Engine Rattle around 4k rpm, timing chain?

[AmishRoadster]

Like PAT said, you can do this, but there is a procedure and often a need to confirm that things are aligned properly. Again, we're happy to help guide you. You don't have to remove the head but IMHO you'll be so close, and with the possibility of damaging the gasket while removing the front cover, I'd just remove the head too. Yes, you would need new head bolts (I'd go studs).
What kind of compression numbers did you get? And how were they obtained? What did your spark plugs look like before you pulled the motor? Any oil burning that you know of? Reason I'm asking is that we're getting closer and closer to a rebuild and I know your plan was drive it fairly soon, and the cost is increasing! It may be OK to freshen it up if the valves and guides are ok... lap the valves and seats, clean up carbon on the head, replace stem seals... all within your ability I'd think.

I have included a picture of what the compression numbers were and what the spark plugs looked like. I got them from a compression gauge i ordered and just followed the directions in the box. I think by disconnecting distributor, holding open the carbs, and cranking it over a few times, and then repeated 3 times for each cylinder.

[Gregs672000]

Thanks for posting. Plugs are the wrong heat range (5 is a little hot, 6 is standard), but are not overheating. Carbs are all overly rich but at least they're consistent. They will need adjustment. Plugs don't look oil fouled to me. Compression numbers are a bit low and variable, but without a leak down test we don't know if that's valve seats or rings... I'm leaning more towards valve seats. You won't be able to check rings by adding oil through the plug holes and rechecking compression while the engine is out, but you can set up a leak down test with an air compressor and a modified compression tester line if you have the right kind/fitting that allows you to remove the guage and attach the air hose to it (some have compatible fittings, some don't) after you remove the Schrader valve out of the end that screws into the spark plug hole (use a pair of tweezers to unscrew it). You're not going to be able to get actual numbers (as in percentage of leak down) but it will tell you where it's losing compression (valves or rings or both). What you do is put the cylinder you're going to test at or near top dead center so that it is on the compression stroke, all valves closed and the piston near the top (doesn't have to be perfect, just that everything is sealed or closed), then securing the crank from turning via a locked in/braced ratchet and socket on the front crank bolt to keep the engine from turning with the air pressure you're going to apply (BTW, the engine can turn either direction so locking this down may take some effort and repositioning, just needs to maintain position to maintain valve seal). Install the testing line/hose, then connecting the air compressor line and applying like 20lbs (doesn't have to be much) to the line (the motor will want to turn, so high pressure is not needed or helpful). You then listen for or feel air coming past the intake and exhaust valves (should be easy with the manifolds off) and out of the valve cover oil fill cap (with the cover on obviously) for rings (air going into the crank case past the rings). You have to repeat this process for each cylinder, but that may tell you what's worn and guide next actions. If it's coming past the valves mostly, then you may make the decision to pull the head and examine the condition of the valve seats, valve face where they seal on the seat, the guides and wear on the valve stems (proper valve spring removal tool required, may be able to rent or borrow). Depending on their condition, you may be able to recondition them to an adequate/acceptable level. If the guides are shot (valve wobbling in the guide) then you're into a head rebuild and outside work done. Also, before all this, take a look at the valve adjusters themselves on the head... they should all be relatively close to the same height when the valve lash/gap is set to specs or close. If you see one or more that are significantly lower than the others (running out of adjustment to reduce lash), that suggests the valve seat is worn out and/or being pounded into the head, allowing the valve stem to raise higher and requiring less and less lash adjustment to create space between the rocker and the cam... head rebuild necessary.

I'm trying to give you as many options as I can. I do not know what your budget is, but in 37 years of ownership at varying points in my life, I've had to consider budget many times! We're getting damn close to doing a complete rebuild, but I'm also cognizant of how expensive this can become and the time involved... also why I asked about your timeline on this project as well as overall desires for owning this car... everyone varies, and what I don't want to see is someone diving in and getting overwhelmed for whatever reason. I've been into my motor many many times, and will be again soon to modify the cam, but this is MY HOBBIE, I LOVE my car, so it's never a question, only a budget exercise.

Hope this helps!

[nismou20]

On a side note, is there any advantage to running Iridium plugs in our cars? I’ve been using conventional BP6es with MSD6AL.

[Gregs672000]

Not likely on a points or Nissan EI other than maybe some longevity. However, I did learn that having the proper plug type can have some difference on the Ford EDIS system I run... it is best to use a double platinum (referring to certain parts in the plug) as the wasted spark system was designed using them. Again, I think it had to do with longevity.

[unklpat]

Let's get back to the original post. Amish roadster is new to these cars, and just wants to drive this summer. Fixing the leaks in his transmission, replacing the clutch, and replacing the timing gear would be more than most new owners should be expected to do. The compression figures are ok for a daily driver. Pulling the head adds another bunch of steps, and money, to a new owner. Those of us who have dove into the wormhole have lot's of knowledge and no fear of the unknown. A new owner should just be able to drive his car. With new timing components He can feel good that his motor will not fail other than naturally. Pat

[sports imports]

My experience with the death rattle at 4000 rpm happened one the way to Shasta many years ago in my 67 2000 with solex carbs and early air filter assembly just outside of Roseburg, Oregon. We were travelling in a large convoy and managed to pull into the hotel parking lot and started to diagnose the problem, off with the valve cover, remove the tensioner, check upper guide to see no wear, make a new gasket for the tensioner, put it all back together and rattle still there. Scratching our heads still not finding the solution. A couple of hours has gone by and all the experts have come by to brain storm. Finally, I am leaning over the carbs and put my hand one one of the wing nuts holding the air cleaner assembly together, and the rattle disappeared. In my haste to get going that morning, when I replaced the air filter, I had not tightened both wing nuts sufficiently and one had come loose after 500 miles on the road. Moral of the story, check everything twice and maybe once on the way!!!

