proengines

A lot of the time it's what's not said that says the most.

I might have an answer to that problem, we had an engine come in recently with a similar problem and the main tunnels measure spot on for diameter but the tunnels were out of alignment. It chewed out the main bearings within a couple of thousand km. I machined the cap registers and closed up the tunnels to hone them but after honing the tunnels aren't quite spot on so we are starting with another block. It might be worth running a straight edge along the main tunnels or the cap registers and checking. This block measured .003"-.004" out when I set it up in the mill and checked it with a dial gauge. The crank would have been running bent the entire time and you could see where it had been running hard against the bearings by the marks on the main journals so there was no oil film between the crankshaft and the bearing in different spots. Tunnel boring it would have increased the piston protrusion and affected the oil pump alignment so that wasn't an option. Speaking of ACL, I had a visit from Paul from ACL last week and had a good discussion about bearings and from that, and because our current supplier of King bearings has for some reason decided to stop importing them, I'm going to change to the ACL race series bearings for the RB's and use them in 2JZ's. It's nice to see a company that does stand behind their product and takes input from their customers seriously.

You don't need to trim down the VG30 bolts, they fit without the extra few threads causing any problems. We sell the Eagle rods for $1050 a set, they are a very nice rod for the price, easily comparable to others that start around $1500 a set. We can do them cheaper for multiple sets.

If you're using aftermarket manifolds, knock the bump out. It's there to match up with the standard exhaust manifold where it kicks in around the manifold stud so you can tighten the nut. Taking it out is worth between 5 & 10% flow on the flowbench. Using the standard manifolds though you will probably lose performance if you take it out as you will have a square edge that the gas will hit on the manifold.

I just checked 2 sets of pistons, one ACL and one Ross which are both the same piston. At the nominal bore size they run .004" clearance at the bottom of the skirt and have .002" taper from the bottom to the top of the skirt which is normal for a forged piston, they are smaller at the top of the skirt because it runs hotter than the bottom and expands more. Do your pistons measure .007" smaller than the nominal bore size at the bottom of the skirt? this would be 3.3985" for .020" (.5mm) or 3.4182" for .040" (1.00mm). The bore should be 3.4055" at .5mm or 3.4252" at 1.00mm. Just out of inerest, was the block torque plate honed? It looks as though the top ring hasn't been sealing in the areas directly in line with the head bolt threads. I've seen similar bore scuffing to what you can see in the photo on the thrust side of the bore due to preignition. I'm not saying that there isn't a piston problem, on the basis of one photo it wouldn't be possible. I just think it is worthwhile assessing all the evidence available before coming to a conclusion. It would be worth your while to have a failure analysis done by a third party who can give an impartial report on your engine. If threads start popping up about the same issue with the same pistons it would be a sign that there is a piston problem but when you think about it objectively, your 6 pistons would have been part of a batch of 300 or 500 pistons machined from a forging that is more than likely used for thousands of pistons and to get 6 pistons with exactly the same fault where other sets in the batch don't have it would be highly unlikely. It's understandable you are pretty pissed off with having to pull your engine back out because there is a problem but apportioning blame shouldn't be the first thing you do. A thread asking if anyone has had a similar problem with the same product would make sense and could be quite enlightening. An ACL product warning based on one case is probably a little premature. ACL do actually issue product warnings/recalls for parts that they have found problems with and compensate for them.

Have a chat to the dealer and then to nissan and explain that it may not be good publicity if these kind of stories make it into the mainstream media. A set of discs and pads would be cheap for them compared to the sales they may lose if this becomes common knowledge. Toyota had a problem over 10 years ago with the turbo diesel landcruisers hammering out bearings and it was looking like a real problem, they turned it around by replacing the bearings and fixing any cars that had this problem. They still cover the problem now, 10 years or so later because they cant afford to lose the buyers. Did you see there is a set of front brakes for sale on the parts for sale forum on here?

It has had the alloy plugs that seal off the oil galleries in the crank removed and been tapped to take screw in grub screws to seal the galleries. You need to remove the old plugs when you rebuild the engine to clean the crank properly. It's a good thing, whoever did your engine did it properly, it doesn't affect anything else.

Pete, $80 for mains, $80 for conrod brgs. I just have to make sure they are back in stock, a shipment should have arrived by now. These are RB30 mains, I just drill the extra feed holes.

