z-ya Posted December 19, 2011 Share Posted December 19, 2011 Yea Tony, but you can't snack on the modeling clay while you are working! I usually swap out the MLS gaskets after 4-5 "cycles" of installing and running so I have a few shop queens laying around. I have found they don't last forever if you do a lot of teardowns. We had one spring a leak last year after building and testing the engine in in sunny Florida, towing it to Atlanta and cranking it in 30 degree weather. Didn't realize they were used. Good use for them. What club do you vintage race with? Do they allow the EFI? I'd love to ditch my Mikunis for EFI, but VRG and SVRA don't allow it. Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted December 19, 2011 Share Posted December 19, 2011 We race HSR since they stay mostly in the South East. They are much more about the show and full fields than picking on rules. They will allow just about anything to race and find a class for it. They now even have X classes for some of the stuff in between rules like EFI. I once saw a rotary turbo 510 that could run 200mph. Most all the classes seem to stretch the rules. The ex-Nascar guys are much faster than a Sprint Cup car, the Porsche's run $40,000 engines with titanium rods, and I'm not old enough to remember racing in the late 60's, but I doubt the front running Trans Am Mustangs and Camaro's sounded like Indy Cars going down the straight. I thought the tires were at least an equalizer, but lately I've seen slicks run in some of the production classes. I don't think there are many protests. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 26, 2011 Author Share Posted December 26, 2011 (edited) Back to the original topic I've received the Ishino headgasket that was supposed to be 1.25mm compressed. I've measured at 2 locations the displacement of the head when tightening the head bolts. Under head weight, head gasket is 1.35mm thick so quite close to what a Felpro gasket is uncompressed also. Once compressed at 70Nm with ARP hardware (so not even the final torque), the thickness of the stock gasket was 0.99mm on one side and 1.06mm on the other. 1.25mm thick compressed stock Ishino headgasket is a MYTH! My story shows also that we absolutely need to double check everything we are doing during a rebuild. We should trust only what we have in front of us. So I need to plan for C plan: send pistons to machinist to have them milled by 0.3mm to match the Felpro gasket thickness I still have. I have to wait a little, it is vacations time, next steps would be only in some weeks then, maybe months since I might have to travel for business in Mexico for one month. Edited December 26, 2011 by Lazeum Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 26, 2011 Share Posted December 26, 2011 (edited) "I once saw a rotary turbo 510 that could run 200mph." By whose documentation and claim. I'd call B.S. on that one. "Could Run" is not a valid claim. My 73 240 'could' run the same speed as our Bonneville car with the turbo engine in it...but it won't. Ever run a 510 at 150mph? Much less 200... Bummer on the head gasket. As stated above, a compressed gasket that was used in a running engine is best kept on the wall for pre-final assembly mockup and checking of clearances. Having it precompressed and lightly assembling the head to the known distance is a proven technique. Good Luck with the machinist. I know Norm did his piston clearancing on the concrete driveway using sandpaper! Edited December 26, 2011 by Tony D Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 26, 2011 Author Share Posted December 26, 2011 (edited) I've never thought about using sandpaper on pistons!!! Maybe I should give it a try?!? More seriously, let's do it clean even if it takes more time & money. Let's do it right... Roads are full of salt so there's no rush to have a running engine before end of March. Regarding compressed gaskets for mockup, I start to have a tad too much for my taste Let's use the latest one the appropriate way! Edited December 26, 2011 by Lazeum Quote Link to comment Share on other sites More sharing options...
madkaw Posted December 27, 2011 Share Posted December 27, 2011 So are we saying there is no 1.25mm compressed gaskets avaialble? I have just finished replacing head gasket on my L24 and the one I removed was right at .047-pretty close to 1.25mm. I believe this was a stock Nissan gasket. The one I ordered from Nissan is a Nismo gasket that also is supposed to be 1.25mm compressed. Wouldn't these make your numbers work? Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 27, 2011 Author Share Posted December 27, 2011 it would but how did you make sure what was announced was correct? As far as I'm concerned the stock headgasket from Ishino I've got is not at 1.25mm compressed as stated here and there on this board. My next options are: to get a new headgasket again and try it or machine the pistons to match the Felpro gasket I still have. The 2nd option is more reliable than the first one so I'm going for machining next Quote Link to comment Share on other sites More sharing options...
didier Posted December 27, 2011 Share Posted December 27, 2011 The 2nd option is more reliable than the first one so I'm going for machining next Do you think they 'll have to disassemble the rods from the pisons ? Not good at all for press fit mounts , multiple operations on same parts . ..... Quote Link to comment Share on other sites More sharing options...
madkaw Posted December 27, 2011 Share Posted December 27, 2011 I would think that a Nismo high performance head gasket that is advertised as 1.25mm would indeed be 1.25mm. At 150$ it would be much cheaper than machining pistons. I also think a MLS type gasket would be very consistent Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 28, 2011 Author Share Posted December 28, 2011 (edited) @Didier, I don't think it would be bad to dessasemble & reassemble the pistons pins as long as there's no material removal in the process. Previous pins were looking fine after teardown to get the rods back to my current setup. I need to check with machinist, if they use a mill, it might fit with rods (unlikely though). @Madkaw, Nismo headgasket could be considered but it has to be accurate. If I want min 0.6mm clearance (0.023"), gasket could not be any thinner than 1.25mm, if it is 1.15mm I'm nearly out. I also have to add shipping cost which are not negligeable from where I am. I was nt going to go to this direction but seeing where I'm at now, it becomes a valid option (Would have I torn down the whole engine yesterday for nothing?? ) Would you have the part number for the head gasket? I don't see any on Nismo catalog that matches the description (p. 20). [edit]: I forgot to say thanks! and please also Edited December 28, 2011 by Lazeum Quote Link to comment Share on other sites More sharing options...
