TimZ

With triple DCOEs? Don't those have brass internals (jets, etc)? I'm generally a big fan of E85, but it doesn't play well with brass, especially if you are expecting the brass parts to do precision metering. Can you get ethanol-resistant parts for these?

They did all that by hand with a die grinder? That looks like a LOT of hours! I think this makes sense on intake all the way up to the valve, but I'm curious about the combustion chamber surface. Seems like the effect would be different there. I used a ball-end bit in my die grinder to add some dimples on the short side radius on my Mikuni manifold. I honestly can't tell if it made any difference, but it doesn't seem to have hurt anything. As roger280zx mentioned above, I think the effect might get negated by carbon deposits pretty quickly on a street engine.

Probably the rest of this explanation is that because of the lower atmospheric pressure, you have less power available, and require a larger throttle opening to get the same power at cruise. Larger throttle opening means lower manifold vacuum, which means lower pumping losses for the engine.

Oh, I see. So this engine is immune to valves hitting pistons if you rotate the cam with the timing chain disconnected? Awesome. So here's what appears to have happened - you made an incorrect assumption about the purpose of the shiny link and assumed that the link was in the wrong place when it probably wasn't. Now you've removed the chain from the sprocket, messed with the cam timing and may or may not be able to get back to where you started. Can you still put it back like it was before you pulled the sprocket? If you can, then do. Then you will want to rotate the engine by hand (DO NOT USE THE STARTER) multiple times until the shiny link eventually comes up on #3. Now if you want to return the sprocket to the #1 dowel hole you can do so, and you will find that the #1 tooth lines up with the shiny link without moving the cam much, if at all. This will only require a very small turn to the cam at most. If the engine hangs up at any point while you are trying to rotate it, then you've borked the cam timing and you need to stop. As madkaw mentioned, your best bet will then be to remove the timing cover and retime everything per the FSM. Removing the head won't help with this. If you are able to get the timing back to the #1 hole and it rotates without hanging up, then you should run a simple compression check to see if you have issues with bent valves. Even better would be a leakdown test, but the compression test will give you an indication as to whether you need to look further.

Okay I'll bite. Why are you trying to rotate the cam more than 10 degrees? It sounds as though you have the timing chain off the cam sprocket, correct? If so, then the cam rotation stop is likely due to one or more of the valves hitting the pistons. You know, like in that other thread you were posting in...

Exactly - it's also worth noting that in order to perform the shit-ton of advanced trig that you need in order to calculate the clearance, you would need to disassemble the engine and take a lot of precise measurements, since you have absolutely no other way of knowing exactly what machining has been done on your motor in the last 35 or more years with suitable precision. Again, THIS IS WHY YOU JUST HAVE TO MEASURE IT EMPIRICALLY.

Here's some hard lines from a 77... http://www.ebay.com/itm/Datsun-280Z-OEM-A-C-Air-Conditioning-Conditioner-EVAPORATOR-HARD-LINES-240Z-260Z-/261968935479?hash=item3cfe90ba37&vxp=mtr and another more complete set... http://www.ebay.com/itm/75-76-77-78-Datsun-280Z-original-AC-lines-AC-parts-/161712930452?hash=item25a6d77e94&vxp=mtr Go to ebay and search on "datsun 280z ac", or whichever model you have, and you'll find lots of various bits. As far as custom lines go, I used stainless braided Teflon line - it will handle the pressures and isn't bothered by the freon. Find a local place that supplies truckers (it's F.B. Wright here in Detroit) and you should be able to find Teflon hoses in the larger -6 and -8 sizes. Also, don't try to re-use the receiver/drier, but you can re-use the stock bracket if you can find one - poke around on ebay until you find a suitably sized new drier with fittings that you like.

I converted my stock system (78 280z) to r134 several years ago - I'm running the stock evaporator and expansion valve with no issues. Not sure which year you had or if yours is the same, but in my 78 they used epoxy to seal the evaporator, which sometimes cracked and leaked. I had this issue (long before the conversion) and remedied it by dremelling out the old epoxy as best I could and re-sealing with JB weld. This has been working fine even with the higher pressures and smaller molecular size of r134 for years now. When I did my conversion I did the following things: flushed the entire system with mineral spirits to clear out the old r12 compatible oil used Ester oil, not PAG. Ester is preferred for conversions due to better compatibility with any r12 remnants replaced the receiver/drier with a generic one from ebay replaced the pressure switch.

The other piece looks like the small access cover for the intake manifold heatshield. If it's that piece, it should fasten to the heatshield in the middle along the edge closest to the head.

Still sounds interesting - once you get your patent disclosures nailed down I'd like to hear more.

As long as the product announcement goes something like this I'm in! In theory I could be interested, but it will come down a few factors - what will it cost, how much complexity does it add, is it tune-able, will it be reliable, how much benefit...

Yes they can be used for that, but this presumes that you know the height of each valve stem and also have a sufficient selection of various lash pad thicknesses to do the "evening up" with. Generally it's assumed that the stem heights are all the same and the lash pads are then used to compensate for the size of the base circle of the cam. Sure, probably... There are those that would argue that you've already gone way past "close enough" already. Others might ask once you've come this far, why not do the rest? In reality if the wipe patterns are pretty similar you are probably close but that's kind of a crude measurement. Stem heights aren't that hard to check, especially if you are already set up for degreeing the cam. If they come out within a few thousandths of each other then you are done. If they don't then you can always degree the outliers and see if there is much of a timing difference for those lobes... The detail stuff is always tedious.

