# Wont start after installing new cylinder head



## 142BHP (Jul 21, 2004)

Hi Guys

I am new to the forums and new to tinkering with my car.
I dont use my Nissan Sabre 200Gxi (Not available there me thinks) so much, so I deicided to do some work to the cylinder head and valves. After recieving it back from the guys at the engineering works we replaced the head as directed in the Haynes manual.

The car started on the second crank of the engine and idled perfectly for about 5 minutes. I switched the car off to check for oil and water leaks and tried to start the car again with no luck. First off it sounded like the starter kept running with the engine but I soon realized that I had no compression.

I checked compression on cylinder 1 at 6 bar, 2 at 3 bar and the rest had no compression. I then rechecked them after 5 minutes and had no compression on any of the cylinders.

Please tell me what the hell happened and if it could be the lifters that is stuck and how do i fix it.

Thanks allot guys

Cheers

Rudie


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## ddude2uc (Sep 7, 2005)

Well, hope you torqued your head bolts with "new bolts" & to value. Never use old bolts when taking off a cylinder head & replacing it... I'm not familar with this motor off hand,

You will not get a precise compression reading if your timing is off any.

I forgot to say, any time you take a cylinder head off. It is good practice to check it for squareness (flattness). Especially on aluminum heads which tend to warp easy. Also, you need to follow the torquing pattern when removing & installing for proper torque value for sealing.


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## wes (Apr 30, 2002)

First off what specifically was done to the cylinder head? Was there a valve job done?

Did you have the throttle body wide open during the compression test? 



As far as timing how would that affect compression readings given that the car is not starting?


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## ddude2uc (Sep 7, 2005)

wes said:


> As far as timing how would that affect compression readings given that the car is not starting?


 Compression readings will be inacurate if the timing is off, if the timing belt/chain is off one tooth or two, it will open up the valves late or too soon, therefore giving a incorrect compression reading regardless if it's starting. You don't need a car starting to do a compression check. First rule is to disconnect the ignition coil & main fuel relay. Pull all the plugs out & hold the throttle all the way open too.


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## wes (Apr 30, 2002)

ddude2uc said:


> Compression readings will be inacurate if the timing is off, if the timing belt/chain is off one tooth or two, it will open up the valves late or too soon, therefore giving a incorrect compression reading regardless if it's starting. You don't need a car starting to do a compression check. First rule is to disconnect the ignition coil & main fuel relay. Pull all the plugs out & hold the throttle all the way open too.


Cam timing, I thought you meant base timing. Regardless even if it is off one tooth it will still read correctly, unless there is never a time when all the valves are closed.


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## ddude2uc (Sep 7, 2005)

There a few instances where I had to adjust the valves & timing for good compression readings, not too many. 

*Major causes of no compression readings*

1. Excessive carbon buildup. Carbon has gotten stuck on the valve seat or valve face. 

2. Valve seat has is popped out. This happens on engines that never get their fins cleaned ( excess heat makes aluminum expand too much). This is most common to happen on the intake seat. If the seat is not damaged by the valve, it can be re-seated into the block, but I HIGHLY reccomend that you take the engine in to an authorized shop to have them do this work. They will also re-cut the seat and valve face. 

3. Ring wear/cylinder wear. This happens to years of hard service. The clearences get too wide, compression is blown into the crankcase. If the cylinder is not too worn or out of round, chrome rings can be installed to re-gain your compression instead of oversizing and fitting the piston with steel rings. 

4. Rings/cylinder scored. This happens when carbon falls off of the head or the cylinder starves for oil. If the cylinder or rings are in really bad shape, they must be replaced/oversized. 

5. Head gasket blown. This happens after years of use or happens when the engine runs too hot. The cause of this is the head bolts relaxing. Always use new nead bolts when they have been TTY. (torqued to yeild)


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## 142BHP (Jul 21, 2004)

The Cylinder head was flowed and I had the intake valves specked 1mm larger on the intake side. All valves were treated to a full 5 angle raduis job and all the new valves were manufactured from stainless steel. I found that just below the rocker arm there were tiny shims.... after checking them for clearance with the cam lobe up i noticed there were no clearance at all, I then slowly worked them off one by one until I had clearance on all of them and I got the motor started with compression on all cylinders(The engineering works must have mixed them up). 

Now i noticed that on cylinder four my compression reading was @ 210 psi and all the other reading was around the 170-180psi mark. What can cause the last cylinder to read so high.

Thanks again for the help so far


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## 142BHP (Jul 21, 2004)

Oh yes ... it is a SR20 DE

The head bolts were new from the dealer and all were torqued according to the haynes manual.. we also cc'd the cumbustion ports in a cloverleaf design to give a compression ration of 10.5 to 1 . The cams were cut to 288 Degrees and the cylinder head was skimmed just enough to clean it up and it was checked for squareness.

Hope this will shed some more light on things


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## Matt93SE (Sep 17, 2003)

I'm going to make a wild guess and say you have oil, buildup on the piston, or something else in cyl #4.

If the engine is running okay, drive it around for a while and get a few heat cycles on the engine and let the rings break in and seat properly. you can't really tell much on a compression test until the rings are properly seated. If they haven't, the compression will always be a little low.


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