To rebuild or not to rebuild...

[Watson]

...that is the question.

 

Hey everybody. I know I'm not very active here but I usually just lurk around, get the information I need and leave. Well I've started a 280ZX project a little while ago and today I pulled the head and have the intention on rebuilding it but I was wondering, should I rebuild the bottom end? Let me first define my goals:

 

I don't care how much horsepower I'm making, I just want the car to feel good. It will do two things; drift and autocross. My initial intention was to fully build the head, e.g. port and polish, valvetrain, bigger cam, and also do headers (with full exhaust) and possibly a different intake manifold. Now with that said, I know the L28s are stout engines and I'm no expert but when I pulled the head, everything looked decent. I'll attach a video so you can get a small idea of the condition of the bottom end.

 

I pulled the head because coolant was getting into the exhaust so I thought it was a blown head gasket. I didn't see anything wrong but again, I'm no professional.

 

TL;DR I'm rebuilding the head, should I rebuild the bottom end on an already factory stout L28E?

 

 

Edited October 28, 2013 by Watson

[Connor280ZX]

The cylinder head could have a crack, or is warped. Of course its hard to tell off the bat, but i'd clean the head up and inspect the surface for cracks or fractures. As far as the bottom end goes... You didn't happen to do a compression test before you began the teardown, did you? Also, how many miles are on the engine?

[BluDestiny]

No, just rebuild the head to get it running. Purepontiackid drifted on a stock L28 for awhile before it started leaking everywhere. I'd get another block as a spare, but a stock L will take you a long way. 

[seattlejester]

A good locking rear diff is a must if you want to do both sports, welding the diff will make you understeer like a pig on an autocross course.

[Watson]

The cylinder head could have a crack, or is warped. Of course its hard to tell off the bat, but i'd clean the head up and inspect the surface for cracks or fractures. As far as the bottom end goes... You didn't happen to do a compression test before you began the teardown, did you? Also, how many miles are on the engine?

That's what I'm afraid of. I hope that's not the case as I have a N42 head and would like to keep it, but if it's cracked or warped..

 

Unfortunately I did not do a compression test before removing the head and it has 180,000 miles on it.

 

A good locking rear diff is a must if you want to do both sports, welding the diff will make you understeer like a pig on an autocross course.

 

I really don't mean to come off as a jerk but this response is sort of why I stay out of forums and other groups. This is completely irrelevant to the question at hand and I'm fully aware of the issues that a welded diff create. That's why my 240 has a 1.5 way differential. That, I did rebuild and install and until tearing apart this engine, that was the biggest project I have tackled.

[seattlejester]

...It was in reference to the purepontiackid's setup. I'm pretty sure he is running a welded diff, and was advising the need for an lsd if you wanted to do both sports. I know the 280zx NA in all versions did not come with one, therefore the advice. My intention was not to imply you did not know anything about either sports, but for some reason you took it as such. A nice introduction thread could have avoided all this I suppose, but too late for that.

 

You did come off as a jerk, don't preface something when you plan on doing exactly what you are prefacing against. Saying you don't want to come off as a jerk, and then informing someone they are the reason that you avoid something pretty much qualifies you as a jerk. And if a simple piece of advice that is relevant off puts you, then why are you here? 

 

I was just trying to give some advice for down the line, because your thought process is wickedly flawed, and I didn't want to go into it. But I guess I will.

 

Your goals that you list don't make sense, you don't care about how much power, you just want it to feel good. What does that mean? Does 10 hp feel good, does 1000 hp feel good, is it torque you are after, is it reliability, what does feel good mean?

 

Essentially you have removed the ability to determine your problem. A dry compression test would have told you if the rings/headgasket are good, a wet compression test would have told you if the valves or headgasket is good. Those two tests could have determined the problem down to the cylinder or which two cylinders your problem lies, but now that you've taken the head off, you won't know for sure what the cause of the problem is.

 

You also pulled it without knowing what to look for? That seems like exploratory surgery, pretty ridiculous. Now that you have pulled it, you don't even know what you are looking at? That's pretty silly. Wear in the ring grooves, if you can catch your finger nail on the cylinder wall, scoring, checking the cross hatching, strange wear patterns, all things you could have checked for the bottom end. Inspecting the mating surface, a pinched gasket, valve and seat mating surfaces, rust traces/trails are all things you could have checked with the head. You could have even checked for compression and determined to a rough extent bearing condition by removing the valve cover and rotating the crank by hand.

 

You pulled the head without draining the coolant? So now you're not even sure how much coolant you had in the cylinders. Or which cylinders had coolant prior to the head removal.

 

Couldn't get the bolts for the manifolds off, so you removed it with the manifolds bolted on and rusted in place? How are you going to hold the head to get the bolts and studs out now? Put the cover back on an roll it over on the top and mar the valve cover? Lean it toward the back and mar the back of the head and the mating surface?

 

Coolant in exhaust, evident by white smoke as you said, should have been checked by draining the oil. Now with the coolant in the cylinders you are not going to know if you fixed it until all that coolant is burned off or flushed, probably two oil changes there.

 

And all this bigger flow, big cam, and such you will be adding. Do you even have a way to adjust the fuel to compensate? The stock ECCS is pretty inadequate when you start playing around with headwork.

