Zed Head

Blue might actually be referring to the book "How to Modify Your Nissan & Datsun OHC Engine" by Frank Honsowetz. On page 15 he describes enlarging the oil-jet from 2.0 mm to 3.17 mm to increase oil flow to the head, but it's in reference to big cams and high spring pressures. Some people, over on Hybridz, have suggested that there is plenty of flow to support both spray-bar and internal oiling. Others suggest drilling out the oil-jet to be sure. Your oil pump condition is probably a factor also, considering the lower flow at low RPM. Seems like Rebello would know about drilling out the oil-jet. Probably worth a discussion since he suggested it. p.s. the flat head of a good bolt should (did, in my case) provide enough pressure to seal the spray bar, with gasket, to the tower. The pressure in the bar is reduced due to the oil-jet restriction. The gasket on my 1976 spray bar was well-compressed and showed no signs of distortion or leakage. It was smashed flat like a typical old gasket, very evenly. No signs of uneven load.

Disconnect the small wire at the starter solenoid, the one that pulls right off, and turn the key to Start. The fuel pump safety circuits are bypassed at Start and you should hear the fuel pump run. If you have a fuel pressure gauge you can measure pressure this way also. It should be ~36 psi.

I've been having the "hot start" problem recently. Here is an interesting thread on the topic - http://forums.hybridz.org/index.php/topic/76282-heat-soak-vapor-lock-problem/page__p__746890__hl__%2Bvapor+%2Block+%2Binjectors__fromsearch__1#entry746890 The thread above spends a lot of time on defining the words and terms, but hot injectors seem to be the common point. I am leaning toward cygnusx1's theory that the problem is actually caused by overheated injector bodies causing the fuel to vaporize as it passes through, or percolate while it's in the channel. This actually results in a lean condition. You might have noticed that you don't really smell any excess gas, it just runs like it's flooded. A miss is a miss, lean or rich. I've had a pretty good lean backfire through the intake when this happened. I used to think the problem was leaking injectors, but the lack of fumes fits a lean running situation better. One change that I made recently was to the holders around the injector bodies. In the past, I had the one piece holder, recently I went to the two piece holder, with the aluminum upper ring and phenolic lower. I almost never had the problem before, I'm having it more often now. Maybe the two piece holder lets the injector body get hotter while sitting. It is also a different engine, but the EFI, intake and exhaust system are the same. I think that the Nissan engineers attempt to fix the problem was the injector fans, controlled by coolant temperature. I've insulated my injectors within the last week to keep them from absorbing radiant heat when the car is sitting, but still have had the problem. Still looking for ways to avoid an injector cooling fan retrofit, but I have one and might try it. Edit - I also have an Aeromotive FPR that leaks down rapidly. So maybe the dry injectors do not get the cooling that a "filled" injector would.

I took a look here - http://www.carpartsmanual.com/datsuns30/DatsunZIndex/Engine280Z/CamshaftValveMechanism/tabid/1603/Default.aspx - and here - http://www.carpartsmanual.com/datsunS30/DatsunZIndex/Engine240Z260Z/CamshaftValveMechanism/tabid/1565/Default.aspx - and see that the 240/260 spray bar is different from the 280Z. Doesn't show a stock gasket on either, so I'm not sure why mine has one (two actually). 30 ounce has a point though, you might do some preventative brazing on your stock tube while you have it out, if you don't want to spring for a custom billet bar.

I happen to have a 1976 spray bar in a box in the garage and just took a look at it. It does have a gasket at the interface. Not a precision piece, essentially a square of gasket material with two holes, one for the oil and one for the bolt. Pretty sure the head has never been touched. p.s. don't forget the hole for the oil.

It won't disrupt anything, it's a straight bolt-in swap. But it might not make a difference. What are the problems with the starter you have?

An alternative is that this is your second car, for fun and a hobby. Buy it, race it around, get some tickets, slide it in to a ditch or two on those icy MN roads, fix it and modify it in the winter and do it again in the summer time. Just a thought. The car isn't really very practical as it sits, especially since you don't know a ton about cars, but it looks like some fun. Someone planning to put all of those race parts on a stock car might easily spend over $5,000. The coil over work and brakes are easily over $3,000, just looking at comparable internet prices. If you were planning to go that route, this might be a deal, if not, they're just wasted parts.

Go racing?

Assume that the engine is worthless and see what the rest looks like. No rust, paint looks good, seats in decent shape, 5 speed, coil-overs, decent dash. Looks like some standard L24 performance mods on the engine. But it could be worn out by now. Find out when it last drove so you'll have an idea of whether or not the various hydraulic parts will need replacing. Over 2 years in MN and the fluids will probably have absorbed moisture. Might need new calipers, master cylinders and slave cylinder. Also find out what "needs some work". The $25,000 number is irrelevant, only the $5,000 number matters.

