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Zmanco

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Posts posted by Zmanco

    What would you do?

    in Nissan L6 Forum

    Posted

    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.

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

    rebuild check list

    in Nissan L6 Forum

    Posted

    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 :violin:

     

    Other than that, the book is great!

    What would you do?

    in Nissan L6 Forum

    Posted

    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.

     

    B) 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? :)

    Pertronix Ignitor vs 79-81 Elec. dizzy

    in Nissan L6 Forum

    Posted

    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?

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    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.

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    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 :)

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    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?

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    Let me know what happens with the deves rings, I wanted to get cast iron rings in the first place, its just a matter of money! How much do those rings run for?
    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.

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    Only the top ring is chrome, right?
    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. $$$

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    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.

    Engine rebuild dilema

    in Nissan L6 Forum

    Posted

    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.

    Unshrouding valves

    in Nissan L6 Forum

    Posted

    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:)

    Turbo rings in a N/A L28?

    in Nissan L6 Forum

    Posted

    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.

    Unshrouding valves

    in Nissan L6 Forum

    Posted

    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?

    Unshrouding valves

    in Nissan L6 Forum

    Posted

    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?

    Unshrouding valves

    in Nissan L6 Forum

    Posted

    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

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