drzed Posted December 22, 2005 Share Posted December 22, 2005 I'm having a difficult time deciding how to proceed with the following project and am looking for advice. I acquired a problematic stroker engine a while back and am looking at trying to use it for a budget upgrade for my 260Z street/drag car. The engine has many good parts such as a knife edged diesel crank, 9mm rods (shot peened with ARP bolts), forged JE pistons (86mm w/floating pins), O ringed block, ported head, custom intake, custom turbo header, and many other things I'm forgetting right now. The problems were mostly oiling problems due to P.O. screwups and improper bearing installation and a poor combination of parts. I can fix the oiling problems easy enough (crank needs polishing, needs new bearings, cam and followers are garbage) but the pistons are the real problem. Somehow the P.O. managed to select pistons with a 20cc dish that end up .045" down the hole! This makes for non existent quench and horrible compression ratio (6.7:1 with my 51cc P90 head). So as I see it I have the following options: 1) Deck the block the .045" (losing the O rings) and go with a 1mm head gasket to improve quench and get back some compression (7.25:1) Has anyone decked the block this much before? Will I lose much rigidity? 2) Try to find some slightly longer rods (134mm or 135mm) to bring the pistons up to zero deck (or mill the pistons if they are out of the hole). I don't like this option as it will require rebalancing the assembly and the costs of rod prep - I haven't been able to find any rods of this dimension anyway. 3) Purchase the proper custom forged pistons (or maybe 87 or 88mm units) and machine the block and rebalance the assembly. Probably more money than I'm willing to spend right now. So I'm looking for suggestions. If I can't work it out I may just put the head, intake and header on my existing engine but I ended last racing season at 21 lbs of boost so I'm starting to worry that the factory cast pistons are going to fail if I push them any harder. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 22, 2005 Share Posted December 22, 2005 I believe the L20 rods are 135mm and utilize the same bearings as the L28, so those meay be a viable option. (Someone correct me if I am wrong). I like the idea of a longer rod as opposed to decking the block. That is just my opinion though... Mike Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 22, 2005 Share Posted December 22, 2005 You could opt for an N-series head. Smaller, open combustion chambers, so the quench wouldn't be an issue. What CR would 44.6cc net you? Quote Link to comment Share on other sites More sharing options...
drzed Posted December 22, 2005 Author Share Posted December 22, 2005 CR would be 7.8:1 with pistons 0 deck or 7.25:1 with them the way they are. Not really interested in keeping the pistons .045" down the hole even with the N series head - in my thinking the pistons should always be within .040" - .050" from the head surface (including gasket thickness). Does anyone here run a turbo engine with an N42 head and 25 - 30 lbs of boost? Any problems with cooling or detonation? I've been running the P90 and am very happy with it. It takes quite a bit of timing with pump gas and has no detonation at all. I can live with a lower compression ratio as the engine in the car now has the factory 7.4:1 and is working quite well. Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 22, 2005 Share Posted December 22, 2005 Does anyone here run a turbo engine with an N42 head and 25 - 30 lbs of boost? Any problems with cooling or detonation? Yep...http://forums.hybridz.org/showthread.php?t=105832 This was on 94 octane Sunoco pump gas and 24psi. The head has been reworked, but most the the work was in the ports. The combustion chambers have mostly just been smoothed and ceramic coated. I have not had much in the way of detonation problems. Had some cooling issues that I have attributed to the electric fan and water pump, and the healthy intercooler that blocks the path to the radiator. I recently went back to the mechanical fan and water pump, and that issue appears to be gone. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 22, 2005 Share Posted December 22, 2005 Love that dyno graph Tim!! Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 22, 2005 Share Posted December 22, 2005 Love that dyno graph Tim!!Sorry - couldn't resist posting it again. Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 22, 2005 Share Posted December 22, 2005 CR would be 7.8:1 with pistons 0 deck or 7.25:1 with them the way they are. Not really interested in keeping the pistons .045" down the hole even with the N series head - in my thinking the pistons should always be within .040" - .050" from the head surface (including gasket thickness). I know what you mean - that's kind of my initial reaction too. However, it's really pretty much the same as using a 2mm head gasket to lower your CR. Quote Link to comment Share on other sites More sharing options...
drzed Posted December 23, 2005 Author Share Posted December 23, 2005 Wow! Those numbers would certainly work for me. Well I may revisit the calculator tonight with the numbers for the N42 and look at all my options. I just have a hard time not using those JE pistons when they are here and paid for. Thanks for the help Tim. Quote Link to comment Share on other sites More sharing options...
