DAW

The P79 is fine. It has large I.D. runners, larger dia. outlet studs than the early manifolds, and better flanges for attachment with the f.i. manifolds, and O2 sensor to boot. It's an art making hp on a budget...more like a sport for me. The downpipe I had referred to I had purchased from Impact Parts in Glen Wild, NY many years ago. It wasn't expensive and it fit perfectly but I don't know if that company even exists today. If it does, maybe they could figure out where they were getting those pipes they sold...it's the type of thing worth a group buy. DAW

I went out and rummaged through a bunch of manifolds and my vote, for use on a rectangular port head, is the W25 off an LD28 (yeah, you heard it right). Similar to the E30 from an early 240Z except it does not have any air-injector tubes/bosses to restrict flow, the I.D. of the runners appears a bit larger (2.8L vs 2.4L), and the outlets are larger. The W25 definitely provides a better mounting flange for f.i. intake manifolds than does the E30. While you're at it, check out the intake manifold from the LD28. It would need injector bungs, and it's tall, but looks like it could have some significant flow plus low-end torque (long runners). DAW

First, the bore of the LD28 is 84.5mm and an overbore to 86mm should be no problem. In fact, 87.5mm is probably fine. I don't have any sonic test data but I have felt down into an L28 posterior water jacket vs an LD28 and it feels to me like there is a lot more cyl wall material on the LD28. It stands to reason that this would be the case.The weight will be more but not by some huge amount; basically a non-issue. An L6 head does not bolt directly to the LD28 shortblock but it is not a giant undertaking to adapt it. The LD28 uses 12mm headbolts, the L28; 10mm. You have to use a drillpress to drill the L6 aluminum headbolt holes out to 12mm. This can be done with the valves & cam in the head; rockers removed. You'll be using a few of the LD28 headbolts and the balance with BMW 1980s-ish headbolts from junkyard I4 and I6 engines. Often a head has been pulled and the bolts are just laying right there. These are 12mm with the correct thread pitch and length, although a few may require double washers. Use an LD28 head gasket. You might be able to use the same one. I'm a little fuzzy on exact details because I put the one I'm driving together in 1994 or '95 and I've driven it since. The next one is a 0.060" over LD28 with L28ET pistons and P90 head using Z22E rods (148.6mm). Static c.r. should be just where I want it and rod/stroke is fine. It works great to test it in the Maxima because the front sump pan has an oil return pipe that was for the vacuum pump on the diesel that works fine for a turbo oil drain pipe. DAW

I think 100mm is too much stroke for anything but a diesel. The 83mm LD28 crank is fine though, and 83mm is definitely not to much stroke...except that it's too much stroke for the L24/26/28 block because these blocks are to short and leave no room for a reasonable-length rod proportionate to the stroke. I'm amazed that I seem to be the only one that has used the LD28 block to build an L6 on Hybrid Z. I just don't see anyone else doing it. It's too easy, especially if you have some L4 experience because the LD28 is exactly the same amount taller than L28 as the L20B is to L18. The L18 timing cover fits the L28 and the L20B cover fits the LD28. The only real issue is hood clearance...so you have to put on a '67 Corvette 427-type scoop..it looks fine, like it belongs there. The quick & easy (ala Putanesca) build is to use the intact LD28 shortblock (140mm rods, big floating wristpins), don't tear it down and modify the aluminum head of choice to bolt-on, depending on c.r. desired, turbo vs na, etc. use an L6 rear sump pan, L20B timing cover, L6 distributor, etc. You're not going to build a high rpm engine this way because of the high comp. ht. of the LD28 pistons, but it will stand up to high c.r.s without detonation. Turbocharging using the P90 head and the stock shortblock makes the most sense and should withstand significant boost levels. Stock c.r. for the LD28 shortblock is 22:1. Turbo would make lots of power without having to spin high rpm and the 83mm stroke would help off-boost lower rpm better than the 79mm L28ET stroke. Think about it...if you go to buy an LD28 crank, get the whole engine or car. DAW

For full-out high rpm, that would be the way to go (or L28ET manifold), but streetability might suffer. DAW

