ozconnection

The thing I found about using the Arizona manifold is that you can use a surprisingly large carburetor on them and get away with it. I'm talking L28's here but I still think that on an L24 you can get away with a 390 or 465 vac Holley no problems. The smaller the main venturi, the sharper the throttle response will be, so it makes sense that the 390 will be sharper than a 600, for example. This is also due to the nature/design of the manifold itself. That divider that's cast into the plenum separates the induction into two halves, so what we have is essentially, by definition, a dual plane manifold. These types of manifolds are popular with the V8 boys because they improve low engine speed torque. Compared to the Clifford 6=8 manifold which has a massive open plenum under the carb, the Arizona is superior for street driving IMO. The issue with the opening of the secondaries is that when they do actually crack open, there is a momentary change of gas velocity (reduction) through the primary venturis as the engine balances the airflow dilema out and shares the demand with the secondaries. This is where the base fuel curve (determined by the high speed air bleeds and emulsion circuits) changes a little and changes the air/fuel balance that the engine sees when the seconaries open. Reversion of the air/fuel mix also changes the air/fuel ratio that the engine sees. This issue is very prominant in my engine, so much so that just bolting on a Holley four barrel outa the box onto my engine results in a filthy rich top end mixture. I had to pull out heaps of fuel via smaller secondary jet to offset this, the proper fix is to play around with the emulsion tubes and/or bleeds to get the fuel curve 'right'. This isn't easily done on standard Holley carbs, especially the generic ones we all seem to start off with. Their calibration is for V8's and therefore when we bolt them to our engines, they'll run but not be optimal. That's why so many guys who get Holley's soon ditch them. They don't know why they can't quite get the tuning right and after mucking around with jets and power valves forever, call them junk. Dual plane manifolds do this, the Clifford wasn't anywhere this bad. So far apart are the tuning requirements of these two manifolds, I can't just change over the manifolds anymore and use the same carb calibration. I'm not suggesting you get out your drill bits and start opening out the holes, as it stands many of them need to be made smaller anyway! I spoke to a carb guru down here and he suggested that if I want to go so far as to getting my carb setup spot on, taking into account all of the L28's issues, he could modify the stock primary metering block to allow for custom tuning of these fuel circuits. I got him to do it for me and armed with a wideband o2 meter, tuning has become fun and vastly more accurate. I'm almost there, and I've learnt a lot along the way. The Innovate website has a forum just like this one and that site has very valuable information for anyone who decides to run a Holley carb on their engine. I'm looking forward to seeing your plugs, until then.... Cheers.

The stiffness of the seconary spring will change the character and response of your engine, either good or bad. The first thing you need to do is realise that the secondaries may not even be opening at 2.2K rpm on an L24. That flat spot you mention may be over enrichment from the power valve, lean or rich main jets or even from the accelerator pump! OR it could be too lean at WOT in that 500 rpm range! Manual or auto trans? Ignition timing, stock curve or modified? Vacuum advance? Stock camshaft profile or aftermarket? Stock head and ports? As you can see, there are quite a few things other than the opening point and speed of opening that can affect your powerband. Oh, and what do you plug electrodes look like? Take a photo of one and post it if you like. I don't want to start writing a tune up regime for you as you would probably have done some reading/research for yourself. All I'm saying is there are a number of other important variables you need to consider. I find that when I tune my combos, I tune the carb first, then play with the ignition timing. Remove the vacuum advance hose and plug it for tuning purposes. As a suggestion, if you're running stock timing, bump it up a couple of degrees to see if the engine becomes more responsive. Listen hard for 'pinging' and back it back down it it does. Cheers.

Thanks man, its a big looking mutha but its only a 450 vacuum operated secondary. The guages are oil pressure, fuel pressure and manifold vacuum. I keep them under there so I can leave my interior stock looking. I also figure that if I have to lift the hood for any reason, its then I need to look at the guages under there. When I shut the hood, then all is well (hopefully!). Cheers.

