DAW

Addendum: oops! in the last paragraph above, I meant to say the longer (I said shorter by mistake) 280Z L28 valves will increase the effective lash pad thickness. DAW

The N47 Maxima head has a heart-shaped closed chamber like the P79/P90 but it does not have the raised roof and attending shorter-length valves. It has the same dia. exhaust valve head as L26-L28 but the intakes are the same dia. as L24-L26 intakes so L28 intakes/seats can be substituted for better breathing. The intake valve spring on the Maxima head is weaker than the other L6 heads and the cam sucks. Unless the 280ZX valves are from a '79 L28E, they are going to be too short by .100" which will decrease the rocker arm ratio and put the wipe pattern off of the valve end (leading edge) of the rocker which meets the rotating cam lobe first (unless you use huge lash pads). Even with any valve spring shims removed, the effective spring tension is going to be high and coil stacking a high probability with any significant cam profile. BTW, speaking of L-series valve length, has anyone tried using a reground (smaller base circle) performance cam in an uncut P79/P90 head (with raised-top pistons for n/a or dished-top for turbo) and installed a set of 280Z L28 valves (.100" longer) to get around buying 16 lash pads? Stock lash pads that I've checked are usually around .160" thick and pads go up to .330". The shorter valves would yield an effective pad thickness of .280". Is anyone as cheap as I am? (I have both sets of valves available to use). DAW

In previous posts, I spelled out the advantages of using the Maxima N47 small cc, closed-chamber f.i. head and that the cam, intake valves springs (and 280Z intake valves if you want to go with larger valves, exhaust valves are the same dia. as L28E already). It makes an excellent choice of heads, especially for retrofitting an L24 240Z from carbs to f.i., using unleaded fuel, and increasing the c.r. (not over the E31 or early E88, but from mid-'72-on). On a Maxima L24E (with slightly dished pistons, maybe 5cc) the head yields 8.9:1. On a flat-top L24 240Z shortblock (use mid-'72-on for the 9mm rod bolts vs 8mm) it should be right where you want it for street/autocross performance on a budget. With some chamber work, it's a good choice for larger displacement (up to about 2.9L) engines but with flat-top pistons you have to watch that you don't end up with too high a c.r. for the cast pistons. With large-cc dish-tops (like '75-'79 L28E) you lose some of the closed-chamber design benefits. The chamber volume increase due to unshrouding chamber work can add some needed volume in these larger engines. BTW, McAdam, I think you might need to reconsider the 280ZX valves you've put into that head and use 280Z valves instead. This info may be useful to a newbie who's searching (as in SEARCH) for a way to hybrid-ize the L24 in his 240Z to increase performance and mpg while he builds a more serious performance engine or plans out his engine transplant. And this type of info is likely more valuable to him than the ill-mannered pissing matches that develop here on this site. I've allowed myself to get sucked in to this in the past but I'd rather distance myself from it now. It's inherent when people are passionate about what they've built with blood, sweat, and tears, but I see respect for others' ideas (and collaborative brain-storming of innovative ideas) on other sites. A good site affords mutual trust and respect that allows a member to present a reasonably sound idea or concept and get other points of view, not be denegrated. It's getting to be a PITA to present an idea, to a newbie for example, as is the topic of this initial post because of all the back-biting going on. Some of the worst offenders don't even contribute to the site, but they rant here showcasing their personality disorders, wasting everyone's time. DAW

Maybe it's just a wash between the open chamber and closed chamber heads. BTW, I'm selling several E31, early E88, late E88, N42 and N47 (L28) heads . Look for them on e-Bay. Also some sets of L28 rods. There are two kinds of problems: there are problems; and there are personal problems. DAW

It's not the header, per se, but might be due to the replacement process of manifolds-to-header since they share the same long gasket. Sounds like you might have a fuel supply problem or air/fuel imbalance (leaking gasket?). It may also be an ignition defect which shows up the warmer it gets..,.like around the time you're heading out? A little more history would be useful, but I'd go ahead and replace the fuel filter, run fuel system cleaner through it and clean/replace the screens in the carbs since they can gum up. Then I'd check the quality of the spark while the engine is crumping and rule-out impaired ignition, or not, if that's the culprit. Unless you twisted the mixture knobs on the carbs (and didn't tell us), it's more likely that the chokes/main jets would stick extended; causing richenning, not leaning, of the mixture. Retrace your steps. DAW

