Engine now in - Datsun Spririt SCR Stage III 3.0 3 L28 Engine

[Albrecht]

The carbs need work. I levelled the floats (all over the place) but I need to install vibration dampening mounts with Thackeray washers.

I strongly advise you NOT to bother with the vibration dampening mounts and Thackeray washers. Complete waste of time on a Nissan L6 engine. It just doesn't need them.

As you clearly have a Harada intake manifold, the supplied and fitted phenolic spacers and gaskets are all you need. They carry the gaskets, and act as insulation against heat transfer. 'Solid' mounting the carbs is absolutely fine on these engines, and any talk of carbs 'frothing' is from the four cylinder world with completely different engine harmonics.

You'll hear lots of people telling you you need them, but please trust me - you don't.

 

[SKiddell]

I strongly advise you NOT to bother with the vibration dampening mounts and Thackeray washers. Complete waste of time on a Nissan L6 engine. It just doesn't need them.

They do have one advantage, they carry an O ring which can be of great help when trying to get a good seal between components which may have an uneven surface.
Other than that, I agree, why is the secondary tuner altering the mechanical timing by anything more than a few degrees (often required to get optimal tune on the rolling road or dyno).

 

[jonbills]

Nick, the cam timing may have been even worse than you say; I'd assume Eiji set it originally in the middle of the adjustment range, so your tuner moved it one tooth and 3 marks. Each mark is 4 degrees of crank so total change would have been 18 + 12 = 30. Which is a lot.

 

[SKiddell]

Nick, the cam timing may have been even worse than you say; I'd assume Eiji set it originally in the middle of the adjustment range, so your tuner moved it one tooth and 3 marks. Each mark is 4 degrees of crank so total change would have been 18 + 12 = 30. Which is a lot.

Forget messing with jets and spark timing and focus on getting the mechanical timing correct
If it was set up correctly (and as Alan said Eiji knows what he's doing) then it will have been setup with a degree wheel (once again as Alan said) to incorporate the cam grind.
I would be very careful with this, contact Eiji, (or the cam supplier....looks like Schnieder) find out what it should be set to then get a dti a degree wheel read up how to do it correctly then set it to what the cam card specifies, otherwise you are in danger of pistons hitting valves, even a light kiss will bend one, and until you get the mechanical cam timing right, carb setting is worthless

 

[zedhed]

Gents thanks for the advice on carbs I'm getting conflicting info here from several sources so will research this more. Seeing I've bought the o ring kit already I guess what I'm wondering is can it do any harm?

As for the other question about altering the timing chain position, the answer is "I don't know". I assume their tuner thought the engine was setup wrong. Eiji Sent me photos of the build with the dial guage and a protractor installed on the crank with everything up. Anyway I've reset everything and the car is now driveable. The tuner in question may have gone by markings but he did spot one misadjusted valve clearance and he also re-torqued the sprocket bolts which were too loose so I'm glad he checked it out. He did not get a chance to drive the car, or as he said he would have reset things until they worked. It's quite possible some other issue stopped the car from starting and it just kicked in after he reset things so he assumed (like anyone would) that his changes were correct, and what allowed the car to start. It is only when I drove the car (and logically I believe I was the first to do so) that I realised something was wrong.

Anyway no harm done and the engine is now correctly mounted with enough clearance to put some miles on it without damage to the zircotec coatings which is the main thing.

 

[zedhed]

I can see the piston top through the sparkplug hole at TDC, so I can hopefully use a long lever DTI from work or maybe one of our lasers or a micro bore scope to guage TDC. I just used the pencil method...

But if I put the sprocket back in exactly the same position Eiji did, resetting the valve timing to where it was, then why should I bother with a protractor ? Eiji already did that...

 

[Alphabettispaghetti]

I'm guessing the other 'tuner' was the place who installed the lump?

 

[zedhed]

No Z farm installed the engine and it was tuned by a local outfit

 

[Alphabettispaghetti]

Its good to make that distinction(for the z farm).

 

[jonbills]

I can see the piston top through the sparkplug hole at TDC, so I can hopefully use a long lever DTI from work or maybe one of our lasers or a micro bore scope to guage TDC. I just used the pencil method...

But if I put the sprocket back in exactly the same position Eiji did, resetting the valve timing to where it was, then why should I bother with a protractor ? Eiji already did that...

Yes, if you're sure you've set it all back where Eiji set it, then you're probably safe. But it is easy enough to check it for yourself with a protractor and a dti.
My protractor and dti only about £20 so not a huge investment.
If you trust the damper marks tdc correctly, then you can skip to putting the dti on the valves to check when they open/close or peak lift etc.
To do all this you only need the radiator out. There's loads of info and books around on how to do it.

