How to do a top end rebuild on a 92

[fiVeleVelsdoWn]

I got a 92 from a friend who said the cam and crank position sensors had gone out and caused the head gasket to blow. He had it torn apart and i purchased the gasket kit and the sensors, got the heads machined and have a pile of parts to put together and now I don't know where to start. Any suggestions?
Thanks for the help.

~fiVeleVeldoWn~

 

[Irish Pride]

When you say that the heads have been machined what do you mean? I don't see any way that a bad cam or crank sensor can cause a bad head gasket.

 

[intimdatr]

^what he said.

 

[rbruso]

Find a shop manual (Helms if you can find it, one of the others if desperate) and look over the section on the heads. Make sure you have all the bits in the diagrams and pay attention to torque specs.

I agree that those two sensors shouldn't have caused a blown head gasket. The heads have to get hot, and either of those two sensors going bad tends to leave the car stopped, not overheating. If this engine has been overheated to the point of blowing a gasket, you may want to tear down the bottom end as well and see what other abuse it has endured.

As for machining, what, exactly, did you have done to the heads? If they have been milled you're going to have a hard time getting timing right. Any material removed from the bottom of the head throws off the crank to cam timing on any OHC motor (except for cars with shimmable pedestals, like older Datsuns), requiring either adjustable cam gears or a different set of heads.

 

[fiVeleVelsdoWn]

I took the heads to a mechanic because there was a slight nick in one of them and he sent me to a machine shop where they just machined the bottom surface of the heads to get the little nick out and clean em up. Will that affect it? And my friend says that the sensors were acting up a little before he redlined the car and blew the head gasket. I did ask the mechanic if getting the heads machined would mess up its placement or anything and he said no cuz they were only taking off a tiny bit. How badly would it mess them up? And how would I know?

 

[Irish Pride]

What did your friend do to confirm that it had a bad head gasket? Head gaskets are not common issues with these cars. In the rare cases where one does get blown its because of severe overheating.

The crank/cam sensors will not cause a blown head gasket. Redlining the motor will not cause a blown head gasket. I take my SHO to 7000rpms every time I drive it. These engines can take well above the redline mark.

Machining the heads will affect the compression and timing. I think you need to get with your friend and find out exactly what the issue/symptoms were before you proceed.

 

[sperold]

Go back to the machine shop and find out what they took off the heads, was it .005", .010", or did they just take the high spot off the "nick". Did they machine the head that did not have a "nick".
You have already bought some fairly expensive parts, so if you are happy with the answer to the machining question, and if everything else looks ok, get the Helms manual on E-bay and begin assembling.

The story your friend told you sounds suspicious, so get a bit more information on why he thought the head gaskets were faulty.... was it leaking water, missing, water and oil mixing in the oil pan, overheating, get an answer from him.

Depending on your location and shipping arrangements, you can probably buy another running engine for what you have in parts so far. I am not suggesting you do that, but it is something to keep in mind. These motors are pretty well bullet-proof and do not need to be freshened-up after some number of miles.

 

[rubydist]

And while you have the heads off it, take a careful look at the cylinder walls for scoring, and seriously consider r/r the pistons to at least clean up the rings if not replace them.