DAW

Sort of an odd choice of induction since the L28 turbo was from an '83 ZXT, he's running a draw-through Holley carb with water injection instead of EFI and an intercooler. My hat's off to the guy for putting it together but I'll bet there are a lot of L6 turbos among members here that make more power with better driveability. Maybe GRM could sample from this group sometime. DAW

Take a good close look at your vacuum hose hook-ups and sensor connections that you may have disturbed during dissasenbly, especially temp sensors (intake air, water, cyl head temps) and AFM connections. An unplugged temp sensor will send a signal of infinite resistance to the ECU which thinks the engine is being run at the North Pole and maximally richens the mixture. Is the fuel pressure regulator vacuum line connected? If not, this might make it load up rich at idle. DAW

Raise the compression ratio first. See the discussions under L6 performance topics. DAW

Assuming the glasspack goes over the pipe and not inside it, I would cut a thin line along the length of the glasspack pipe segment with a torch. It's delicate but it can be done. If you don't know anyone with a torch then maybe you could try to heat up the glasspack pipe with a propane torch and go back to hammering. DAW

Do not put a P79 head on a dished-piston L28 block unless you're going to supercharge or forced induction. For a na engine you'd be going from bad to much worse because the P79 would drop the c.r. below 8:1 vs the N42 head you removed. The P79 would be good for you only if you have the .080" surface cut done and all the associated alterations described in the P79 article/site. A P79 head will be from a non-turbo '80-'83 280ZX and these use a flat-top piston because they moved the volume (10.9cc) from the earlier style dish-top and put it up into the roof of the chamber (most of it anyway, they were able to bump compression a bit due to the better chamber design). DAW

The Maxima head should be an N47 not a P79 (it looks like a P79 combustion chamber though, except the chamber is less deep in the Maxima head so it uses the 240/260/280Z length valves and not the shorter valves used in the 280ZX heads (P79 & P90). If your money is funny and you are trying to squeeze out some performance on a tight budget you could consider putting on a maxima head as-is (except transfer your cam & oiler setup to it)... what you'd be giving up is 2mm of intake valve diameter (42mm vs 44mm); but what you'd gain is a significant amount of performance boosting compression. It's a tough call but bang for buck I think your car would benefit vs the stock, emissions oriented configuration. Victoria British sells the intake valve seats for $6.95 each. You've already got the valves. You could call for quotes on R&R six valve seats in the head and bring it to the machine shop with intakes dissasembled to save some labor. Alternatively, you could do the head swap with no valve exchange and see what you've got and you'd know that there's more power to be had if you want to do the intake valve exchange at some later time. DAW

Some repair manuals actually give the dimensions of the piece of wood to cut to block the timing chain from slacking when you remove the valve timing sprocket. I don't have them in front of me but it's basically a 2" wide, 3/4" thick x 6" long block of wood from which you cut away a triangular section. The resultant piece is 2" wide at the top and extending down about 2.5" at which point it tapers down to about 1" wide at the tip. Very important: drill a hole in the upper portion of the block and thread some electrical wire or a wire coat hangar or a big zip-tie through it and tie it, leaving a tail of about 8"; you're going to have to remove the block once you've reinstalled the timing sprocket and there won't be room in there for hands. Let's see, there were a lot of questions...if you put L28 intake valves into the N47 L24 Maxima head it will require new L28 intake valve seats installed. The site referenced above re Nissan head mods is great, lots of info there. The N47 Maxima head is sort of a hybrid of the L28 N47 head and the L28 P79 head (except it has smaller, L24 intake valves). The P79 mod/shave/shim/valve exchange makes sense except I think it is far less expensive to have L28 seats installed in the Maxima head, L28 int. valves, and use an L28 cam (from an N47 or P79 head). As to the turbo cam specs, I don't have them but there was very recently a parallel thread which discussed them re one year having 10 degrees retarded cam timing but otherwise the same lift & duration. An OEM turbo cam generally won't produce as much power in a na engine as the OEM na cam will; at least that's what I gather, and putting a high perf. cam designed for a na engine into a turbo engine may make less power than the OEM turbo cam. DAW

Maybe you could put a glass of water on the roof of the car and video record/enhance the changes in ripples with tuning adjustments. DAW