The ACL's are a good bearing, the race series bearings have a hardened steel backing which keeps them well located in the housings even when they have had some heat. They are fairly soft which is a good thing if there is anything floating around in the oil as it can embed in the bearing. They are not hard on the crank either, not really an issue with an RB as the crank is pretty hard to start with. I still prefer King bearings, the material is better, only one layer of bearing material about .015" thick on a super hard backing, the alecular material has a melting point almost 3 times higher than the babit on a regular trimetal bearing so there is less chance of delamination even under extreme loads and heat. Nissan bearings are made by NDC and are a trimetal bearing, I have seen these delaminate when they cop some detonation. I haven't used Nismo bearings, I'm still pretty sure that they are a trimetal bearing, one benefit I suppose is you can buy them graded to adjust clearances but then if the bearing housings are not on size they should be remachined anyway. I haven't had problems getting spot on clearances with the king bearings, all the bearings in a set are guaranteed to be within .0001" tolerance so there is no chance of tolerances stacking up and changing clearances. The other benefit of Kings is the price, they're cheap as dirt compared to Nismo bearings as they are a standard replacement bearing.

The HX bearings run an extra .001" clearance over the H series.

Big lift and short duration is normally better than low lift and big duration, thats why so many pushrod engines now run roller cams, they can lift more for the same degree of camshaft rotation and the area under the valve (if you graphed it) is much greater for the same duration, meaning more gas can flow through for the same duration. This works very well for a n/a engine but with turbos it is a little different. An RB can run a fairly agressive lobe due to the large bucket diameter and can lift fairly quickly. I think it is worth running a fair bit of duration on the exhaust cam as you increase the time that exhaust gas is flowing out of the port and I'd say it provides smoother exhaust flow to the turbo, especially with twin turbos where you only have 3 cylinders feeding each turbo which means only 3 pulses every 2 rpm. Extra duration on the intake cam usually means more overlap (depending what sort of lobe centres the cams are set on in relation to each other). A little extra overlap is a good thing (apart from at very low rpm) with a turbo engine as it provides good scavenging. The overlap is when both valves are open at the same time, at the end of the exhaust stroke and beginning of the intake stroke and with a turbo engine there is air being forced into the cylinder which means that more of the burnt gasses can be purged from the chamber allowing fresh air and fuel to fill the chamber and a better charge to burn on the next stroke. This is called scavenging and is a good thing for power. A lot of 2 stoke diesels run superchargers, turbos or both for just this reason. You also lose a little of the fresh charge out the exhaust which will burn in the exhaust and expand, keeping the turbo spooling. That's a really long winded way of saying I think it is worth running some extra duration, for a street/strip/track combo engine, I like the HKS 264/8.7mm lift cams, they make a lot of low rpm power and spool the turbo quickly. The last one we did was running a 35/40 single with a fairly small exhaust housing and was making 18psi under 4000rpm. Peak torque was under 5000 and was almost a flat line from there onwards. It made an easy 320rwKw at 7000 and would have kept rising but the ignition was breaking down (coils). I just thought I'd add, the 8.7mm lift is the actual valve lift, the lift on the cam is 9.1ish but once you subtract the .4mm or so valve clearance it comes out at 8.7, I'm pretty sure the Tomei 9.1 lift works out the same way. By the way, I love that word "fettling", reminds me of the old pommy educational movies they used to make us watch as a fitting and machining aprentice. I can just see an old guy with a shirt and tie and a dust coat using a bearing scraper to "fettle" an RB head.

If it is a copy of the jun baffle it's better that the tomei one in my opinion. When you fit the tomei ones you lose part of the windage tray setup, that being the piece that the jun style baffle is welded to. The tomei ones supply a thin plate that bolts in instead with no louvres etc.. The jun style baffle has 4 large trapdoors that allow a lot of oil to flow in around the pickup, the tomei one has some holes with rubber flaps that don't allow as much oil to the pickup. Either work better than no baffle but I'd go for the jun style one. We've used them in 8 or so engines and not had a bearing problem since. Performance metalcraft does some nice work so I imagine it's very well made.

Guys, if anyone is interested, Eagle H-beam rods are now available for RB25's and RB26's. Eagles are a great rod, we've used them for years and not had one fail. These are a straight drop in and use ARP2000 3/8" bolts. The best part is the price, $1150 a set, if people can organise to buy 3 sets between them they will be just under $1000 a set. Adam, I wasn't holding out on you about these, I only got the details this afternoon.

Pete, .050" timing is what most cam manufacturers use as it's where the lift becomes a little meaningful. SAE timing is at .006" lift from memory. It doesnt really matter what you use as long as it's repeatable, RB's are a bit of a prick to measure lift, I made up an extension for the dial gauge that bends in under the cam and down again, you just need to be careful that you get the gauge parallel to the valve axis each time.

You wont need to machine the head to fit those cams, that's why they make them with a smaller base circle. If the base circle diameter is 2mm smaller and the distance from the centre of the cam to the top of the lobe is the same, you will have 1mm more lift without increasing the height of the lobe. You will have to use shims 1mm or so thicker as the clearance is set between the bucket and the base circle of the cam.

