Datsun Roadster Forum-311s.org

Bent valves I bet, causing them to stick in the guides. My friend, I hate to say it, but she's done. Very unlikely that the cylinder walls are not damaged beyond a simple hone job, so it would need to come out to be bored. With that much metal I'd be concerned about the mains and rods anyway. I'm really sorry and I hope this does not sour you on Roadsters. Probably time to start a discussion on your power train options going forward.

Put a pencil/screwdriver in each spark plug hole, and rotate your motor by hand. if no movement, then broken piston. Also look for any valve springs sitting higher than any others when on compression stroke. That is an indication of a missing valve seat. Ask me how I know...... Pat

You will most likely have metal fragments in your intake manifold, after the valve seat was chewed up by the piston. Mine only idled for 7 seconds before the piston broke. Pat

Well, what I thought was piston damage was just junk.

I can't remember which is the oil passage hole to the head. How is the head?

Head looks ok to me...I don't have a valve spring tool to pull them out got one coming. Running a lil rich on my idle circuit, I had mostly just been idling trying to figure the noise out.

I shot some fluid thru the oil passage in the head and it's def not blocked. Didn't test rocker itself or the passages in the block yet...

Bottom end turns over super quietly and smoothly no sign of any noise or sticking there.

PS: whatever engineer placed the stud right under the rear carb was a very sick man








Exhaust leak...could have been some of my noise.

The sticking valve may also have been from lack of lubrication...kinda goes without saying. May not have been bent, but certainly could be as well.
Suggest you get a machine shop to clean and diagnose the head condition since there is very little you can correct at a home shop.

So at this point you probably need to make a decision...do you tear the whole thing apart because of the metal in the pan? (that could have been crap in the pan left over from it's prior life) -or- do some more careful diagnostics to try to determine the actual problem?

Both are reasonable approaches, but the metal in the pan makes one question the assembly somewhat.

If the crap in the pan was just crap in the pan that wasn't cleaned out, you are really going down a deep rabbit hole.

Personally, I would tear it all apart because there is so much poor PO work around, but that may be completely unnecessary since nothing looks bad so far in the lower end.

If you want to verify there is no occlusion in the block, put the pan back on, fill it with oil and spin the bottom over with the starter.

The oil galley is the rear most passage on the block-distributor side-COVER THAT WITH A TOWEL. Oil should flow freely out of that galley. If it does, the problem is up top. If not, you are pulling out the lower end for sure.

Head gasket blocking oil flow to head?

rwmann wrote: Sat Aug 28, 2021 8:17 am Head gasket blocking oil flow to head?

Meaning there was no hole in the gasket? Never seen that, but possible. It's easy to confirm by checking the gasket-should be a hole or sealing ring that lines up with the galley..

If there is no oil coming up the galley, someone have have installed the cam bearings wrong or that galley is completely blocked. Both would be rare, not good, but certainly possible. That is why I would put the pump and pan back on and spin it with the starter.

That will tell you for sure if oil is making it to the head.

You can use the prime the oil pump method. Put the pump and oil pan back on and oil in. I took a piece of round stock and flattened the end and used the drill to spin the pump CCW. I forgot to plug off the distributor oil feed line and had oil coming out of there. With head on it took a long time to make it to the top. Without the head should be much faster.

With the starter you have to hook the transmission back on but it will certainly pump the oil much better. If I had had my starter hooked up I would have used that method instead.

Curtis, the engine appears to still be in the car, trans attached unless he went ahead and pulled it. To spin the pump with a drill he would have to R&R the distributor, tach drive and remove and realign the distributor drive gear which is much more effort than bolting on the starter back on. 5 minutes for the starter, Right?

JT68 wrote: Sat Aug 28, 2021 9:58 am Curtis, the engine appears to still be in the car, trans attached unless he went ahead and pulled it. To spin the pump with a drill he would have to R&R the distributor, tach drive and remove and realign the distributor drive gear which is much more effort than bolting on the starter back on. 5 minutes for the starter, Right?

Yup, you're right. His tear down makes it look like it is out already. I don't think I would ever attempt what he has done. I hate crawling under a car. I want to move and have a garage with a lift.

What do you think about the rod nuts and bolts?

I also don’t see anything in the pics that’s catastrophic. Might want to cut the oil filter in half and take a close look. If those metal shavings are also present, it’s probably from a new/recent issue (like you said, within the last 100 mi). If not, they’ve probably been stuck to the oil pan for some time as they never were suspended/circulated since the last oil change when the first vid was taken showing the engine running smooth & quietly.

Well, so sorry to have jumped the gun on declaring her dead... it looked like the piston was hammered, but it was hard to tell from the pic. JT68's post sums it up I think. There are a lot of cooks in the kitchen right now, so I'm gonna let you cook and see how the cake comes out. Really hope this works out well and that there's no significant issue!

Curtis wrote: Sat Aug 28, 2021 10:07 am

What do you think about the rod nuts and bolts?

Good eyes on the rod nuts, but nothing to worry about. Nissan originally used really tall nuts on the rod bolts (7/16" tall or so). They later switched to more standard nuts, but left the bolts long, so that is what you are seeing. I've never seen any difference in reliability with the various nuts. I guess Nissan just decided the long nuts weren't needed.