 

Now I know I've come across as an ass. I tried not to, but you provoked me. My little quip was something to keep in mind, so you don't end up trying to autocross your welded diff to be disappointed like I was. You were already beyond what I would have suggested, but I wanted to post a little advice to keep track of where the thread was headed. Now I'm not interested.

 

Good luck.

[Watson]

...It was in reference to the purepontiackid's setup. I'm pretty sure he is running a welded diff, and was advising the need for an lsd if you wanted to do both sports. I know the 280zx NA in all versions did not come with one, therefore the advice. My intention was not to imply you did not know anything about either sports, but for some reason you took it as such. A nice introduction thread could have avoided all this I suppose, but too late for that.

 

You did come off as a jerk, don't preface something when you plan on doing exactly what you are prefacing against. Saying you don't want to come off as a jerk, and then informing someone they are the reason that you avoid something pretty much qualifies you as a jerk. And if a simple piece of advice that is relevant off puts you, then why are you here? 

 

I was just trying to give some advice for down the line, because your thought process is wickedly flawed, and I didn't want to go into it. But I guess I will.

 

Your goals that you list don't make sense, you don't care about how much power, you just want it to feel good. What does that mean? Does 10 hp feel good, does 1000 hp feel good, is it torque you are after, is it reliability, what does feel good mean?

 

Essentially you have removed the ability to determine your problem. A dry compression test would have told you if the rings/headgasket are good, a wet compression test would have told you if the valves or headgasket is good. Those two tests could have determined the problem down to the cylinder or which two cylinders your problem lies, but now that you've taken the head off, you won't know for sure what the cause of the problem is.

 

You also pulled it without knowing what to look for? That seems like exploratory surgery, pretty ridiculous. Now that you have pulled it, you don't even know what you are looking at? That's pretty silly. Wear in the ring grooves, if you can catch your finger nail on the cylinder wall, scoring, checking the cross hatching, strange wear patterns, all things you could have checked for the bottom end. Inspecting the mating surface, a pinched gasket, valve and seat mating surfaces, rust traces/trails are all things you could have checked with the head. You could have even checked for compression and determined to a rough extent bearing condition by removing the valve cover and rotating the crank by hand.

 

You pulled the head without draining the coolant? So now you're not even sure how much coolant you had in the cylinders. Or which cylinders had coolant prior to the head removal.

 

Couldn't get the bolts for the manifolds off, so you removed it with the manifolds bolted on and rusted in place? How are you going to hold the head to get the bolts and studs out now? Put the cover back on an roll it over on the top and mar the valve cover? Lean it toward the back and mar the back of the head and the mating surface?

 

Coolant in exhaust, evident by white smoke as you said, should have been checked by draining the oil. Now with the coolant in the cylinders you are not going to know if you fixed it until all that coolant is burned off or flushed, probably two oil changes there.

 

And all this bigger flow, big cam, and such you will be adding. Do you even have a way to adjust the fuel to compensate? The stock ECCS is pretty inadequate when you start playing around with headwork.

 

Now I know I've come across as an ass. I tried not to, but you provoked me. My little quip was something to keep in mind, so you don't end up trying to autocross your welded diff to be disappointed like I was. You were already beyond what I would have suggested, but I wanted to post a little advice to keep track of where the thread was headed. Now I'm not interested.

 

Good luck.

Well this is the internet. No personal interaction voids any sort of personal touch as every interaction is up for individual interpretation. My apologies.

 

As a quick summary the cylinder walls are butter smooth and I was not burning oil so with my minimal knowledge, I can only assume the bottom end is good. I do however need to replace the rear main seal. I have discovered the head is warped. I would feel better just buying a new head than trying to fix it.

 

The manifolds were still on because it's damn near impossible to access the bolts that the two manifolds share with the head in place. Removing the manifolds with the head off was a cakewalk and no damage was taken to any part as they were removed.

 

Again, horsepower is not a goal of mine. I want the engine to have a quick, fluid, responsive feel. I realize the run of the mill L28E is not a power house and that's okay, but a N/A well flowing engine is enough satisfaction for me. That's why I posted no horsepower goal, otherwise I would have everybody saying "get a turbo or you're wasting your money".

 

Although it is not mentioned in my original post, I will be using a Megasquirt ECU.

 

I don't know who purepontiackid is so I hope you can understand where I made no connection to a differential recommendation assisting my bottom end building question. I do appreciate your in-depth input though. That's one of the best responses I've seen on the internet yet and it does give me some insight on my errors prior to head removal. For what it's worth, none of my cars, past or present, have ever, nor will they ever see a welded differential. I don't think I will be rebuilding the bottom end...

[Connor280ZX]

That's what I'm afraid of. I hope that's not the case as I have a N42 head and would like to keep it, but if it's cracked or warped..

 

Unfortunately I did not do a compression test before removing the head and it has 180,000 miles on it.

 

 

N42's are pretty good heads... '80 ZX's come with N47's stock, so thats an improvement. However, if you do find that its cracked, you might be able to get it filled depending upon the damage. And if its warped, i think in some cases a resurfacing of the head can fix it depending upon how its warped.