DAW

McAdam, glad to see you finished that P47 head project. McAdam points out some important points about the Maxima L6 head. There are a lot of misconceptions about this head. First, it already has L28-sized exhaust valves which need nothing. It is the intake valves which need to be replaced with L28E valves; and new seats. E31 undersized exhaust valves can be replaced with L28 valves by grinding the seats out in an E31 head, but putting larger intake valves requires replacement of intake valve seats, be it an E31 head, or a P47. The N47 Maxima head isn't really a sister to the P79/P90 head because those have a higher roof to their combustion chambers and, accordingly, shorter length valves. The Maxima N47 is more like an evolved E31 as it has similar chamber cc and the same length valves and roof height, but a reconfigured combustion chamber design. It's easier to just call it "P47" though so that's how I'll refer to it too. The Maxima L6 cam is an economy grind with less intake lift and soft intake valve springs. The Maxima "P47," is a modern E31. It differs in that it has a true closed-chamber configuration, larger exhaust valves, f.i. provisions, round exhaust ports with stainless steel liners, and through-the-cam oiling instead of a spray bar. It is a viable route to a performance engine of 2.8L or less. When used on anything of greater displacement, it requires the use of dished pistons which defeats the advantage of the closed chamber head. The 0.080" shaved P79/P90 approach is more an alternative to using the open chambered N42/N47 head on larger displacement engines (that should be using unshaved P79/P90 heads and pop-up pistons), than it is an alternative to the "P47". DAW

Find an N42 or N47 head for parts. Get rid of the Maxima intake valve springs and valves, leave the exhausts as-is. Have new L28 intake seats put into the Maxima head and lap-in the intake valves from the N42/47 head and use the intake springs. Get rid of the Maxima cam. If you're not installing an aftermarket cam at this point, use the N42/47 cam (and matching rockers). Unshroud the valves. Find a set of L24 rods with 9mm bolts (late '72-'73 240Z or late L16s). Take the N42 pistons off their rods, have the rim of the piston dish turned down until it is just in the same plane as the floor of the dish. Install milled pistons onto L24 rods (in the process, match up the weights of piston/rod assys and match rotating masses onto common crank throws). You'll want a bigger than stock cam for this because this set-up will yield well over 10:1 c.r. You might have to run octane boosters or racing gas to run this way. If you want a more streetable/practical set-up then do the piston/rod hybrid as described but just use the N42/47 head as-is for about 10:1 c.r. The Maxima head is better suited to 2.4-2.6L displacement performance engines and is an excellent retrofit on a 240Z shortblock in a conversion to f.i. The piston/rod hybrid approach gives a better rod/stroke than the stock L28 and bumps up compression. DAW

I haven't tried the plugs discussed, but I did notice this Ebay ad @$1.69 per plug. They may have the extended tips available if you were to contact them. DAW

I'd recommend finding a set of L28ET piston/rod assemblies on Ebay. I've picked up several sets at a very reasonable price. You're looking for pistons with the same dish as the L28E pistons of '75-'79 but you want P90 stamped on the top of the piston, indicating L28 turbo '81-'83. They will be on rods that are shot-peened; unlike the non-turbo L28 rods. The rings are different for the turbo also, if I'm not mistaken. Your F54 block and crank are the same as the turbo L28 and with a P90 or P90A head you are mostly there. Turbo injectors flow more than n/a injectors and the ECU is different so you'll want those, but otherwise it's a straight-forward conversion. DAW

You could fudge toward the tighter side of spec but it's not worth the risk of burning a valve to go tighter than that. I set valves by grossing in on the setting before I finalize, e.g., if the setting is to be 0.010", I check with 0.009" and make sure it passes, then confirm that 0.011" won't pass without significant pressure, then go for the consistant drag with the 0.010" feeler as the fine tuning tie-breaker. I set cold and double-check hot. Eventually you get the feel for the action of the final snug of the locknut in that cinching down doesn't bring the post down; it actually elongates the effective length of the post a bit, and you can plan accordingly. DAW

I don't think you'll have any valve-to-block or to-piston problems but you do need to change the intake valve springs to L28 springs. There are ways this can be done with the head on the car by getting a cylinder to TDC and applying compressed air to the spark plug hole which will keep the valve shut when you take the spring off and replace it. Your Maxima has only 8mm rod bolts and 1.77ish" rod journals so don't push it too hard. A 240Z L24 (post mid-'72) shortblock would be more durable and give a higher c.r. with the Maxima head than the L24E shortblock. DAW

