Random Misfire while cruising

[Mark Maras]

 New valve seals and checking guide wear would be my next step. It's possible the #4 seal was damaged when it was installed.

[siteunseen]

Try googling "cylinder head rebuild service" in your country. They are very common in the States. They would make it like new for cheaper than buying another one. Actually if you find one close by they could fix yours without removing it, possibly? I would think there's a way they could test your questions on bad seals or guides etc. maybe just by pulling the valve cover off and visually looking around. If you have a damaged seal someone with experience could tell by viewing it.

[jalexquijano]

On 10/23/2020 at 3:17 PM, siteunseen said:

You say no one in Panama can work on the L motor.

How/who put that Schneider cam in? As I recall it came from Ebay crook California Datsun with a "Far 311" cam. Please correct me if I'm confused. Very often occurence with me. 

 

Schneider cam installed here. Is there anyway i can replace the valve seal in that cyl without talking the head off? 

 

On 10/24/2020 at 9:55 AM, siteunseen said:

Try googling "cylinder head rebuild service" in your country. They are very common in the States. They would make it like new for cheaper than buying another one. Actually if you find one close by they could fix yours without removing it, possibly? I would think there's a way they could test your questions on bad seals or guides etc. maybe just by pulling the valve cover off and visually looking around. If you have a damaged seal someone with experience could tell by viewing it.

Yes i guess they could check on the valve seal of that cylinder before i can spend money on changing valves, valve seals and guide.

[Zed Head]

 

[jalexquijano]

Tried contacting several suppliers but no e-mails are being answered. California Datsun is not being helpful also.

[jalexquijano]

On 10/24/2020 at 9:55 AM, siteunseen said:

Try googling "cylinder head rebuild service" in your country. They are very common in the States. They would make it like new for cheaper than buying another one. Actually if you find one close by they could fix yours without removing it, possibly? I would think there's a way they could test your questions on bad seals or guides etc. maybe just by pulling the valve cover off and visually looking around. If you have a damaged seal someone with experience could tell by viewing it.

What about the PCV valve? Could the valve be stucked and the cause of the fouling of that 4th plug? 

[jalexquijano]

On 10/24/2020 at 9:54 AM, Mark Maras said:

 New valve seals and checking guide wear would be my next step. It's possible the #4 seal was damaged when it was installed.

Just got an email from California Datsun. Company argues that such head is perfect and it should not have any problems at all. My problem is either electrical o fuel delivery? I already did the electrical test as you advised and i see small blue spark, whats left then before i open the valve cam cover? 

[Mark Maras]

 

29 minutes ago, jalexquijano said:

Just got an email from California Datsun. Company argues that such head is perfect and it should not have any problems at all. 

 Sounds like gas-lighting to me.

I'd pull the valve cover and look carefully at the valve seals. A good light should help when looking between the spring coils. Compare #4 with the rest and see if you can see any difference between them. I'd be looking for a torn or distorted  top of a valve seal or one that may not be pushed down all the way.

[AK260]

 

 Sounds like gas-lighting to me.

I'd pull the valve cover and look carefully at the valve seals. A good light should help when looking between the spring coils. Compare #4 with the rest and see if you can see any difference between them. I'd be looking for a torn or distorted  top of a valve seal or one that may not be pushed down all the way.

 

Totally agree with Mark, California man is trying to blow you off with a vanilla response / Jedi mind tricks. Did you tell him the other plugs are OK and you’ve checked the electrical system? If he knows that then he is purposefully missing the point. A decent supplier would have at least recommended some further tests.

 

I would do what Mark suggested and if you have a decent phone with a decent camera on it, it may be easier to see what you have by taking pics and zooming in. I often find my iPhone 11’s camera is able to see much more detail in dark / tight places on the car than I can with a naked eye.

 

Also, should you find something wrong, you can send photos to the Cali-man.

[jonbill]

did the plug #4 gap closing thing ever recur? 

in many of the photos, plug #4 doesn't look bad enough to not fire. are you sure it is 4 that misfires? some of the others look lean enough to misfire. 

[jalexquijano]

Plug closing has not recur. However i recently installed a set of NGK BP5ES and after 5 minutes of warming, plug 4 came out fouled in dry black oil. I will do a test drive tonight. Saturday i am opening the valve cover. I will not spend US$500 in a set of new valve, guides, seals and seats just for the sake of eliminating all posibilities. 

