thetremendousti

Due to my stellar decrease in performance and the fact that I can't drive it for a while (grounded ) I need to overhaul my '81 engine. I just have a few questions about what to look for first and what to do...

1. I have 176K miles on the engine, should I consider re-boring? I do not want to have to since it will end up costing me a whole new engine.
2. Is there a place that will sell complete rebuild kits for this engine?

I have made a list of parts I should replace, what should be added to the list, and what aren't necessary?

Spark Cables
Thermostat Housing gaskets (3)
Cold start valve (wear)
EGR valve gasket
Throttle chamber gasket
Intake/Exhaust gasket
Distributor gasket
Water pump gasket
Valve Cover gasket
Timing chain, Chain guide, Chain tensioner and gasket next to it (see image)
Head gasket
Pivot bushings (6)
Valve spring seats and oil seals (6)
Front cover gasket
Piston rings (6)
Rear oil seal
Main bearings, and bearing caps (6)
steel net and Baffle plate

What am i Missing and what is not necessarily necessary?

NismoPick

Why do you want to rebuild the motor again? It's only got 176k miles. Unless it's been mistreated it's whole life, it's not really time for a rebuild. And you didn't mention anything that sounds like an upgrade...

I'm confused on why you are doing this.

thetremendousti

I Just need to get my power back and restore the original motor, my motives aren't upgrade aimed. I'm doing this for help! Oh, by the way nismo I used your cardomain pictures for a graphic arts project in school that 2+2 is *female doggin!

snwbrderphat540

get new main bearings and a whole new everything for the timing chain and piston ring set. and get your own honer. thats what me n mah dad did. but gotta make sure everything is still all in tolerance and shizzle. and if your gonna do this might as well get some flat tops. or if you go a P series head go get it re-surfaced but also shaved down some. ask shady he knows the amount. then you get a raised compression and make mucho more HP over stock.

NismoPick

Unless you are in a tight money crunch (or an expert at engine rebuilding), take the block to a machine shop. They will get the bearings & rings needed, and can usually get you a rebuild gasket kit for their discount price. And... it's professional work.

Like Snw said... spending all that money to be right back at stock is kinda a waste. You could keep the bottom end stock, but at least get the head worked.


And which pics did you use?

snwbrderphat540

i dont trust machine shops for assembly. nor would i EVER pay someone to have that much fun by putting MY motor back together. thats MY JOB!!!!

did you even do a compression test yet? whats it at? oh and you dont have to remove the crank so you dont have to get a rear oil seal. unless yours is leaking. my dad mighta even re-used the stock main and connecting rod bearings. not sure. but his WHOLE timing chain setup is brand new. we rebuilt everything. the machine shop re did the head but we assembled it. and we did the honeing and assebmled that ourselves to. cylinder walls are so shiney after you hone them.... mmmmmmmmmmmm

NismoPick

Like I said... use a machine shop UNLESS he's an expert. Rebuilding motors isn't like playing w/ Legos.

Reused the orig bearings? That defeats the entire purpose of an engine rebuild... especially since bearings are the cheapest part.

thetremendousti

How much should i raise the compression, like just get some L24 pistons? Last i checked back in dec i was about 130 +/- 5 difference on all 6 cylinders; but I've been low on oil and leaking and horsepower is lackluster

NismoPick

I suggest doing some component / part research here:

http://www.ozdat.com/ozdatonline/enginedesign/

Low on oil? Did you try adding a quart? Where is the leak? Is the motor burning oil? And lack of hp can be fixed without rebuilding a motor...

snwbrderphat540

what year car is this? and yeah thats low its not necessary but i would rebuild if i had teh time and money. and im prolly wrong about the bearings. lol. but he didnt remove the crank so i doubt he re-did the main bearings then. the rod bearings though i believe were knew. thats prolly where i got my confusion from. but he mightve done those to who knows. he gets impatient though and then starts to cut corners. like on my paint job. rushed right into the first clear job and it was thin and crappy and then he went into teh second clear job before i could take a look at it. so there is a run in the door/fender seam but thats it really.....