It's not just about mass flow of gas i.e., how much you force into one end of the manifold and how well it comes out the other. The "best" flowing manifold may not always be the best performing manifold throughout the usable rpm and load range. Take an L28ETT manifold and run a pipe right off the turbo flange with an adapter and it will probably outflow all of the manifolds, but that doesn't mean it will provide the best performance on a n/a engine. The reason the "skinny" manifolds offer a performance advantage over the "fat" is because of the scavenging effect. The best skinny manifolds are true 3s-into-2 design. That is, they are two 3cyl manifolds cast together. Not just any three cylinders either, they are grouped by ignition interval to optimize the "suction" effect produced by high speed gases flowing past a port that is just opening so that not only are exhaust gases expelled more efficiently, but the intake charge is actually pulled in to some extent by this action. Velocity of exhaust gas flow is the important factor with this effect. A tri-Y design provides the optimum scavenging for low to mid range, coupling cyls 1&6, 2&5, 3&4, but that makes for a lot of pipes and junctions and will become limiting at high rpm. The best ones from the 3s-into-2 aspect are the early 240Z manifolds. Some later 240Z manifolds/downpipes do not adequately maintain separation of the 3 port segments from each other and they are more like 6/1 manifolds. The problem with them is that they are for 2.4L volume of exhaust flow and might prove restrictive for 2.8L and larger. The "fat" manifolds are just huge chambers designed to concentrate exhaust heat so that unburned hydrocarbons are broken down, and this at the expense of scavenging effect. The manifold for the P79 head is good from the volume aspect and it has a 3-into-2 design. One drawback is that the O2 sensor locates between the two 3-cyl segments so that it samples from both and this allows some communication between the two segments but this may be a minor compromise and worth it for the sensor. The down pipe(s) should not join right together like the 280-280ZX pipes do, rather they should have a length of run like the 240Z (except with larger pipes) if nothing else, the 240 junction should be eliminated and a 2-pipe collector with 2.5" or 2.75" collector fitted. You might still be able to purchase a downpipe from MSA that is made that way. I think that may be what's now used on their "twice-pipes" setup. Alternatively, you could take two 240Z systems and try to fabricate dual secondaries (maybe a balance tube where you eliminate the junctions) to run on back into a single dual inlet muffler. Remember, as the gas flows through it will cool and reduce the volume and larger pipes may not be as critical toward the rear of the car as near the engine. As to headers, make sure the primaries are equal length or don't bother. Early Cyclone headers are good for an L24 due to the small dia tubes, NISMO headers are the best I've seen for L28 or larger and have well-designed collectors/junctions. Sorry if this is to exhaustive a discourse but I'd rather do it this way than write four posts equal to the same volume. DAW

I am certainly no expert on this, but I should think that 0.040" over is no mistake with this block and youm are very safe here. DAW

Do things one step at a time. If you do the rising-rate fpr, that may be enough. Only if you still need more fuel do you need to go on to other enrichenning measures, and then only according to how much more you need re which to use. DAW

The rising rate fpr isn't cheap but would be a good place to start, then fill in if needed with the enrichenning tricks or turbo injectors. DAW

You could figure it out mathmatically if you know the piston dish, c.r., displacement/6, and the ring land-head gasket thickness volume (this one could be tough, 6.75cc should be close for this). DAW

Al, you might be interested in another one to include: LD28. Square port "skinny" type. I don't know if there is any advantage over the L28 "skinny" manifold but it may have better port match since I think it a true square port manifol (nice on a P90 na engine). Stay away from the "fat" emission manifolds (except for a rowboat anchor). DAW

That's an empirical method that's been used for years. One thing is certain, stopping the pinging is a good thing no matter how you do it, but you might also try enrichenning the mixture, if you haven't done so, to get rid of the ping at a given timing advance because if you can leave the advance but get rid of the ping, allowing you to use the advance setting, performance and throttle response overall may improve. DAW

For a budget build up like this I've described a way to use your '77 280Z dished pistons but have the tops shaved down until they become flat tops with a reduced compression ht, using L24 rods which improves rod/stroke ratio and along with an N42 head, makes almost 10:1 compression, and in the process a method of assembly of the piston/rod units into the engine in such a way that the engine is far more balanced than random assembly order would provide. Try to find it by search, probably in the L6 forum. If you can't find it, I'll provide particulars. Forget about extrude-honing your manifold at this point and porting and polishing, your money could be much better spent. Once you've increased compression, cam and headers come next and when the compression goes up, you'll have to enrichen fuel supply. Minor modifications can be done at first, but as you increase horsepower, you will need more & more fuel. DAW

Lockjaw, your friend who built the L6 with the head shaved 0.110" without shimming the cam towers at all, and ran 8.10 in the 1/8 mile...is that because he didn't make it the full 1/4 mile? just kidding. You can put it together however you want, but let's hear a 10,000 mile progress report (that's less than most people drive per year). If the tensioner is in its bore (it probably won't be unless a travel limiter has been added; big oil pressure loss too when this happens), the repositioned guides will likely be partially sawed through by the chain, the shavings into the oil, and the chain and sprockets excessively worn. Going fast on a budget is good but having to tear it down and rebuild it again early is a PITA.

