Datsun Roadster Forum-311s.org

So I have been flighting leaking valve stem seals...

I have replaced the valve stem seals a couple times and they are insanely tight. I end up having to pound them on. Is this normal????

When they instantly leak and I take them off I can see where I am breaking them when I install them. I install them as gingerly as possible but the metal keeps cracking...

Was there ever a different size post for the valve seal in the U20 head? Am I just a big dumb idiot and hulk smashing these things on? I always oil them up and tap them on as gingerly as possible but they are really hard to get on and off....

Anyone have any ideas?

Thanks in advance!

Never had a problem with these, they should just slide on. Found this video on a H20 seal replacement https://www.youtube.com/watch?v=-njUatjaRwQ

Seal install at about 14:20 in the video. I believe the U20 and R16 5 main bearing blocks use the same valve stem seal.

Check your valve stem diameter. I attached a screen shot from the manual.

They should be very easy to install, with minimal effort to push them on. Sounds like something is not right with your head. Why don’t you post a picture of the guides without the seals in place, someone might spot the problem.
Dave

They slip onto the valves really easy, its getting them set down onto the stud/post that the valve guide is inserted into where I have to beat them on

I attached a photo from the internet of where my issue starts.

Ill go take my valves off tonight and try and get a photo.

Thanks

jrusso07, I just watched the video and mine were 50 times harder than that. I had to get a torch and heat them off the first time.

That looks like stock U-20 guides, are you using Nissan seals or something from the aftermarket? It might be that the seals you are using are not compatible with the head.
Dave

You must have the wrong seals or guides. They go on with finger pressure-no tools required.

If I were a betting man, I'd bet JT has some for sale. I have a couple of sets but I'm keeping em just in case.

Use a dial caliper to check the guide diameter and inside of the seal

Scott, There are many company's that make seals all over the planet

We have sold only one brand, Stone of Japan for 36 years, the company that Nissan used in all their kits and sold as repacked in Nissan card stock.
Give them a try. I have never had a complaint or return and I've sold thousands of these.

https://datsunparts.com/collections/eng ... 9248949432

Dean

Hey Dean!

So those are the ones I purchased. I've actually purchased two sets now. The head has been rebuilt but I have no idea how anyone would make the post larger.... I'm going to measure the post with a caliper tonight. Does anyone know what a stock unmolested post diameter should be?

Thanks

I have no clue why they are not working for you. I have never changed this product. Can you measure the top of the guide with a caliper and share with me the diameter?

Dean

Nissan made oversized guides, but I expect they were smart enough to retain the original seal size.

Someone may have made some oversized guides that were oversized on top and used a different seal.

The correct diameter for the top of the guides is: .560"

Yes, we have correct stem seals in stock!

My seals fit my U20 head w stock guides and they fit just fine on #1 cylinder. They are essentially Nissan. They also fit over the SI guides, at the top where the valve seal sits, with their diameter spec being .565 confirmed by Chris at SI.
"Most likely some cheap mechanic repurposed some oversize guide material and did not change the top dimension for the seal which is a different dimension then the section that presses into the head" Chris SI
Dean

Scott, If you need guides we are WD for SI and have them and they are specifically made for the roadster. We have standard and oversize in stock. THe Nissan valve seals fit both without issue.

https://datsunparts.com/products/datsun ... 3062798520