You also need to take into consideration the dwell time of the piston near TDC. This changes with rod/stroke ratio, so it's not always the same, either. The area of concern is basically the overlap period of the cam, and how that coincides with the travel of the piston as it approaches and leaves TDC. The piston is tracing out what essentially looks like a sine wave (it's not exactly a sine wave but close enough for illustration purposes), and the "flatness" of the top of that wave is determined by rod/stroke ratio. The longer the rod, the flatter the top of the curve, the longer the piston hangs around at the top of the bore, the more chance you have to crash into it... So essentially this means that there is no good way to say what cam will definitely work and what won't without knowing a lot of information about your particular engine. This is why most people just figure this part out empirically.

Just to be clear, I ran the L475 grind for a long time and was really happy with it. It's just weird that the specs don't jibe with what's published for the l490. Xnke - I'm pretty sure that the "Ron" that gave him the updated spec was Ron Iskendarian, so it likely came from Isky. That said, Isky does do a lot of regrinds, so perhaps it's possible that this used to be a 490 and got reground. Still, weird that Ron would give him that spec if it's supposed to be a 490... Madkaw - sorry, I feel like you've already got your solution and now I'm just prattling on over pedantry, but that is confusing to me. Did the rest of the info on the updated cam card match the l490?

Hmmm. Weird - the spec looks more like the L475, but 1 degree more duration.

Those numbers look like they must be correct, especially given that they match really well with your measurements. However they look like your cam must be something other than the L-490 grind. Is that your understanding?

If I did my math right your 0.050" numbers should be Intake open 12 btdc close 50 abdc Exhaust open 50 bbdc close 12 atdc That's closer to what you are measuring, but I'm still curious about the ~10 deg discrepancy in duration. The website is also showing 0.010"/0.012" cold lash setting. Maybe try setting the valve lash to those numbers and see what you get. If that doesn't work try setting them both to zero lash. Also, where is your wipe pattern coming out on the rocker pad?

Agreed - Ron is very helpful and easy to work with.

No problem - it can be pretty confusing given that the meaning of the numbers flips depending on which quadrant you are in. Also I should have been more specific - I was looking for the actual valve lift at 69 and 31. However this just made something click in my brain - the 69 and 31 numbers don't make any sense. Those numbers would yield a 0.050" duration of 280 and that's way too close to the "advertised" 290 duration. So I went and checked Isky's website and the L-490 cam should have 242 deg of duration at 0.050". Your numbers are coming out at more like 230/233 intake/exhaust (again I'm assuming you meant 15 ATDC above), so it's still not quite right, but that's more easily attributable to lash pad/wipe pattern/valve lash/etc. Sounds like a call to Isky is in order.

So they are not both the same - intake opening is later than spec by 31 deg, and closing is earlier by 19 deg. I'm ASSuming that you meant 50 ABDC... Just out of curiosity, what are the measured valve lifts at the spec (i.e., 31 BTDC and 69 ABDC)?

What does the timing for the valve closing look like? Is it also ~30deg late, or is it something different? Are your timing numbers for .050" or something else? I don't think Isky does this, but I have seen one cam card that gave .050" timing, but the .050" was to be measured at the cam and not the valve. Their cam card didn't mention this, and it took me a while to figure that one out.

Could also be plugged tank vent - does the problem go away if you loosen the gas filler cap?

I think your suspicions are correct. I had a fixed back racing seat with high wings on the seat and back in mine for a several years. Once your finally got in it was comfortable enough, but it took a very specific ingress/egress routine. I've switched to OEM Miata seats and I'm much happier now. A fixed multipoint racing harness on the street would be _at best_ really frustrating - unless you are racing every weekend, you would almost certainly grow to hate it pretty quickly. At worst it could be dangerous - During street driving you have many additional tasks that don't happen during racing at the track that will now be impossible without un-belting, Rolling down the passenger side window or checking your packages that are sliding around on the rear deck, for instance. Need something out of the glove box? Nope. Maybe even adjusting the radio, depending on your seating position. And always remember to close the door _before_ belting up. They also won't be much help if you get pulled over for speeding. As far as OEM seat selection, I would recommend against any seats that have integral seat belt mechanisms. They are great from an OEM point of view and they do a better job of having the belt in the right position, but they put all of the accident forces into the seat mounts, and the Z's chassis was not designed for that. That type of seat is probably too big for the Z anyway, but I thought I'd mention it.

Yep - this can happen pretty easily. So yes it's possible that this could have happened at the muffler shop, but if it did it was likely due to simply flooding the engine on startup, not hooning. Also, fouled plugs happen when carbon deposits form on the center electrode's insulator, essentially grounding it out and making it impossible for it to create a spark. These deposits are pretty stubborn, and carb cleaner or brake cleaner won't touch them. The only thing I've found to be effective is to burn the deposits off with a propane torch - you have to hold the flame on the electrode area until it glows red and looks white again all the way around the center electrode.

I understand, but CXRacing is setup as a business with a storefront and everything on ebay, so I don't see how this could be the case for them. I just bought some V-band clamps from them and the process was automated with no such option.