BRAAP

There's not really a set stroke length that is a "line in the sand do not cross" point, just that the longer the stroke for a given reciprocating weight, the greater the 2nd order harmonic. (Stroke length and its affect on the 2nd order harmonic has been discussed in this thread). Finding that compromise of acceptable buzziness, durability, and displacement is key and being partially subjective as well as objective will take some trial error to find that balance, which will be different for different applications. Hoping to carry this out in the LSx foundation as well, at some point in the future.

Nice find. Wish I would've known about his a few months ago. I ended up building my own 90 degree pigtail for tunnel clearance, this is much nicer.

Very cool. Looking forward to seeing this come alive.

It's all good.

Legit thread here guys with several mature level headed adult responses and advice, no need to sensationalize, tear apart specifics, or add nonsensical advice. Jon is only trying to help keep this thread on track, please do not go out of your way to stir the pot.

Sorry for the offtopic, but WOWzers! Love your combination of wood, interior colors etc. Steering wheel is gorgeous. Any more pics of the interior?

We generally just Heli-coil, but that particular bolt hole was beyond using over the counter inserts being grossly oversized, offset, and angled, hence the offset of the custom DIY insert. I like the set-screw idea for the head oil supply, similar to fuel metering jets for carbs... ;- )

Set screw with stud-lock eh? Hmmm... Sorta like this bolt hole fix on the infmaous highprofile P90 head. Not in any Datsun how-to book, nor giving my sources or providing a link.

Matt, Ouch, your pump has passed quite a bit of debris, explains the little flake of aluminum siting on top of the forward restrictor port and the clogged head restrictor starving the top end. After what we discussed a few months back and now seeing this, I do strongly recommend completely disassembling the block and removing all oil galley plugs and restrictors for a thorough cleaning using brushes in the galleys. There are two galley plugs in the block, one at the front, one at the rear and the two restrictors on the block deck surface. Remove those so all debris that settles behind them can be removed. As we discussed previously, Rebello does remove those from the block to clean out that passage. Dave taps it just deep enough to get small screw in it and pry it out of the block. Any machine shop should be able to build you new restrictors using rod stock. Just take your old restrictor to them, tell them duplicate them with the desired hole sizes, (stock hole size for the forward, the Honswetz hole size for the main feed above the oil filter. They should be able to build them for cheap, just tap it into the block. Any automotive machine shop should be able to source the galley plugs, or possibly through your Nissan dealer. I do stock those plugs,pretty sure I have the Datsun L-series in stock, too bad you aren't in the states. Another option for the block galley plugs is to drill and tap them for pipe plugs which we do on all of our performance builds. Hope that helps, Paul

BMW E30 318 with an L6; http://forums.hybridz.org/index.php/topic/51696-my-hybrid-z/

Due to the frequency vs revs and being somewhat dependent on load, if internal knocking, possibly all 6 busted pistons skirts or timing chain slapping the front cover. Something else that comes to mind is exhaust system smacking the body/engine mounts, or alternator is smacking the block.

If you do this, let us know how it goes. 7% gain in torque across the entire rev range "should" be expected with 2 full points of compression ratio increase, if you don't have to pull any timing, but those gains with just over 1 point of compression bump and that much retarded timing is not the norm and any engine builder would agree highly unlikely from compression bump alone. Other factors at play such as induction system differences, exhaust differences, possibly cams, etc. I repeat, compression ratio bump alone, especailly with that much less igniton timing, can NOT and will NOT deliver that much more gain, there are other factors attributing to that gain. Over the years having seen first hand and reading online from those that have done the open chamber flat top piston L28 combination, they more often than not follow the example in this quote, same engine, same dyno. Quoted from another thread on this exact topic; http://forums.hybridz.org/index.php/topic/85907-attn-flat-top-28-with-e31n42-head-guys/page__p__815174__hl__fromsearch__1#entry815174 The car in that example can been seen here; http://forums.hybridz.org/index.php/topic/53922-wolfd-79-280zx/ The public discussions of people that have actually done this I feel speak for themselves. With so many threads on this and other forums covering the Flat top open chamber heads rattling and not performing up to par vs that combination actually working and being an improvement, that alone should be a flag to those considering such combination that more is at play to make this combination work successfully than just slapping an N42/47 head on a flat top short block. I am not saying it shouldn't be done, just go into it knowing the most likely outcome and hopefully if do find the fix that allows that combination to work, you'll share the secret. Ok, I wont argue this anymore, I've said all I have to say on this topic, you guys build what you want and I encourage you to report your results whether it worked as expected or not.