[Gregs672000]

Ya, I think I remember That! You gave me a ride to Shasta cause my car was down, and you were testing whether or not using two air filters on the Solex carbs improved air flow... we decided it did after Rosco spent several hours passing cars at warp 9...

[sports imports]

Different year , same car. Two air filters zap strapped together made the car breathe very nicely.

[Gregs672000]

Different year , same car. Two air filters zap strapped together made the car breathe very nicely.

Breath those carbs most certainly did, but I do recall holding my own breath a few times !
Ah good times, good times...

[AmishRoadster]

Gregs672000 thank you for the full write up! I will see if I have all the equipment needed to perform the test. From what it sounds like I will need to pull the head off to replace the timing components correctly. This leak down test sounds like it is to see if the head has leaking issues or if the block is the problem (due to the variety in the compression readings). I remember watching a Wheeler Dealers episode where they tested the head for leaks by pulling the head and turning it upside down, then poured gas in each of the valve areas for each cylinder and if the gas leaked through you knew you had a leak there. Not sure if that same test is applicable or would work with the U20 head. The reason I ask is if I cannot get my hands on the fittings and equip to get the test you described completed, and I already need to take the head off, would the gas leak test work?
I already had it in the back of my head that I would want to get the head worked on so I can run non-leaded gas. I wasnt planning on doing it so soon but if I need to take the head off and buy all the gaskets it seams to make sense.

Also, I was looking through my phone and found a video I took on my last right this winter before I knew I was pulling the engine. It is crappy quality but at around 8 seconds into the video you can faintly hear the noise, in the video it sounds almost like a ringing sound. I figured I would post it in the slight chance someone could hear that and maybe know what it is.

https://youtube.com/shorts/vFd7eZinwlY?feature=share

Thanks again all!!

[itsa68]

Just throwing this out there.
The noise on the video reminds me of when my alternator pulley had cracked its hub underneath the pulley nut assy, but I could not see it.
At higher rpm the noise would occur because the hub was cracked but the nut still held in the pulley in place.
Noticed rust dust around the nut assy at the pulley hub face. Took the nut off and found the pulley hub had cracked thru in the shape of a rough washer shape of the nut face.
New alternator was required as I could not find a replacement pulley.

Cheers
Ray B.

[unklpat]

That noise is not timing chain rattle, but a squeal of some sort? The head does not need to come off when doing timing components. Your compression numbers are fine for now, and can be fixed later with a full rebuild. Look at the pivots that your followers ride on, opposite side of head than the valve springs, and look for uniformity. if you see some of them shorter than others, that could mean issues with valve seats. Pat

[AmishRoadster]

Started working on removing head last night. I removed all the head bolts and just need to pop the head off now. Any tricks of the trade to removing it? I assuming I need to break the head gasket seal and then it should be easier to lift up. I didnt know if there was an easy way to use leverage to pop it up.

[spl310]

Yup, just overcome the gasket and go. I have gingerly used a pry bar in an exhaust port for leverage.

[Gregs672000]

Sometimes tapping/hitting it with a RUBBER mallet will help break the seal. Be sure you got all the bolts, including the two 10mm at the front of the head and the 10mm on the upper chain guide, often missed. Just a word in general: If you find something is requiring a lot of force to come off or go back together, always pause and ask questions.

So, looks like we're gonna evaluate the head. Some initial pointers: number all the rocker arms 1-8 with a sharpie as they must go back on the same cam lobe as before; there is no need to remove the cam towers, just the caps to remove the cam, number them too if not already; don't set the head face down on a hard surface with valves extended, you can damage them, so either remove the cam first or use wood blocks or something to create space to protect the valves while you remove the cam with the head on the bench.

Regarding the testing, yes you can use fluid to see if the valves seal up or leak. Since you have gone this far, I would go ahead and get a C-clamp style of spring compressor and plan to remove the valves, springs, etc and inspect the valves and seats (I can post a pic of mine if desired, or link to one on Amazon). I'll leave it to more expert folks to chime in on unleaded fuels and stock U20 seats, but if these are good I'd just keep them because I don't think it will make a huge difference at this point (but I'm not an expert!). We can talk about what to look or feel for regarding the valves and the valve stems/guides. Hopefully the valves and seats will still be workable, you can clean things up, lap the valves (look it up, youtube, not hard), replace the stem seals and get many more miles out of it. Or, you may decide to have it rebuilt if things are too worn...
Make sure you get or have a copy of the manual, you're going to need it! (In our tech wiki). Must have a reliable torque wrench!
Let the fun begin!