Jared, I'm just poring over repair manuals, e.g. Chilton's Import Autos 1990-1994. I scan the crankshaft specs with a particular spec in mind and it doesn't take long to find a contender rod source. Finding the big-end width is perhaps the most difficult but Flatlander and other high performance parts warehouses often list Pauter, Crower, and other manufacturers' specs that coincide with stock specs and are invaluable. A trip to the local library can be worthwhile as they'll often have Mitchell's Manuals which are not commonly found in auto parts stores and are generally oriented towards serious, professional mechanics. DAW

I am a little concerned about losing strength when removing metal but there are a lot of engines running the 1.889 size journals. Unless the SR20 and 3sgte and many others are running forged cranks then I'll take the risk, especially with the L18. The L24 has a 1.967" journal and the L24E has a 1.768" journal. The L24E would never stand up to any hp, but it has twice the amount of metal lost than what I am planning. BTW, it looks like I can use pistons from an Acura RSX-S (K20C) in the L18 (1mm over = 86mm bore). They are compession ht. = 30mm, pin dia. = 22mm, dish vol. = 9cc. The original pin ht. = 38.1mm and the rod length of 130.2mm combined = 168.3mm. The 3sgte rod = 137.4mm and the Acura piston has a 30mm pin ht., so 167.4mm is the combined length and the offset grind to the crank journal adds another 1mm for 168.4mm and I think the L18 piston may sit slightly down in the bore as the block ht =L28, rods are same length and piston pin ht. is the same but the stroke is 1mm less in the L18 so it must sit down 0.5mm below deck stock. DAW

Jared, Waterhouse Motors in Tacoma, WA will do the L18 crank for $100 ($25 per journal), so I'd assume an L6 would cost $150. I think that's the going rate because I saw a price listed in a racing engine site that does domestic 8cyl cranks for $200. I'm going to pick up Toyota bearings for the rods, have the crank ground and start searching for pistons. DAW

The diesel head/valve cover assy. is shorter than the gas head/valve cover by about the same distance as the LD28 block is taller than the L28 block. With the gas head on the diesel block it sits 20mm higher. No interference on my Maxima and I think the engine could be dropped slightly on the mounts in the Z to ensure hood clearance. DAW

monologue. I didn't mean to say L28 130.2mm rods themselves in the last post, but that length range rod with a 1.887" big-end from some other source with the right cap width. DAW

Addendum: BTW, using the above approach while using the LD28 block/crank foundation, stroke could be increased from 83 to 85mm using 1.887" big-end rods with the cap width of the 3sgte rods, L4-L6 rods. The rods would be around the 152mm range and the r/s would be relatively high, around 1.8 or so. DAW (of course this could be done in an L28 block using L28 rods (130.2mm) and yielding r/s of about 1.5 if you want a r/s in that range). DAW

Hey Jared, I received my 3S-GTE rods and they look like they'll fit the niche nicely. I checked on other rod applications which would fall between the stock L6 journal dia. and the Toyota journal dia. and it looks like there were some Volvos (B23?) with around 1.925", which falls between 1.967" and 1.887". I think I stumbled on some 4 cyl Isuzu rods (4Z series) which could also potentially provide bearings for a modest grind of the Nissan crank. However, I was struck by how relatively inexpensive it is to have crankshaft rod journals offset ground. What makes the most sense is to have the L6 (or L4) crank rod journals offset ground in the process of reducing their dia. by 0.080" (2mm) from 1.967" to 1.887" (in order to use the Toyota rods). This increases stroke (and thereby displacement) to the engine. An offset change to rod journal throw center doubles the distance of actual stroke change. So the math...an 0.080" reduction in journal size done eccentrically, towards the outside of the throw, means that the journal centerline has been displaced by 0.040", increasing the stroke by 0.080" total. That means an L28 crank goes from a stroke of 79mm to 81mm, and an L18 crank goes from 78mm to 80mm. The Toyota rod length of 137.4 yields a rod/stroke of about 1.7 on the offset-ground L28 crank. What's left is to find a set of pistons which suits the choice of n/a or turbo application. The 3sgte rods are full-floating 22mm pin. The piston selection is the final variable to nail down and then the block gets overbored (or not) after the piston dia. is selected from available sources. Budget dictates whether an OEM std. dia. piston from a JY core engine, or an aftermarket forged, hypereutectic, or cast OEM-style (but in o.s. dia.) will be the source. Delivered to your door vs rooting around in a JY is not an insignificant accessibility factor either. I think I'll put together an L18 using this approach because I have one sitting around which I'll use in one of my PL510s as I have aluminum flywheels, etc., which won't work on the 6-bolt cranks of the larger L4s and I may want the shorter block to meet some vintage class requirements (vs the taller L20B, LZ20 & LZ22 blocks). This will be essentially equivilant to an L28 crank/block build (except for 78 vs 79mm stroke difference which means piston choice compression ht. for the L6 needs to be 0.5mm less than what I come up with for the L18 if the piston deck hts are to be the same in the calcs. Theoretically, this approach would provide an approach to building an L6 mildly stroked to 81mm (between stock [79mm] and LD28 crank [83mm]), increase the ratio of rod/stroke, and allow a wider selection of piston choices than using L24 or L28 rods which are press-fit 21mm pins. DAW

