seeking a fairly mild boost in power but it shows you what is possible and power creep is addictive.

One thing that I have read many times on Z forums is that the L28 engine can be just as well mannered with a stage 3 cam as a stage 1,  that a stage 3 camed engine can have a smooth idle with more oomph with no penalties.

It would be interesting to hear what anybody has to say about the stage 1 - stage 3 debate.

Share this post


Link to post
Share on other sites
48 minutes ago, grannyknot said:

Like I said, these guys are the best.  That s30 engine calculator above that 240260280 posted is not only a great tool but lots of fun mixing and matching, swapping heads and pistons to see how much potential power you can squeeze out.  I know you are seeking a fairly mild boost in power but it shows you what is possible and power creep is addictive.

One thing that I have read many times on Z forums is that the L28 engine can be just as well mannered with a stage 3 cam as a stage 1,  that a stage 3 camed engine can have a smooth idle with more oomph with no penalties.

It would be interesting to hear what anybody has to say about the stage 1 - stage 3 debate.

To this point I would say go as big as a stage 3 . I know Chickenman is running a pretty large cam with the Bosch EFI with a little tweaking . Idle shouldnt be an issue , but can’t swear to that with the stock EFI. Probably with be a bit more stinky at idle. 

A 39cc chamber will get you around 9:1 

Share this post


Link to post
Share on other sites

madkaw: 
Honestly the car runs good considering the mileage and age. Whatever I'm doing is because I have the time and space for the next few mths. The rear crank seal leaks, rear transmission seal leaks, oil pan.  I'm only doing these things since I have the time and space now.  what I dont want is to have that car have a problem further down the road where it is not drive able and I don't have time to really get into it.  Its for convenience right now thats all.  I'm the first to say "if it aint broke don't fix it" which is why Im having a hard time moving fwd with this. I hear what your saying though and very aware.  What I need to do is get the car out of storage (May) and look at these things again. run these compression tests ect. I have a camera scope i can send in the sparkplug hole to take a peek as well.
Facing = Decking (some people say facing)

grannyknot: How fancy to meet you here as well! lol

 

Share this post


Link to post
Share on other sites
54 minutes ago, cronoz78 said:

madkaw: 
Honestly the car runs good considering the mileage and age. Whatever I'm doing is because I have the time and space for the next few mths. The rear crank seal leaks, rear transmission seal leaks, oil pan.  I'm only doing these things since I have the time and space now.  what I dont want is to have that car have a problem further down the road where it is not drive able and I don't have time to really get into it.  Its for convenience right now thats all.  I'm the first to say "if it aint broke don't fix it" which is why Im having a hard time moving fwd with this. I hear what your saying though and very aware.  What I need to do is get the car out of storage (May) and look at these things again. run these compression tests ect. I have a camera scope i can send in the sparkplug hole to take a peek as well.
Facing = Decking (some people say facing)

grannyknot: How fancy to meet you here as well! lol

 

Running good goes to my point, but I understand the -while I’m there might as well. There’s also curiosity and the - I want to rebuild a motor -feeling too.

Good luck and there’s always help here

Share this post


Link to post
Share on other sites

So the compression check will be a solid indication as to whether or not you need to do a total rebuild. If compression is good maybe just gaskets, seals and a head cleanup might be all you need. If compression is low then maybe “while you in there mentality makes sense”. Rings and bearings for sure.
My situation leads me to a total rebuild. I have 2 cylinders in the low 140’s. They should be around 170. I have a loose timing chain (stretch or the tensioner is bad.) I can hear it slapping the cover, and freeze plugs that leak due to corrosion. So I’ve decided to do the whole engine.
The other side of this coin is this. You have the engine out, all the accessories removed might as well go all out and get it all done. I can appreciate this approach. I don’t like unfinished work or unknowns.
If you have the time, I’d lean toward a total rebuild. The cost isn’t much more and you’ll learn a heck of a lot. As far as cams go. I’ve never been a big fan of turning a nice engine into a poorly idling engine that is just fast and not a great car to daily drive. I want a little more power but I don’t want to sacrifice a smooth running reliable engine either. They run best the way to were born minus a few minor things.
Consider finding a ZX engine with a P79 head, of just the head. You’ll get some extra power and not radically change the original design. I got my ZX engine for $400, with a warranty. Start looking at car-part.com for engines around you.
My 2 cents.


