Camshaft ID / Timing help, please

[ericbauer]

Hi everyone,

 

 

I bought an old Nissan at auction last year & measured a slightly low 150psi / cyl when I picked it up.

I didn't get any history on the car from the PO, but decided to enjoy it as is over the summer, and had a great time with it.

https://vimeo.com/41685762 & https://vimeo.com/43905308

 

Fall came around and compression took a further dip down into the 100psi / cyl range and that's when I decided to tear it apart for a rebuild.

On dis-assembly I had several pleasant surprises:

 

 

 

 

 

 

The PO went to town on this thing!

Diesel crank, 89mm bore, L24 rods, 37cc combustion chambers, and by my math a stout 12.1:1

What I had been enjoying all summer was a tired stroker motor and I was already pretty damn impressed...

 

Got everything back from the machinist (later than promised), and decided I really wanted to have the car running again for a specific event.

That meant a compressed time frame in addition to a busy regular day job schedule. Push came to shove and it required a string of several late nights.

 

When it came time for final assembly, I thought I made sure everything lined up at TDC the way it was supposed to.

Made sure crank timing mark was correctly lined up at TDC before I put the head on.

Used a new chain, lined up bright links, and stock ("A") cam gear marks.

Rotating by hand through a full revolution it felt "a little" tight at TDC for each cyl but I assumed it was due to everything being new.

 

As a disclaimer I've owned a 240Z for the past 12years and have successfully built two different engines for it over the years.

While I don't consider myself a super expert like most of you here, I feel relatively confident with my L6 mechanical knowledge.

 

Well, while it did fire, it never idled. Move the ign key from START to ON and it would immediately die.

It seemed unhappy timing wise. I re-checked all the marks and everything still seemed correct.

So I went down a path of checking everything else: carbs, distributor 180 out, ignition... to no avail.

 

When I finally gave up, I pulled the head and found pretty much what was I expecting at that point:

 

 

My cam was overly retarded and I hit exhaust valves.

 

 

 

So I'm starting over...

 

There's never enough time to do it right, but there's always enough time do it over...

 

 

I've had the cam profiled by Isky and here are the results:

 

lobe center 105

valve lift calc. with rocker ratio of 1.5

 

intake @ 0.020" lifter rise

duration 310deg

open 50 btdc

close 80 atdc

cam lift 0.376" (9.55mm)

valve lift .564" (14.32mm) 

 

exhaust @ 0.020" lifter rise

duration 316deg

open 83 bbdc

close 53 atdc

cam lift 0.384 (9.75mm) 

valve lift .576" (14.63mm)

 

overlap 103deg

 

 

Based on other clues I've come across on this engine, I'm guessing the cam might be a Kameari unit, but I can't get my numbers to jive with their advertised values. Am I reading their info wrong? I'm confused by their listed "77deg duration"...

 

http://kameariusa.com/L6_SuperDragCamshaft.php

 

Have some of you seen these kinds of values before?
Do they ring a bell?

 

 

 

I'm only just starting to understand the finer points of degree'ing a cam, sorry if this is a dumb question...

But based on the measured values I should have the cam 1.5deg ATDC to be right in the middle of the valve overlap, right?

Does that mean I should NOT be using the default Nissan "A" tick marks for a new timing chain when putting it back together?

 

Is that what I (probably) F'ed up?

 

 

 

 

Thanks in advance for your input...

 

-e

 

[Leon]

1. That is friggin awesome!!!

2. That's one hell of a cam. High RPM powerband and better suited for racing than street driving.

 

Degreeing will be difficult without a cam card but you did your work and had Isky profile it. Now that you have the specs, why not set it up again and see what you find? Have you read the cam degreeing sticky?

 

BTW, what octane were you running/plan to run? Will this be a street or track car?

Edited June 4, 2013 by Leon

[T-Bone028]

.....IM SORRY WHAT?!?!?!  That track video shot by Josh Clason/Depth of Speed with JDM Legends was the SINGLE biggest push to install the triples I had sitting around!!!!!  I wanted that sound, singing through the rev range and classic nostalgic power.

 

Unfortunately, I cant help with advice on degree'ing the cam...but congrats on a BEAUTIFUL car.  Hope you get it running again soon...and please feel free to take gratuitous pics of anything/everything!  

Edited June 4, 2013 by T-Bone028

[steve260z]

Besides the great car the videos are great! Thumbs up to the video guy.

Like the 240 as well. 

[Xnke]

CHECK FOR VALVE TO PISTON CLEARANCE when you reassemble. It's likely that if the cam is not very very close to where it should be, it'll hit. Any big cam like that needs to be checked, it may be that you need deeper valve reliefs in the piston. (I think this is very likely.)

 

When you get into long duration cams, it may not hit when installed straight up, but retard the cam a few degrees and the intake might hit, advance the cam and the exhaust might hit. Even better chance with a high lift cam like that one.

Edited June 5, 2013 by Xnke

[ctc]

Double check your head gasket thickness as well if you changed it. That can cause contact on a tightly clearanced engine. When I built my stroker, I had to recut the pistons because of an error in compressed gasket thickness.

[ericbauer]

Thanks for all the kind comments guys!

 

Yes based on what I've figured out about the car it MUST have been regularly tracked back in Japan...
I'm TRYING to have someone do some research for me through Japanese DMV to track down PO.

I found a clue that the engine was probably built by RH Factory in Nagoya - they are out of business now, but they used to be pretty famous for their L6's...

 

The intake port job is massive. Out of curiosity, while i had it out, I asked Rebello to flow the head & he confirmed that below 7500rpm it's ported way too big, but above... it really sings. It came with an 8500rpm rev limit in the MSD 7 box... funny how the Japanese seek out US parts and some of us here in the States seek out Japanese ignition parts.

 

There was an older thread on here that described some wild Japanese L6 stroker builds with massive intake port jobs... well that's more or less exactly what I've lucked out with apparently.

 

Considering how wild the cam specs are, it really wasn't THAT bad on the street. Definitely not ideal, but not horrible either.

I drove it 750miles back home to SoCal when I first picked it up. Epic drive through the desert!...

 

I got to open it up at WSIR and it felt oh so good...

 

I've been waiting too long to get a car like this & it means too much to me that I knew I was never going to daily drive it.

When I rebuilt it (or errr.. tried to) I decided to respect the obvious intents of the previous owner and did not detune it.

I'll be running 100oct from the local Union76 at nearly $9/gal. Pricey? Absolutely! but oh so worth it, I think.

 

The headgasket I used during the rebuild was the same measured compressed thickness as the one I removed.

I was able to remove it without bending/damaging it so I'll keep it around for test re-assembly.

 

I'll re-read BRAAP's sticky again and see if I missed something - thanks for the link.

 

 

-e

Edited June 5, 2013 by ericbauer

[ericbauer]

I thought I'd post an update since it's been a little while.

 

I tore the Skyline's block apart and proceeded to compare/contrast the new JE pistons, with the cast Nissan pistons my stroker came with:

The ONLY difference I found is that the JE pistons' valve pockets are 1.5mm shallower than the cast pistons my engine from Japan came with.

 

I've also confirmed that my six exhaust valves are bent.

 

JE pistons are at machine shop to see if there's enough material to drop valve pockets a further 1.5mm

I've been told my bearings and rings are ok to re-use.

The head's waiting for six new valves as well.