I consider the E31 and '71 E88 heads to be in the open-chamber head category. When I refer to closed-chamber heads I'm referring to heads that are flat and except for a discrete combustion chamber (i.e., peanut-shaped, or heart-shaped chambers). In the L4 heads this includes the SSS heads and W53/W58 heads, while the U67 heads are strikingly similar to the N-series L28 heads. The N47 Maxima L24E head is closed-chamber while the N47 280Z head is not. I think people should go with what works for them. I've offered my favorable experience with closed-chamber L4 and L6 heads vs my experience with the L4 and L6 open-chamber heads because I feel it's my civic duty to do so. It's really not to my advantage from an economical standpoint because it means a poorer selection in the JY of W53, W58, P79, P90 and Maxima N47 heads. I have a lot of E31 and '71 E88 heads I acquired when I thought that was the hot ticket and I'd use them if I needed a class-rules engine but otherwise I would definitely use the L24E N47 as first choice in an engine of 2.4 to 2.8 L displacement regardless of f.i. or carbs., but that's just me. DAW

Alright Jared, you piqued my interest in this enought that I just bought a set of shot-peened 3sgte rods off of e-Bay for $125. DAW

Excellent work, Jared! (although you may have just doubled the price of used 3sgte rods). 0.078" is a lot of grinding on your crank journals so you need to try to minimize that through thinner-walled bearing shells and big-end rod resizing. If you already know, don't be insulted but when a rod bearing is spun and the surface of the big-end is torn up, a machine shop can remove material from the mating surface of rod-to-cap thereby reducing it's diameter. It is then machined to restore the original dia. to match the o.d. of the bearing shell. The center remains the same in location but there is a (minimal) loss of big-end material in the process. So theoretically, you could have the big-ends of the 3sgte rods bored to a size matching the shell o.d. of an alternate choice of rod bearing which has an i.d. of larger than 1.889". I doubt you could bore it so far as to meet the o.d. of the Nissan rod shell without weakenning the Toyota rod, but you might be able to find a bearing closer to 1.967" i.d. with the appropriate shell width, oiling hole location, and tang configuration matching the 3sgte rod's which would fit the rods you have resized and afford less crank journal grinding/weakenning. DAW

Welcome, newbie 028 and thanks for the encouragement to keep going. You can be newbie swither's stand-in (he asked the initial question on this)because I think he probably fled a long time ago. Of all the anecdotal declarations on this topic there seems to be a paucity of accounts from those who have built both open-chamber and closed-chamber head L series performance engines. It's usually on camp vs the other with few who have spent time in both camps. Another pitfall is looking at evidence re detonation tendency from engines with big cams. You might as well compare engines with 8:1 c.r. because the tendency to ping is diminished. This is like comparing two mufflers for their restrictive properties on a 3 liter engine and using different brands of 4.5" mufflers to conduct the comparison. Common sense tells me that in high compression engines with stock cams in place, if one or the other head choice pings more I can extrapolate that the pinging champ is not the one I want to use as the foundation for the engine I'm going to build up and put through the wringer or even use for a performance street engine. I'd assume I'd be able to run more advance and leaner stoichiometry on a street engine and get better mpg (with equivilant performance as the other head choice) if I excluded the foundation from "the engine that ping built." Another misguided notion is that experience from an L4 Nissan doesn't directly correlate to an L6 with equivilant parameters but differing by two cylinders in length, or that 2-cycle, open vs closed-chamber head experience has no bearing. (Hey, I'm talking about my CAR here, not some WEED-WHACKER!). My intent was to teach a newbie the value of reasoning for himself the options instead of accepting rubber-stamp formulas; that time didn't stand still when Nissan stopped offerring the N42 head. DAW to achieve equivilant performance but better mpg A basic premi

Hey, check out this guy. Is he out in left field or what? What a hoot! http://www.kb-silvolite.com/index2.php Sorry, couldn't resist. DAW

