Jonas240z Posted October 23, 2004 Share Posted October 23, 2004 Hello guys; I just got done installing my rebuild engine today. I hooked up and checked everything, all the hoses, connectinons, wires etc. and everything was in place. I tryed to prime the engine by turning it over with the ignition disabled and then i went ahead and tried to start the engine after hooken the ignition again......and the car just went BOOOOOM!! Super loud...like and explosion (backfire??) and black smoke came out of the exhaust pipe! My ears are still ringing...and i don't know what's wrong. I'm afraid of trying to strat it again, and i also can't aford to be making anymore explosion sound because i live in and apartment complex...and people already started to complain! Does anyone know wht could be wrong?? and how can i fix it?? PLEASE GUYS I NEED SOME HELP!! THANKS! Anyone around the Huntington beach CA area willing to help is welcome Quote Link to comment Share on other sites More sharing options...
Guest 240zt Posted October 23, 2004 Share Posted October 23, 2004 Sounds like a backfire Dunno how to solve it sorry. Though i dont think you screwed any thing up Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted October 23, 2004 Share Posted October 23, 2004 Sounds like you may have the distribitor in wrong, and the timing off.... Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 23, 2004 Author Share Posted October 23, 2004 I think i have the dizzy in the right position...one thing that i remember is that i was going to use a 280zx dizzy ( from a junkyard) and when i mounted it to the front cover the rotor was pointing at like 10'o clock, but then i decided to use my 240z dizzy (converted to electronic pick up..pretonix maybe??) because i knew it works, so i mounted it and the rotor was pointing to 07:00...I don't know why. Also i didn't mess with the timing of the dizzy ( wich was set to advance all the way past all the marks, [ the 240z ran fine like that]). Quote Link to comment Share on other sites More sharing options...
zcarnut Posted October 24, 2004 Share Posted October 24, 2004 Did you connect the spark plugs wires correctly to the distributor cap? The L-series distributor rotates counterclockwise (when viewed from the top). To check rotate the crankshaft until you have the #1 cylinder piston setting on TDC by using the timing marks. Make sure that you are on the compression stroke of #1 cylinder (open the oil cap and look at the cam lobes for the #1 cylinder, both intake and exhaust lobe should be pointed up). If not, then rotate crank another full revolution. The distributor rotor should be pointing at the tower corresponding to spark plug wire #1. Then check the remaining wires using the 1-5-3-6-2-4 firing order sequence. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 24, 2004 Share Posted October 24, 2004 I think i have the dizzy in the right position...one thing that i remember is that i was going to use a 280zx dizzy ( from a junkyard) and when i mounted it to the front cover the rotor was pointing at like 10'o clock, but then i decided to use my 240z dizzy (converted to electronic pick up..pretonix maybe??) because i knew it works, so i mounted it and the rotor was pointing to 07:00...I don't know why. Also i didn't mess with the timing of the dizzy ( wich was set to advance all the way past all the marks, [ the 240z ran fine like that]). I think this is your problem. The distributor is driven off of a shaft which goes diagonally down through the timing cover and connects to the oil pump and is driven off of the front of the crank. If you didn't keep the shaft in the same position when you removed it and reinstalled it, then you'd be pretty lucky if you just stuck it in there and it was right. Really lucky. To fix you should put the engine to TDC#1 (pull the valve cover and make sure the valves are closed and it really is TDC#1) EDIT--looks like you can just look in the oil cap-- and pull the distributor cap. The rotor should point to where the #1 spark plug wire is (roughly). If it doesn't, then you'll have to remove the oil pump and reposition the shaft. It runs on a gear on the front of the crank, so you'll have to pull it down to disengage from that gear, then twist it a little bit, then plug it back in. This is much easier if you have a buddy to stand next to the front of the engine and twist the rotor while you are twisting the shaft. If not, you pretty much have to guess, then attach the oil pump, then get out from under the car, plug in the dizzy, see if it is pointing in the right direction. Then if it isn't you have to get back underneath, pull the oil pump move the shaft again, put the pump back on, get back out, put the dizzy back on and check, etc... With a friend it shouldn't take more than about 10 minutes. Also, you may have to remove the front sway bar from the frame to access the oil pump bolts. Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 24, 2004 Author Share Posted October 24, 2004 Today i checked the timing of the cam and this is what i found out: the engine is at TDC with the two front cam lobes pointing up (valves closed, rocker arms loose) , the timing mark on crank pulley pointing to 0*, and the "V" groove and cam trust plate mark aligned with it. What i noticed that the rotor is pointing to about 2:00. The only way that the rotor points to the #1 cyl. is to have the piston at TDC @ the intake stroke ( lobes pointing down). Then i guess the shaft is 180*off...but i remember that when i assembled the engine, i put the shaft on and checked the alignment according to the Tom Monroe book and it was correct...so could i have assambled it with the cam lobes pointing the wrong way?? or does it matter? And can i just fix it by turning the shaft 180*?? Thanks for all the help! Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted October 24, 2004 Share Posted October 24, 2004 If it doesn't' date=' then you'll have to remove the oil pump and reposition the shaft. It runs on a gear on the front of the crank, so you'll have to pull it down to disengage from that gear, then twist it a little bit, then plug it back in. This is much easier if you have a buddy to stand next to the front of the engine and twist the rotor while you are twisting the shaft. If not, you pretty much have to guess, then attach the oil pump, then get out from under the car, plug in the dizzy, see if it is pointing in the right direction. Then if it isn't you have to get back underneath, pull the oil pump move the shaft again, put the pump back on, get back out, put the dizzy back on and check, etc... With a friend it shouldn't take more than about 10 minutes. Also, you may have to remove the front sway bar from the frame to access the oil pump bolts.[/quote'] You'll need to rotate the shaft until you have it in right. Really the buddy system is the best way to get this done. Some people cut the #1 plug wire tower off the cap so they can make sure it's in right whent he dizzy is in. Quote Link to comment Share on other sites More sharing options...