madkaw Posted December 28, 2011 Share Posted December 28, 2011 I just mow noticed where you are from - so I understand the shipping issue. Both MSA and Courtesy Nissan advertise the Nismo gasket. Maybe one of them would ship to you. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 28, 2011 Author Share Posted December 28, 2011 (edited) Hmmm. I haven't seen it on MSA. I'll give a call to them. As a club here, we have some deals. If he does not work, I can deal also thru the US with Courtesy. I used to live there so I have loads of friends who could help Edited December 28, 2011 by Lazeum Quote Link to comment Share on other sites More sharing options...
z-ya Posted December 28, 2011 Share Posted December 28, 2011 Tomei is an alternative to the more expensive Kameari gaskets. http://www.ebay.com/itm/Tomei-Head-Gasket-Nissan-L6-90-5-1-2mm-/330658590661?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item4cfcc9afc5 Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 29, 2011 Author Share Posted December 29, 2011 Thanks for the proposal. I think a lot since the last trial and the most reliable option (= less likely to fail) is to machine the pistons. From a cost standpoint, it would also be even with a new gasket: cost of the gasket, shipping & customs fees (70€ for a package worth 200$). I'll end up with a gasket at 300€ probably what the machine shop would quote me. Quote Link to comment Share on other sites More sharing options...
z-ya Posted December 29, 2011 Share Posted December 29, 2011 Thanks for the proposal. I think a lot since the last trial and the most reliable option (= less likely to fail) is to machine the pistons. From a cost standpoint, it would also be even with a new gasket: cost of the gasket, shipping & customs fees (70€ for a package worth 200$). I'll end up with a gasket at 300€ probably what the machine shop would quote me. And, you can use inexpensive OEM gaskets if you machine the pistons. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 29, 2011 Author Share Posted December 29, 2011 And, you can use inexpensive OEM gaskets if you machine the pistons. ...or the new Felpro gasket I still have in stock Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted December 30, 2011 Share Posted December 30, 2011 Lazeum, I am in similar circumstance. I preassemble my engine, check a few clearances, then travel to Germany for a few weeks. Fly back, repeat. At this pace, I am shooting for a March completion even though I have all the parts sitting on the bench. As you said, CHECK EVERYTHING. I spent the last 2 days just measuring bearing clearances. As far as head gaskets, I found the most economical solution to be the 0.6mm metal gasket from Nisson Motorsports. You can order from them directly and they are available. About $150. You will need to cut the piston top to match and yes the machinist will need to remove the rods to chuck them. I think we paid $15/ea last year for this service. Check each piston's clearance individually and try to get all of them to match in height. Sometimes you can get slight variations in the rod lengths. As for the 200mph 510, that was an exaggeration in relation to the engineering, sophistication, and high level of build that the car displayed. It passed a lot of tube frame v8 monsters and had a multi-second lead within a few laps at Road Atlanta. My disclaimer to land speed record followers. It's high downforce aerodynamics would never allow over 150-160 I would guess, but it could get to that speed very quickly. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 30, 2011 Share Posted December 30, 2011 (edited) If your rod lengths are different, you DO NOT machine the pistons differently! In that case the rod caps are Blanchard ground and the big and small end rebushed/reamed/honed to a standard C-to-C dimension. Changing the piston height will result in reciprocating weight differences...meaning removal of more material off the other "taller" pistons than otherwise would be necessary to weight-match them all. More work than is necessary given the ease of rod resizing--even in production engines they seem to "settle or stretch " over time and most machine shops have the rod machine in their tool inventory. This is a basic part of the overhaul process for even a stock build: hone rod big and small ends C-to-C and round. Reaming/Boring to standard or even a concentric round hole is a common rod overhaul procedure. In fact most people accomplish this step by slightly offset small-end bushings or by dozing the hole offset when opening the piston pin bore in the rod for the larger 22mm performance pins that come with most pistons. Rods are to be sized Center-to-Center before assembly so the only issue that arises is piston machining due to piston pin height variations which is then corrected at deck height check. Then every piston/rod is identical or rod/stroke ratio, pin height, and deck height. As to the 510, I'm more than simply a follower in that category...at least until Hondata tops our record. Many cars reach 150 easily and quickly, that's relative child's play. Start shooting for a Red Cap and things get a bit more difficult. Edited December 30, 2011 by Tony D Quote Link to comment Share on other sites More sharing options...
Lazeum Posted December 30, 2011 Author Share Posted December 30, 2011 For your info, I've measured up to 0.1mm between pistons. However, I don't know where it is coming from: crankshaft rod shaft center lines? rods length? pistons geometry? pin differences? block deck not fully flat? Measurement error? I believe at some points, I have to ignore this variation. It is a street engine. I try to do it cheap (if I can say so... ) but especially right but it hasn't have to be perfect at all cost if it not worth it. 0.1mm variations of stack between multiple machined parts sounds very acceptable to me. I will however ask the machinist to remove the same amount of material between pistons so variation will remain. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 31, 2011 Share Posted December 31, 2011 That is quite a bit, and can only assume it is from the poor tolerances in machining the pistons. The difference, if you have kept your rod C-C length standard, and your crank stroke has been checked to be identical (they can vary!) then it's down to the pistons. Thing is without measuring all this beforehand, you really never know where the stack is different! After machining, measure the weights, and equalize them all to the lightest one within 0.5 gm normal, and if you have a good resolution digital scale 0.1 gm. Of course this goes to rod ends, rods overall, etc... Let me see, what was that phrase again? "While you're at it..." Quote Link to comment Share on other sites More sharing options...
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