My crankcase vent system has its origins from two points, one is from the front 3 runners and the other is from the rear three. The picture below shows the pickup from the rear three. The other vacuum line travels to my brake booster. Why choose two origins? I wanted a good vacuum draw onto the PCV valve. I also looked at the size of the rubber hose that connects to the PCV valve. I figured two smaller lines would approximately equal the larger hoses cross sectional area. Also, if there was to be some oil vapor or mist sucked into the cylinders, it would be shared amoungst all six cylinders, not just three of them. The hose that connects to the top of the rocker cover also plumbs back into my air filter assembly and any vapours that come from there are sucked back into the engine via the carburetor. No more fumes into the cabin that way. A properly sealed setup the mimics the factory setup as closely as possible.

Not hard really, there are two vacuum access ports on each bank of runners. These are threaded so I bought some brass fittings and adapted a brass tee block which also had the same thread as the PCV valve. Have a look at the picture and you'll see how I did it. Note the allen bolts and the phenolic spacer which eliminates any interferance between carb and manifold.

If ever in doubt...do it again. If you're not sure, then chances are 'things' are not right and they must be corrected before proceeding any further. A new gasket is a good place to start. A loose manifold is common and can be corrected by using a little locktite on the threads or do as I did and replace all of the studs with long high tensile allen head bolts. Much easier to tighten up with a 6 inch long allen head bar stock on the end of a 1/2 inch socket. You can actually torque all the bolts to spec that way. Not essential but handy and a 5 minute job to check, even when hot! Fuel puddling... get that carby off and get it sorted. It sounds like it needs some serious lovin or binnin. Get a carby on there that works! The intake manifold. Studs holding the carb onto the manifold can be wrapped with some plumbers tape before you install them. That eliminates the chance of leakage in this area. I would do it for piece of mind. Cheers.

http://i662.photobucket.com/albums/uu343/nissantiques/Nissan%20Y70%20turbo%20head/Y702Lhead018.jpg

I'll be honest and say I don't know a thing about Carter carbs so your specs and adjustments mean nothing to me! What I will say to you is that during the break in period is not when you want to be fiddling around with your carb to any great extent other than to adjust simple stuff like idle speed. A sloppy rich or dangerously lean carb will shorten engine life in different ways, but it will shorten engine life! Can I say that if the effort has gone into rebuilding your engine, give it half a chance to run right by making sure that things like your distributor and carburetor are in half decent running order, and a new Holley may solve your problem, at least it may have a calibration that's somewhat close to what you need. Even if it isn't the carb fouling things up, you know your carb, at least, shouldn't be the culprit! Once you've managed to sort out the basic running ie proper idle, you can then move onto tuning the rest of the carb to your needs. The whole exercise sounds like you have a massive air leak somewhere, so triple check everything on the induction side of your engine, even to the point where you strip it all down and reassemble it. A single carb setup is straightforward to remove and reassemble, I know! Good luck! As far as starting your engine, when warm, you should be able to simply turn the key and the engine should fire up without blipping the throttle. When cold, one press to the floor with the throttle should activate your electric choke (if you have one) and dump enough raw fuel into the manifold via the accel. pump to again fire the engine right up. If it starts and dies, then its a mixture issue, either lean or rich but mostly lean and with a rev to your rpm's, sounds like it's lean due to an air leak somewhere. All of this applies to stock or mild cams, big cams are more 'cranky' when they're cold and harder to set up with a smooth hot and cold idle due to their lopeyness. Not impossible, just harder. I hope this helps a little. Cheers.

Yes, good point! Thanks.

