Zmanco

Did you bed the pads in yet? The method I've used is to go out on a deserted road and accelerate up to about 60 mph. Then brake hard, but not a panic stop, down to about 5-10 mph. Gradually accelerate up to 60 mph and do it again. Repeat this 4 or 5 times. You want to get the brakes and pads good and hot, but not overheat them. Then drive the car normally to let them cool. As it has been explained to me, two important things are happening: 1. no rotor is perfectly flat, and this is speeding up helping to get the wear pattern on the pads to conform better to the irregular surface of the rotor. Assuming you have new rotors, this isn't something that is visible to your naked eye, but it happens and means that more of the pad will be in contact with the rotor. 2. some pad material becomes embedded in the rotor surface, much like racing tires leave some rubber on the track. This improves the tires grip, and for brakes, improves the coefficient of friction, meaning the brakes feel like they "grip better". The first time I ever changed brakes (new pads and rotors) I didn't know about this, and the first few stops felt worse than the old brakes. Eventually after several hundred miles of driving they broke in themselves. This process speeds that up.

Hi All, I asked this question at the end of another thread but never got a response, so I hope it's ok to ask it again here. Has anyone done the vented 4x4 toyota caliper swap with the later bigger calipers (S12W with 4 large pistons) and NOT swapped to the 15/16" master cylinder? I ask because I read that this was required for the swap for the non-vented swap, but when I did that and left my stock m/c in, everything was fine. I had no problem with a long brake pedal.

I'm going to make the switch to the toyota calipers and vented 300zx rotors, my dilema is whether to use 12-8 or 12W calipers. From this thread and a few others, it appears that the 12-8 have one large and one small piston, while the 12W has both large. That makes me think the fluid requirements are greater for the 12W, hence the recommendation for larger M/C. I was all set to order the 12-8 as I believe they will be more than adequate for my needs, when I checked availability of pads. It looks like there are a lot of choices for the 12W and very few for the 12-8. That concerns me, especially if there will continue to be performance pads available in a few years for the 12-8. I currently have the 12-8 non-vented calipers installed with the stock master cylinder on my '73 and have no issues with a long pedal. However I wonder if the 12W might need the 15/16' master cylinder upgrade which adds additional cost. I'm sure it's better, but is it required? So my question is if anyone has tried the 12W caliper swap, and used their stock M/C with good results? For now, I'm going to leave the drums on the rear, if that matters. Thanks.

I had trouble finding a Maxima flywheel, so I had my flywheel turned on a lathe and got down to 16 lbs. Going any further would have required machining which was going to start ringing up $$$. The total cost including resurfacing and rebalancing was about $120. Definitely makes the motor rev up and down faster and feel more lively. I'd say it was money well-spent as long as you do it while you have the flywheel out. I wouldn't do this as a stand-alone project as it would be too much work for not enough benefit.

I found some hard plastic tubing that was the same ID as the vacuum line for the brake booster at my local True Value Hardware Store. It was all of .49 a foot. When I put my triple webers on the nipple was in a different spot and I didn't want to force the old hose to bend in a new way. After 3 weeks, and a few hundred miles so far it's working great. I think the key is you want something with a stiff wall so the vacuum won't collapse it. This would be much cheaper, and easier, than changing your booster, assuming there is nothing wrong with the booster of course. Good luck!

Any thoughts on the benefits of larger valves vs. a higher CR?

The "how to rebuild your Datsun engine" book says to put the head on first, and then put the timing cover on. To ON3GO's point, one time I followed that advice and for the first time ever had a coolant leak into the oil sump. Turns out I had pinched the head gasket ever so slightly pushing the timing cover on so that it wouldn't seal tight against the block. Needless to say, if you haven't replaced your timing cover with the head on and engine and radiator in the car after just having rebuilt everything, you haven't lived Lot's of fun to clean an oil/coolant mixture off your new clean engine too Other than that, the book is great!