Z train is right, I was off target on the pilot bushing. The crankshaft, pilot bushing and input shaft are all spinning at the same speed when the clutch is engaged, so it wouldn't make a noise while you're cruising. Examine the the things that all spin at the same speed as the crankshaft or come in to contact with it and you might come up with something. Maybe your throwout bearing is touching the springs. Z train, did you mean input shaft? Isn't the output shaft spinning at a speed proportional to road speed, independent of RPM?

Doesn't seem like a common noise. Has the car been sitting or driven regularly? Is it always 2800 RPM, no matter what gear or just 2800 RPM in a certain gear? Have you checked the fluid level in the transmission? Could be the pilot bushing.

You could put a small rheostat in line somewhere and adjust it up until you get desired performance. Or get a few resistors and do trial and error to see what you need. That way you can just go for it and make it work, but still be safe on the wiring. Plus, the heater circuit might already have a fuse in-line, or you could/should add one.

It's inside the alternator case.

I think that the spherical shape of the stock "washers" is designed to take up any thickness differences and equalize the load between the intake and exhaust manifold flanges. A flat surfaced shoulder bolt will only put pressure on the highest surface, plus it will put a bending load on the bolt if there is a thickness mismatch. Might work if both flanges at every location are of the same thickness.

Piling on: If you use the RT-style mount with the Energy Suspension GM transmission mount, suspension work is super-easy. The differential will hang from the mount instead of sitting on the cross member. You can remove the Nissan front diff mount entirely. No need to support the diff to change bushing or stuts or springs. Just one more benefit. I noticed when I was working on the clunk problem also, that if you strap the diff down too tight it can be drawn down on to the cross member, generating more diff whine and vibration in the cabin. In my case, the mount was so worn that it wasn't really holding the diff nose from moving up or down.

yoshi, you didn't say if your ZX is a manual or automatic transmission. If it's a manual, and you have a fuel supply problem, it wouldn't be so RPM specific. Try changing gears and see if the problem is speed or RPM related. You mentioned a new throttle body. Why did you change the stock one? Did you go for a larger TB for "more power"? Upgraded FPR? If you're running the stock ECU, what features of a different FPR would be an upgrade? Seems like there might be more to your story. Have you been upgrading for performance, or is this a stock 1980 280ZX? Ted, you didn't really say what the solution to your problem was. Did you have EFI on your 240Z?

Didn't mean to be a downer. The topic comes up often and generates lots of discussion. Here's an interesting thread, in a similar vein, with lots of good insight - http://forums.hybridz.org/index.php/topic/102085-200-whp-na-build/ The short stroke of the L24 crank lowers your displacement also. The calculator shows 2.569 L. From what I've read, the lightened flywheel alone will make it feel "revvier", and some moderate flow work on the head will actually make it more rev happy. My limited knowledge...

Another clue would be to remove the water pump/alt belt next time it's making noise, then start the engine and listen. You'll just run off battery power and the engine won't overheat in the time it takes to see if the noise is still there or not.

According to this calculator (which seems to be pretty accurate) your piston will protrude out of the bore by 7.1 mm. http://www.ozdat.com/ozdatonline/enginedesign/ RB26DETT pistons look close but will give you an 11.25 CR.

Probably depends on if the corrosion is on the piston seal surface or not. I had a tiny little scratch in the bore of one of my calipers from the PO's rebuild (I think he dragged the dust cover holder wire across the surface) and the brakes worked fine but the caliper leaked fluid. Fully rebuilt calipers are surprisingly cheap. I think I got one for about $30 at OReilly auto a year and a half back.

Check the restriction in the block for blockage. Maybe you have low flow/pressure to the head.

I've seen it discussed over at Hybridz. The main concern is whether or not there's enough flow through the orifice in the block to get equal oil supply to all of the holes. I guess you could get an imbalance, although it doesn't seem likely. Some say there's plenty, others drill out the restriction in the block to be sure. You might search around over there to get a better idea. Why is the cam shaft being replaced? `

In #6 you said the bar was still plugged. Can you dig out what ever is in there? Might be informative. The holes on an internally oiled cam shaft are just as likely to get plugged, I believe. Pretty sure I read an account on another forum about a plugged internally oiled cam shaft causing some destruction.

Have you actually seen the holes in the cam shaft at each lobe's base circle, or are you assuming from the service manual. A picture would be interesting.

That's a very good point. One could probably estimate a likely range of location on a single cylinder's compression stroke and get a fair idea of where the other five would end up. #1 location - 120, - 120 more, - 120 more, etc. Or you could just eyeball the cam shaft, after multiple shutoffs and see where the lobes end up. That might be enlightening. We're not trying to tear down the concept, just doing some process development, to help people avoid some pitfalls. Plus it's just a good reason to BS about cams and what they do, and practice reading cam cards (which can be confusing - to me).