Dale FZ1

Get the shaft checked that it is straight and true. If there is a slight bend, you have trouble. If your oil gallery is clean + clear of obstruction then you'd be looking for something else to have caused the contact between journal and cap. Any reputable cam specialist or reputable engineering shop could do the check for minimal $$ and before you go doing anything with the head that may not need doing.

Get the camshaft checked for runout especially on that journal.

Try one if you have access to it, otherwise make adjustments to the stock bracket with an angle grinder. Cutting disc and a sanding disc worked well for me

+1 An overlay would be great - especially if it's torque before/after. Maybe you could consider playing with cam timing and move the torque curve around to suit your goals, and then get more serious with ignition timing. Carbon deposits can cause problems with hot spots and preignition, but that doesn't seem to be something commonly encountered by people making mods?? Properly configured water injection will make a difference in controlling knock, but if your main aim is bigger power numbers then best go to a GT3037. Be interested to know if you've got a 0.68A/R turbine housing too.

+1 If it takes time to get this done, then get the return date for vehicle inspection extended. Pointless to spend $$, time and effort just to do some half-arsed "fix" that isn't. You might beat the authorities, but really you're only cheating yourself. Third defect in 6 months suggests other more major issues to attend to?

I'm assuming most people do not install the tensioner spring and stopper, and manually tension the cam belt. What sort of deflection is generally seen in the belt when tensioned? I've done mine until it feels "right" but what is generally achieved by those doing their own?

I found the R33 spec factory manifold gaskets pretty well matched already, but checked and touched up both sides where necessary. That lump in the exhaust port I smoothed out the sharp leading edge considerably and blended them in to the overall port shape. The short radius in each port, leading onto the seat was where I spent a fair bit of time. Ex-factory that really was an abrupt edge and needed work. Overall, not much material taken out but quite a bit of finishing work that the factory doesn't do. I'll have an idea later this month if I'm happy with my work New head bolts not essential, but aren't expensive and should be replaced if the engine will see a bit of work.

I think it depends on the intended use of the car. Agreed that putting in a numerically higher ratio will equate to a wider road speed range, but with 4.1 ratio it's still geared to at least 250km/h in 5th. Who wants to go faster than that? Retaining stock diff ratio with the extra grunt of the 30DET should provide fewer gear changes but may give rise to more frequent traction issues when driven in anger. I do think it's a matter of preference, and I'm not considering a gearing change for my setup. Aaron seemed to think his 2.5 is a touch busy on the highway, so I'm interested to hear experiences after making changes. Probably a good idea to do the engine first and diff later for a definitive answer. From memory Cubes tried it long ago.

You could try swapping in a Z32 spec diff, but why bother? You're then reducing the torque multiplication at any road speed in any gear, and undoing the purposes of building a bigger engine with more torque. 3.9 gears would probably make it a touch less busy and may achieve fuel consumption improvement but you'd never recoup the cost in terms of fuel savings. I'd only do it if that made the car feel how you want it to.

Get more specs. Those impeller dimensions seem mismatched. Are you sure the compressor exducer (max size) isn't 71mm? Lardy Stagea would do well with GT-RS or perhaps a Garrett GT3071 0.63 if boost control could be guaranteed. Impeller sizes on those are ~ 71.1mm comp, and turbine 53.8, 60mm respectively.

I think this is one of the biggest hurdles. You need to know what the parts are, and that they are spec'd to work together. Then the actual assembly of things has to be first rate. Things like matching the turbine to manifold are important and can't be overlooked if you want an engine to have a realistic chance of making the power its parts are spec'd to support. Big difference in flow requirements for 370 and 480rwhp if that's what you want to target. Can only suggest dropping the system to double check, especially if you potentially have a back pressure problem to chase. If you want 20psi boost, then install a spring spec'd to 20psi. Make life simple, and use your controller to stop creep and bring the boost rise on sharper. Are the comments about lumpy idle disappointment about the sound, or nagging concern that maybe the cams installed aren't what you believe them to be? That's a lot of lift to be having in a 25 head - was it machined to accept the cams? Maybe the tuner is producing the best results with the machinery presented?

I'd be looking for something with a bit of quality and suitable for forced aspiration. The top ring construction/design has to deal with a lot of pressure and heat so you'd be best to chase something chrome/moly. Talk to a reputable machinist rather than put yourself out on a limb. Quality rings aren't super expensive, and obviously you'll be needing other parts (gaskets, sealant) to put a 30/25 together. Work out with them what you need and order it in one hit.