Sweets

You dont need to rebore the L series engines EVAR! Ive seen a block with over half a million miles on it, and that sucker looked brand new.

If you think rebuliding your engine will restore your hp, you will be in for a big suprise when you get it back together and drive it for the first time. Sounds like a big waste of money to me.

If you think the power is lacking, then get it dynoed and see.

snwbrderphat540

at 130 PSI from the ZX's factory 180 psi i could definatly see his motor loosing power. prolly only aboot 20hp though. nothing serious. and rebuilds are fun. and i never said bore, i dont think any one did, hone yes, it will re-smooth and re-groov the cylinders and the new rings will def be thicker so you will have the proper compression and oiling back.

Sweets

Well, you are grounded... so I guess if it gives you something to do then go for it. It couldn't hurt anything. Oh, I guess it could though.

lww

What year is your Z? If it has an N47 with dish pistons it should read about 160 psi, not 180 psi.

What do you think is making your engine "loose" power?

Who diagnosed the problem and said a rebuild was necessary?

When you did the compression test, did you do a dry or wet compression test? You can get a 20 or 30 psi difference between the two.

Did you run the motor up to operating temperature before doing the test?

What kind of compression tester did you use? Cheap rubber bushing tester from Harbor Freight or professional screw in compression tester? This can affect your reading by 10 or 15 psi.

snwbrderphat540

i have a N47 in my 77.... or 78.... i forget now damnit 280Z.... soo lww.... fastest way to get a higher comp ration? other wise ima try to build an SC setup for it. lol.

thetremendousti

yeah i've been adding quarts for a while now and used about 4 already, :-( On the valve cover it kind of pours out of the gasket and onto the spark plug area, I will see if I can take a picture of it later. I don't know if it's burning, but it's coming out of the valve cover gasket!

Mine is an '81 all stock, and I'm pretty sure it is a P79. Nobody really diagnosed it, I just want to get in and see if I can get more power!, I did a cold, dry compression test and I found the sheet of paper where I wrote the numbers and I ran an even 140 across all 6 cylinders :-). I used one of those $40 screw in ones *ouch*

snwbrderphat540

did you try a new valve cover gasket and re-torqueing it? lol.

lww

As has been mentioned before, I've seen 200k mile engines have no appreciable wear on the interior engine components.

140 psi even across all 6 cylinders on a cold/dry compression test is excellent.

Therefore, I summarize, you have no need to disassemble this engine unless it's smoking profusely out the tail pipe.

Go and clean up all your electrical connections, replace all your vacuum hoses, then do a full tune-up.

snwbrderphat540

excellent????? not excellent, but it should be fine. mine on a cold dry test on the one motor was factory specs at 124k

thetremendousti

Hey so i took off my valve cover right, and I washed it out to remove some gunk and there is a hard sealant lining the inside. It's all cracked and it still sticks but I'm afraid it will fall off and screw with my rockers, it's not RTV what is it and what should I do??

snwbrderphat540

all valve covers have that. so i have no clue what to tell you... leave it? lol

NismoPick

Looks fine to me....

FubarI33t

I'd have to say. The fastist cheapist way to raise comp is N42 on flat tops. But if you can't find a N42, a shaved P79 works great. It's the shimms you have to find. Last I tested was back in dec. And I tested 192-196 across all 6. And I burn a gal of 20-50 oil a week. Stock engine.

snwbrderphat540

how can you burn that much oil but have those compression numbers. are you sure your burning the oil? something doesnt add up there broseph

Niku-Sama

yea the most your going to have to do with the cylinders is have them re honed, if for some reason its scored on the inside of the walls then well you got bigger problems.

i say if you do any thing you replace the valve cover gasket and if its gunky in there mabe try some synthetic for an oil change or 2, or you could dump a bunch of ATF in there and run it for a few and then drain it, just not straight atf, i'd cut it with a quart and a half od 15-40 but you kinda do thesem things at your own rick because it may clear out goo keeping it from leakin more, you run the atf and it clears the goo out and you leak hella bad.

and unless you've got funny sounds from the bottom end or your mixing water and oil i would leave it