78 280z engine tear down and rebuild N42 block and head. flat top pistons

[cycloid]

Hello

I just wanted to start a thread dedicated to rebuilding my Z.

I have already removed the head and the exhaust manifold. I still have a few other things to remove tho. I plan on giving the engine bay a paint job and also powder coating the z parts since they are out of the car. I have been very careful in putting all the nuts in bolts in bags and labeling them. So far everything has been great. I haven't broken any bolts or cut any wires. Thankfully have not had to break out any penetrating oil either. All is well.

At this point I am almost ready to start inspecting and cleaning up parts for the rebuild.

I do however need a little assistance.

I cannot fully rely on the service manual since my pistons are not the original ones. I am not sure how I should go about this. A fellow forum member told me that with my combo the compression ratio is close to the detonation threshold. He also told me that this combo is not uncommon. I'm sure with the proper tuning the engine will run fine. Im hoping to get some help from someone who has worked with a similar setup. flat top on n42 crank case and head.

I first want to start off by selecting parts. I am not to sure exactly where to begin as far as part selection.

I think the best place to start tho is going to be with the header selection. Is there a recommended header for my setup?

also while Im at it. Id like to get my block painted up. Is there any good cleaning solvents that someone recommends? I don't want to use anything that will hurt the cylinder walls or the deck surface. any block cleaning tips would be greatly appreciated

Id love to hear some advice from you guys and would greatly appreciate some guidance in my Z journey.

some vids and pics of the car as of now.

my freind and I tried to replace the timing chain. on the startup after the chain replacement I heard a valve get bent and also the car would not stay on. I did the chain work myself and this time it stayed on but I was unable to avoid the valve issue that occured when the work was done on it the first time. This just goes to show that you cant always rely on an automotive mechanic school graduate.

the stuck valve

loose rockers

cylinder walls

[siteunseen]

I had good results with laquer thinner and a very strong degreaser that came from a local chemical supply, not sold in retail stores, and small wire brushes from the welding section at Lowes. Brass bristles for the aluminium.

Edited April 30, 2012 by siteunseen

[LeonV]

Carbs, or even better, standalone EFI is preferable in running a flat-top L28 with a small chamber head, i.e. high compression, especially since a hotter cam is typically used alone with it. Factory EFI was not designed for this.

A header is not the first place to start. In fact, it's the last place.

Do some research. High compression, flat-top L28s have been around for decades. The information is not difficult to find. You can also buy the How to Rebuild and How to Modify books as they relate specifically to L-series engine rebuilds.

[siteunseen]

Like LeonV says, the "How to To Rebuild L Series" by Tom Monroe was the best money I've spent on my 280Z. And Blue's Tech Tips from Atlanticz.com was the best $0 money, he could charge for that info, it's priceless. If you plan on a paint job for the body you should pull what's left and start from there. $2000 to paint and you will not want to pull the motor out or I would not, the fenders a very thin, an elbow would make dent.

Edited May 1, 2012 by siteunseen

[cycloid]

Okay so I purchased both L series books. I have started on the how to modify book.

I am feeling a little bit more comfortable with the situation. I hate to sound dumb but I would please like to know

if using a dual su carb or triple carb setup with a different cam, new valves and exhaust will be okay to use with the flat top pistons. what other mods might I be looking at?

could someone give some advice? what would you do in this situation?

here is my end goal

Id like to have a dependable daily driver.

something to have fun in.

not looking to build an extreme race car.

I would like to go with a triple carb setup

Id like to keep my budget at around 2000-3000 (not including paint, tools, labor)

Ive started on cleaning up the block like it says in the L series book. I am wondering what to do next with the head. should I have the head sent out to a machine shop for reconditioning or could I simply replace my bent valves and start looking at some cams?