I have a chance to pick up an E31 head with a "lopy" cam in it. The guy selling it doesn't know anything else about it, except to say the guy before him rebuilt the L24 and that it pulls strong. He's selling it because he's parting out the entire car. My current engine is as follows: - recently rebuilt N42 block w/flat top pistons .030 over and moly rings. - 6:1 header - Weber DCOE 40 mm carbs - N42 hear recently refreshed to stock except for mild cam (.441 lift, 260 duration). Engine pulls strong to 6k, but falls off fast after that. I figure the next steps for me for more power are a more agressive cam and maybe some head work. I figure I have 3 options: A) buy the E31 head and use it as-is on my block. buy the E31 head and move the valve train over to my N42 head to take advantage of bigger valves and the new valve seals. C) pass on this head and wait until I can buy a new cam/valve train which will likely cost me at least 4 times this head/cam. FWIW, my current setup does not ping with 36 degrees total advance. LEngine says that my current CR is 10.2:1 and that with the E31 it would rise to 10.6:1. I'm curious if anyone has any experience comparing the slightly larger valves of the N42 to the slightly higher CR of the E31? Since I drive mostly around 6000 feet elevation I'm not too worried about the higher CR, especially with a longer duration cam. So what would you do?

I have a follow-on question for John and Dan. I have a '73 240 with L28, flat top pistons, N42 head, mild cam, header, 2.5" exhaust. I've been running with a 70-73 stock distributor, don't know which year. I have had the pertronix in it along with their coil for 3 years and it has been great. I took the distributor apart when I installed the pertronix and cleaned it up, new grease on the ball bearings, etc. Vacuum plate moves reasonably well. I also have a spare '80 ZX distributor and am getting ready to install triple weber 40s. My question to you is if it's worth swapping over to 80 dizzy and module to get the better advance curve, or just leave things as they are, which has been rock solid reliable. I'm guessing that I'm going to have to give up the vacuum advance with the webers anyway. If it matters, I do most of my driving around 6000 feet altitude. What do you think?

I have no personal experience with them other than what was discussed above, but a few people whose opinion I respect have said they are as good as cast iron rings get. No one said anything negative when I was asking around for my rebuild.

What kind of revs is he turning? If he makes 160 lbft torque at his hp peak that would be 8200 rpm. Wow!!!

FYI, I have found a source besides VB for a .030 over piston set with moly top rings (ITM) and have them ordered. If I was only doing a refresh on a basic transportation vehicle to get another 50k miles out of it, I'd just put it together with what I have now. But with everything apart it just doesn't make sense not to do it right. It's not that much more $$$. That's how I'm rationilizing it

Now that I have found quality sources for both cast iron and chrome rings, I need to decide which way to go. I really hate the thought that I might have sealing issues and that I would tear it all down again (which leads me to the cast iron) but I also wonder about the cast iron living at high revs (~6500 max) on a NA engine. Any thoughts from those who have tried both?

I picked up a set of the Deves cast iron. End gap measures almost exactly the same, so I guess I have an issue with how my machine shop measured the bores. I guess it's time to take the block, pistons, and rings over tomorrow to work this out. The Deves set were $90.33 before tax.

Yes, just top ring is chrome. I found a set of Deves cast iron rings that I'll pick up tomorrow. I'm hoping that a different brand will have an end gap within spec. Otherwise I'm thinking it will be boring over .020 and new pistons. $$$

Silent, how long is "a while"? I really don't want to do this again any time soon as it's expensive and a lot of work. Are we talking about 5-10k miles, or 50k, or 100k? I realize no one can tell me any exact number, but if it's only a few thousand miles (which I doubt) then that would cause me to go with chromes for sure.

I'm in the process of rebuilding my N42 block. After hot tanking the shop told me that there was only about .002" between my flat top pistons (not from this block) and the bores, so they could just hone it and not bore it 20 over. I liked this because that meant I wasn't going to have to replace my pistons. However, now that I'm trying to find rings I'm having all kinds of problems. I picked up a set of Perfect Circle std (top chrome ring) and am finding that the end gap is coming in between .020 and .022". The How to Rebuild your Datsun book says .017 is max. I was told that Nissan used to have some .005 over rings, but according to Courtesy Nissan they are NLA. So what do you recommend I do next? Do I have any options besides taking the crank back out, and going .020" over with new pistons? I'm really trying to avoid that expense if I don't have to spend the $$$. Another issue: I had the block honed for chrome rings. But I've also heard how hard it is to seat chrome rings. My car is a weekend toy car, driven hard to 6500 rpm. I've got a mild cam, late model 5 speed and 4.11 so the revs are always above 3k and usually higher. I do a few track days each season. Do I need the durability of chrome top rings, or will cast iron be ok? I've heard that moly-faced would be best, but haven't found a source for L28s.