Thanks, John. It's in a street legal BSP 240Z, I think I'll transfer it to my PL510 with the louder pipes so I can't hear it. DAW

You can lead a horse to water...turns out there are horses that you can't even lead to water. DAW

Thanks, John. BTW, I bought a rebuilt R190 4.44 that I've autocrossed with and it is NOISY. I haven't looked into it yet, but I'd like to hear you say that they are all noisy! DAW

I don't think a comparison between an 0.080" shave/shim/revalved P90 head is a valid comparison to an uncut or mildly shaved N42 head because of the huge amount of mass removed which likely affects heat dispersion. A P90 and N42 would need to be compared on an engine with equivalent displacement, bore/stroke, rod length, etc. and I rarely have seen such a comparison. One reason for this is that the P90 has a much larger combustion chamber volume which means you can't just slap the heads onto the same shortblock and have a valid comparison. The P90 would need the suitable pistons to work as designed. This means that an F54 flat-top shortblock (8.8:1 c.r. with P90 head) has to have raised-top pistons such as the Euro version which only increases c.r. to 9.3:1 or so, or a more prominately raised-top piston to yield 10+:1 c.r. to compare to the F54/N42 engine. Alternatively, a dished-top piston, 2mm gasketed, N42 turbo engine could be compared to a flat-top piston, 2mm gasketed, P90 turbo engine. With the same turbo (limited boost due to c.r.)/injectors/ ECU used it would provide a fairly level playing field to compare. This is really the crux of this argument, you have to limit all variables except the heads and that's rarely done. What is crucial for many people is that they do the comparison themselves or they'll never trust the opposing point of view. That's the way people "KNOW" what's valid. DAW

I have noticed a difference in ping tendencies on two 2.8L, 10+:1 c.r. engines I have (both with N42s) with same ignition advance and same stock cams but different stroke length and rod/stroke ratios. One pings alot even with fairly rich mixtures (unless I back the timing off at the expense of throttle response and mpg) and the other never pings with a much leaner and more economical mixture. I'll let the reader guess which N42 application has the greater tendency to ping...I'm not going to contribute more hearsay myself. One factor differring between the two engines is that one is a mildy modified f.i., and the other triple sidedrafts. The one that doesn't ping has somewhat higher c.r. and higher cylinder pressures on compression test. My gut feeling is that if I switched inductions between the two I would be leaning the carbs and richenning the f.i. but that's a hunch, not knowledge. I have to actually do it before I know. For myself, I've learned something worthwhile by contrasting two engines while holding a major parameter constant (cyl head combustion chamber configuration). When these type debates come up I see people touting their results as spectacular (I believe them) and I'm very impressed. What I don't see is the same people doing the legwork to compare the variable (such as N42 vs P90) for themselves before they speak out and therefore not being in a position to comment with credibility. You have to wonder when you read accounts of successful builds using an N42 or P90 head whether the same c.r. engine and setup they built would be less powerful, more powerful, essentially equivalent, or have a hole in a piston with a P90 or N42 respectively...but no one seems to compare for themselves, they just jump on their bandwagon and campaign their cause. To compare, you've got to do a comparison and not present a diatribe on your personal engine setup as it is. Change the variable at hand and report back. (boy, am I goin' to hear it on this one) DAW