The Maxima head is not going to raise the compression too high on your '75 L28 block as it has dished top pistons and 8.3:1 c.r. the Maxima head may take you up to about 9.5:1 which is unlikely to ping on premium gas and you should definitely notice an increase in performance. However, ideally the intake valves from the L28 head should be swapped into the Maxima head (44mm vs 42mm) for better breathing at high rpms. I'm not sure about the cam specs re L26 vs L28 but an L26 cam could only be directly swapped into a '75-'76 L28 head (N42) as they have the oil rail systems. The early style cam towers & oil rail would have to be transferred to an N47 type head to run the early style cam from a 240-260Z. That shouldn't be any big deal but I don't know if there's any advantage with a 260 cam. I looked up in factory manuals the specs on '72 240Z and '77 280Z and the durations and cam timing specs are the same, with the 280Z cam lobes having slightly more lift. So if the 260Z cam is the same as the 240Z, you might be actually decreasing performance. DAW

The N47 from the '73 didn't come on it originally and it is either a 280Z head or a Maxima head (you could tell by the size of the intake valves: 44mm if Z; 42mm if Maxima). Don't worry about the oiler rail absent on the N47, they went to internal cam lobe oiling on N47 and later heads (see the small holes in the lobes providing oil; whereas E88 has none, oil rail instead). Gasket scraper: solid Craftsman type first for heavy stuff, then razor blade type to finish. I wouldn't worry too much about small bits of debris falling into bolt holes. You could blow it back out with compressed air, but some holes you will be blowing coolant back up too, possibly in your face. It's easier to set the valves once the head is bolted on (remember the cam position has to correspond to the position of the E88 you removed). You don't need shims for valve adjustment like some cars use, it's just an adjustable post/pivot with a jamnut (you might be referring to lash pads thicknesses or cam tower shims but you shouldn't need to alter anything there). DAW

First I think you should run a compression test as it will tell you if there's a problem cylinder or two and you should be able to get some idea of the c.r. I'm thinking a stock L28 F54 engine cranks warm at 170lbs and that's 8.8:1. My F54 with N42 head cranks 210lbs and that's about 10.2:1, so you should be around 195-200lbs if you really have 9.8:1. Unless the head was shaved or you have pop-up pistons, you'd have 8.8:1. Look at the plugs when you run the compression test to look for mixture problems. Set the valves (unless it's a P90A head, not a P90) and check the cam timing index marks. If everything checks out mechanically, then make sure you're getting a good quality spark to the plugs, and you have adequate fuel flow. DAW

The Saab turbo is probably a Garrett T3. I picked one up at a JY to rebuild and it has an external wastegate although I think the later model Saabs might have internal wastegates. I know what various cars came with T3s but what I need to know is what cars (or trucks) came with T4s as OEM turbos? DAW

They aren't riveted. What you're seeing that look like large rivet heads are the fixed/welded end of a bolt which has a nut on its other end and that's what you need to get to to remove. Pull all the trunk/tire compartment panels you can to see where these nuts are. You may also have to drop the tank some to get the bumper shocks out. DAW

I'm talking about a horizontally cut relief at the top of the cylinders. One per cylinder, on the exhaust valve side of each bore. Nissan put them there to allow them to use larger exhaust valves in the L26. The L24 has the same bore but didn't need the reliefs because they used the smaller valve. If a later head is put on an early L24 block then they have to be ground in. Not a big deal and you can do a better flowing job than the factory does but is it's not done the exhaust valves crash into the block. DAW

OK that's good, must be an optical illusion. BTW, do you see the eyebrows in the block at the top of the cyl bores and does the pad on right side of block have "L26" stamped in it? DAW

I've seen a particular OEM alloy wheel on these cars which is a mesh-type center with a polished rim. They appear to have a low offset and I picked one up in a JY

I know I got an exhaust shop to help me with the custom exhaust I made. At first he said "no can do, pal, you've removed the catalytic convertor". I told him that Diesel Maximas didn't have caytalytic convertors! He fabricated the little piece I needed and welded it in. As I left I think he was mumbling something like "...why would someone put headers on a diesel engine"? DAW

Don't sell the diff! (or if you do, sell it to me). DAW

I just now pulled the full width of your block photo into view...it definitely looks like pistons in cyls # 1, 3, & 6 are from a different source than those in #2, 4, & 5. That's a big problem and once you see something like that you should assume nothing in that shortblock was done correctly. DAW

Thanks guys, I think you're right about picking the lowest specific heat value material which is practical. I'm going to stay away from flammable liquids and go with ammonia (although alkaline burns aren't good either). Specific heat of water is 4.19 kJ/kg K; oil is 1.67; and ammonia is 0.47. What I'm building is a sensor that can generate a sensitive/responsive signal linked to change in vehicle speed (e.g. acceleration). DAW