Pete, I too like hard numbers. Those are two different engines with two different tunes, (AFR's reflect such). Unless the entire exhaust systems were the same from the header to the tail pipe, and the inductions is the same, from air filter to manifold, injectors/carbs, cams the same, head work, if any, the same, etc, those two dyno sheets are apple and oranges. Even if those were identical twins in every respect, it would show a trend, but again, apples and oranges. How about this. We know that compression ratio increase is typically worth 3% power gain per full point of increase, all else being equal. So next time you guys have a dyno day/session, using a known stock compression Z car with quality pump gas in the tank, after the base line run has been established, retard the ignition timing 5 degrees, run it again, then retard the timing another 5 degrees, run it again. Note how much power was lost for 5 and 10 degrees of ignition retard. From all the L6's I have built and tuned myself, I have found when not knock limited, the open chamber E88, N42 and N47 heads with dished pistons will produce best torque when the full mechanical ignition advance is between 38-40 degrees BTDC, again when not knock limited due to bad fuel. As an aside, many variables will affect how efficient the chamber is which will have a direct correlation on best power ignition timing, (swirl, plug type like projected tip vs non, etc). An engine that can make best torque at a lower ignition timing indicates the chamber is more efficient at getting the job done of combustion converted to push on top of the piston. Higher compression ratios do help as well. The GM small block V8's are a good example. The traditional SBC with typical pre-Vortec heads prefer 34-36 degrees ignition advance. The LT1/4 and Vortec, 32-34, the LSx, mid to upper 20 degree range. The chambers and how the ports allow the air/fuel in and out has been evolved into more efficient designs requiring less ignition timing to get the job done. With that said, having a low ignition timing numbers due to knock preignition/detonation is not an indication of an efficient chamber, just a band aid for an inefficient chamber that isn't able to make use of the fuel being burned in it.

Pete, I agree with you to a point. That point is when compression is raised to a point that ignition timing has to be backed off due to ANY preignition/detonation, it is from that compression up that you are loosing more power from retarding ignition timing than you are gaining from the compression ratio increase. Typical L6 Datsun, that threshold is MUCH lower than most typical aluminum head 2 valve designs, again, I believe that is due to the discussion in the thread I linked. The L-6 "should" be able to run as much as 11:1 compression ratio without having detonation issues, but that isn't the case, it rattles terribly at a mere 9.5:1 comp ratio on pump gas. Yes, there are few out there that seem to be getting away with running more compression ratio and "almost" full ignition timing, but that is more than odd than the norm. Someone running a P90 at only 34 degrees full advance N/A is giving up power if that same engine can run more ign timing with higher octane fuel or less compression ratio. By winning races, assuming that is autocross or road racing, is not necessarily an indication he is producing any where near max performance that engine could produce, that is more an indicator the driver is savvy at the task of driving. I've seen on numerous occasions cars that are far less capable spank other cars that are far more capable. Know of daily driver Yugo that was stomping many C5 corvettes, and even Porsche on one track, witnessed first hand a bone stock '85 Chevrolet Celebrity OE junk type tires with a tired 2.8 V6,, (I think I still have that VHS around the house) annihilate all the C5 Vettes including trailered Z06 race car on race tires, a couple FD RX7, S30 Z cars, L6 and V8 powered, etc. Driver was the factor there, not the car definitely not the engine. The norm being that gains of approx. 3% per full point of Compression ratio bump, all else being equal. If you bump the comp ratio up on the Datsun L6 by 2 full points you should expect to see 6% power gain, optimistically, maybe 7 or even 7.5%. On an L6 that is producing 150 HP, even an optimistic 7.5 % is only 11.25 HP increase from raising 2 full points, say from 8.3:1 up to 10.3:1. Due to the L6 propensity to detonate at elevated compression ratios, you would end up having to back the ignition timing off so much you would be throwing away more than 15HP i.e. 11 HP gained from C/R increase only to remove 15+ HP from retarded ignition timing. Realistically it would be more like 20+HP loss from the retarded ignition timing. From the SDS (Simple Digital Systems) web site tech page; http://www.sdsefi.com/techmods.htm I maintain that it is far more advantageous to run only as much compression ratio as a particular power-plant can manage on the fuel to be used that does NOT engage in having to retarding the ignition timing. That means if you run higher octane fuel and can advance the ignition timing or lower the compression ratio and can run more ignition timing, then you weren't running as much ignition advance as the engine prefers in the first place, i.e. knock limited, and you were sacrificing more power from that than you were gaining from any compression ratio increase.