Always a controversial subject, but jmortenson provides more than heresay in his references compared to the strong opinions in other posts. Re the detonation issue, I don't look for validation in a modified engine that may be more forgiving re ping due to the non-stock cam. I think the more fair comparison between heads (with respect to factors such as sensitivity to variances in air/fuel mixtures, mpg, ignition advance, etc.) causing ping would be between two engines with comparable parameters and c.r. and the same stock cam in both. This is where the weak links show up and you can infer from them that you are buying insurance for your engine's life and for uncompromised performance under a wider range of conditions in the engine which is least-susceptible to ping. I think comparing a slightly shaved (not the huge 0.080" formula) P79 or P90 head on a euro-spec L28E (offset raised area on piston top) yielding about 10:1 c.r., vs an F54 flat-top with N47 (L28) head or N42 respectively yielding about 10:1 c.r., both engines with stock cam and cam timing, would provide a better platform for baseline comparison of combustion chamber effects. Set up with the same manifolds & injectors and transfer the engine management system from one to the other and swap the motors into the same chassis and compare dyno results, and drive real-world ping-generating conditions and record pings using a detonation sensor input. With each engine, vary fuel & timing parameters and chart against ping prevalance. I'll choose the cyl head that pings least, with parameters being equivilant under demanding conditions, to use on a modified engine with higher compression and a performance cam because common sense tells me to select the quench configuration that yields the best baseline results. From personal experience, I know my preference (I'll keep the hearsay to myself) but I'd put more stock into a controlled comparison. DAW

OK, this idea was mainly about driveability and versatility in a mainly street-driven car and not a 500+ hp application. Like I said, it would be of no value in that application. It's more in line with Volvo low-pressure turbo concepts and power/efficiency technology and it could be flawed there as well. Just an idea. I haven't seen instantaneous throttle response on the turbo'd cars I've had, more like ho-hum, followed by a huge rush of power and I've attributed this to the low static c.r. Let's say 3.5lbs @1400 rpm and I'm talking about a mini-turbocharger acquired from some non-U.S. market econobox where they try to squeeze h.p. out of small displacement engines to avoid taxation based on displacement. You're probably right but unless you have a variable-pitch impeller and variable dia. tubing and intercooler volume, I don't see how a single turbo capable of producing 500hp is going to provide instant off-idle response with a 7.5:1 c.r. without creating a scene at a traffic light. DAW

How about, instead of external wastegate plumbing, a manifold (stainless steel) to port off of the two junctions to drive a small primary turbocharger? It would be a primary stage, limited in flow and boost by function of inlet plumbing dia. but quick to spool, cutting down on lag time effect inherent in the large secondary turbo off the main manifold. The small primary would never be able to develop more than low pressure due to flow restriction (let's say 2-3psi max at 2,000rpm) by definition, but would always be there for low-speed driving and cover what's lost by the engine's relatively low c.r. The output plumbing from the primary small turbo would also be small in caliber to enhance low-pressure flow, enhancing throttle response, and could be run through a progressive, small primary plate/large secondary plate, throtttle body to maximize responsiveness off the main boost. The primary throttle system would be separate from the secondary but uses the same metered air source (otherwise the primary is useless; it's quick response output would be lost into the main intercooler volume). The off-idle TPS function is off of the primary throttle plate and the wot functions are off of the secondary plate. It would need to run a separate, small intercooler with isolated plumbing if one is to be used at all for the primary turbo. So what happens at higher exhaust flow and intake manifold pressures; does the primary run backwards? No, first off, it's limited in flow in either direction by size restrictions of the small turbo itself and the plumbing dia. used. An anti-reversion/diverter valve is included such that once intake manifold pressure meets the maximum output of the small turbo, a check-valve function prevents counter pressure and potential damage to it, while a mini-bov acts, once the check-valve closes, to keep the primary freewheeling while the main system is providing boost. I've been thinking of a basic turbo pressure-storage system anyway, so maybe I'll incorporate it to store some blow-off air pressure to supplement the primary throttle response system described here. I'm just thinking out loud (er, on paper) so go ahead and tell me why it won't work for a dual purpose autocross or street car. If it would work, it might be of some benefit to a road race car out of turns, but would be of no value in all out race engines or drag racing. DAW

I haven't been over to Delta cams for awhile. They profiled an L4 cam for me one time that I had no info on and they were good to work with and I remember being impressed with the good quality/price of their work. Does anyone have experience with their cam grinds, especially for L6 turbo, or rocker arm resurfacing? DAW

This one is transverse but Volvo makes a lot of cars & trucks that don't see the U.S. market. Maybe a RWD application or a RWD trans that can adapt? DAW http://www.swedespeed.com/news/publish/Volvo_News/article_329.html

