DAW

There's a nicely done Civic around here with an Acura V6 mid/rear engine. The car has big boxed rear quarters and looks like a Renault 5. Charcoal grey metallic, it looks like a production car and is quick in autocross. I think I've seen it in a magazine or two. Personally, I don't care what brand of car or components are involved and appreciate the engineering, creativity, fabrication skill, workmanship, and performance. DAW

Ditto the above. My money would be on the corrosion on the now relatively loose nut (12mm) on the starter strap that connects directly to either the starter motor/solenoid or the battery cable/solenoid. While you're there, check the solenoid primary/ign switch wire connection. DAW

The combination you've described doesn't work. The pistons are sticking up out of the block 2.6mm due to the L24 rods (133mm) used with L28 crank and pistons. L28 rod length is 130.4mm. I don't understand the high compression ratios you are talking about. L28 dished pistons have 10.9cc dish. There are 4 E88 heads. If you use the rare early one (like E31) you boost c.r. modestly above stock N42 c.r. of 8.3:1, maybe to 8.9:1. The most common E88 gives the same c.r. as the N42 head on the N42 shortblock, 8.3:1. If you use the E88 from the L26 it will drop your c.r. probably just below 8.0:1. As you can see, the particular E88 you are using does make a difference in c.r. but none of these combos result in c.r.s that are incompatible with turbocharging. So why not just use an N42 head? it has the proper valve sizes and injector notches already there. DAW

I'm naive here but could the cam designers be looking for optimizing low-end off-boost performance to minimize turbo-lag, knowing that the intake profile has to remain constant but compressed intake charge will increase with r.p.m and can increase intake filling at a relatively low duration on boost? Looks like there may be two approaches, one for maximum boosted h.p. and one for maximum driveability off boost with more modest max h.p. gains. Could this be the case? (and don't beat me up because I'm just theorizing) DAW

Addendum...maybe I should clarify why you would swap the Maxima cam for a 240-280ZX cam..the Maxima L24E has economy-minded intake lobe profile with less lift and a weaker intake valve spring than the L24/26/28 Zcar does. DAW

Oops, that's 0.120" over to go from 83 to 86mm. BTW, if your budget is really tight, you might be able to get by without overboring and just replace you rings. Nissan blocks are extremely tough. DAW

This is an excellent head for what you're doing. Don't worry about the burrette, you can calculate the cc if you can get the specs for the cc of piston dish on the Maxima L24E. It isn't very much and your flat tops will raise your c.r. higher than the L24E c.r. of 8.6:1. I'll guess your c.r. with this head will be about 9.0:1 so you may want to have it shaved a modest amount (0.15-0.20") to raise it another 0.5 c.r. or so. However, if you're going to overbore that will increase the c.r. also, so you might be able to skip the head shave. With your displacement and budget, you could skip the intake valve swap and use the 42mm L24E valves. You do need to swap the cam for a Z cam ((L28E from an N47 or P79 head would be easiest since it is rifle-drilled for rocker oiling vs 240Z and N42 spraybar oiling). You need to swap in the Valve springs for the intake valves also (from the 280Z head). BTW, if you decide to have the head shaved you can back off the rocker arms so all valves are closed, and the machine shop can shave the head. If they tell you you must disassemble if they are trying to rob you or they don't know what they're doing. Just clean the head well after and use compressed air to get rid of any possible shavings. As to exhaust valve/block clearance you need to notch the top of the cyl bore on an L24 (even with a 0.40" overbore. It's not hard to do and you can do it without tearing down the bottom end. If you need to overbore for wear reasons then don't just do 0.40". Consider 0.80" (83 to 86mm), and use Sterling pistons that are made to use L24 rod length. Then you can skip bore notching and head shaving, and increase c.r. and displacement and preserve the favorable rod/stroke ratio of the L24. DAW

OK, I searched and found the SU Needle book here: http://www.minimania.com/Search_Inventory.cfm DAW

