TimZ

Ahem... SHP - Shetland HorsePower

I'm currently using that Nissan head gasket. Yes the gasket is a conventional fiber gasket - metal reinforced as I recall. Same stuff as the stock gasket with holes where the stock sealing rings used to be. I was hoping maybe the Cometic Phuzion gaskets would be available for the L-series, since the Nissan piece is getting hard to find and was pretty freakin expensive last time I checked ($240 for the gasket - $40 each for the rings ). The idea looks similar enough that I hoped maybe I could just use the Phuzion gasket with my fire rings. Anybody have a good method for cutting holes out of a standard stock gasket?

The answer is 42. Don't Panic.

Just put these items up on ebay - gotta pay for my new valvetrain somehow! Turbo Exhaust Manifold with ext WG provision T64 Turbo, .81AR O-trim w/ Inconel heat shield T04 On Center turbine housing 0.69 AR O-trim Set of 6 Siemens Deka 72lb injectors Polished Upper Thermostat Housing - L-series 4" Stainless Flex Exhaust Coupling 16" Electric Puller Fan 14" Electric Puller Fan Polished EFI Intake Manifold Weber "Big Throat" 60mm Throttle Body

A rough surface exposes more surface area to the cooling medium, and a slightly turbulent flow over the surface should help with heat transfer.

Thanks, John - that's exactly what I was looking for. Called Courtesy Nissan and ordered one a couple of days ago. Now I just have to wait and see if the right pump shows up. They did actually find that part number after a search for a Maxima Diesel water pump, so it looks pretty promising. Interestingly, I talked to a tech rep at Evans Cooling last week, and he indicated that I'd probably be fine without making any changes to my cooling system's radiator or water pump. His main concern was whether the rad had a low enough restriction for the new fluid, which is slightly more viscous than straight ethylene glycol coolant. Since I'm running an aluminum rad with a 1.25" tube core, he didn't think that would be a problem. I ordered 3 gallons of NPG-R from Irv Hoerr Racing. The "R" formulation is a bit thinner than the regular stuff, and has an even higher boiling point (400 degF). It also freezes at a higher temperature (-10 degF). Since it has no water, it doesn't expand when it freezes, so storage at such temps should be fine. I'm pretty sure the only way my engine will ever be started at temperatures that cold would be if the garage is on fire...

Interesting. If the web runs the length of the head, then I'm not sure that it would account for the anecdotal evidence of #5 being a problem area, especially not if the N42 doesn't have the flash. However, it does sound like removing the flash would at least change the flow characteristics - hopefully it wasn't "added" in an effort to address the "#5 issue" . Also - sorry - I didn't realize that you didn't have the whole thing cut up already. What you've shown is extremely helpful, I didn't intend to ask for more free work. AWWWW, COME ON - you can always JB Weld it back together... Again, sorry - it sounded like you had a scrap N42.

Those are some really helpful pics - thanks Jeff! I assume that the other cylinders don't have the web, right? Do you have a pic of one of the others? Also very curious if the N-series heads had the same issue.

Thanks Tony - great advice. Since I already have the head pulled, I think I should be able to come up with a plan for flushing the block, and the heater core and rad separately. On the reverse flow thing, I have had thoughts about that as well, but haven't figured out how to plumb things without a ton of changes...

Well, maybe, assuming that the extrude hone material doesn't have the same issue that the water does. For instance if if the problem is simply a "bump" in the flow path, the extrude hone would take care of it. If however, the problem was an area where there was no flow path, the extrude hone material wouldn't do much - its purpose is more to smooth out the existing flow paths, not to make new ones. Also, smoothing out all of the internal passages would probably not help cooling efficiency - rough surfaces have more surface area, and a small amount of turbulence from the casting sand marks is probably also helpful.