Jared, I wasn't going to post again on this thread but I feel like I ought to caution you on some options you're considering. You are doing a good job of calculating specs and working "out-of-the-box" to put together a hybrid engine but you are not weighing all the variables. Assuming that you are building an engine using L28 block, L28 or LD28 crank while optimizing r/s, you are searching for rods longer than 133mm. One important parameter I think you haven't included is rod cap width. An advantage in using L-series rods is the consistant cap width. When you attempt to build your hybrid engine and are selecting rod lengths you want a rod with equivelant or slightly wider cap width (wider can be narrowed, too narrow are useless). Ideally, you want a rod with an equivelant rod journal size matched to the stock L6 journal dia. of 1.9670-1.9675". You can use a rod with a slightly larger large-end dia. by selecting bearing undersizes, usually 0.010" or 0.020" increments, for that particular rod to match up to the L6 journal size. Conversely, you can machine the crank journals (added costs) to match a rod with a too-small large-end dia. to the L6 crank. You don't want to trade off crank strength though, and undersizing to 1.768" dia. weakens the crank too much. One category of rods source generally would be V6 engines because the cap widths are usually too narrow compared to L series engines and other inline 4 and 6cyls. Rods in that category include Mitsubishi 6G72 with 1.9650 dia. end, Hyundai Sonata 3.0L with 1.9685 dia., and Acura 3.0L with 1.9676. A rod source you might consider is SR20DE. At 136.3mm length and 1.886" journal you could have you crank machined and still maintain adequate strength. I don't know the cap width, however, to determine if they'd be suitable. Anyone have this spec? Another inline rod to look into would be Volvo B630F. Large-end dia. fits their 1.969" dia. journal so using 0.020" undersize Volvo bearings works out to fit the stock L6 journal if the cap width is useable. Anyone have that spec? Work those variables out first and then look to piston sources to fit. You might be able to transfer a rod-piston assembly unit but to end up with the bore size and pin ht. you want it's unlikely. You could move the rod journal effective centerlines inward or outward in order to change stroke if you have the journals undersized (increase throw length on L28 or decrease LD28) and/or fit the rod choice to correspond to block ht. and piston pin ht. to make it all work out and you could conceivably have an LD28 140mm rod small-end reworked to shorten effective length while reducing the pin dia. and lightening the rod. A long post but I don't feel like I wasted the reader's time or squandered the space. DAW

I had an L28 block over-bored to 89mm and all components set to build the typical L6 stroker using LD28 crank but once I looked further into the follow-the-sheep approach of the build and crunched the numbers, I chucked out that plan and arrived at another I feel is more sensible. I was going to do the L24 rod (133mm) on LD28 crank (83mm), r/s=1.6, recipe passed down from grandpa, but worked out other options I feel are better choices for my use: 1) use LD28 block, overbore 0.060" to use std. L28E or L28ET 86mm pistons, or 0.100" overbore to use oversized pistons, stock LZ22E rods (148.6mm) and LD28 crank (83mm), r/s=1.79, or 2) use LD28 block overbored 0.020" for std. LZ22S pistons or Mitsubishi Eclipse pistons (85mm with 21mm pin), or 0.100" for oversized pistons (piston rim needs to be machined down .75mm [several options available for differring dish cc's]), stock LZ20E rods (152.45mm) and LD28 crank, r/s=1.84. Since I'm not using variable camshaft timing, I chose option #1 with r/s=1.79, readily available rods & pistons with no piston machining required, choice of flat-top or dished pistons, easy and cheap build for 2.9L displacement or buy oversized pistons for 2.97L. If a 1.69 r/s is desired (stock LD28 configuration, i.e., diesel), the LD28 140mm rods can be used (I haven't seen any documentation that these rods are significantly heavier than the large-pin Nissan Comp. 140mm rods), with roadster pistons or others with higher pin hts., but why chose 1.69 when you could choose 1.79 for your high rpm engine??? I'm bailing out of this discussion and I'll live and let-live re how we differ on what factors are significant, or insignificant, in selecting components for a high r.p.m. engine. I find my current approach more unique and intellectually satisfying to me than my initial choice of 133mm rod/ 83mm stroke. When it comes to rod size, you can say short rods rule but I'll stick with mine. DAW