Sent from my iPhone using Tapatalk

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Av8ferg said:

So the compression check will be a solid indication as to whether or not you need to do a total rebuild. If compression is good maybe just gaskets, seals and a head cleanup might be all you need. If compression is low then maybe “while you in there mentality makes sense”. Rings and bearings for sure.
My situation leads me to a total rebuild. I have 2 cylinders in the low 140’s. They should be around 170. I have a loose timing chain (stretch or the tensioner is bad.) I can hear it slapping the cover, and freeze plugs that leak due to corrosion. So I’ve decided to do the whole engine.
The other side of this coin is this. You have the engine out, all the accessories removed might as well go all out and get it all done. I can appreciate this approach. I don’t like unfinished work or unknowns.
If you have the time, I’d lean toward a total rebuild. The cost isn’t much more and you’ll learn a heck of a lot. As far as cams go. I’ve never been a big fan of turning a nice engine into a poorly idling engine that is just fast and not a great car to daily drive. I want a little more power but I don’t want to sacrifice a smooth running reliable engine either. They run best the way to were born minus a few minor things.
Consider finding a ZX engine with a P79 head, of just the head. You’ll get some extra power and not radically change the original design. I got my ZX engine for $400, with a warranty. Start looking at car-part.com for engines around you.
My 2 cents.


Sent from my iPhone using Tapatalk

I agree with all of this except the cam perception. It’s not the cam that makes for poor idle as much as the ability to tune. My 490/290 cam probably isles as good as a stock engine , but I have the ability to tune it. OEM EFI doesn’t allow tuning, but I think you can get away with some cam mods which do wonders for these motors . 

  • Like 1

Share this post


Link to post
Share on other sites
I agree with all of this except the cam perception. It’s not the cam that makes for poor idle as much as the ability to tune. My 490/290 cam probably isles as good as a stock engine , but I have the ability to tune it. OEM EFI doesn’t allow tuning, but I think you can get away with some cam mods which do wonders for these motors . 


Madkaw,
What kind of EFI are you using? Sounds like he’s interested in a cam upgrade. I know a guy that had a black pearl 78 that put a performance cam in. He could never get it running smooth with EFI so he decided to switch to carbs and it was fast but it didn’t run as smooth as a stock engine.
Not sure if Cronoz78 wants to keep the car injected. TI would be nice to know all the additional mods to get an EFI engine running well with a cam upgrade. Like do you need bigger injectors, fuel pressure reg?? Not sure.


Sent from my iPhone using Tapatalk

Share this post


Link to post
Share on other sites
8 minutes ago, Av8ferg said:

 


Madkaw,
What kind of EFI are you using? Sounds like he’s interested in a cam upgrade. I know a guy that had a black pearl 78 that put a performance cam in. He could never get it running smooth with EFI so he decided to switch to carbs and it was fast but it didn’t run as smooth as a stock engine.
Not sure if Cronoz78 wants to keep the car injected. TI would be nice to know all the additional mods to get an EFI engine running well with a cam upgrade. Like do you need bigger injectors, fuel pressure reg?? Not sure.


Sent from my iPhone using Tapatalk

 

I am using megasquirt - so I have a distinct advantage to tune my EFI. But I have read of guys who have success with a tweak here and there and can run stock EFI with a bigger cam. The cam really wakes these motors up, but power is addicting. The stock motors (L28’s) are all in at 5000, so a cam does wonders. Since it’s been reported that the stock EFI does fudge on the rich side at wide open throttle, someone could get away with more power with the stock EFI.

Going carbs changes everything . 

Lots of info on EFI upgrades . EDI has come a long way

Share this post


Link to post
Share on other sites

I think my $5 volume knob from Radio Shack wired into the coolant sensor wires would do the trick for a bigger cam.  I can flood it out now with it turned all the way clockwise.  I can't remember if it's a 1K pot or a 5K though.

Share this post


Link to post
Share on other sites
14 minutes ago, siteunseen said:

I think my $5 volume knob from Radio Shack wired into the coolant sensor wires would do the trick for a bigger cam.  I can flood it out now with it turned all the way clockwise.  I can't remember if it's a 1K pot or a 5K though.

Interesting - but makes sense . Cold engine needs more fuel. 

  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.