You said that you had the SU book I referenced. I think you should read it more closely because it tells you where to look for the info you want. It references the "SU Reference Catalogue" and the "SU Carburettor Needle Profile Chart" as where to find SU needle diameters at 1/8" increments for virtually all SU needles. Why would you seek out hearsay when factual data is readily available? BTW, the technique for needle profile modification is very specific and requires a drillpress to spin the needle while removing small amounts of material with fine sandpaper. You mention that you might try to do this using a dremel tool...I hope you don't mean you're going to apply the dremel to the needle. If you mean you want to chuck up the needle in the dremel, I think you'd be better off with an electric drill because of the rpm and because a lot of drlls have a trigger-hold mechanism that you could lock on while holding the drill in a vice so that everything is steady. Also, if you are setting out to custom profile your needles for your engine/altitude/rpm use-range, you might want to start with stock needles rather than something like an SM because you can remove more material (richen), but not less. If memory serves, I think the SMs were a little too rich at top end but too lean in mid-range for my engine so I was better off starting with needles too lean throughout in order to add richness anywhere I needed it. DAW

Check the flapper door in the Air Flow Meter to make sure it's not stuck open and check all connections to sensors, looking for corrosion of the terminals. DAW

SMs are not the only performance needles for SUs. SMs are from Citreon (or some other older European car) SU carbs originally. There are other choices and what's best is to modify a needle so it's custom-tailored to your engine. There are factors other than the needles which you'll want to modify also e.g., damper spring selection, damper oil type (use ATF and don't overfill as this adds wt to the piston), choke linkage if it's hanging up at all (affects needle ht), and ignition timing (affects throttle response). If you really want to get results, read the SU book I told you about in one of your parallel posts on this subject (I'm not being critical, just trying to focus your search), and a good source of SU parts is APT (Advanced Performance Technology, 595 Iowa Ave, Suite C, Riverside, CA 92507, 800-278-3278). Their roots are in English sports car racing and what better place to look for SU tuning experience? DAW

The most luck I've had tuning SUs is by custom altering needles by turning them with a drill press and squeezing at specific points with superfine sandpaper. Squeezing = richenning. Where this is done on the needle is determined by performance at a given rpm which corresponds to the position (ht) of the needle as measured by a standardized small straw or aluminum tube placed into the damper piston (oil caps off and oil drained). It's a little complex but really not that bad and the yield is great both in performance gain and efficiency (mpg). Read "How to Build & Power Tune SU Carburettors" by Des Hammill, it's a great little book which contains sound and simple methods to gain a lot of power and driveability from your engine. DAW

Aftermarket oil gauge? If so, and it's mechanical, the line is probably leaking where it connects to the gauge. If stock oil gauge (electronic), then maybe its brake fluid from clutch or brake master cyl? Trans oil coming up speedo cable casing due to blown seal at trans/ speedo connector? DAW

It sounds like the idle mixture was off or unbalanced. Get rid of the low octane gas, put a Uni-Syn on the carbs to confirm the airflow is balanced both at cruising rpm and at idle. My experience has been that since the idle mixture adjusters set the height of the main jet which affects the entire rpm range mixture, it's best to have these close to symmetrical, even if the idle initially feels a bit rough, rather than to spend a long time trying to balance the idle mixture where one jet may end up higher than the other. DAW

The N47 Maxima L24E head U.S. market, has round ex. ports with liners. I saw the sq port reference too, and it made no sense. However, I wouldn't rule out the possibility that there is a JDM counterpart with sq. ports (like the N47 sq port L28E head I have). An ardent discussion about these heads, but it's essential that comparisons be kept equivilant. Basically, there are three categories of the L6 heads: "small, medium, and large" combustion chambers. For the "large" chamber heads (about 53.6cc), use is dictated by larger displacements or lower (turbo) compression ratios). There's only two choices, both are closed-chamber design: P90/(a) and P79 (not big cut & shim-modified). P90 is my first choice here due to sq ex ports and mech valvetrain. The biggest controversy seems to be in the "medium" cc chamber range (about 44.7): N42/L28E N47 (open-chamber) vs P90/P79 (closed-chamber) cut 0.80", shimmed towers, & N42 valves (longer) placed ($) vs late E88 (open-chamber). E88 has small intake (42mm) valves and valve seats for leaded gas, whereas the L28 heads have hard seats and larger intake (44mm) valves. If your engine is a smaller diplacement, or you can run a c.r. well over 10:1 with a larger displacement engine, then the "small" chamber series is for you (around 42.5 cc). Most of these are early pre-unleaded fuel heads and will need the valve seats replaced. All are from L24 engines and have smaller 42mm intake valves than the "medium" and "large" heads from L28s (44mm intakes and harder seats). The E31, and early E88s (open-chamber), have small 33mm ex. valves. The L24E Maxima N47 head (closed-chamber) differs from the others in this category as it has the larger, 35mm, ex valve already in it (same size as L28) and has hardened seats that the others lack. The closed-chamber Maxima head is good to go with it's ex valve as-is and this head is my pick over the others in this category as the one to go with, both because it is the later closed-chamber design and especially considering it also has f.i. notches and bolt holes in the intake surface. I'd prefer the sq ex ports ala E31 but there may be JDM L24E head out there that way. You'd need a donor L28 head to upgrade valve size in any of these "small" heads. In the Maxima head you need to have L28E intake seats placed, intake valves and springs transfered, and the L28 cam transfered. In the E31 and early E88 you need to have both intake and exhaust seats placed and transfer all (in & ex) valves. My interest in this discussion is to provide some guidelines for some who may not have experience in putting these combinations together so that they realize that there are some choices that weren't available during the initial evolution of the L6 which may have advantages (like f.i. and closed-chamber heads and hardened valve seats) and that the desired c.r. is the main determining which category of heads to choose from. DAW