TomsCoupe Posted October 24, 2004 Share Posted October 24, 2004 this may be a dumb answer, but did you disconnect your fuel pump too? if not, then fuel was being pumped into the engine and that may have caused the backfire. Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 26, 2004 Author Share Posted October 26, 2004 Thanks for all the help guys!! yesterday i got it up and running . The problem was that the dizzy was 180* off....and i thought i had it done right during assembly, that's why it's a good idea to triple check! There is another problem now tough....the valvetrian is very noisy! I tried to adjust the valve lash ( tighter ) and it just made it worse. I hope it's not the valves hitting the pistons cuz' it sounds pretty loud. The bad thing is that i'm not mechanic nor i have any prior experience (i barely started working on cars earlier this year)...and i don't know if i did something wrong or how to identify it. I need some help Quote Link to comment Share on other sites More sharing options...
Drax240z Posted October 26, 2004 Share Posted October 26, 2004 What did you set the valve clearence to? Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 26, 2004 Author Share Posted October 26, 2004 I set them .002" thighter than stock....i did them hot, so that would be .008" intake, .010" exhaust instead of the stock .010 and .012". But the noise didn't go away so then i set them even't thighter (.006" and .008 hot! )and now it's pretty noisy!! My cam is aftermarket and i lost the spec sheet so i don't really know what to set them to. Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 26, 2004 Author Share Posted October 26, 2004 I also purchased the nissan motorsports pistons that have a sligthly raised dome...that's why i'm afraid that the valves are hitting the pistons( is there a way to check for that without taking the head off the block), could that be a posibility or is it just the valvetrian that is making the clicking noise? The car actually feels fine... just a little vibration through the steering wheel and that anoying clicking noise! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 26, 2004 Share Posted October 26, 2004 How did you set them exactly. I mean give us a pretty good run down of what you did. Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 26, 2004 Author Share Posted October 26, 2004 First i when i assembled the motor i set them stock cold (.008 intake & .010" exhaust ). Then after firing the engine and letting it run for 20 mins. i took it for a test drive and i nottised the noise coming from the valvetrian. I got back home let it cool for 15-20 mins. took the valvecover off and when ahead and set them to .008 and .010 (hot) ...which is .002 tighter than stock (hot). I did that to get rid of the noise. I ran it again and the noise didn't go away. So i set them .002" tighter to .006 & .008 (hot) and then the noise was still there ( and i believe even louder ). I did all that after running the car to normal temp. and let it cool for 15-20 mins. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 26, 2004 Share Posted October 26, 2004 If you had interference between the valves and pistons I think you would have found it when you were assembling the engine most likely. You did turn the engine over with a ratchet at some point during the assembly right? Maybe when you were adjusting the valves during the assembly? I think something isn't going right with the way you're adjusting them. I'm not trying to insult your intelligence, but I've seen one common mistake probably 5 or 6 times over the years, and here it is. The shadetree mechanic will adjust all the valves without ever turning the engine or without making sure the valve was all the way closed before adjusting the gap. You did make sure that the valve you were adjusting was CLOSED before adjusting it, right? If you adjusted some of them with the lobe not straight up, then you would have a hell of a racket because you might have some HUGE gaps between the rocker and cam. I always pull the plugs and use a little starter switch I got from Harbor Freight. I turn the engine until the cam lobe points pretty much straight up. Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 26, 2004 Author Share Posted October 26, 2004 Yes i did turn the engine manualy during assembly ( felt a little resistance tough, every 180* or so, is that normal). I'm pretty sure i adjust the lash with the lobes straight up? I'll triple check today....but now my question is: what should i set them to...Stock or thighter? and cold or hot? And if the noise doesn't go away what else could it be? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 26, 2004 Share Posted October 26, 2004 If you had the plugs out than the only resistance you'll feel is the valve springs, which is still a decent amount. If you could turn it over by hand I doubt that the valves are hitting the pistons. I'd go .008/.010 COLD and double check the gap when they're hot. If it takes you a long time then do them cold. The reason is the longer it takes the more the gap will open up. So the first intake valve you do might be .008 and the last one might be .010 when its fully hot. Bastaad just asked a related question about going tighter than stock setting. I really don't think .008/.010 hot is going to hurt anything, but DAW disagreed with me, and he usually knows what he's talking about. Best to err on the side of caution and make sure you are doing it right before you start messing with the clearances. If this is on a 240 there really isn't much else to be making noise. If you try again and you still can't get it I suggest you take it to a shop that deals with Z's and have them double check your work. Quote Link to comment Share on other sites More sharing options...
Jonas240z Posted October 26, 2004 Author Share Posted October 26, 2004 Thanks alot jmortensen. I'll do that and hopefully i'll get rid of the noise! But if not i'l just take it to a shop. Thanks again everyone! Quote Link to comment Share on other sites More sharing options...
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