The turbo pistons are stamped P90 and I think they use different ring widths than the N42-type pistons which have the same 10.9cc dish as those on the na L28s of '75-'80. I'm not sure that's true, check it out to confirm. The rings on the turbo engine likely have a different configuration/edge profile than their na (P79) counterparts; this is fairly typical of turbo engines. I expected the turbo pistons to have drilled oil ring holes like NISMO pistons but I think I remember seeing T-slots like garden-variety pistons. I've been told that the L28ET has shot-peened rods where the L28E doesn't. I compared the two recently and it appears to be true. None of this means you can't put a P90 head on an N42 shortblock and build a turbo engine in the fashion of an L28ET, it just may not be quite as efficient or durable. If you're on a budget, I wouldn't let it hold you back. DAW

I'm surprised someone hasn't popped up with your answer yet. I don't have this written down but I'll supply a crude measurement for you to work with. I suggest you find the true spec though. I just went out to the garage and found a box 'o rods and grabbed an inches-scale dial caliper on the way. I checked an L18/L28 rod and an L24 rod and I got 1.054" for both, or 26.77mm. Most likely that was 27mm when new but I'm guessing. They had some corrosion so maybe it was 26.5mm new, I don't know. Please return the favor and let me know what you turn up for out-sourced rods in a useable big-end dia. that are equivilant or slightly larger than that spec. I remind you again to avoid V6 sources as they will likely be too narrow. Regards, DAW

Truce Dan. I've stopped looking at the posts on this, it makes my head spin. John, thanks for the clarification on "proud." I was proud of my valves and my pistons until they collided. DAW

Ok, I'll respond to my own post...I see how to present the archive/library idea of edited posts with cross-referencing, by doing it on Site-Support forum and I'll put it there. DAW

I'm referring to whoever the shoe fits. By "contributing to the site" I was referring to "Contributing Members." While not a criteria to participate, there seems to be an inordinate amount of disruption and counter-productivity to this site by malcontent members who drag the site down rather than support it. I visit many other technically based sites (various technologies) and I don't see the prevelance of personal conflict that often overwhelms this site. I've been sucked in before and am a guilty party at times but I acknowledge it and have tried to reform. I believe something that could benefit HybridZ is if admin would select and flag/rename with keywords particularly long and controversial topic discussions, and place them into an archive or "library" that can be browsed rather than the needle-in-the haystack Search approach. Very often key concepts are discussed in a thread that are salient to the topic but not in the title. If the searching member were selecting specific words in an answer to his question he wouldn't have the question in the first place. Topics such as "N vs P" could be contributed to in a structured "technical article" format for the reference library, cross-referenced with other L6 performance topics, and broken down into a "data, tests, etc." section and a "personal experience/opinion" section which are listed in pro and con categories. The back-biting commentaries have to be extracted/edited out. BTW, I couldn't present this type of idea in an admin forum thread because I don't see a way to communicate by presenting such a topic unless you post onto an appropriate old-topic thread already initiated by admin. I might be missing a way to do it. As for you, Dan, you have a wealth of knowledge and experience and I've learned a lot from you, but speaking honestly and candidly, I think you have an aggressive, inflexible, know-it-all approach to presenting your point of view that doesn't serve you well. I've noticed a trend on the site wherein a member posts a topic and other members just send PMs rather than take the risk of posting and becoming fodder for disrespectful members. My $0.02. DAW P.S. admin: ban me if you want for speaking up, I won't miss this.

Thanks John, you're right 12v; not 16v. I'm working on a 2.3 16v engine for my '82 230CE euro-spec MB to replace the 2.3 8v and I'm working on an AQ 171 Volvo Penta crankshaft, rods, pistons, and 16v head for a stroker build for my son's Volvo 242 (no driver's license yet, but a car)and I guess I've got 16-valve on the brain. I thought that lash pads cost more than that and times 12, 24, or 36 to get the right ones would add up. Prouder? What the hell does that mean? DAW

With a 1980 ZX and N series head, you're OK with sourcing those L28 valves. Length is equivelant to the Maxima L24E valves. When you said you used 280ZX valves I just assumed you mean't the more plentiful F54 280ZX engine with the P47/P90 head as your valve source. I was thinking about what I said about using the shorter valves where longer valves belong and I think I had it wrong about the rocker arm ratio direction. I guess it would actually act like it had a super thin lash pad in place and increase the effective ratio while moving the wipe pattern towards the pivot, not the valve. Regardless, the coils would bind. Good luck and I'm interested to see the results, it looks like a good formula to me. DAW