This has been my suspicion, too, and the reason that I started this as a separate thread. My suspicion is that the "#5 issue" is more due to eddy currents or cavitation caused by the flow path inside the head. That end of the head gets the coolest water, so I don't think it's an issue of the water getting progressively hotter from having to pass over all the chambers from back to front. Tapping the head above the exhaust ports and returning the water to a plenum is an interesting idea, but I would think you would also want to modify the water inlet(s) to the head, so that the water could have an even flow path over each combustion chamber, and I'm not sure how that would be accomplished. It seems to me that if you left the water inlet at the existing port at the rear of the head, you would have to play some games to balance the outlet flow from each cylinder to keep from "starving" the cylinder that is farthest from the inlet - maybe something like use a -4 on cyls 5 and 6, -6 on 3 and 4, and -8 on 1 and 2. It also occurred to me that if the problem really is mostly isolated to cyl#5 and if it is caused by eddy currents or cavitation, it's possible that the problem could be solved by simply tapping the water jacket at #5 and bypassing a small amount of water from there (maybe just use a -4 line), just to change the flow path a bit and eliminate the dead zone. This of course depends on exactly where the flow problem is located - you could just as easily make the problem worse. Those chopped up head pics would probably be pretty helpful here... Personally, I'm kind of leaning towards the Evans NPG solution, but they require elimination of all water from the system, which isn't that easy without pulling the block. They have some flush chemicals that are supposed to help, though. Also, they mention requiring a higher flow pump, which I don't think is readily available for the L-series. Anybody know anything about the diesel water pump? I thought I had heard something about it having a higher flow capacity at one time.

No, and don't let anyone tell you it is bad. You DO own the head, right? You did pay him for those services, right? Did he have you sign a non-disclosure agreement? This is the same kind of thinking that lets EFI tuners charge you for tuning services without ever giving you any evidence of what they actually did. I have personally seen several examples of fairly well known tuners charging big bucks for doing virtually nothing. Not that this necessarily applies to Rebello in this case, but posts like yours only serve to keep vendors honest, IMHO. Now if you had some sort of agreement not to disclose, or he did the work for free, etc., then it is a different story, but I seriously doubt that this is the case. Showing examples of work well done should only be good for his business, and any work that you charge a premium for ought to be able to stand up to a peer review.

Okay, I've been meaning to start this thread for a couple of days - in another thread I was talking about some problems (dropped valve seat) that I incurred recently on cylinder 5. I've heard several times that #5 is problematic due to water flow issues, and johnc posted the following in that thread: Now, my car is still street driven and I'm a bit concerned about running cooling system pressures that high for fear of blowing out my heater core - anybody know if that's a rational fear? This certainly would be the easiest cure for the problem, and contrary to popular belief I do like elegant solutions . I've heard of ideas of re-plumbing the water flow through the head - as I recall there are some bosses between the intake ports that can be tapped to allow water to be plumbed in in that manner, but I've never seen what that solution actually looks like - has anybody seen this done successfully? Any other ideas?

I'm staying out

Talked a bit more with Ferrea today, and they referred me to these guys: http://cheprecision.com/html/seats.html Interesting use of copper alloys for better heat dissipation -they recommended going to a wider, deeper seat for more contact area, both for heat transfer to the head and from the valve. Next, I'll need to see just how much deeper I can go.

Yep - this has occurred to me, too. Those seats have been in there for quite some time, so I'm thinking the added temps just kind of put the seat over the edge. At the same time, I'd rather not have a similar failure in the future, so if I'm replacing the seats anyway, I'd prefer not to under spec things. There isn't any obvious evidence of detonation, but it's most likely unrealistic to assume that it never happened - I'm running a bit higher cooling system pressure than stock - 18psi as I recall. Perhaps I'll start a separate thread on that subject. My builder had the beryllium seat idea too - I'll research that bit more, but aren't there wear issues associated with those?

It was just some copper gasket seal and gasket remnants - the head gasket is the Nissan Comp one that uses separate fire rings that have machined grooves in the block. The gasket only seals the oil and water passages. Due to the difference in compressibility between the fire rings and the gasket, sometimes the gasket needs some 'help' to seal until a couple of heat cycles and re-torques have been done.