What is the idle rpm? Does it seem to be working to crank when it's hot? DAW

I'll try to take some photos if someone will accept an e-mail attachment and post them as I have no website set up. Photos of combustion chambers of E31, early E88, late E88, N42/47 280Z, N47 Maxima, and P79. It's difficult to equitably compare heads unless you're using a head with the same cc and valve size as the comparison head and the cam/setup is the same and they are both tried on the same shortblock. It's no surprise that a shaved P79 would out perform an E88 of an equivilent cc if the valves in the E88 had been changed to be as large as the P79 (44mm/35mm). Apples and oranges. Perhaps the most equivilent comparison of the two chamber types would be between an E31 with L28 ex valves installed, and an N47 Maxima with 240Z cam (and oiler bar towers) and intake springs; these would go onto an L26 (flat-top) shortblock for a c.r. of about 9.5:1 (ballpark). These heads have cc's about the same and would have 42mm/35mm valves and same valvetrains once setup as above but the big difference is that they have different chamber configurations (and sq vs rnd ex ports). The parameter that's important to me is if one head allows detonation more easily than the other at a given fuel octane and timing setting (and mixture). If they produce the same power at conservative settings but one allows me to further advance timing for throttle response, power, and mpg where the other can't due to ping...then in my mind the less ping-prone head is the better all around choice for stock, hi-perf n.a., or turbo use (as it will allow more boost without detonation and ECU-mediated timing retards). My gut feeling from similar exercises with U67 (open) vs W53 (closed) L4 heads is that the closed chamber has the edge at the same c.r. However, to duplicate the c.r. the open chamber head has to be on a larger displacement shortblock so it's apples and oranges as is the case comparing an N42 to a P90 (unless it's a P90 that's been cut & shimmed to be the same cc as N42). The E31 (or early E88) vs Max N47 set up as equivilents is the closest/fairest comparison of the two chamber types. BTW, if I get these pics I'll include one of the port-flange side of an L28ET turbo ex manifold. I'm thinking it could be used on a round-port head (liners removed of course; PITA but not that big of a deal). I have a square-port N47 head on one of my engines which probably came from a JDM used crate motor. So there are N47s with totally different chamber types and port types and the common denominator seems to be cam tower-oiling, vs the spraybar-oiling of the N42. DAW

