CA18ET knocking, low idle, shutting off. help!

Ok, my dad and I both believe that the knocking is in the top end. It sounds more like a rattle or a tap. After about a minute or two of just idling, it starts to struggle and die. I went to drive it once and it made a huge BANG and shut off. It started right back up and i reversed back down the driveway. I'm guessing bent rod? Possibly messed up valve? So, even though I want to do a swap, I need the car running NOW. Hahaa So I'm now think about replacing the head. And since I don't feel like paying a shop tons of cash for their work that I can do myself, I want to replace the head. My question is, how do I get a new head to put on her? Or whats the other options, such as rebuild?

thanks, Jake.

Could the "huge bang" have been a backfire?

I start with the top end.
Rent a compression tester if it is within specs you're good. If not then you will definitely need to take it off, take it apart and check to make sure nothing is bent and that they are air tight when closed. If they aren't replace all the valves and grab yourself a gasket set and reassemble.

I've been here before. Twice. At least you only have 1 head lol.

I assume it could have been, as soon as it banged, it shut right off. That sounds right though. There is a local shop that does an hour free of diagnostics, think they would hate it if I let them compression test it and then just drive off? No obligation, right? I suppose I can start on something today then. Its been parked for a month or so... Hah

If you had a bent valve you would not get a good reading at all. If you can do a compression check like we do on aircraft engines, then you may be able to see where the problem is. Compressed Air is introduced into the cylinder with the piston at TDC and you can listen for any leakage. If blowby, then air will come out the breather. If a valve is bad, then the leak will be heard in the exhaust pipe or intake. If you can rig this up, it may take several tries before you find TDC perfectly, although with the #1 cylinder being suspect, you use the timing marks to find it. We put 80 psi into the aircraft engines for this test.
Hopefully, you have an ignition issue instead of a bad mechanical one!

So, I just performed the wet compression test for the first cylinder only, and it was 142psi. Meaning one of two things; the oil created a temporary seal for the bad rings that I have in that cylinder, or that my first compression test was a fail. Later today, I will be doing another DRY compression test. If the cylinder goes back down to 125 or if it goes down at all, I would be having bad rings. Which, this local shop might want to replace the whole block if it's in the rings.. They said "If it's in the bottom, we'll have to replace it." Is this correct? I mean, I assume the rings aren't something for an amatuer to replace, but even a shop with a Nissan guy? Hah And if I'm getting the block replaced, no way am I going with a sohc or non-intercooled. It's ca18det or sr20det notch top. What do you guys think? I'll post the results of the second dry comp. test later today.

When you compression check all 4 cylinders you should have a better idea of where to go from after that. And +1 to ca18det or sr20det swap if one of your cylinders has really low or no compression. ca18et is not worth the time or money to rebuild.

Should I redo the wet test with all 4 cylinders included? That would make sense..

Yeah, it's pretty much confirmed. The shop said that what they would do is swap the engine, of course, they want to do it back to stock. I have a friend with a ka24de for sale for cheap. No transmission though, but I can get one for like $75. I'll need a driveshaft as well, and exhaust. Hah So, this car s to be a KA. Not quite what I wanted, but this is not the end. Just the begining! And with the way it's going, I'm looking into an SR later.

p.s. Who wants to buy my old CA and tranny? Hah