Murph

G'day joe! Hmm been a while since I've thought about the VQ idea, still love to do it though. I have heard though that the piping for the turbo on the VQ30DET would clear the strut tower on the zeds. This requires either the manifolds or piping to be modified...... or to modify the strut tower. Maybe one day when I have some $$$ to build up a nice zed I'll go the VQ.

The head is an E88 with a lot of km's on it.....not exactly sure but were talking ~500000km. From another forum we pretty much worked out the tight clearance on the inlet valves was due to valve recession into the soft bronze seats, whereas the exahust vavle seats are steel, so don't suffer the recession problem. The large clearances on the exahust valves were just due to general valve train wear. As is that valve I can't get within spec has a clearance of between 0.1mm and 0.15mm. I'll only be running this motor for another few months and it isn't causing any problems, so I figure I'll leave it well alone. Compression test before doing the vavles came up with 150 130 110 135 120 120. I'd say it's no coincidence that no.3 inlet vavle clearance (or lack of) was the tightest, and no.3 has the least compression. I'm planning on doing another compression test some time soon.....should be interesting to see how it changes.

Just out of interest I'll try starting it without the choke tomorrow morning.

I do still use the choke to start it cold. The thing was, before, even with the choke, it wouldn't fire up straight away. Did the original single carb on the K have an automatic choke?

Another huge difference I have noted since doing the valves is how well I starts! Previously when cold it'd turn over for say 2-3 seconds before spluttering into life, then I'd have to hold it at say 1500-2000 rpm for about a minute if I didn't want it to just die on me. Now, it just instantly fires into life with a much more "fruity" note, and will idle immediately. It feels a bit stronger in the top end now, but the huge difference is the low end and mid range torque! It pulls so effortlessly at lower RPM now. It's like driving a different car.

Still haven't heard anything back from him. Seems he can't get at a computer over there too often. Will pass on any info I get as soon as I get it.

Be careful when you undo the lock nuts if they're tight! One of the ones on cyl 6 was pretty damn tight and when it did go I smashed the knuckle of my index finger into the top edge of the block, which made a nice 1cm long gash to the bone. This is bad. Anyhow, do them cold as it will take a while your first time. Just give it go, not too hard at all, you'll get the feel for it pretty quickly.

I've just put it back together and WOW! The motor is so quite and smooth! I've always commented on the amount of mechanical noise from the engine and it's always had a tick from the top end.....now no more tick, and it's virtually silent! Generally runs a bit smoother and a little stronger. Idle is still a bit lumpy, but not too bad. Gotta do a 20min drive tonight, see how she goes. Thanks for all the help everyone!

Cap looks ok atm, but you never know. I've just adjusted the valves and only have to put the rocker cover back on, then I'll take it for a spin, see how it goes.

I'm in the middle of adjusting my valves at the moment. I'm doing them cold as this is the first time for me. So far I've found that all the exhaust valves have had a much larger clearance than .25mm and all the inlet valves have been very tight. Now I've just come to the inlet valve on number 3 and I simply can't get it with in spec. The largest I can get the gap before the stud doesn't screw down anymore is less than 0.05mm when it should be 0.20mm. There is a gap there now at least. So any ideas why all the exhaust valves are loose and the inlet tight. Also, is it a big concern that I can't get inlet no. 3 in spec? If all goes to plan I'll only be running this motor for another few months at most.....so I'm not too worried if it's perfect or not.

I stand corrected! The door flapper type is a VAF. Do these units convert to the exactly correct voltages for the factory tuning of the L-jet box, or does it need some form of retuning (however that's done with an analouge ECU I don't know)? I'd be tempted to stick with the flapper type till you can afford to go proper aftermarket managment or a later model nissan ECU, eg RB20. If you have someone in your area that can tune the nissan computers they are a good option.

I'll have another look at it tomorrow just to be sure. Mind you there aint much point reving my motor over 5k.

Linkages are good, carbs open together. Previously I'd pulled the brake booster line and plugged the hole, and it seems to run exactly the same. I'd say at this stage I'll be chasing up blockages in the fuel line/fuel pickup and valve adjustment. Thanks for all the suggestions everyone, greatly appreciated.