Thanks Paul, the first 2 of the roughed in views are really great, that's the first time I've been able to really see where the grinding was done. It's a lot harder to see in a picture AFTER it's all polished. I do have a question: on the N42 head, why did you take material off the bottom half (as viewed in the picture) of the chamber? Seems like it would just lower the compression without having much impact on flow. Or does it impact flow? Also, what did you use to do the rough in work? Was it a stone, or perhaps one of the sandpaper tubes (don't know the proper term for it)? I'm building up my confidence to attack this:)

I believe that's true for the NA 75-80 where the top ring is 2 mm. But the flat top pistons in the 81-83 NA are 1.5 mm which I believe is the same as the turbo. Any of you turbo guys out there able to confirm that?

I've had a heck of a time finding rings here in CO for my flat top pistons in my N42 block. After returning the wrong rings twice (both times with L24 rings in an L28 box) we've found a new source who has Perfect Circle chrome rings. But they only stock the turbo set, not the N/A ones. They (the warehouse) says that the only difference is that the turbo set has a chrome second ring where the N/A is cast iron. They say that there's no issue with this, and that seems to make sense to me. But before I put them in I wanted to check here to make sure I'm not missing something. I'm only planning on this rebuild once BTW, the shop honed the cylinders for chrome rings.

Another question: after hot tanking, could I do this without taking the head apart? Of course my concern is leaving behind any pieces of aluminum. What if I tape the valve cover on and mask off the all the manifold openings and oil and water passages? Or am I playing with fire?

Jon, thanks, that helps a lot. I'm debating whether I should attempt this. I've never done any porting or other head work myself and have read that unless you know what you're doing, you should probably leave it to someone else since you can make it worse rather than better. I do have a scrap N42 head that I can practice on, so I'm kind of leaning towards trying it. It seems like I'd only be taking off at most 2 or 3 mm of material. Does that sound right? I wish I had someone here in CO who could "look over my shoulder" so I don't take too much off. As good as dapiper's picture is, I would feel a lot better if I had a before and after pictures to use as a gauge. Anyone have anything that would help?

dapiper, I took the liberty of cropping a part of your picture and added a few arrows where I think you ground away some material. Is that correct? http://home.comcast.net/~dbailin/n42_chamber.jpg Also, anyone know why I can't post pictures? The posting rules box at the bottom left corner of the editing page says I may not post attachments.

I've been reading a ton lately about improving heads, and I have to say that this site has the best information, by far, that I've found. In my case I'm currently rebuilding my bottom end (N42 block, flat top pistons) and have my N42 head off the engine. A few thousand miles ago it was rebuilt and I added a mild cam with .441 lift and 260 degree duration. For intake/exhaust I have weber DGVs and MSA 6:1 header w/2.5" exhaust. Before anyone gets on me about the DGVs, I plan to switch to Megasquirt FI once the engine is broken in. My question right now is about unshrouding the valves. If I understand it correctly, the idea is to remove a little material so that the valves can flow better when they are only partially open. Assuming I've got that right, I've put 2 arrows in a picture of my head. The green one is supposed to pointing to the side of the head farther in and the yellow is pointing towards the same side, only closer to the head surface (and top of the piston when it's at TDC). To unshroud this valve, is it correct that one would remove material just near where the green arrow is pointing, or would you also take material off near the yellow? Although I didn't take a picture, I overlaid my head gasket and the inside edge of each cylinder is very close to the edge for each chamber in the head. I hope my question makes sense, please let me know if it doesn't PS. Just realized I can't attach a picture yet, maybe because this is my first post at this site? Use this link to see the picture: http://home.comcast.net/~dbailin/head1.jpg Daniel '73 240Z