1990 300zx timing setup problems

[zister]

hi everyone!
A little stumped here i have had to reset the timing belt on a 90 twin cam and all was going well with lining up the marks then all of a sudden i cannot get the crank to rotate, all it will do is move basicly a little bit between the #1 stroke then stops dead either way the starter wont even turn it.

did i just mess up something horribly wrong or am i missing something, i have never had this eevent happen on any other motor i've ever worked on and i am at a loss to what it is, is there anyone who can help with this puzzle

[t.mcginley.jr]

If you can't get the engine to turn fully without resistance then STOP and take it all apart again. With the spark plugs out you should be able to turn the crank with a ratchet 360 degrees and feel no major resistance. Take the tensioner off, the belt off, re-align the crank sprocket to the mark on the oil pump, re-align each of the camshaft sprockets with the timing marks on the backing plates, then put the timing belt back on. You will have to adjust each camshaft sprocket a few teeth to get all the lines on the belt to line up but the marks on the backing plates will get you close. Once the marks on the belt line up with all the cam and crank gears, COUNT THE TEETH/COGS BETWEEN THE MARKS. Here are the counts for each section:

http://www.300zx-twinturbo.com/cgi-bin/ ... t&total=70

Then put the auto-tensioner back on and follow the FSM's procedure for adjusting the tensioner to get the gap around 4mm. At that point you should be able to rotate it fully with no resistance.

Hopefully you haven't damaged any of the valves by trying to start it like it is. You can do a compression or a leakdown test once you get it back together properly, the results should let you know if you messed something up. If you did, its most likely a bent valve from making contact with a piston.

[solaire]

Also read through this if you're still lost

cant-turn-crank-360-deg-after-new-timin ... 86122.html

[zister]

thanks for that info however it still wont rotate more than say 10 to 20 degrees, its a dead hit to like it is hitting something solid there is no flex at all like if it were pushing on a valve or compression resistance if you can picture the keyway at 2:00 it wont return past 1:00 very very little rotation. how is the oilpump driven, is it possible the gear is jammed, the confusing part is all of this happened while it was apart ,i never really moved the crank while i was attempting to alighn the cams but i did move it enough here and there where i would get compression resistance now i cant get enough rotation to even get any compression, so i am still at a loss! any other ideas?

once again thanks for any help

[ED03GV_626]

I'm having the same issue with my Z. never did anything that could've bent any valves, and the car ran beautifully when I decided to replace the belt.

my crank only rotates from (when imagining a clock) 12:00 to about 4:00.

[zister]

yes i had that and much to my amasement i found 6 broken exhaust valves what the !!$%%^#@@%$% how? but it did and the limited rotation was due to the broken valve heads sitting on top of the piston not allowing the full stroke #1-- #5--#6 so if your only getting from 12 to 4 then i would likely say your getting valve contact too so i would check the belt again set the cams passenger side to nuetral where they turn and then just spring away on their own reset to #1 tdc and recheck that all the lines on the belt match the crank sprkt timing mark and all the cam sprkts timing marks are the same way. i didn't believe it either but suprise!!

good luck