R16 early vs late valve stem seals

[ppeters914]

Searched, but didn't find anything for the R16 1600.

Car runs good, but once warmed up, it smoked like crazy. Diagnosis indicated machine shop installed the wrong valve stem seals. To prove or disprove this theory, the valve stem seals were replaced. A few short test drives and no smoking.....yet.

Unfortunately, the only seals we had at hand are the later style. I have an SAE aluminum head that uses the early seal. Here's a pic of the valve stem seals (courtesy of Rallye Enterprises...ignore the part numbers).
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1600_valve_stem_seals.PNG

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I understand the valve spring compression is affected, but does anyone know if there are any critical short or long-term negatives to using the late-style valve stem seals in an SAE aluminum 1600? I'd prefer to leave these seals in for now, then change them out for the proper seals as a winter project as we're frantically trying to have the car done and sorted to drive to Shedd (less than 4 weeks from today!).

Also, would there be any real advantage to machining the head to use the late-style seals?

Thanks.

[redroadster]

What's the story on the engine ?
That you know of ....put which ever valve seal fits , pretty quick & easy oil rings being clogged also very possible

[david premo]

Pete, are you running a higher lift cam than stock? If so that might be the issue, when I have put higher than stock lift cams in the 1600 I check the retainer clearance to make sure it’s have the bottom of the retainer hitting the top of the valve seal. I typically have the machine shop cut the outside top of the guides and that takes care of the problem as it drops the top of the seal substantially. And yes early and late seals do interchange, as there is no difference between the earlier and later valves. The only thing that you do is not use the valve spring washers when you’re using the late seals as they come with the washers built in.
Dave

[ppeters914]

I am running Performance #1 - G15 / R16 grind - 420 Lift at the valve / 260 degrees duration from DatsunParts.com. I do not know what, if anything, the machine shop did when they did the head. I'll have to ask DEF whether he did or did not use the valve spring retainers.

[david premo]

So Peter, I was working on a R16 head this week so I checked the clearance for retainer to seal and what I got was about .424 at fully closed. So I think that’s your problem.
Dave

[23yrRebuild]

I typically have the machine shop cut the outside top of the guides and that takes care of the problem as it drops the top of the seal substantially.
Dave

Hi Dave, I'm trying to fully understand your machine work description, as I've highlighted in your quote. Are you saying you've had the cylinder head machined (spot faced) or machined down, in the area around the guides, not the top of the guides themselves ?

When I bought the late valve stem seals (sombrero style) from Dean years ago, he explained directly to my machinist, that he needed to machine the inner valve spring step on the cylinder head. Since then my engine has had no issues with my Isky 266 cam w/ higher lift (somewhere in the 0.430" region).
All is good with your info, I'm just a little confused by it
Respectfully,
Mike

[ppeters914]

So Peter, I was working on a R16 head this week so I checked the clearance for retainer to seal and what I got was about .424 at fully closed. So I think that’s your problem.
Dave

It's just Pete not Peter, please.

Sorry, but you'll have to school me as I don't understand.

The original excessive smoking problem appears to have been resolved by replacing the valve stem seals. Since the only seals on hand were the late hat seals, we'll be replacing them with the early umbrella seals that I just ordered.

[david premo]

IMG_1120.jpeg

So Pete,
What I have done is the outside diameter of the guides are reduced to the same diameter of the Chevy guide and then I can utilize the Chevy Viton seal. Look closely at the guides in the picture and you can see where they are turned down to accommodate the Chevy seals. In doing so you gain a lot more room for higher lift camshafts without risk of damage to the valve seals.
Dave

[ppeters914]

IMG_1120.jpegSo Pete,
What I have done is the outside diameter of the guides are reduced to the same diameter of the Chevy guide and then I can utilize the Chevy Viton seal. Look closely at the guides in the picture and you can see where they are turned down to accommodate the Chevy seals. In doing so you gain a lot more room for higher lift camshafts without risk of damage to the valve seals.
Dave

Sorry. I think I understand what you''re saying, but I cannot see it in the picture. I also don't understand how using the Chevy valve stem seal gains any room. I'm thinking pictures before and after valve guide machining, and another picture of the Chevy and Nissan seals side-by-side might help.

At this point, machining valve guides and using Chevy valve stem seals are all academic until the head needs a rebuild, which I hope is never in my lifetime.

[Gregs672000]

He machines the outside diameter of the guide to accept a Chevy seal... you can see the step in the guide. But regardless, if it ain't broke don't fix it. As far as I know that seal will work fine and the mod is only needed with a high lift cam.

[ppeters914]

He machines the outside diameter of the guide to accept a Chevy seal... you can see the step in the guide. But regardless, if it ain't broke don't fix it. As far as I know that seal will work fine and the mod is only needed with a high lift cam.

Ahhhhh..... now I get it... sorta.

Is the Chevy valve stem seal shorter?

[Gregs672000]

I believe that's the case.

[david premo]

So the U20 head has much greater allowance for higher valve lifts than the R16 head. Push rod vs overhead cam. I’ll be working on another R16 head soon and will be doing the same thing so I will take some better pictures of the modifications.
Dave

[Curtis]

Buy these and you're done with it. Put them on mine, perfect fit no messing with it.

https://datsunparts.com/collections/cyl ... ella-style

[david premo]

I am not sure how much valve lift those are able to deal with. Did you check it with setup springs for max clearance?
Dave