Don't worry about the headbolts, some will show rust. It can be enough to weaken the bolt but you would already know that because they would have snapped on removal. I like to put bolts back with the threads they were with, but with the rusted head bolts I'd swap them to a hole with no rust on reassembly use anti-seize compound on all. I'm wondering about #6 piston vs 5 & 4 in the photo. It looks like #6 has no valve reliefs and the others have the reliefs (it may be camera angle). Also, if this is a factory L26 it should have horizontal valve reliefs at the top of the cyl bores on the exhaust side for clearance of the 35mm valves with the 83mm bore. I don't see them but again it might be the photo. Nissan blocks are incredibly tough and a ridge is rare. Washing the cyls down by dumping fuel from a stuck float isn't good but if the rings were really bad you would expect to see oil in the upper cylinder and/or scoring of the wall. Pull the rockers as suggested (keep them in order) and use solvent (I think I've heard kerosene works well) to leak test for a valve seat leak (or a crack). If there are a mix of piston top types, you should take big steps back away from that engine and look for a replacement. DAW

Sleeper Z, I agree about the restrictor idea in the radiator making no sense. I drove from Chicago to LA in June one time in my '72 510 and needed to be there by a deadline. It had the original radiator and the core was fairly plugged up by sediment. I had to go through the desert in the middle of the day and the only way I could make it at high speed was with the heater on full blast and removing clothes. Open windows created drag and buffetting so I had them up with the quarter windows cracked. So on the interstate if someone glanced over there I was with it 95 degrees out, 70mph, windows up, sweating like a pig with no shirt on. I have some questions for you re specific heat because I'm working on another project. I need a liquid media to use in a passive system (container) in which I have a thermister installed. I want a material that will quickly change temperature with change in response to temperature changes of the aluminum vessel it's in. How would water, propylene or ethylene glycol, ammonium or alchohol or mineral oil compare? The temp range is ambient 32F to 100F. DAW

OK, so timing is set at 20 degrees at idle with no load on the 7.4:1 c.r. engine and the ECCS system which is computer-managing the timing and changing it with all loads. Put a conventional distributor in a turbo engine (or high compression n/a) and set the timing at 20 degrees BTDC and see what happens. At least you can set/adjust the timing on an L28ET. On most OBD II cars you can twist the distributor back & forth and the computer just ignores you. As to altering resistance in a circuit that uses resistance as the input by which the computer alters the air/fuel ratio it gives the cylinders to burn, it's the same as changing jets in a carburetor; it accomplishes the same thing. It is not the only means of adjusting A/F ratio to get the best performance. Adjustments in fuel pressure, injector size, duration of opening, etc., can all be used to affect A/F but these may be better suited to cover demands due to increased boost or c.r. rather than low speed hesitations on a stock engine (you may also spend $1,000 more than what you needed in order to accomplish exactly what you needed to). Whether the resistance input to the ECU is changed by AFM door spring pressure or swapping thermistors, either air inlet temp or cyl head/water temp, for an alternative one other than the Bosch OEM to send the desired value to the ECU to calibrate the A/F, or adding a specific value of resistance by adding series and/or parallel resistors doesn't much matter, it's the A/F end result which matters. Rather than accept anyone's advice, tip or opinion, the best way is to buy an A/F Monitor and see first what you have that's yielding a certain drivability or performance problem that's typical of over-lean condition, then use it to follow any changes you make to improve performance (by whatever means you choose to do it). If mixture is already rich enough, then try improving throttle response by advancing the timing as the pistons are better protected than if it's lean. DAW

I remember reading somewhere about a resonance cancellation using a sound wave generator. This sounds great for quieting exhaust (or better yet, programming in a nice Italian note) and minimizing backpressure from obstructive resonances but it won't change gas flow characteristics i.e., more flow through a large tube than a small one. You would have to start with a huge dia. tube (needed for high rpm use), then introduce enough acoustic counter bombardment to resist the flow of gas at low speed so that back pressure was created. Heavy metal might do it, or some rap...hey, that's what those guys are doing at the stoplights..backpressure, yeah that's it! DAW

Tony, BTW I found a V8 Mercedes radiator (aluminum) that fits well in place of the Z radiator and is a bit longer but narrower, enough to be shifted to the right side so that I run the air filter to AFM hose through that space and lets my intercooler hose run out the hole in the radiator support, normally used for the AFM intake hose. DAW