a_z_story

@DuffyMahoney Siamese shmiamese

Yes, I misread the syringe and all of the numbers were off by +5. I edited my post above to correct. Even so, they all did measure over the reported 42.4cc CC volume for the E31..not sure what to think about that.

I measured the volume my combustion chambers tonight with the stock E31 valves in place to get a baseline volume comparison. I used what I had layin' around - quarantine MacGyver style. A skii wax scraper, and an equine syringe and some died water with a oil (thinking that might reduce the surface tension). Measured from front to back, 43.5, 43.5, 43.5,43.5, 43, 44 cc. I'd guess my instrumentation was accurate to the nearest .5 cc - I think the diameter of my syringe made for some slop unfortunately. I did each 3x and took the median. The sneaky bit of volume that I didnt immediately realize I wasn't resetting each time was the space around the ceramic in the spark plug - I think this may account for .5 cc or so. Anyhow, I figured I share to get thoughts from others, and maybe inspire others to do this. I'd recommend the narrowest, tallest pipette/graduated cylinder/syringe that can do 50-60cc depending on the head you're measuring. Edited because I misread my syringe and noted all volumes off by +5.

I just bought this book last night off Amazon. Looking forward to nerding out while in lock down at home!

Those seem like some really impressive flow numbers compared to those other cylinder heads. Makes me feel a little better about going down this E31 path, although I realize these results are likely unobtainable for noobs like myself. I found this thread saved in FAQs that touches on some of my questions from my OP (more N42 focused) , and have an active thread running on the Church of L series as well on the subject if anyone's curious. The question that I have not seen an answer to is what material should be targeted to balance combustion chamber volumes? Quench pads? Material around the Spark Plug? Or is this not even a valid concern? Pure speculation at this point from me. Thanks all!

Hi, I hope HybridZ is the forum website that meets these criteria for everything Datsun S30/L series engines...but if that's not the case... is there another community online that raises the bar? Facebook groups, forums, instagram hashtags, etc? Michael

Looks good @DuffyMahoney - what are your thoughts on keeping the intake ports rough to stir up the A/F Mix? Those valves loook yuuuge. And what's going on with those valve guides? Looks like they have a portion cut out? Your combustion chambers look like they had the edges knocked down at least. Did you volume test them? If so, I'm curious to know how they compared, and what the acceptable tolerance is between them. I keep editing my post as I answer my own questions, and come up with new ones..ha!

Hello, I'm going to take a die grinder to my E31 combustion chambers and intake and exhaust ports to deshroud and port match the intake and exhaust manifolds. Not looking to go too crazy, but I have a steady hand and feel pretty confident that I can make improvements. I believe the green lines in the image below are the areas to focus on. Is there any reason to cut into the quench pads? Maybe use that material to equalize combustion chamber volume? The first photo shows some some rough surfaces that I would also assume should also be smoothed out. I'm having the larger valves from an N47 cylinder head installed, so does it even make sense to deshroud prior to the valve job? I''ll be mating this head to a N42 L28 bottom end with flat tops.Thanks in advance for your input.

This is my third rebirth into auto tuning forum life. From Honda, to BMW and now Datsun. There is so much tribal knowledge that exists in these forum sites that do not pass over to youtube, or current social media platforms. (HybridZ is social media, old school btw) So far I'm really impressed by the wealth of knowledge and the helpfulness of this community. I dont think you get the same long term commitment from followers on the traditional social sites, although I do participate there as well for the classifieds. If anyone in Colorado wants to share their knowlege, resources, parts (mehehe) with me post pandemic, hit me up! @a_z_story on instagram

@newzed Yep, I totally was. I now see how it's not a factor in displacement. However, I would think the compression ratio calculation is total cylinder volume at BDC (combustion chamber+head gasket volume+deck height+piston volume+displaced volume) / total volume at TDC (combustion chamber+head gasket volume+deck height+piston volume). Essentially the biggest volume/smallest volume. The combustion chamber, head gasket volume, cylinder head dome or dish all being part of that volume of air being compressed into the combustion chamber. Is that incorrect? We might be saying the same thing too...Lots of learning going on right now, so thanks in advance for the willingness to share the tribal knowledge. Michael

Really appreciate the thorough responses Jon. I just picked up the L28 today and spent the afternoon getting it down to just the bottom end. Was interesting to remove the oil pan and see that the crank appears to have been lightened and balanced previously. Cylinder walls are smooth. No surprise flat tops already in there though... ha! I think the N42 block will be a nice foundation for what I hope to build. It seems like folks have the ping problem with the non-high quench heads more often in the 10:1-11:1 realm...would you say that's accurate? You mentioned your 11:1 build pinged badly - was the head or block decked on that? and did you try a 2mm headgasket? This is the output from that calculator I mentioned previously. Doesn't seem like the combustion chamber volume is taken into account in the total displacement value. It would be slick to slap that .540/310 cam into the e31, do the larger valves and run SUs for now and be able to transition to triples in the future with no downside from a conservative cam choice. I'll try to seek out Greg Ira and get his input...hell, maybe his cam? If you care to follow, and are on instagram, I made an account dedicated to the build. @a_z_story

@jmortensen - Thanks for the insight - I should have been a bit more clear, I'm targeting 10:1 so nothing too outrageous as far as I can tell. Would like a reliable street engine that can run on higher octane pump gas. Does that change your camshaft suggestions at all? My initial thoughts are to use the N42 block, L28 crank, rods and flat top pistons with a 1.3mm head gasket, and then the e31 with the N47 valves, mild porting and combustion chamber work, and an aftermarket camshaft (put my $ into the head). Thought behind using the e31 head is to have the smaller combustion chamber with the flat tops to increase compression, and to also allow the use of my SUs (triples someday) and square port header. I entered this mix into a website engine calculator and came back with 3.0L (manually adding the combustion chamber volume to the cylinder volume) and ~10:1. I've seen several threads discussing similar builds, so I think this is somewhat on track... I still need to see if my cylinder head and and the block have been decked at all. I'm also curious to know what boring 1-3mm over would do? I also spent some time reading about a theory of using an L24 crank and rods with l28 flat top pistons to make a "unstroked" bottom end, which was an interesting idea but I'm not sure it ever came to fruition. Seems like you'd loose torque, but reduce the rotating mass? Tradeoff? Seems like there's a lot of ideas on the internet, but people never build em out! @newzed - That makes sense. It's an internally oiled cam, so does that get supplied oil through the e31 cam towers? I thought I read the origional e31 cams were solid and oiled with the spray bar. Mine looks to have both systems in place.

Hello, I am trying to understand why my E31 cylinder head might have a "H" stamped camshaft from a 280zx L28E in it? After scouring the web, I've found one comment stating that it performs like a stage 1 upgrade, but it seems like the lift and duration specs are less than a L24 and L26 camshafts. Is there more to it than that? Segue into my build plans... I'm looking at mating this cylinder head to a N42 block with flat top pistons. I'm exploring all sorts of combos using parts from the two motors I have in my possession (L24 with E31 head mentioned above, L28 with N42/N47 combo) . I'm interested in a high compression N/A carbureted motor build to put into my 10/70 240z. Michael