yo2001, there's the rub...you know you could make more power if you advanced the timing more with the open chamber or lower rod/stroke engines...but you can't because of detonation. I'm limited to the stock cam in the autocross car (F54/N42) and this really brings out detonation tendencies. The car is quick but I know it would be faster if I could advance the timing (faster, that is, until the ring lands are fractured or there is a hole in a piston). The rod/stroke ratio of the LD28/N42 has the potential to be higher because of the huge 46.5mm comp. ht. Every decrease made in comp.ht due to piston selection allows a longer rod and thereby an increase in rod/stroke. The choice of L28 piston (38.1mm) and 148.6mm rod (Z22E) makes for a readily available and economic (compared to buying custom pistons) combination yielding 148.6/83 rod/stroke. If r/s is the key to minimizing pinging, then a combination like this should allow use of any type head with a stock cam. DAW

The 130.4/79mm is the F54; the 140/83 is the LD28. DAW

Nathan... Solex, Weber, and Dellerotto side drafts work alike (except for chokes and accelerator pumps) but the same linkage should work. When I lived in Italy I used to go to the junkyards in search of sidedrafts on wrecked Alfa Romeo police cars. I'd find pairs of all three types and as I remember, there weren't any significant differences in the linkages. DAW

Datsun Dude, if the head is shaved 0.080" and the cam towers are not shimmed too, the chain doesn't have plenty of tension; it has plenty of slack...too much slack to be compensated for by tensioner, guides, etc. Either the towers have to be shimmed 0.080" (which means thicker lash pads or longer valves with shimmed valve springs), or the chain needs to be shortened a specific amount (this isn't a popular approach) and I'm saying that if that amount might equal 1/2 link that it might be possible to save a lot of work to accomplish the same goal. Adjusting/compensating for the incurred cam retard due to shaving the head is good until about 0.020" or so, any more than that and you've got to deal with the excess chain slapping around. DAW

Guys, re comments above, I am speaking from experience re ping tendency on open vs closed-chamber heads. I've put Nissan L series motors together both ways and it's been my experience that the closed chamber has an edge re ping tendency (both with the same stock cams and c.r.) the closed-chamber had slightly smaller bore & stroke but both had similar rod/stroke. With a cam, there might be no ping with either head but with stock cam I think it tends to isolate detonation problems. so I'm not talking theory, just practical experience. Those who have "shaved their heads" may not be doing a true comparison as they may have transformed toward closed-chamber configuration. Maybe more interesting is what I observed between two 2.8L l6s I use. Both have the same stock L28 cams and both have high compression one is 9.8:1 and the other is just over 10:1. Both have unshaved open-chamber N42 heads. Two different stock flat-top shortblocks, the F54 has triple side-drafts; the LD28 has stock/modified EFI with analog/non-O2 sensor ECU; both have headers. The LD28/N42 doesn't ping...ever, and it's the one with the higher c.r. (cranking pressure is 209-215). The F54/N42 cranks at 198-205. I can set initial advance at 12 on the engine with the higher c.r. but only at 8 on the other due to pinging. So why does one ping and not the other? (I don't know; I'm asking) Could it be the f.i. provides a more consistent stoichiometry than the side-draft carbs? (Accelerator pumps are working fine and jetting should be rich enough). I assumed the LD28 was more resistant due to the thick piston crowns and 46.5mm of comp.ht. but now I'm wondering if the rod/stroke could be the main factor (130.4/79 vs 140/83) with the TDC dwell duration providing a more even burn, or whatever. What do you think? DAW

P.S. When I referred to removing the damper plungers I actually mean removing the oil and replacing the plungers thereby eliminating their function. You noticed improvement when removing the oil...but remember, you reduced some resistance to piston rise by doing this and noticed improved response...the more significant factor is that you lightened the piston by removing the oil. Switching to a lighter dashpot spring should have the same effect. DAW