My apologies for not clarifying. Referring to the Multilink that was designed on the CRAY super computer in the '80's installed on the 240-SX, Z32, Q45, J30. I am not familiar with newer design used on the 350-Z/G35, totally different design an have not owned one.

I have not ran the Comp Ratio calcs out, but if you had a 9.2:1 with no squish, vs 11.2-4ish ish with the squish, (what the MN47 and OE flat tops calculates out to), then 9.2 "should" be less sensitive to detonation. Though if this is the setup that you were running and you have visible signs of detonation, you can expect more detonation if no measures to combat it are taken. The Aluminum Datsun L6 is hyper sensitive to detonation, ask anyone that has ran the N42 or N47 with flat tops at only 9.4:1 compression ratio. It rattles like a diesel at that compression ratio which older technology iron head engines can run all day with no detonation. To keep those from rattling you have to pull so much ignition timing that you are loosing more power from retarded ignition timing than you gained in compression ratio increase, 1 step forward, 3 steps backwards. I feel the reason for that is addressed in this thread; http://forums.hybridz.org/index.php/topic/59029-head-cooling-on-cylinder-5-solutions/ If this were my engine, all to remain mostly stock or even mildly prepared, if using factory dished pistons I would use the N42 or N47 head. If flat tops are to be used, then the P79 or P90 to be used. Either combination will perform similarly. In my mind it just isn't worth trying to split hairs for some specific compression ratio. It is far more important for producing power, engine longevity, fuel mileage etc, to build in only enough compression ration to allow the engine to run its optimum ignition timing rather than have to retard the ignition timing because some "target" comp ratio in an engine known for being sensitive to detonation, i.e. ideal/safe compression ratios for other aluminum head engines don't carry over to the L6.

As Tony mentioned, dye penetrant the lands and dimension the pistons. Checking for collapsed skirts are an easy cheap way to check for damage. If the skirts are collapsed, no need to bother with the dye penetrant. If the skirts are good, then dye penetrant the lands. Dished pistons with the MN47? The one benefit the MN47 brings to an L6 is its squish pad which requires flat top pistons, or a piston with its dish formed in the shape of the open chamber so its flat area matches the flat area of the head, retaining squish. Using dished piston with the MN47 eliminates the squish, the only benefit the MN47 brings to the mix over the Z car N47 or N42 head, especially if you go through the trouble of installing the larger L28 Intake valves/seats, opening up the "D" intake port, etc. with the MN47 Unless the combination of a dished piston L28 and MN47 has another benefit I am unawares of, (Tony??? ) in my opinion it would be far less hassle to just install a standard N47 or N42 head and end up with less chance of detonation and if the MN47 is stock the N42/N47 will deliver more performance on pump gas due to being able to utilize the full ignition advance that the heads make best power with and the larger intake ports/valves.

:lmao:

Would love to see some pics. This should help; http://forums.hybridz.org/index.php/topic/57387-“how-to”-post-pictures-on-hybridz-the-easy-way…/

Ya know.... if you get the urge for more power over than the M52 is willing to deliver, the LSx fits quite nicely under the hood of the E39... A few examples! http://forums.bimmerforums.com/forum/showthread.php?t=1489862 http://forums.bimmerforums.com/forum/showthread.php?t=1423081 http://forums.bimmerforums.com/forum/showthread.php?t=1517185