Like I said at the outset, "blah, blah, blah." Note Isky refers to going to exotic and extreme measures to do such things as increase the block height. In this case, two blocks are sitting in front of you and all you have to do is pick the one that you feel will work best. With the same stroke and bore, and factory available passenger car rods and pistons equally plentiful to select from, would you pick the block ht that yields 1.6:1 rod/stroke, or 1.8:1? What if you didn't have the inconvenience of using a hood scoop on the 1.8:1 engine...would you still pick the 1.6? I see in Isky's article that he teaches us what Adobe is and I appreciate the cutting edge technology offered, but I think the most appropriate quote relating to this discussion is from Carl Rogers, "When the only tool you have is a hammer, you tend to treat everything as if it were a nail." DAW

Oh, you might need to use a cowl induction hood or an L88-type scoop, so better forget the whole thing. c'mon Dan do you still believe the world is flat? Just because you didn't think of it, it doesn't mean it can't or hasn't been done. SBC builders often choose 6" rods to achieve good rod/stroke ratios (same rod length as LZ20E) and SBMopars have high factory rod/stroke ratios. This is not a factor that automotive engineers ignore in engine design. If Nissan wouldn't have gone to the V6, I'm certain that the next generation gasoline L6 (with longer stroke) would have had the same increase in block ht as seen in the LD28, L20B, LZ20, LZ22 with rods in the 145.9mm to 6" range. LD28 with N42 head clears my 810 hood with no mods at all, underhood insulation padding intact. For the 240-280Z chassis I have a 240Z dealer-mod hood, which is cutout over the valve cover and uses a riser center buldge/scoop with side openings (inlets/outlets) on it (a Nissan designed remedy for vapor-lock problems) that adds clearance and lower underhood temps as well. I'm using 280ZX headers on the 810 chassis with the tall block and they fit fine, but 280Z headers on the tall LD28-block hybrid L6 might interfere underneath a 240-280Z chassis, which makes turbocharging a good approach at the outset to obviate such problems. DAW

I find the fastest easiest way to figure out combinations of rod length, pin ht. (compression ht.), and stroke length is to assume zero deck ht. with the stock configuration and go from there. e.g., L28 at TDC: pin ht. = 38.1mm. Rod length = 130.2mm (I've always used 130.4 in calcs but I'll trust F. Honsowetz's number of 130.2). You only need these two factors when using the stock crank. If you change cranks you need to add or subtract 1/2 of the change in stroke because the effect at TDC is the change in actual crank throw length, which times 2 is the stroke change. For L28, 38.1 + 130.2 = 168.3mm. You can get 140mm rods (either FJ20 with 22mm pin or LD28 with huge pin [approx. 23.5mm]), so subtract 140mm from 168.3mm and that's what pin ht. you'll need to make it work out at zero deck ht.; in this case = 28.3mm for your custom pistons. A piston with less pin ht. will sit down in the bore at TDC and conversely, more pin ht. results in + deck ht. (and top ring/top of bore distance problems). The LD28 rods are more plentiful than FJ20 rods but the larger pin dia. might pose more of a problem in making custom pistons. Always consider hybrid engine components. Look at specs to find an alternate sources for rods & pistons, especially pistons. There might be sets of Mitsubishi or Volvo pistons out there in JYs for pennies that meet the specs of the $$ custom pistons you're about to have made. If you find some by looking through tables and tables of specs, the least critical factor, and the most flexible factor to deal with, is what bore dia. to make your block to fit the available pistons (as long as you keep the overbore sensible). The best thing about using the taller LD28 block is the expansive choice of stock Nissan rods from L4B/LZ4 engines you can pick from which all give enhanced rod/stroke at low engine-build cost: 145.9mm, 148.6mm, and 152.45mm, and can be combined with readily available factory pistons to yield zero, or near-zero, deck hts. Use the same approach as above calcs but use for LD28 block: 46.5mm pin ht. + 140mm rod = 186.5 as your working distance for a zero-deck, 83mm stroke engine. DAW

