A Few Camshaft Questions

[XYZ]

Hi all,

 

If anyone could assist with their knowledge I'd appreciate it.

 

I've just had my car back from the mechanics, who have suggested a new cam grind be obtained due to fairly flat performance/acceleration.

 

It's a 260z with an EFI 280Z engine and 5 speed manual. It has extractors and I'd say a 2.25" system. All else seems fairly stock, with a new scorcher electronic distributor having been fitted the other day.  

 

It makes a fair bit of noise from the muffler, but doesn't accelerate with any 'snap' or 'urge'. It just doesn't feel like a 6 cyclinder should! My mechanic seems to think it is lacking from about 3500rpm, but I think it's lacking across the entire rpm range - indeed, there's no danger of it even breaking traction in first gear.

 

Or, I'm thinking I might just be a bit of an unrealistic prat given this is an old car and I'm used to big engined modern cars? 

 

A 25/65 cam has been suggested to liven it up a little. I've been quoted between $800-$1000 to supply and fit same (a new Tighe cam, not a regrind).

 

Any thoughts or suggestions?

 

Regds

 

 

 

[PB260Z]

Hi Mate

 

What ratio diff are you running ?

My car has the same engine & gearbox, i changed to a 3.9 (was 3.5) and the difference was noticable. Still not a rocket but definately more spirited.

 

Cheers

 

PB

[C.A.R.]

A cam won't fix what you're describing. It sounds like there is an engine issue - possibly related to tune.

 

Either that, or you have a tall diff ratio fitted. Do you know what the ratio is?

BTW avoid Tighe cams. Order a 733a from Clive Cams in Melbourne.

Edited February 5, 2016 by Lurch ™

[HKSZ]

do a compression test first

[XYZ]

Thanks gents - much appreciated.

 

I'm not sure as to ratio, nor am I sure how to tell. It sits on about 2600rpm at about 100km/h if that gives any indication.

 

I'm sure my mechanic tuned it as that was one of the things on his to-do list - it got new plugs with the distributor. I did notice some tell tale cracking in the rubber hose between the manifold and air filter, but am not sure if this has cracked all the way through. Just remembered too I also noticed a very very minor and sporadic miss in first gear when under light acceleration (ie slow travel through a car park)

 

I think I'll just need to source a mechanic familiar with Nissan/Datsun here in Brisbane to sort these issues out for me! Bloody old cars!!

 

Thanks again guys

[dat2kman]

Yes,,, get a Clive cam.

Even though the other mb s lcal.

You running stock EFI setup as fitted to the L28 E?

 

If so, did your bloke get the injectors cleaned and tested, stock flw 18cc at 100% duty.

Cleaning should improve spray pattern.

Also do nt go to "wild" on the cam, as the EFI setup rums an Airflow Meter with a spring laded flapper valve, a aggresive cam will cause flap valve to jst touch the 0 volt sensor segment, which shuts engine down. ( increasing dle speed, and altering tension n AFM flapper solves this, PITA to get it right!)

 

You couod also have fitted the not so hgh flwing twin butterfly throttle bdy, these are ex California smg/EPA requirements, and really stifle airflw.

A swap to an XF Ford Falcon throttle bdy s a bg imrovement.

[PB260Z]

Hi,

 

Standard diff ratios for a 2+2 are Manual 3.7 and Auto 3.5.

 

You memtioned that you had a cracked air hose. The L-Jetronic system relies on zero leaks between AFM & Head for best performance. Any air leaks will result in the car running lean and depending in how bad also running rough and missing.

Power delivery should be linear from just off idle all the way up.

 

Cheers

 

PB

[C.A.R.]

 

I'm not sure as to ratio, nor am I sure how to tell. It sits on about 2600rpm at about 100km/h if that gives any indication.

 

 

There is your problem.

Was the car an Auto before you the 280ZX engine & gearbox was fitted?