I think people get the impression Torque come from stroke alone, HP comes from bore alone, others tend to locked into some variation of this ill conceived logic. Probably started when people were installing longer stroke cranks and their engine wee producing more torque so there for stroke is the only means to gain torque. The 383 SBC is perfect example. All being equal, (engines ability to breathe, rod to stroke, ratio etc), torque comes from the displacement of the engine. Whether that displacement was obtained from an under square bore/stroke, square, or over square combination, if the engine has the same rod to stroke ratio, same ability to breathe, same cam specs, same induction, exhaust etc, it will generate essentially the same torque and HP at all points in the rev range. Where things start to change is when the physical strength of the components are exceeded such as piston speeds due to long strokes and very high RPMs. At that point for a given piston material, stroke and or RPM must be limited to keep the engine together. Since HP is a function of Torque AND RPM, the higher up in the rev range you can produce the torque being developed, the greater the HP created. Look no further than F1 or sport bikes for examples. Liter class bikes, sport or other wise, producing in the neighborhood of 70-80 ft lbs of torques though the engines that produce that torque at higher RPMs are producing more HP. In summation, there is NO magic under square, square or over square combination that is best for all production engines in track environment. Every engine has its strengths and weakness regarding ability to breathe, (heads induction, exhaust), available space in the crank case for stroke length and available deck hight for rod length. While research may uncover trends for a particular engine, those same trends will not necessarily carry over to another engine due to the variables mentioned. In trying to generalize ideal design constraints for making power for a track car, these guidelines are safer bet to follow than a specific "bore-stroke-rod length" combo. What may be an ideal combo for one engine will not be the ideal for a different brand/design, (2 valve vs 4 valve is one variable that changes a lot of "ideal" design parameters). Always build as much displacement as can be built within the engine and/or rules of the class to which you are racing. When limited by displacement, build as much bore as possible to allow as much valve area as possible to allow the engine to breathe, (again within the physical constraints of the engine and/or rules), make up the rest of the displacement in stroke and use as long a rod as possible. Then build the engine to make as much power as high as possible in the rev range over enough RPM range to span the gear ratio drops of the gear box being used. Of course there are other variables that could alter those guidelines due to the fact that not all production engines are created equal, all have weaknesses and strengths. It's how you best minimize the weaknesses and bring out the strengths that will make the difference, hopefully better than the guy next to you on the start online. Then there is the chassis to contend with, the drivers ability... I digress...

LSx engine oil primer. I realize that just cranking the engine over on the starter with the coils/injectors disabled is the norm and most have done so with no ill affects with that method, I just prefer to go that little extra pressurizing the oil system prior to spinning the crank on the starter. Feeds 4 qts of fresh oil under pressure into the engine oil galley just above the oil filter, (also back feeds to the pump), with a piston using compressed air. Built in piston stop at the bottom protects the pistons seals, manual flow valve etc. Worked perfectly today. Engine was LM7 short block that had been sitting for over 3 years, fresh top end. Removed valve covers to verify oil made it up and out the pushrods. Rest of the sump capacity poured in over the top of the rockers. Engine fired right up on first crank, no oiling issues. End cap and pistons bits prior to assembly; Engine Oil Primer with piston, manual flow valve, high pressure clear hose connected to LSx galley cover; Disclaimer. If anyone attempts to duplicate, be sure to use a shut off valve and a clear tube capable of the pressure being applied. Air can and will still get past the piston due to the ABS/PVC not so smooth inner walls and if left unnoticed will push all the oil out of the galleys, bearings, etc leaving you worse off than before you started! Also, the piston is not necessary, but I built it that way as means to reduce the possibility of rapidly introducing air into the system once empty.

Short version, fired up the engine today! WOOHOO! Long version. Built a DIY LSx engine oil primer, (air actuated piston forces 4 qt’s of fresh oil in to the engine oil galleys via the port above the oil filter), worked out perfect, RTz was on hand to help with pressurizing the oil galleys and film the video. Just cranking the engine over on the starter with the coils/injectors disabled works fine, I wanted fresh oil to the bearing before spinning the crank. After a few electrical checks to verify wring was correct, no back feeds were going to keep the start engaged, pressurized the fuel system, etc. Then bumped the starter and the engine immediately came to life on all 8 cylinders, WOO HOO! Here are some pics of the oil system primer and video of the start up. Flames! As a gag we clamped an old dead Turbo onto one of the exhaust Mani’s, it would barely spin, (boost gauge sitting on the intake)

My hands down favorite shop door, bi-fold aircraft hangar style. Makes for nice awning when open. Or for your shorter height door, hinged at the top sweep out design for more sun/weather cover with the door open. Could install a man door as well, split at the middle if using the bi-fold.

If the intake is the original OE intake, the NON EGR version of the N42 was available on NON california '75-'76 cars. If the car was destined/sold from a California show room, it will have EGR, i.e. the famed '70's California Emissions. That is the general rule of thumb, as always, exceptions may exist. Only way to know for sure is to go look for yourself. If the car is too far to go see in person, have the seller take pics of the intake, looking down for the top, preferably from the passenger side and or back side. Hope that helps, Paul