Well, I had alluded to it in a couple of other posts - a couple of weeks ago I had a something go south on #5 (it always seems to be #5). Got the head pulled last weekend (finally), and was puzzled for a while... At first glance, it looked like something got ingested, but the more I looked, the weirder it was - there were only marks around the intake valve, none around the exhaust, and the turbine wheel showed no signs whatsoever of anything having passed through it. Turns out what happened was that the intake valve seat came loose but was held captive by the intake valve. It got the crap beaten out of it for a while, which also held the valve open and let the lash pad move and get crushed by the rocker. Eventually it found its way "home" and the valve held it in place, since I didn't hammer it any more after it started having problems. So, it appears that this is the weak point that the higher exhaust temperatures from the GT42 uncovered - apparently this is fairly common in turboed air cooled engines where elevated head temps are more common. So, in addition to getting some new valves (with higher temp alloys), I'm going to be in need of some valve seats with higher temp capacity. I've been looking around a bit for valve seat insert suppliers, but I've not seen much for 1800 degF EGTs. Anybody got a line on a good supplier?

Okay, I'm in too Probably not helpful, but here's mine - I guess I kinda went the other way with the wires and hoses:

I agree that you probably just need a stronger impact wrench - 250 or 350 lb-ft capacity would most likely work better. 180lb-ft is kinda small. btw, is this a steel or aluminum flywheel? Impact wrench is probably okay for fastening a steel flywheel, but you'll likely deform an aluminum flywheel by tightening with an impact wrench. For AL, use a torque wrench.

As I recall it was on the order of 20 or 25 lb-ft. Much, much lower than the head bolts, as you just found out - sorry to hear that.

Not BRAAP, but I would imagine that this is the point on the pad where the tip of the cam lobe was contacting at max lift. The radius of curvature of the cam lobe is smallest there, resulting in this being the point where the cam exerts the highest pressure on the pad. As an analogy, think of this as being the edge of the knife, rather than the flat side of the knife.

You might be surprised. The cam lobes are only surface hardened. Once that hardened layer gets worn through, the rest will happen pretty quickly. Not saying it isn't bad metallurgy, but for either a bad wipe pattern or oiling problems, two hours is plenty of time for something like this to happen.

Wasn't trying to piss you off - you showed a wiped cam and asked how it could have happened. I just simply mentioned one thing that I had seen wipe a cam in a VERY similar fashion on my engine before. I'm not an inexperienced kid, either. I'll ask one more question, then I'm going to leave it alone. When you say you checked for oil in the head - how did you check? I can't tell for sure from the pic, but it looks like lobes 1 and 2 were okay. If you checked by looking through the filler hole, that's pretty much all you would have seen, and it looks like those two lobes were getting oil. If you look at the spray bar, those two lobes get supplied directly from the cam tower, while the lobes between the cam towers have to all share from the back tower - my experience was that at idle when the pressure was low, the lobes farthest from the tower (3, 4, 5, 6) had problems getting oil to the lobe/rocker interface and were just dribbling oil on the retaining spring area. Your cam appears to have a similar pattern of good/bad lobes. As I said at the beginning, could have been any number of things - that was simply one more thing that nobody had mentioned yet.

Any of the things Braap mentioned could have caused this, but I have to say that a different thing came to my mind. Specifically, the "dual" oiling system. There is usually a restrictor in the bock that allows adequate oil flow for one or the other (internal or external), but not both. This is done in order to maintain pressure at the mains and not bleed it all out in the head. What can happen is if you try running the "dual" oiling setup is that the spray bar just dribbles oil out at idle and doesn't even hit the lobes, while at the same time killing pressure in the internal cam oiling system such that neither oils the cam adequately. Also, I've always be leery of removing the restrictor, as I think the "belts and suspenders" approach for "protecting" the cam can pretty easily come at the expense of the oil pressure at the mains, which is arguably a more catastrophic failure mode. For 99% of the vehicles out there, the stock cam oiling system works just fine - why mess with it? One other thing - there was a post a while back about how most modern oils are not that suitable for the kind of metal to metal contact that happens at cam lobe/rocker interface, due to reduced zinc content. There are some oils out there that still have zinc: http://forums.hybridz.org/showthread.php?t=108608