Rebuild not starting - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

BaliLover · 01-15-2013, 10:13 PM

Recently got around to dropping my rebuilt motor(rebuilt head installed onto rebuilt block) in but on first try it just stumbled and sputter, caught once then died rapidly. While it was running I heard a repeatative snapping noise from the head. Upon removal of the valvecover I see I have 2 collapsed HLA's and a rocker arm with the guide on the wrong side. I replace the HLA's, and move the rocker arm guide to the correct side (the guide was stuck to the opposite side and not allowing the arm to move smoothly, causing the snapping noise.) I crank everything over by hand and theres no noise to be heard, but under its own power it still won't start, just seems to almost catch then flood out. I checked the timing 3 times, both cams are where they should be, pointer is at TDC on the crank pulley, and the timing marks on the chain are set perfect. Double checked the CAS, reset it for good measure, and still no luck.

At this point I decided to do a compression test to make sure I didn't bend a valve, and quickly discovered that all 4 cylinders are sitting around 85psi, well under the manufacturer minium specs of 110. The pistons are 8.8:1 weisco, and the HG is an Apexi 1.1mm that got copper sprayed but I don't think that would cause such a low compression reading unless I'm wrong. What I'm assuming, since its low evenly across the board, is that I didn't get the headbolts tight enough when it was on the stand. The headbolts were brand new Nissan bolts so I'm assuming they should be fine, but what is the proper retorque technique? If I loosen all of the bolts to start over I'm sure I'm gonna pour coolant into the cylinders and ruin $50 in syn. oil, but I don't really have any other way to know how much more to turn the bolts since the manual never gives a final torque figure, they just tell you to torque it to a certain point, then turn it 90 degrees.

Anyone got any tips/pointers/or opinions?

BaliLover · 01-15-2013, 10:13 PM

Update:

Reread the manual and noticed it says to turn the bolts 90 degrees twice; I only remembered turning them once. Go through the BS to pull the cams so I can access the head bolts, turn them another 90, reassemble everything and now I'm MUCH MUCH worse off. A compression test now shows almost no compression on 1 and 2, 95psi on 3, and almost nothing on 4. FML

rcdad123 · 01-15-2013, 10:35 PM

take the cams off and do a leak down test. that would determine if you have any valves that are bent and would also eliminate the chance that a cam lobe is keeping a valve open. remove all of the spark plugs before you do a leak down test, that way you can hear a leak in between cylinders. good luck

rcdad123 · 01-15-2013, 10:38 PM

BTW, make sure all of your valve clearance are within spec. if you had the valves and seats resurfaced, the valve lash has to be readjusted by changing the shims.

BaliLover · 01-16-2013, 07:11 AM

I'll have to get a leakdown tester then. The valve shims are all within spec, book says I should have no more than a .0025 difference between the shims and guides, and my biggest difference is .001. As far as I was aware, a missized shim shouldn't cause a major compression issue, it would cause cam wear and a loud valvetrain.

01-15-2013, 10:13 PM	#1
BaliLover Leaky Injector Join Date: Jun 2004 Location: Central Florida Posts: 68 Trader Rating: (0) Feedback Score: 0 reviews	Rebuild not starting Recently got around to dropping my rebuilt motor(rebuilt head installed onto rebuilt block) in but on first try it just stumbled and sputter, caught once then died rapidly. While it was running I heard a repeatative snapping noise from the head. Upon removal of the valvecover I see I have 2 collapsed HLA's and a rocker arm with the guide on the wrong side. I replace the HLA's, and move the rocker arm guide to the correct side (the guide was stuck to the opposite side and not allowing the arm to move smoothly, causing the snapping noise.) I crank everything over by hand and theres no noise to be heard, but under its own power it still won't start, just seems to almost catch then flood out. I checked the timing 3 times, both cams are where they should be, pointer is at TDC on the crank pulley, and the timing marks on the chain are set perfect. Double checked the CAS, reset it for good measure, and still no luck. At this point I decided to do a compression test to make sure I didn't bend a valve, and quickly discovered that all 4 cylinders are sitting around 85psi, well under the manufacturer minium specs of 110. The pistons are 8.8:1 weisco, and the HG is an Apexi 1.1mm that got copper sprayed but I don't think that would cause such a low compression reading unless I'm wrong. What I'm assuming, since its low evenly across the board, is that I didn't get the headbolts tight enough when it was on the stand. The headbolts were brand new Nissan bolts so I'm assuming they should be fine, but what is the proper retorque technique? If I loosen all of the bolts to start over I'm sure I'm gonna pour coolant into the cylinders and ruin $50 in syn. oil, but I don't really have any other way to know how much more to turn the bolts since the manual never gives a final torque figure, they just tell you to torque it to a certain point, then turn it 90 degrees. Anyone got any tips/pointers/or opinions?

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01-15-2013, 10:35 PM	#3
rcdad123 Zilvia Addict Join Date: Jul 2011 Location: san diego Posts: 639 Trader Rating: (0) Feedback Score: 0 reviews	take the cams off and do a leak down test. that would determine if you have any valves that are bent and would also eliminate the chance that a cam lobe is keeping a valve open. remove all of the spark plugs before you do a leak down test, that way you can hear a leak in between cylinders. good luck

01-15-2013, 10:38 PM	#4
rcdad123 Zilvia Addict Join Date: Jul 2011 Location: san diego Posts: 639 Trader Rating: (0) Feedback Score: 0 reviews	BTW, make sure all of your valve clearance are within spec. if you had the valves and seats resurfaced, the valve lash has to be readjusted by changing the shims.

01-16-2013, 07:11 AM	#5
BaliLover Leaky Injector Join Date: Jun 2004 Location: Central Florida Posts: 68 Trader Rating: (0) Feedback Score: 0 reviews	I'll have to get a leakdown tester then. The valve shims are all within spec, book says I should have no more than a .0025 difference between the shims and guides, and my biggest difference is .001. As far as I was aware, a missized shim shouldn't cause a major compression issue, it would cause cam wear and a loud valvetrain.