Nismo280zEd Posted June 27, 2006 Share Posted June 27, 2006 This one is just really agrivating me. We've had a SOHC 93 maxima that originally had leaking cam seals, so we replaced them ourselves while motor was in car. Turned out to be a bad idea, ended up scratching the housing and cam so new seals didn't seal. So we took the engine apart, took the heads to a local maching shop here (napa) a guy named richard did the heads, he's done work for us before a couple other houston Area Z guys here. He said the scratches couldn't be fixed that basically the cams and heads were toast. So he found a set off another 93 SOHC for 250. We got them home, started to assembly the heads, putting manifolds back on, plugs, etc. Found 4 exhaust studs broken off in the heads. So we take them back up to Napa, they are extremly apologetic, fix everything for free. So we finally get this motor all back together the other night... turn it over, nothing. I check the timing, ok it's off, restab the dizzy. turn it over again, one cylinder kinda tries to fire. Ok maybe it's flooded. give it a couple min, check some more things, find a vacumn hose laying loose, conect it. Try it again, three cylinders try to fire but won't start or even half start. Try again nothing. So it's about 8:30 we've been workn' on this car for months. My father and I are both pissed. so we call it a night. I come over today and compression check the motor as we pulled the plugs and they spark and we verified fuel. Guess what absolutely ZERO compression. Now i've only delt with a couple engines fully apart at my age, 2 Porsche 911 motors, severl Z motors, this VG30 series motor, and a 95 Ford Taurs SHO motor. I know for a fact the pistons are going up and down. Everything was lined up properly on the cam timing and triple checked. The engine was hand rotated through prior to starting to verify no issues with valve hitting pistons. We have rebuilt the heads on this car before and even when it had bent valves it still read like 60lbs compression. Same with the Z motor. Now maybe I just lack experience with blown motors, but I don't see how it is physically possible to have ZERO compression. I also checked the gauge on my car so I know that's not it. The only thing i can think of is maybe the wrong cams were installed or something and the valves arn't actually closing. You guys have any ideas before i take a 50lb sledge hammer to this damn car? -Ed Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 27, 2006 Author Share Posted June 27, 2006 I forgot to mention i sprayed oil in the piston after the first compression check to see if it helped, it did nothing, thus leads me to believe the heads. -Ed Quote Link to comment Share on other sites More sharing options...
mtcookson Posted June 27, 2006 Share Posted June 27, 2006 Check your cam gears themselves, make sure you have those one right, and double check your timing belt install. I got ahold of an 85 Maxima engine that was supposedly burning oil. I found oil in the intake so figured likely the PCV. Tested compression and found it to be low on all cylinders. Figured I'd take it apart to inspect but found in the process that someone had put the cams gear on wrong. The left (front) was on the right (back). Swapped them, double checked the timing belt, and all is good. That would be my guess first hand. The chances of ruining the pistons/cylinders are usually quite low, bent valves is a possibility but you took the right steps in assuring that wasn't an issue. May pop off a valve cover and just kind of watch the valves moving while hand cranking it to see if there are any oddities going on in there. I guess there could be a chance that the head is warped... but I would think you'd see compression on at least one cylinder so I don't believe that is it. I'd check those things first and see if there is any issues with what I mentioned. Quote Link to comment Share on other sites More sharing options...
Thumper Posted June 27, 2006 Share Posted June 27, 2006 Sounds like somebody is having almost as much fun as me. I think its either a broken camshaft or something with the cam gears or timing chain. Open up the oil cap and check to see if both cams are rotating if they are then its must likely the cam gears are wrong. Good luck Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 27, 2006 Author Share Posted June 27, 2006 Well we are about 2 hrs into tear down, we'll find out soon enough what went wrong. I'm sick and tired of this damn car, does anybody want a Maxima? Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted July 8, 2006 Author Share Posted July 8, 2006 Ok you guyz are not going to believe this one, well maybe you will. So we tore the engine down turned out... we lined the crank sprocket up wrong, we lined it up with a mark that was on the gear instaed of the dot or indention on the gear that evidently a previous shop or someboy put on. Either way we were retarded for not catching this. The cams turned out to be about 90deg off of timing. So i'm thinking, great... were F*&*ed and have to rebuild the head again. Figure we might as well put the timing belt on right first and see which cylinders arn't holding compression now. So we get it timed correctly, start compression checking. Every single freakn' cylinder was 210ish!!! Not one single bent valve. Isn't that amazing? The car is running now and sounds pretty good. Just thought i'd leave this crazy story on here. -Ed Quote Link to comment Share on other sites More sharing options...
mtcookson Posted July 9, 2006 Share Posted July 9, 2006 That's amazing. Glad to hear it came out good! Quote Link to comment Share on other sites More sharing options...
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