Throttle response is directly related to ignition timing. You want to run as much initial advance, generally speaking, as you can (without causing ping somewhere else in the rpm range) to get the best throttle response. The "popping" you describe is due to lean-out on throttle tip-in, which amounts to poor throttle response. In general, when you tune the SUs, you'll synchronize airflow, record where the jet ht is (# turns on idle mixture knurled ring), run each one in and then back 1 1/2 turns to start out with. When you adjust these keep track of the turns by referencing to the large and small steel balls imbedded into the rings. Snap the throttle open off idle (you can do this with the car parked). If there is hesitation, advanced the timing a couple of degrees at a time until hesitation is minimized. You now work with the needles by checking at progressively higher rpms identifying lean spots you find by hesitation on throttle snap. Eventually you will be removing the plungers and marking a straw or lightweight balsa or plastic stick at about 1/8" intervals and placing them into the dashpot where they bottom out in the piston. Revving the engine will cause the pistons (and the little marked sticks) to raise a specific amount corresponding to the specific rpm. The mark on the stick is calibrated to a specific location on the needle which can be mic'd. Hesitation at a particular rpm/piston ht/needle at the jet location, means the mic'd thickness needs to be reduced to allow more fuel flow at that point. You may be able to record your needle thicknesses at the standardized intervals, noting which intervals are too lean (thick) and look in a British racing catalog to find a needle which suits your carbs/engine based on this tuning right off the shelf. However, turning the needles down using a drill press is not that bad and it's highly gratifying when you finish the tuning. Look at that book again on SUs. I think he may have some needle profiles and part # in the appendix. Once you get the higher speed lean pops and sags tuned out you will have done it through richenning measures which will reduce ping, so you might be able to advance the timing a bit more (keep the total within reason). When you go to fine tune the idle mixture, try to keep both jets even and don't get lost or move them too much because you can get way out of whack trying to chase a few rpms for best idle. Remember you are moving the entire jet which has an effect throughout the rpm range. As to the plungers, I don't think that their removal will effect driveability as much as removal of the damper springs (that's what I was referring to). I think lighter springs and lightweight damper oil should be done before needle changes. It would be great if you put in some "blue" springs and run 3-in-1 or sewing machine oil or whatever in the damper plunger wells and your problems disappear! DAW

Dan, I didn't see it as a friendly jab in the ribs. I read it as an insult and to be blunt, it's not the first time it's happened to me or other members by you but I've held my comments in the past. As to sticking to the pertinent aspects of the discussion, the thread was about P90 vs N42 heads. I had categorized L6 (not E88) heads as "small, medium, or large" ranging from 42.5cc to 53.6cc, and as stock or reworked(e.g., 0.080" shave), and open-chamber type or closed-chamber f.i. heads. Dan, you went off about E-88 heads which was not the point of my post or the thread. The specs on the L26 E88 head that I hadn't mentioned was definitely useful info but I don't see that justifying disparaging comments. I certainly didn't intend to start a firestorm and I now regret that I spoke up. However, I perceived your comments as berating and patronizing and I think that is unhealthy for the forum. When that type of thing happens but goes unaddressed, new members are discouraged from taking a risk with a question or idea because they fear the will be humiliated and badgered by rude comments, and old members lose respect for their peers. It's not about ruffled feathers or thin skin, it's more about the principle. I'm out on this discussion and I have no hard feelings, I just wasn't ready to bury my head in the sand like I did the first time around. So now I didn't bury my head but I'll bury the hatchet. (I'LL BURY IT IN YOUR HEAD!) just kidding, have a good one. DAW BTW Pete, the extra 5 was a typo

I hadn't seen this thread in a while and I was surprised when I scrolled back to page 5 and a post 5 by Dan Baldwin. Dan, your comments are rude and inappropriate. I don't even know you. I have 4 years of post-doctorate education and didn't do that with a short attention span. Keep your provocative, condescending comments off the forum. DAW

Think British sports cars. You could pick up a British sports car racing magazine at a bookstore and look for ads selling SU carbs & parts for sources. The Hitachi SUs you have are called HS series in England. APT is one source (http://www.aptfast.com) and for HS carb dashpot springs they list: 12-oz. Green ($6.79); 8-oz Yellow ($6.79): 4.5-oz. Red ($10.78); and 2.5-oz. Blue ($11.98). If your springs have a color-code then you'll have a reference point. If not, then you'll have to trial and error. However, I can almost guarantee they didn't use 12-oz. springs, more likely 8 or 4.5-oz. Given your compression ratio and the type of problem you're having, you could just put 2.5-oz. springs in and go from there. This may also allow you to bump your initial timing up from 9 to 12 degrees which will further improve throttle response (without the ping). The next step if the lightest springs aren't enough would be to lighten the piston. Some British racers try removing the spring altogether but you get problems like when you removed the oil-dampner plunger...too eratic. DAW

A final thought...what you have is what you have; road racing for that engine is out of the question. However, It might well kick *** in an autocross car! Lots of grunt coming out of those tight corners! DAW