 

[Albrecht]

No Z farm installed the engine and it was tuned by a local outfit

Sorry to be harsh, but it needs to be said: The "tuner" apparently has no idea what he is doing. Messing about with the cam timing to that extent when it was already set as part of the build by Eiji proves it. It's such a fundamental part of engine dynamics that I honestly can't understand how they came to the conclusion that it set wrong...?

You'll be lucky if you haven't kissed a few valves. Hopefully all will be OK if you're confident you've re-set the cam timing to where Eiji had set it, but if it was me I'd want to be double and triple checking just to make sure anyway.

Putting 'O' rings / anti vibration mounts and Thackeray washers on the carbs and manifold is going to lead to synchronisation and carburettor linkage problems further down the line. These engines just don't need them. Nissan never used them on any of the triple carb kits they made and marketed and never used them on their Works race and rally L6s. They are simply not necessary. They are necessary on other engines where engine harmonics can cause fuel 'frothing' and loosening of jets and fasteners (that's where the default knowledge comes from) but the L6 typically doesn't suffer from such things.


Stick with it. By addressing a lot of this yourself you'll build up your knowledge and experience, and you won't need to use a 'tuner' except perhaps for final rolling-road tuning.

 

[zedhed]

Sorry to be harsh, but it needs to be said: The "tuner" apparently has no idea what he is doing. Messing about with the cam timing to that extent when it was already set as part of the build by Eiji proves it. It's such a fundamental part of engine dynamics that I honestly can't understand how they came to the conclusion that it set wrong...?

You'll be lucky if you haven't kissed a few valves. Hopefully all will be OK if you're confident you've re-set the cam timing to where Eiji had set it, but if it was me I'd want to be double and triple checking just to make sure anyway.

Putting 'O' rings / anti vibration mounts and Thackeray washers on the carbs and manifold is going to lead to synchronisation and carburettor linkage problems further down the line. These engines just don't need them. Nissan never used them on any of the triple carb kits they made and marketed and never used them on their Works race and rally L6s. They are simply not necessary. They are necessary on other engines where engine harmonics can cause fuel 'frothing' and loosening of jets and fasteners (that's where the default knowledge comes from) but the L6 typically doesn't suffer from such things.


Stick with it. By addressing a lot of this yourself you'll build up your knowledge and experience, and you won't need to use a 'tuner' except perhaps for final rolling-road tuning.

I have thought about this and I will stick with the solid mounts for now. As I say the tuner did what he thought was right at the time although I didn't understand the rationale myself, however the exhaust clearance thing was a mistake which should have been spotted. Assuming I ever get my strut brace back from Z Farm I will probably have to bend it to suit the new engine height. It was pretty close already. Perhaps that's why Z Farm never put it back on? I wonder if I'll ever know.

Albrecht, how do I check the valves aren't kissing the pistons? Got a step by step guide?

 

[Rob Gaskin]

No Z farm installed the engine and it was tuned by a local outfit

And so your contract was with Z Farm I assume who sub-contracted the tuner.

So worst case scenario you have a bent valve or two - you may have a problem with the warranty. Let's hope all is well.

 

[Albrecht]

Albrecht, how do I check the valves aren't kissing the pistons? Got a step by step guide?

Now that you've put cam timing back to what Eiji built it with, it should not be happening.

But if any of the valves touched any of the pistons whilst the cam timing was out of specs, they would at least leave witness marks on the piston crowns. Very hard to see with the cylinder head in situ, and I can only think of a borescope/endoscope as your best option.

Very hard to diagnose any slightly bent valves in my experience (very bent valves are easy...) but a leak-down test might help. The easiest way - and I'd probably do this if it was my engine - would be to take the head off if it displayed even the slightest symptoms of valves not seating correctly.

Mention of a valve lash issue by the 'tuner' makes me wonder whether he found this after he'd altered cam timing, or before. Valve clearance changes can be a symptom of valve seat issues (including bent valves...).

 

[zedhed]

Hi Albrecht how do I check if valves aren't seating properly, leakdown test or other method?

 

[Albrecht]

A compression test should give you an idea of where you stand. I'd start there.

 

[zedhed]

I've done that already and all cylinders are about the same within a few psi of each other. Are there further checks I can perform?

 

[Albrecht]

Can't think what else you can do realistically without taking the head off for a look inside. If you're convinced that the compression test results showed a healthy engine, then by all means proceed with final tuning.

If you've got away without valve damage then I'd say you've been very lucky.

 

[SKiddell]

Zedhed.

If you have access to a compressor, You could try a leakdown test (you can make one or buy one), its a little more involved but compliments a compression test, it will highlight any leakage paths when the engine is static and valves are closed, if you have a bent valve it will be heard as a slight hiss from either the inlet or exhaust tract and show up as a percentage loss.

 

[zedhed]

thanks Gents, I will find a compressor, as this sounds like an easy enough check... I would imagine that the cylinders with bent valves would have different compression, and that some valves would bend more than others, and this would cause uneven readings. So because compression is pretty even across all cylinders, I'm hoping there is no problem...