Yeah, I thought that too. I might just add that these cars weigh 1450 kgs (about 3200 lbs) each, plus the trailer which I guestimate to be around 500kgs (1100lbs) so that totals almost 3400 kgs (7500 lbs), without driver. Now, how much does a Z weigh? In retrospect, I think that what I did was prety dumb too, the weight of that trailer and car combo would've far exceeded the safe towing capacity of my tow bar arrangement, anything could've happened, fortunately it didn't. (Oh did I mention a flat tyre on the trailer on which I stuffed my original 30 YO jack with! Buggar!! ) Does anyone have a material preference for the welsh plug that goes into the back of the head. Mine was removed but not replaced. I heard that a steel one is better than a brass one due to 'sacrificial' issues. Is this true??

Y70 head is back home with me. Needs a clean, found some random aluminium filings around the ports and it needs the rear welch plug put back in. Otherwise it looks good with the intakes having a lovely short side radius. The injector notches were also welded up by request to reduce port turbulence. New intake guides too. The exhausts were OK apparently. The valve seats look wonderful, I hope they flow as well as they look! The edges of the chambers need a little smoothing to remove the new sharp edge caused by facing the head. Just some small stuff but I wonder what I'd have to pay to get that done. I thought I paid enough in the first place.

Kameari make headgaskets. They have a huge range. They are expensive. You need...you spend....you get. Cheers.

Good idea! I would include some sort of boost and temperature switching device that could monitor temperature and boost and determine when it would be appropriate for the device to switch on and cool things down. You dont want to cool things down before they've had a chance to warm up. Be careful that what you're proposing doesn't cause too much flow restriction. No good boosting an engine only to have it strangled by something like this. Cheers.

I guess this illustrates the versatility of the L Series engine nicely. The Cedric may not be a fast car because of body weight and engine specification. The camshaft profile may limit how quickly the engine accelerates to redline but it's the same camshaft that allows this sort of towing capability to take place. You should 'feel' how toey the car is now since towing that lot. Feels like a rocket ship The L20A head has been reworked and I'll be picking it up on Monday. Some pictures to follow soon. Cheers.

If you look carefully, all that 'crap' on that induction setup is the same as what you've got on some of the twin Su setups. Emissions!! The intake and exhaust are mated together like that to avoid having to run water coolant throught the intake manifolds. The 'stove' setup is much quicker at warming up the engine and therefore the engine runs cleaner more quickly. Emissions!! The big problem is that, like Blue 72 has found, you can't run the intake manifold easily by itself unless you plug that big hole at the bottom of the plenum. This is when you need something like a 'P53' intake. See the picture attached. With some adapter plates I ran 2 and 4 barrel carbs on my engines. They're not bad when adapted this way and could also be the basis for a simple draw through turbo setup perhaps!

Porterhausen states he wants a revver. That's the natural behaviour of the L Series! Don't discount the short stroke L24 or L20 cranks for your L28 block. That'll make it rev even more!! Small port heads will change the character of your engine as will displacement, cylinder head type/mods, camshaft type, induction choice, exhaust system mods and compression ratio. Don't isolate small port heads as an achilles heel just yet, Daeron! I still have a lot of work to do!

But what does the "M" represent? I've got an L20ET with the "M" signature as well but this one has the tiny crank journals and rods (think Maxima L24E) and an O5L head on it. I even had an H190 diff centre with this marking. It was built with a pinion shaft support which I deemed to be some sort of H/D part perhaps? All of the other H190's I've seen don't have this support. Cheers.

I came 'this' close to getting one .........from a 69 model! The car looks like this... The engine from that car looks like that....

If you lived in Australia and visited any number of junkyards, you'd find setups like this on Skylines (C210's) 260 and 280C's (Cedrics). Nothing new to us down here. Performance wise, nothing special at all really. Cheers.