Still have to do that yet. Still doesn't explain it choking up at idle.

Fuel lines are fine. I checked the fuel bowls and there's no gunk in them. The carbs were compleltly cleaned and kitted 3 months ago. My mechanic said they were in pretty good condition.

I did 7 runs at the drags a week ago, so it should be used to a caning. Wasn't reving it past 5k when this problem started either? I will look into the valve clearances though, no hard.

A little bit more info. Just took it for a drive and the smoke cleared up after about 30 seconds or so. Still a little puff on gear changes as per usual. At about 700rpm the airflow in both the carbs sound fairly equal, however if I crank the fast idle up a bit, say 1200-1500rpm, it sounds like there's more air going into the front carb. Can't be sure though. It did drive quite nicely though.

ARrrrrrhhhhhHHHH!!!! It's all getting more confusing! Today I made two new gaskets for the balance tube between the inlet manifolds as one was leaking, and the other fell appart while handling it. Now when I've fired it up, it's blowing blue smoke again, a problem it's had on two occasions a over the past few weeks. Previously I attributed it to a stuck PCV, however I have verified that it is working fine atm. When pushing the piston lifting pins, revs will increase a bit then drop back down to about the same revs but running very roughly. It does this for both carbs. Using the hose in ear trick I had a listen to the air flow into the carbs and while the overall volume sounds about the same, the front carb has a lumpy pulsing sound to it, where as the flow in the rear sounds totally smooth. Any ideas what is going on? I'm somewhat stumped now. About a week ago a compression test came up with 150, 135, 110, 130, 120, 120. Doing a wet test they came up by about 10psi, so I can be pretty sure the valve guides are somewhat worn. I might try another compression test later....see what it gets.

Can't answer your question, but a MAF (mass air flow) is a type of AFM (air flow meter). AFAIK all the nissan AFM's are all MAF's. The other type is the VAF (volume air flow) as used on many toyota's and mazdas. The third way of sensing engine load is with a MAP (manifold absolute pressure) sensor, but that isn't an AFM as such.

Both pistons seemed to move quite freely.....and they should considering they were both completely cleaned out three months ago.

Something of interest I noticed this afternoon while having a play with it when I got home, was that when you pushed the piston up in one carb, revs would increase, when you pushed it up in the other they would decrease. This would suggest a tuning problem wouldn't it? Sorry for the complete noob question but I was brought up on EFI, still have a lot to learn about carbs!

So these SM needles would be suitable on an otherwise stock L28, with the 240Z carbs? I had heard before they were more suitable for an L28 with a mild cam. How much did the needles set you back beandip? I'm quite interested in these as I'll be building up an L28, still using the 240Z carbs sometime soon.

It's quite possible I suppose. Tomorrow when I get a chance I'll get under there and check the fuel filter for gunk (just before the elec pump).

This afternoon I took the zed for a bit of a blat down a nice straight empty road in the middle of nowhere. Went quite nicely up through 2nd gear, then 3rd, 4th, then just after hitting 5th at about 160km/h I see car in the distance, so hard on the brakes back down to 80km/h or so. Now when I got back on the accelerator the engine was loosing power, sort of pulsing on-off-on-off a few times a second much like when it's not getting fuel with vapour lock problems. Over the next few k's it seemed to go away, till I got home and found it wouldn't idle anymore. It'd drop to about 500rpm and splutter away. While driving it still feels ok, but sounds pretty sick/lumpy at idle. It isn't blowing any smoke or anything like that. It's lowish on fuel at the moment, but probably still 15 or so liters in the tank. It's definantly still firing all it's cylinders. Any ideas what could be causing this? It's been about 3 months since it was last tuned (carbs were rekitted then) and has been regularly driven in that time. Btw, it's a 260Z 2 seater, basically a stock L26, with 240Z carbs and and electric fuel pump that bypasses the mechanical pump. Any help is greatly appreciated, Justin

Whoops. Yeah meant to add rings to the list. My thoughts are pretty much the same on the injection system. Not worth the hastle.