[Mark Maras]

 Hopefully it's just a valve seal.

[jalexquijano]

On 10/28/2020 at 2:04 PM, AK260 said:

 

Totally agree with Mark, California man is trying to blow you off with a vanilla response / Jedi mind tricks. Did you tell him the other plugs are OK and you’ve checked the electrical system? If he knows that then he is purposefully missing the point. A decent supplier would have at least recommended some further tests.

 

 

 

I would do what Mark suggested and if you have a decent phone with a decent camera on it, it may be easier to see what you have by taking pics and zooming in. I often find my iPhone 11’s camera is able to see much more detail in dark / tight places on the car than I can with a naked eye.

 

 

 

Also, should you find something wrong, you can send photos to the Cali-man.

ok here is the diagram or picture of the engine. After removing the valve cover how can you determine if its the valve seals, seats, guides or valves that are torn? Visually how? I wouldnt like to spend 500 usd in parts which are not damaged. 

[siteunseen]

Your wasting time with Al Allen. That's over and done with. 

Like I suggested before, find a cylinder head shop. That's your only option. You can keep trying to get an easy answer but there is not one. 

Buy another car. Or learn how to work on yours. Quit buying on ebay. If you want to save money get a Buick.

[jalexquijano]

My question is crystal clear. Anyway of determining which is the part that is damaged without removing the head?

[Mark Maras]

 @jalexquijanoOn this site search "valve guide seals". DAVEWM (as well as others) have good descriptions of the procedure to change the valve seals. You only have to remove one valve spring, #4 intake. Stuffing the cylinder with rope, using the valve spring compressor shown earlier in this thread, remove the valve spring retainer, lower the valve slightly, rock the stem back and forth to try to gauge the guide wear. If there is little to no sideways movement between the valve stem and the guide, use a straw to install the new (you'll probably have to buy a whole set to get one) seal and reassemble the spring. If there's considerable sideways motion of the valve stem, the head will probably have to be removed to repair that guide. Once again, before you buy a spring compressor and a set of seals, do your homework. Search this site and probably YouTube too. They have lots of videos. Should you decide to go ahead, you'll have the cost of a valve spring compressor, a set of valve seals and maybe a valve cover gasket. You might also check to see what a local shop would charge to inspect and change that one valve seal.

[jalexquijano]

Took a picture of plug 4 after idling for 5 to 6 mins. This time is a hotter plug. Question can i get thosr valve seals from any supplier or should i stick to the parts that california datsun used to rebuilt my engine?

[Mark Maras]

 I believe they're all the same. @siteunseen or anyone else what is recommended?

[siteunseen]

I got mine from local Nissan dealership. Brownish color.

Here they are @zcardepot.com

https://zcardepot.com/products/valve-stem-seal-set-oem-240z-260z-280z-280zx

.

[jalexquijano]

Valve seals being shipped. Already did a test with ngk bp5es and cylinder 4 still fouls.  Not so bad as ngk bp6es spark plug but still fouls. 

[Mark Maras]

@jalexquijano Are you going to replace the seal or have it done by someone else?

[jalexquijano]

I am talking the cylinder head out to verify everything is fine and replace all seals. Im done with testing. 6 years testing and same issue.

[jalexquijano]

Can someone elaborate in the correct and safe procedure to remove the cylinder head and replace the broken or torn valve seals on cylinder 4? I watch a video on youtube of a guy inserting a rope inside cylinder 4 and a special tool to decompress the retainer spring. I guess its.better to remove the complete head. Also which gaskets will i need to replace?

[Mark Maras]

I don't see the need to remove the head. Either way you'll have to come up with a valve spring compressor. IF, the compression is satisfactory in all cylinders, leave the head on. Removing it may open a Pandora's Box of broken bolts and studs. The rope in the cylinder and the lever action spring compressor is the easiest method of changing the seals. Watch several different videos until you can't find anything else to learn and then go for it. That's what I do.

[siteunseen]

I agree with Mr Maras. You are only focused #4 so I assume you'll pull the head for that one cylinder? I would take the easiest route and try the rope technique first. He's right you'll need a valve spring compressor. The first time I had to do that I bought a $15 from a chain store. It worked for me.