DemonZ Posted December 23, 2005 Share Posted December 23, 2005 I believe the L20 rods are 135mm and utilize the same bearings as the L28, so those meay be a viable option. (Someone correct me if I am wrong). The L20A rods are the same as the L24, 133mm. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 23, 2005 Share Posted December 23, 2005 Thanks, my bad Quote Link to comment Share on other sites More sharing options...
Yokohama Posted December 30, 2005 Share Posted December 30, 2005 drzed, you could just give me the JE pistons, I am very sure that I could put them to very good use with my L28ET! Have you considered welding the chambers of the P90? Quote Link to comment Share on other sites More sharing options...
DAW Posted December 30, 2005 Share Posted December 30, 2005 drzed, you said the rods are 9mm bolt but didn't say whether they are L18/28 or L16/24 rods. If they are L28 (L28ET rods come shot-peened) then a set of L24 rods will help (then you have to deal with positive deck ht but the right gasket will fix that. Assuming you have L24 (133mm c-c) rods in there and have that much piston dish and additional below-deck volume, I think you should forget an N42/47 L28E head and consider a Maxima L24E N47 head. You can keep your O-ringed block and end up with a workable c.r. You'd need to install L28 (N42-length) intake valves/seats and valvesprings but I think it's a better solution than decking the block. Toyota 3S-GTE rods are 138mm and the right BE width and 9mm bolts but have a smaller BE dia. (0.080" smaller than the L6's) so you could have your LD28 crank offset-ground to use those rods...it would have to be in the "destroke" direction...you'd lose one mm off the top-extent of the crankthrow so you'd be down in the hole just over 2mm instead of the one...and you are adding 5mm rod length (assuming you have L24 rods) which would then bring the piston almost 3mm positive deck...any room to trim the top edge of the piston to reduce compression ht? The Toyota rods use 22mm floating pins so you'd have to bush down to 21mm if the JE pistons have 21mm pins. You need to know the compression ht. of the pistons you have and verify that there are L24 rods in there and not L28. DAW Quote Link to comment Share on other sites More sharing options...
drzed Posted January 2, 2006 Author Share Posted January 2, 2006 Thanks for the info DAW. The rods are 133mm 240Z 9mm rods. The Toyota rods seem like a good choice for an offset ground diesel stroker crank going back into the diesel block. 83mm + 2mm + 2mm = 87mm stroke? Sounds like a good start on a theoretical engine build eh!?! So I made a choice a couple of days ago and came up with the following: My pistons are actually 86.5mm so I gain a very small amount of compression from what I had previously calculated. I am keeping the block for a future project and using an early N42 block instead (for the supposedly better rigidity). I'm decking the block 0.030" and using a .6mm composite head gasket for about 0.040" piston to head clearance and 7.3:1 CR (just slightly less than stock). After ready the articles on the SDS website I'm looking forward to a low compression high boost engine. This should work well and allows me to use the P90 head I have and keep the balanced bottom end together. Thanks for all the replies (and the offer to take the pistons off my hands) Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 2, 2006 Share Posted January 2, 2006 Yeh, L20B rods are a bit long, at 146mm, but they work nicely in an L20A to work the rod ratio up to the stratosphere... Tight Ring Stack and custom pistons, for sure! In Japan, N42's were boosted to over 2 bar routinely using old school technology, so that shouldn't be a problem. As Tim has shown with that Dyno Chart, it's doable... (Gives him a chance to post it again...LOL) With that low a compression ratio, you might want to look into a retarded line-staging scheme to the timing so you can build boost at the line and launch under almost full boost. You will be loosing time unless you get something to spool that baby---man, I wouldn't want to road race that thing, off bost tractability would be like a Yugo... Let us know how it all works out. Good Luck! Quote Link to comment Share on other sites More sharing options...
drzed Posted January 2, 2006 Author Share Posted January 2, 2006 Ya, if I ever take the car to the dyno and the graph looks anything like Tim's it will become part of my signature below! As for building boost on the line I haven't had a problem yet - the trans is an auto and I foot brake at the line with a 2700 RPM stall convertor. It takes a second or two for it to start to spool but it builds about 10 lbs of boost by the time I leave - 1.57 60 ft time. I had an intercooler hose blow off late last year and it's pretty doggy without the turbo. Who would have known that a 7.4:1 engine with a cam wouldn't build any power without the turbo !! I think the cranking pressure was about 135 psi when I checked - very sad indeed. Quote Link to comment Share on other sites More sharing options...
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