Boost falling away at the top end is normally a sign of rising backpressure, which is why I'd suggested the exhaust system as first area to check. Is the muffler/s a proven thing? Easy to confirm your belief about them by dropping the system from just before the cat, and run on the dyno like that. If it makes the power then that would be where you spend money to fix it, otherwise it's cost you bugger all and given ideas where else to look. Something that I've seen overlooked is whether people port match the T3 housing flange to the divided T3 stock manifold. Trying to force great quantity of air into the turbine past that 5-6mm lip is going to cause a lot of problems with efficiency. If your tuner has the experience he would surely be looking at these obvious things anyway? What plan has he got to find the problem? A couple of pics of your engine setup and current dyno sheets would be good..

1. Look at the exhaust being overly restrictive (mufflers, cat) 2. Same for inlet/filter 3. Check to see your unions at all points between compressor and throttle are perfect. Where is the boost gauge feed being taken from? From the manifold, closest to the inlet valves is best because that accounts for losses through the entire inlet tract. The unknown factor of compression ratio is a bit problematic because that will have significant bearing on what boost ceiling you should set. The cam and turbo spec suggest you'd be chasing 500rwhp out of an engine that can hold power to 7500rpm, but no sign of porting, quality exhaust manifold (6boost style), crank balancing, or a quality harmonic balancer to deal with those revs and mass-flow throughputs. All components have to work together. From the first post though, you should find 400rwhp an easy target to hit, so check the three suggestions. Good luck and keep us informed.

The limitation on cam lift comes from valve spring dimensions, and how much they can be compressed before encountering spring bind. You'll strike some variance, but without machining the head to counter that problem my RB25 head was best spec'd with max lift under 9.0mm. It is something best tested on the bench with measuring equipment, and in consultation with a spring supplier who will work with you or your machinist. My view is that the 25 head is a sound "street" spec head, while the 26 is made for "race". Uprate your cam spec for sure, but keep it under 9.0mm / 265 degrees and it will serve well. If you want more than that probably best to go straight into a 26 head and use the bigger/better hardware available for it. I don't see sense in spending money on a 25 head to try to emulate the results of a 26.

Pump won't come off without sump off first. Removing and installing sump in-car can be done but it's messy and difficult to ensure a good oil-tight engine when reassembled.

Having seen both on a bench, the 26 offers bigger exhaust ports, and allows for the fitment of significantly higher lift cams vs the 25 head. Didn't measure the valve sizes, but exhaust valves in the 26 looked maybe +1mm as well. To me, that means the 26 head is a better platform to make big power. That said, there are plenty of 30/25 combos producing ~ 300rwkW and not revving hard to do it. While I think the 30/26 is a better thing, whether you get much chance to demonstrate that will depend on where you run the car and how much $$ you pour into the build. eg. for an 8000rpm 30/26 you'd be wanting forged rods, very good crank balance, very good harmonic balancer, and oil pump. The bills add up quickly if you want to spin the engine hard.

Here's the comparison of spring sets. The small difference between the two mains is evident, and it is about one full coil. There is noticeable extra preload required when installing, but I don't believe it will give a ridiculous boost to oil pressure. The effect is probably similar to adding a couple of washers/shims into the standard stack as Joel has done.

I've looked at the desired operating oil pressure as having to fit with multiple parameters set by things including bearing clearances/quality, top end restrictor sizes, operating rev range, power loading on the crank, drain-back capabilities, and the capacity of the pump itself. In many ways it's like sizing up a turbo - you're balancing pressure against the total actual flow requirements. Even the oil viscosity comes into the equation when you think about it. The flow has to be efficient, and geared to the engine's needs (and hence the reason for the original question). Mine is not going to be an "extreme" engine - far from it. It fits the bill as a straightforward 30/25 build, with some attention to detail using mainly stock type parts. That means revs limited to 7000 and power around 280-290rwkW; but it will be used often in club events. It's not a show pony build but something to be used for a purpose so it has to survive. At first glance Cubes seems to be running higher than "desirable" pressure, but it hasn't resulted in any failures for him . Still it is worth knowing the oil pump spec he has when trying to decide optimal sizing for the oil feed restrictors to the head. On consideration I have decided that the slightly heavier spring will be used, and I will monitor the results from this. I will post pics of the comparative spring sizes since it seems Cubes is the only engine builder to have tried this mod and be prepared to discuss. I'm happy to share any results as perhaps most other people swap in stock pumps without any other changes. I'm working on the idea that a mildly upgraded engine requires some mild improvements to the oiling system which can include operating delivery rate. Using stock pump gears, this would be achieved through bumping up the operating pressure within sensible limits. I think Michael's rule of thumb looks good, and thanks for the advice If I'm not happy then I have the ability to revert it to stock. Any other comments from those who've actually played around with this stuff is welcome - cheers.