Like you said, you need to figure it all out in advance. Figure out several scenarios or combinations and then look at them in terms of cost, parts availability, downtime for machining work, etc., and what you'll have at the end. If you're going to end up with a huge investment into an L6 by piecing it together, you might consider what sense that makes vs installing an RB 6cyl, SR20, etc. Search this site well and you have to have "How to Modify Nissan/Datsun OHC Engines" by Frank Honsowetz at the bare minimum to figure out the combinations you're considering. Look at L4, LB4 and LZ4 dimensions in that book. The same problems you're faced with re trying to fit a taller performance package into too short a container were solved by Nissan by making the container taller, not by smashing down the contents to make them fit (and compromising performance in the process). L28 rod/stroke was already a compromise from the L24 because they had to use shorter rods when they put in longer crank throws in the same ht block (although a shorter pin ht would have, and does, make more sense to enable a longer rod). This situation was the same as in the L16 to L18 evolution. The evolution from L18 to L20B (same bore, longer stroke) was addressed by increasing the block ht. The same essential thing needs to be done with the L6 as with the L4 if stroke is increased more than that of an L28. Nissan did exactly this with the L6 when they increased the stroke length from 79mm to 83mm. The LD28 block is the same ht as the L20B block. Don't smash down the contents to fit into the container; use a taller container. Simply put, if you are not going to use the taller L6 series block and you want a favorable rod/stroke, you won't be using an LD28 crank. If you use the L28 block and want to increase rod/stroke over stock L28 you are limited by choice of reasonably priced or accessible rods. I'll break up this post and look at some options for using the L28 = L24 = L16 = L18 block ht. DAW

In a nutshell, the L24-L28 block is too short to reach a favorable rod/stroke with anything but an L24 crank (or an L28 crank and custom pistons). Do the math. The LD28 block lets you use the LD28 crank (83mm stroke) with appropriate-length rods. There are many possible combinations of rods/pistons depending on purpose, budget, availability, etc. I know, tell me how it can't be done and why a 1.6 rod/stroke is superior to a 1.8 and blah, blah, blah...DAW

I'm a little perplexed...your problem is described as if your chokes are not working properly and when you pop the hood and manually activate the chokes the problem goes away- - have you tried adjusting the chokes according to the Datsun service manual (including fast idle adjustments by bending linkage rods the proper amount, etc.)? At any rate, the SU chokes are troublesome even when properly set, and if they stick they will throw the mixture off on one or both carbs through out the entire rpm range once it's warmed-up. On one of my dual SU cars I eliminated the mechanical chokes altogether and configured a primer line system like some aircraft engines use (they don't have accelerator-pump carbs either). It can be activated from inside the vehicle (the planes are this way too). Fast idle is by throttle cable (or by your foot if you don't want to set up a separate cable) if you don't use a check-valve in the primer line, the engine vacuum will draw in extra fuel but this isn't necessarily a bad thing because with a manual fuel shut-off valve in the cockpit (interior of your car) you can modulate the extra fuel during warm-up. A non-butterfly valve manual choke. This setup is also good because SUs can leak down the fuel bowls a bit while sitting and they may collect condensation inside once they do and with a mechanical fuel pump it may take a bit of cranking to get useable fuel to the intake manifold; whereas with the primer setup configured with a small electric fuel pump - - once you open the valve and tap the pump button for a few seconds, the engine fires instantly...a nice feature in battery-killing cold weather. I've never tried setting up an ether-filled reservoir for this primer...let me know how it works out if you try it. DAW

It's about carboxyhemoglobin levels leading to anoxia that's getting you high. Chronic CO poisoning is to be taken seriously. The key justification for a sunroof in a Zcar is that CO is lighter than air and will accumulate around your head. With the windows closed, if you're seeing water condensation on the glass you may well be inhaling a high concentration of CO because another by-product of combustion is H2O. You may not die in that sauna from acute CO poisoning but it turns out that repeated exposures, chronic CO poisoning, can cause more severe and permanent brain damage. DAW

If your compression test is 165lbs. warm, and a stock cam, you either don't have 10.0:1 c.r. or you have holes in the pistons. DAW