 

If what you say is correct, with the RPM Vs highway speed, I'd say you have a 3.5 or even a 3.36 ratio diff fitted.

 

Fit a 3.9 and the Zed will come alive

[PB260Z]

Just thinking, is your speedo acurate ?

If it is then looking at the colour of the drive gear will tell you diff ratio, and easier than popping the diff cover off.

Another way to tell is count the input v output revolutions

[HKSZ]

I autocrossed a 280zx and tweaks that cost nothing are

 

set 17deg advance running 98 fuel

run some injector cleaner

take rocker cover off and move cam sprocket to number 2 hole

release AFM spring by two teeth

adjustable potentimeter on cold temp sensor

[XYZ]

Again, thanks everyone for your interest and knowledge. 

 

Yes,,, get a Clive cam.
Even though the other mb s lcal.
You running stock EFI setup as fitted to the L28 E?

If so, did your bloke get the injectors cleaned and tested, stock flw 18cc at 100% duty.
Cleaning should improve spray pattern.
Also do nt go to "wild" on the cam, as the EFI setup rums an Airflow Meter with a spring laded flapper valve, a aggresive cam will cause flap valve to jst touch the 0 volt sensor segment, which shuts engine down. ( increasing dle speed, and altering tension n AFM flapper solves this, PITA to get it right!)

You couod also have fitted the not so hgh flwing twin butterfly throttle bdy, these are ex California smg/EPA requirements, and really stifle airflw.
A swap to an XF Ford Falcon throttle bdy s a bg imrovement.

 

I'm pretty certain it's stock. I'll take some pics of the engine/efi and post it up.

 

The mechanic didn't clean the injectors.

 

 

Hi,

Standard diff ratios for a 2+2 are Manual 3.7 and Auto 3.5.

You memtioned that you had a cracked air hose. The L-Jetronic system relies on zero leaks between AFM & Head for best performance. Any air leaks will result in the car running lean and depending in how bad also running rough and missing.
Power delivery should be linear from just off idle all the way up.

Cheers

PB

 

I'll put a smear of silicone on the crack and see if that works.

 

I drove it again on the weekend to reassess and there is a bit of acceleration urge in the lower rpm and then upon reaching higher rpm, it just doesn't accelerate with any urge - it's almost (non turbo) diesel-like, if that  makes sense ie once it hits about 4000 rpm, you can plant your foot flat and it doesn't react as though your foot's flat.

 

 

There is your problem.
Was the car an Auto before you the 280ZX engine & gearbox was fitted?

If what you say is correct, with the RPM Vs highway speed, I'd say you have a 3.5 or even a 3.36 ratio diff fitted.

Fit a 3.9 and the Zed will come alive

 

I checked the plate and yes it was an auto. Can a standard diff/gearbox place fit this ratio off the shelf or would I need to order parts from a specialist?

 

 

Just thinking, is your speedo acurate ?
If it is then looking at the colour of the drive gear will tell you diff ratio, and easier than popping the diff cover off.
Another way to tell is count the input v output revolutions

 

The speedo seems pretty spot on.

 

 

I autocrossed a 280zx and tweaks that cost nothing are

 

set 17deg advance running 98 fuel

run some injector cleaner

take rocker cover off and move cam sprocket to number 2 hole

release AFM spring by two teeth

adjustable potentimeter on cold temp sensor

 

Thank you HKSZ

 

Thanks for your help gents. Kind regds

 

 

 

[PB260Z]

I checked the plate and yes it was an auto. Can a standard diff/gearbox place fit this ratio off the shelf or would I need to order parts from a specialist?

Yes, any competent Diff / Gearbox shop can do the swap

However you need to confirm what diff is in it now, Ratio, R180 or R200 and which type of half shafts ?

 

A photo of diff will answer the R180/R200 question

 

 

 

Cheers

 

PB

 

PS: have you got a couple of EFI workshop manual ? it is simply written and explains not only the operation of the system but also trouble shooting.