That's what my Bosch belt is cross referenced against.

When I think back to Grade 10 high school chemistry, I recall that chemically combining compounds resulted in products with significantly changed physical properties. This includes their molecular weights and densities. The same concept applies to burning fuel in your engine via the 4-stroke process. My recall is now not as good, but if you know the chemical composition of your petrol it is possible to work through a few chemical equations to get an idea of the difference in total combined molecular mass pre and post-combustion. High school chemistry will only get you so far though, and engineers are a quantum step beyond that. Engineers know that when designing and sizing different aspects of your 26DE head they need to factor in what it takes to shift gases that will change their physical properties during combustion. Therefore you will always see inlet valves and ports bigger/better flowing than the exhaust. Provided your flow bench has shown a measurable improvement from stock to modified, you have had some sort of a win.

No issues with the workmanship on the pipework there - looks very neat. Was there any sort of modelling done to arrive at the length and diameter of your runners? The ID tag on the cartridge indicates a GT3282 plain bearing unit. I'm presuming it is a split pulse housing you've used. Any more information on it?

Has anyone tried modifying their operating oil pressure by changing or shimming the springs in their stock pumps when putting together their engine? I've seen the comments about stock 26DETT pumps vs the N1. Checking over a stock 25DE vs 26DETT pump I noticed that the 26 has a main spring ~ 6mm longer than the one used in 25. Otherwise they appear to be the same spec, and the inner helper springs are identical. The heavier spring should give a higher operating pressure but I don't know if it's worth bothering. Bearing clearances are stock spec so there's nothing to gain there. Interested to see if anyone has modified their stock pump like this rather than using N1 pumps etc. And if so, what resulted?

During my initial evaluation of the compressor map for your 3071, I felt that the compressor was not likely to do better than ~ 260-265rwkW on a mechanically stock RB25. (ie. no cams/porting). To be honest I still have that opinion, but can wear a plus/minus 5kW variance. Using the similar but different HKS 2835 Pro S there have been exceptions claiming up to ~ 290 but I don't reckon that was representative of the breed. Remembering that phrase pressure differential across the engine and what it entails might give a guide where to look for further improvement. Now if it feels like it is nosing over somewhere around 6000rpm there is sign of a restriction that may be causing torque to drop off prematurely. As I commented about my 3037 Pro S setup, it held maximum power for over 1000rpm - a good outcome in my books. Yours should be able to do something similar. Checking back through your thread, it is possible that the exhaust system is responsible for a post-turbine restriction that effectively causes a raised pressure differential across the engine. More boost then does not equal more mass-flow, and hence the power noses over. Assuming I'm right, if that restriction is dropped then you should find the torque @ 6000rpm plus does not fall away as quickly, and your power output will climb. example: Pulling out the removable baffle in my system gives a 23rwhp gain without any tuning changes. But in that instance the noise gain is intolerable for the road. I'd reckon that is the first place to check, although cams are definitely part of the equation if chasing higher levels of system efficiency. Examine your dump design and diameter up to the cat, and consider the muffler configuration.

Definitely the mechanical process of changing components isn't difficult. And if your preferred supplier is prepared to wear the cost of carrying the cost of surplus parts from the build then it sounds like you're onto a win-win case. My concern would be as consumer having to wear the cost of a complete turbo + GT30 rotor + housing + rebalance. Bear in mind that with the shift to physically smaller TO4B syle comp cover it probably won't shift the top end mass-flow as easily as the T04E, but eliminating the need for a turbine spacer would be a positive. If you're serious I want to see pictures of this unit being built and installed, and most importantly given a comprehensive rundown on how it goes on your 33. I'd even fly down from Queensland to see for myself if invited. Keep us updated because this could be an interesting variation on the 3071 spec. I have to say it appears an odd mix, and wonder why HKS with their specialty mix/match range for the Skyline didn't make something similar. cheers