1985 Nissan 300ZX Turbo
We picked this car up for my youngest brother as his first car for $800.
It was decent, ran ok, body wasn't the greatest but I've seen worse. Gradually
it started running worse and worse so I finally decided to take a look at it and
see what the problem was.
I went through the normal stuff trying to find problems with the ignition
and fuel injection systems but to no avail. While working on it I happened
to peek into the coolant system and noticed a milky looking mixture... right
away I though, oh great the headgaskets must be bad. Turned out to be much
worse than I thought...
I started pulling a head off and finally got down to the cylinders. What I found
next was just amazing. From what I can figure out, one of the previous owners
must have turned the boost up beyond what the fuel system is capable or handling
stock. The engines stock have no aftercooler system and have small-ish injectors
at about 259 cc. Basically, the engine likely wouldn't handle much more than 10
psi without an aftercooler and fuel mods. There was a boost controller inside
the car so I'm quite sure that's what happened.
As for what happened internally... the pistons were tore up very badly.
All three pistons on the passenger's side were scored all over the top
and a couple were actually missing a pretty good chunk of metal out of
the outer edge. Definitely some detonation or pre-igntion going on there.
Luckily I had bought a couple 1985 Nissan Maxima engines a while back
so I had a spare I could use. I bought the Maxima engines under the
impression that one burned oil and the other had a broken timing belt.
I figured I'd put the two together for a single good engine but after
working on the engine that burned oil I found out this wasn't needed.
I started pulling it apart and noticed oil in the intake, and a decent
amount at that. I figured that could easily be a pcv issue so I was relieved
that there was likely no internal issues. The more I started pulling things off
of this engine the more I found out how good of condition it was in. I finally
decided to do a compression test before taking off much more but something odd
happened. All cylinders were low... extremely low. Most were in the 120's and a
couple dipped down to 90 psi. I knew that couldn't be right at all as there's no
way this engine would be low on all cylinders unless the belt had broke, and that
wasn't the case with this engine. I figured maybe I just wasn't spinning it fast
enough since it was sitting on the floor cranking it with a slightly charged battery.
I decided not to pull the heads off since I knew there was no possible way for
the engine to be internally bad. I started swapping items onto this engine from
the original turbo engine and in the process found something strange. I noticed
the headgasket wasn't stock. It actually appeared to be metal. I thought about
it for a little while and figured if they were indeed metal I'm going to pull
them off and sell them as metal headgaskets are quite rare for these engines.
I got the first head off and found out they weren't quite what I expected.
Turns out they were Felpro headgaskets, which do have metal in them, but
aren't all metal like I was hoping. No matter though... I've heard that
for whatever reason the Felpro headgaskets don't work all that well on these
engines, so that worked out pretty well.
I threw on some stock headgaskets, which work more than well enough for a turbo
setup. There are guys making incredible amounts of power out of these engines
on the stock headgaskets, so this will work fine. I should mention that while
I had the heads off I noticed something even more amazing... the cylinders
still had the hone marks in them. This isn't rare, but it just proved more
that this engine was in excellent condition as I had thought.
After getting the heads back on and getting it all torqued correctly I
began swapping parts back over. Finally got it to the point that its
pretty much ready to be dropped into the car. My dad came out to help out
and asked me about the clutch. The clutch that was in the car was a SPEC
stage 3 that includes a 6-puck, sprung hub disk. When I first pulled it
out it appeared to be in pretty decent condition but when I went to inspect
it again, it turns out it was pretty worn down... new clutch time. While
I was at it I decided to take a look at the flywheel as I hadn't really
looked at it much yet. The flywheel was terrible... there are fractures
all over the friction surface meaning it was likely overheated terribly.
That's pretty much where I'm at now. I ordered a clutch and will take
the flywheel in to get resurfaced if possible. Worst case, I'll just buy
a stock flywheel that's in decent condition to put back in there. I believe
it should all work out pretty well though and the car should be a blast.
As an idea of what kind of upgrade the Maxima engine will be, the stock
84-86 turbo engine has a compression ratio of 7.8:1. The Maxima engine
has a compression ratio of 9:1. Many will say that 9:1 is too high for
a turbo motor but this simply isn't true. For the power output most people
will go for in a street driven car, the 9:1 compression ratio is plenty
low enough. You retain excellent low end power, which is much needed
for the street. You also gain power throughout the entire rev range and
most importantly, you can spool the turbo much quicker.
A lot of the Z31 300ZX guys actually go with a 9:1 compression ratio
setup as it works out great... how great? There are many guys making
in the range of 300-400 horsepower to the wheels on the stock internals.
There's even a guy making over 500 rwhp on the stock internals of a
Pathfinder engine, which is essentially the same as the 87-89 300ZX
normally aspirated engine and the 89-94 Maxima VG30E, all of which
have a compression ratio of 9:1.
So, in the end this should come out to be a pretty worthwhile project
and should be a blast as a daily driver. More to come soon.
On to the pictures