Not to play devil's advocate, but the hp increase in the ZX vs Z L28E is associated with a 0.5:1 increase in compression, not 0.2:1 (8.8 vs 8.3:1 c.r.). There's a rule of thumb re expected hp/c.r. change which I don't have in front of me but .5 is not insignificant and can be felt in the seat of the pants dyno. I've found the N42 to ping on a 10:1 2800cc with 86x79 engine but not on a 10:1 2800cc with 84.5x83. There's probably a good explanation for that re piston speed around TDC with regard to stroke length and rod/stroke in the 130.4/79 engine vs the 140/83 engine. I'm thinking about low-pressure turbo for the 10:1 engine that doesn't ping for the next step up in performance since I've never heard it ping using premium gas. Another option would be to increase the c.r. over 10:1 by putting on a head with smaller chamber volume than the N42 such as an E31 or early E88, a severely shaved/shimmed/lashed or Z-valved P90/79...or, the best choice re cost, f.i. provisions, minimal prep work, closed chamber...the N47 Maxima head with 280Z intake valves/seats, springs and cam. Not many people on this site have really explored the use of this head. Granted it has round exhaust ports vs square but it looks to me like a turbo exhaust manifold can bolt to either type of head. This is a totally different head than the 280Z N47 head, even though they share the same casting #. There is a possibility that this head was used on JDM L24s and had square ports. I think the emmission laws which dictate the liners may be different in other countries as I've seen P90s on Japanese n.a. L28s. The Maxima N47 comes on the U.S. L24 with slightly dished pistons (maybe 2-3cc) and a c.r. of 8.6:1. This means it has the chamber volume approximately that of an E31 but the configuration of a P90/79. Comments are welcome. I ask only that you have personally seen the chambers of an N47 Maxima before you comment. Please don't discourage beginning builders by speaking negatively about something you're purely speculating on. I don't want to sound preachy but several years ago I was told by many "experts" including NISMO techs that I couldn't put together a long-rod stroker using an LD28 shortblock and L28 top-end. Turns out they were wrong and they were speculating rather than speaking from experience. (I've been driving the car for years now and it performs well and is very reliable). DAW

Hopefully this is some deranged lowlife...and not a series of sniper attacks by a team of terrorists...communicating, setting up the shooter, and facilitating egress from the scene. It's either paranoia or the writer in me that comes up with these ideas...what if this week the MO switches to blue 4dr sedans spotted after serial shootings of a certain profile of victim, e.g. middle-aged caucasian women... So let's hope it just some scumbag nut on a rampage. DAW

P90s are going to be far scarcer than an N42 because most are in use as the OEM/head of choice for the L28ET, whereas the N42 is from a stock 280Z L28E and in much higher production volume. One twist is that there are P90 heads on some Japanese market (JDM) L28 non-turbos that come in through the used engine importers. Some of these have been bought, N42/47 head grafted on for a 10+:1 engine, and freeing up the P90 head to build a turbo engine. DAW

I've thought about converting the triple side-drafts to throttle bodies by gutting the carbs and adding bungs and injectors, after I originally thought I'd do a blow-through setup. I have a brand new Cartech triple side-draft plenum which I waited a long time for them to make because they had to dust off the molds and wait until they had enough orders to cast several at the same time. That was about 10yrs ago. DAW

yo2001, I don't have a web site but I could e-mail an attached photo. I put an L24 rod next to it for reference. I was wrong on the pin dia., it's 25mm not 23.5mm. The outer dia of the bushing appears to be about 28mm. I don't know the accepted limits on reducing the bushing bore (e.g. to 22mm). I've got the opposite problem and have to go from 25mm to 26mm for the Mercedes pistons. BTW, if you get the photo OK and have a website maybe you could post it for others? Thanks. DAW

Big as in 23.5mm pins. It has 9mm rod bolts and a wider beam than the other L series rods. It most closely resembles the 12100-B2501 Sports Option NISMO rod except it has bolts/nuts vs 12-point bolts tapped for into the rod. See pg 39 of Honzowetz's book "How to Modify..." the rod shown is the 148.6mm version but looks otherwise like the 140mm version (which the LD28 resembles). I can't find my postal scale but it is not a massive, heavy unit. As Bob H mentioned, they are made to handle 22:1 c.r. I've just started yet another project where I'm building up an LD28 overbored shortblock (to mate an L6 P90 head) using a Mercedes-Benz 87mm piston (big floating pin, strong piston) to fit to the LD28 rods, and milling down the head to the compression ht and shape I want. Has anyone welded injector bungs and t.b. flange onto that LD28 intake manifold? Hood clearance looks like a problem but performance potential looks like it might exceed the stock L6 f.i. manifold. DAW

LD28 rods also use big, floating wrist pins. DAW

I'm toying with an idea to run propane into the air injection passage/ports in my Starion ESI-R. There are small jet valves in the head operated by rocker arms which are designed to introduce auxillary air to lean and promote combustion swirl (and they notoriously cause cyl head cracking). Mine are not operational at present but I'm wondering if they could be used to introduce propane supplement at boost by direct injection? I know I'm not at a DSM site but there seems to be a good brain trust here. DAW