I think it's because you guys never had easy access to these small port heads, it was never really considered to be an option by engine builders. Head developers decided that it was easier to make a hole larger than smaller, flow gains confirmed by flow testing. It was decided that this was the right direction to take. And since these heads were built to be used by racers and the top end power was there, the street guys figured that big port heads were the shortcut to greater power as well. When we study the engines from some other makes, like the Ford Cleveland engines, the large port 4V heads had ports so large, they were essentially deemed useless even in racing circles. No port gas speed!!! Racers then opted for the smaller 2V heads, which had smaller ports and flowed less air (verified by the flow bench during testing and development) but these smaller heads comprehensively smacked the cars equiped with the 'better flowing' 4V headed engines. Even the aftermarket realized this and sold port tongues or fillers for those guys who ran 4V heads and wanted better engine response to match the 2V boys. Hmmmm, can we try some small port heads on our engines? This is exactly what I'm proposing. If there is a limit to top end power due to the small ports, a 'bigger' camshaft should fix that, shouldn't it? What about port gas speed? It should be there, all the way down to the bottom of the rev range, not just limited to the top rpms. And the way I see it, make the port too large and the port velocity through the head may never reach optimal speed until you're bouncing off 8K rpm (if even then). Just ask the Ford boys!! Cheers.

Mate, if you want to live long time, don't put engine parts on creme carpet!

If you can afford to regularly 'blow your engine up', send some of your money to me! It can help to pay for the mortgage and school fees, the rising cost of fuel and groceries and the plane ticket to your place so I can drink your beer and help you rebuild that L engine of yours! Sounds like a plan. Cheers!!

Port taper is what I think you might be referring to. Nice thought but that would require a custom built intake manifold. The manifold I intend to use has varying length runners so it would be impossible to do. Triple whatever manifolds lend themselves nicely to this because, even though the shape may be a little different from runner to runner, they're all the same length. L Series EFI manifolds also lend themselves to this type of runner porting as well. Not much of a taper though as the port runner walls are very thin. I believe the optimum port runner taper is about 4 degrees from a paralleled walled runner. I don't think your risking 'foot in mouth' here Daeron, come with me and enjoy the ride. It's something that has been in the back of my mind for a long time but 'convention' has it that porting involves making the hole or volume larger not smaller, generally. That 'fact' is a well worn path in automotive tradition. What I'm challanging here is convention, to see for myself if taking this path is productive for me and my application. This may not be what most of you guys seek as you're all running much lighter cars than me, hence the challange to develop an L Series engine with as much low rpm torque as I can get. I think I've beaten this line to death so I won't keep saying it. Rang the shop doing my head today. It's just needing the valve seats to be machined and I'll get it back. Then I'm going to take a 'few' pictures and share them with you all. Until then......

http://forums.hybridz.org/showthread.php?t=144304 Try this, in there I give you the dimensions of my 'tool' and how to use it Ha Ha.

I've installed my new Holley carb. Took about two hours to install, check float levels, replace a faulty needle and seat on the primaries and get the thing to idle smoothly. With my innovate wide band on board, I went for a few runs around the block. Tuning is so simple, it's ridiculous. Turning a couple of screws on the top of the new block sandwiched between the bowl and the original block, I had the thing tuned up in about 30 minutes of driving around, testing on flat, slight incline, heavy incline, off the mark and part/full throttle. The most significant thing of note is the low rpm torque! At 1500rpm in O/Drive, the thing just pulls, don't worry about shifting down, it just pulls. On the flat, it accelerated very well from this rpm. Impresions so far....best throttle response/torque of any of my carbs and by far the easiest to tune. Just pull over to the side of the street, pop the hood and tweakit!!! Excellent. The following are a couple of quick snap shots of the booster arrangements in the carbs that I've used before compared to what I'm using now. Notice how none of the boosters fit into the mouth of the venturi, except the dogleg version. To improve the signal, I use a couple of slightly modified venturi sleeves to amplify the signal to the main fuel well even more. The next stop is to the dyno for another run, to compare it to my previous best. What the dyno doesn't tell you is how the car feels on part throttle and something that is quite subjective but you'll have to take it from me, it's those boosters and the ease of tuning which has impressed me most so far.