Edited May 3, 2012 by cycloid

[Zed Head]

Still seems odd that someone would put flat-top pistons in an N42 block, then use the stock 78 ECU and AFM, when you can get the pre-assembled setup by buying an 80-83 ZX engine. But, apparently, some people feel the N42 block is made of better metal (higher nickle content?). Or maybe a PO had some P79 pistons laying around and needed to get it running. What did your receipts show? Any comments about new pistons?

Seems like you might have three options:

1. Get a P79 or P90 head to go with the flat-tops, to get a more stock CR of ~8.8. This would be the factory stock 80-83 ZX engine, essentially, and could probably run well with your stock 1978 ECU and AFM. It might take some minor tweaking but the engine was not much changed from the 75-79 Z engines.

2. Old school with carburetors and a hot cam. This would be mainly mechanical tuning with jet changing and timing adjustments, etc. to get things working right. There are lots of people on this forum that know carb tuning.

3. Modern aftermarket EFI, like Megasquirt or Haltech. This route would be more electronic with tuning by computer, and could be as simple as adjusting just fuel through injector opening times alone all the way to controlling timing through a crank angle sensor along with fuel requirements. It would require a computer and more hardware, but could give you more flexibility, with enough electronic gismos added, like IAC controllers, and O2 sensors, etc. Here's a link to browse if you want more insight in to what's involved - EMS - HybridZ

Don't forget to check the emissions testing requirements for your car in your state before you get to far.

[cycloid]

Thanks zed head. All of the choices sound very enticing. I may end up going with an aftermarket efi. Ill save a little bit of money and get to keep a lot of parts.

Im a little concerned about the head tho. I was looking at some info and it looks like it is recommended to replace all the head hardware (springs, valves, rockers, cam) I am sure the headwork is going to add up pretty quickly.

I was looking at some head rebuild kits and the one I saw was around 800 dollars. for that much I can get a 5.3 lm7 with the harness and a 5 speed trans.

Id really love to go with a bone stock ls based swap. I may just do an ls swap if the l28 rebuild turns out to go past my budget.

I properly removed the head by following the exact bolt loosening sequence to prevent warping. The cam lobes look okay. they do not have that polished finish to them. Do you think I could take my complete head to a reputable shop and see if the rockers and cam are still salvageable??

would be really cool if they could just freshin everything up instead of having to buy all new head parts.

anyone had any experiences in prepping up a head?? how much money ballpark might I spend on having my valves done and getting my *cam back up to par at tune shop?

btw. I was not able to find any info on the pistons. Looks like it might have been done by the previous owner or the paper work was not included in my folder.

I did find one of those coins that get glued to the block. ( it says warranty void if removed ). I bought an lq4 at a engine salvage once and I saw one of those same coins. My thoughts are that this motor had some work done on it by some shop or it was purchased at a yard.

Edited May 4, 2012 by cycloid
added information

[LeonV]

Read the head section of the "How to Rebuild" book, this is why you bought it...

In a nutshell, you can take it to a machine shop to do guides, seals, seats, and check valves. The cam can be cleaned up and reused as long as you keep each valve with its matching lash pad and rocker. It's cheaper if you perform disassembly/assembly yourself.

Edited May 4, 2012 by LeonV

[cycloid]

Sorry Leon. I guess Im just being a little too anxious. I will try to simmer down a bit and continue reading the book. Thank you for the advice.

[Zed Head]

You might consider getting a used head or used engine to use while you figure out which way you want to go. All four options described above will give a different type of car. The engines are surprisingly durable compared to 70s domestic engines, and used parts still have a lot of life in them, even with lots of miles. You could probably get back on the road for under $200. I bought my car not running because I thought I might put a V8 in it. But after I got the stock engine running well and drove it around, I lost the urge. A V8 car is a totally different beast.

By the way, I think that you'd get more feedback if your thread didn't have the huge pictures in it. I don't even want to open it anymore because it takes too long to load all of the images.

[siteunseen]

I've been trying to reply for 5 minutes! Download time is forever even though I have nothing to say but I bought an N42 reworked head, valves and sides ground and new stems etc., for $250.