1992 240sx : Blew Blue Smoke, Rebuilding Engine, Valves In Head Are Blue???

[boryan]

I have a 1992 240sx, currently doing a rebuild.

My car was blowing blue smoke. Everytime I would let it idle it would blow smoke as soon as I would step on the accelerator. I know that the oil is getting into the #4 piston. I am doing a rebuild right now and when I took the head off, i noticed that the Valves on the #4 cylinder are a baked on blue. I am going to buy a rebuild kit from Topline which will include the piston rings which might be the cause of the oil leaking into my cylinders. Does anyone know if I will need to replace the valve seals? And if I do, what is a good place to buy them? I am attaching a picture of the blue valves.

Oh and by the way, my top timing chain tensioner was broken off and flopping around on my timing chain. Do you really need to replace that tensioner or could I just take it off?

[boryan]

Here is another picture of the head. Here you can see all four cylinders. They all covered with a white glaze and the #4 cylinder is the only one with the blue glaze.

[boryan]

Here is the photo of the broken off timing chain tensioner that was clanking up my engine. I am so lucky it didn't fall through and get torn up my the gears.

[rogoman]

Since you have the head off, it's a good idea to replace the valve stem seals; while you have the valve assemblies taken apart, check the valve seats/valves for wear and check the valve springs for proper tension.

You should be able to buy valve stem seal from the same vendor where you got the rebuild kit; if not, get em from a Nissan dealer.

The piece that you're showing in the last picture looks like a top chain guide rather then a chain tensioner. For the top chain, the top and left side guides are not needed and should be removed according to a Nissan tech bulletin. The right side (passenger's side) chain tensioner is needed.

I don't know what your experince level is in engine building but make sure to at least hone the cylinder walls prior to installing new rings. Measure the piston-to-wall clearance to make sure that it's not excessive. If excessive, you may have to bore to the next oversize.

Also be sure to check the rod/main bearing cleances while you have the motor apart.

[boryan]

This is the first engine rebuild I'm doing, but I read up a bit on it, but the reason I called the chain guide a tensioner was because I was writting the post at 3:00AM, sorry.

So, I have the head off but I haven't been able to take the springs out yet. Do you know what tool I could use to do that? Should I just check the valve head diameter with a caliper to check for wear?

Now for the cylinders, When I took the pistons out there appeared to be no significant ridge, so I was just planning on honing them. But how would I check for the piston-to-wall clearance? Should I just stick a feeler gauge between a piston and wall?

I checked the cylinder head for distortion and it only had .005mm of play. I also checked if the main journals were lined and they also only had .005mm of play. However when I took the rods off the crank shaft, some of the bearings were cracked and came off in two pieces. Would a significant problem be the cause of that?

Thanks a lot for you advice rogoman

Modified by boryan at 12:54 PM 4/24/2006
Modified by boryan at 5:28 PM 4/24/2006