Just a tip, have a very close look during assembly at the clearance between the oil squirter and the side of the piston, if you move the piston from front to rear in the bore you will see they run very close. We modify the locating lug on the squirter slightly to move the squirter away from the piston.

That's a really odd failure. The small end clearance is only .0002-4" which is really just enough for the pin to push through with light thumb pressure. How long did the engine run before this happened? It's strange for there to be enough side load on the pin to force the side of the piston out, even with the pins seized in the rod. Any decent engine shop will warranty their work though, have you spoken to the shop yet?

Going off that first picture I'd be 99% sure it's had a gudgeon pin come out and been running against the bore. Do you have any closer up photos?

That price sounds pretty good! We use a vertical mill with a 14" flycutter running at around 850rpm. I'd love to have a dedicated surface mill but can't justify the cost for the volume of work we put through.

.010mm is 4 ten thousanths of an inch. .010/25.4=.0003937" I'd run the pistons with the clearance they have built in to them, maybe .0005" less for a street engine. Remember that if you finish the bore to smaller than the nominal size, every .001" smaller in bore size will close up your ring gaps by around .003" (using Pi*diameter) The Venolia's run extra clearance cold as they have a lower silicone content that others and have a greater coefficient of thermal expansion, so when they are hot the clearance will be similar as they expand more and take up the cold clearance.

Off the top of my head an Ra of 25 or less works fine, we use a CBN cutter on the block and a PCD cutter on the head. Waviness is important too, we've had blocks come through that have been surface ground and look great but you find that the grinder wheel drops down where it runs across the bores and rises up between them where there is more metal to cut. Sometimes it takes .003-4" to mill them flat again. I think any finish that you can catch your fingernail on is probably too coarse. (very cheap Ra gauge!) I've heard that the new ACL MLS gaskets are made by Cometic. If the price is right though it may be a good thing.

A cometic MLS gasket is $330 or so. We've used them for quite a while without any failures. The block and head do need to be very flat and have a good surface finish to seal properly, it's the same with any MLS gasket.

The ACL piston in the photo above is made by Ross. The milled spots under the head of the piston is where they normally have the Ross brand. They also use spirolox where mahle pistons use round wire clips. All the mahle performance pistons are a dark grey colour rather than shiny alloy. ACL don't really try to hide the fact, they also supply Ross with the piston rings they supply with their kits. The ACL pistons for the RB26 are a little too thick in the skirts in my opinion, you could lose a fair bit of weight without losing strength. Compare them to a Wiseco or JE and you'll see the difference.

Get hold of a manual master gauge and check the pressure with that. Most workshops would have one and probably wouldn't charge much to check it for you.

I think I've posted something before about this, We've used Arias, CP, ACL/Ross, JE, Venolia, Wiseco and SPS pistons in RB engines and never had any of them fail because of piston design or material problems. Some have advantages and disadvantages, from my experience Arias are a nice piston, well finished but the rings supplied are a little ordinary. CP are a very nice piston, the same sort of quality as JE and both run fairly tight clearances. Ross makes most of ACL's forged "sport compact" style pistons, these are solid, great sizes, really good rings but do run a little extra cold clearance because of a lower silicone content which does make the piston a little tougher. They are also a bit heavier than others. Venolia pistons are tough as nails but run big clearances, a little more than ACL/Ross. Venolias are supplied without rings and there are some pretty ordinary ring sets being sold with them, some even with a cast top ring. Wiseco pistons are excellent all round, well finished, good balance, great ring pack with narrow 1.2mm steel top rings, round wire clips, most have coated skirts and small cold clearances. SPS make great pistons, they are a little dearer than most but they will make exactly what you want, whatever ring style you want, weight etc.. With the cold noise issue, as a rule of thumb, the lower the silicone content of the alloy used the tougher the piston will be, as the silicone content increases, the clearance decreases but the piston becomes slightly more brittle. There are other advantages/disadvantages of different silicone contents and people will argue until they're out of breath what is better but really it depends on the application. For a street engine that is driven regularly and doesnt get a proper warm up something with a slightly higher silicone content will work better as the piston is more stable in the bore even when cold. For a race car this doesnt matter as much as the engine is warmed up before it is driven. Materials are improving, most of Mahles range now are extremely strong and run tiny clearances, their Subaru pistons are only running .0025" clearance which was pretty unheard of a few years ago for a forged piston. Eventually they will be available for most models but currently their market is dictated by what sells in america, so Subaru, Mitsubishi, Honda and Toyota are well catered for. They will make custom pistons for anything but it's a slow process as their production is dictated by Nascar customers as that's their biggest market so custom orders can take a while.