Cam install/Spring height/Rocker dilemma

[Mayolives]

More food for thought. After a recent valve job, I could not get enough lash on several valves. I'm using Schneider's cam, springs and retainers, The billet was new when I first installed it. Then I discovered that several rockers were touching the retainers on the outer edge and were actually pivoting on the retainer and not on the valve stem. The solution was easy. By sanding/smoothing off the underside of the rockers, I was able to get the proper lash. Several of the rockers had small "nicks" on them, indication to me that they had been touching the retainers before I refreshed to top end.

[2eighTZ4me]

Perhaps I used the wrong terminology Bryan, but the retainers themselves have different depths to them. Meaning, the Racer Brown retainers vs. a stock retainer, vs. a Schneider retainer -ALL of them put the valves at different heights solely by which retainer was used.

 

Don't believe me? Look about 3/4 of the way down in this thread

 

http://forums.hybridz.org/showthread.php?t=137647&highlight=cam+wipe+pattern

 

Yes they DO have something to do with installed spring height. You can clearly see the difference in spring height. I just went through this whole ordeal 2 months ago. The wipe patterns were all different as well due to the geometry presented by a taller installed spring vs. a shorter installed spring. Had to use different thickness pads to compensate.

 

I guess what I meant to say is that the retainers he was using was from a different cam setup, thus causing the installed height to be so tall that he can't get the rocker under the cam.

[1 fast z]

The pad sits ON top of the valve. The retainer difference has NOTHING to do with wipe patterns. The height difference you are talking about is just circular support for the taller lash pads, so they do not spit out. A wipe pattern can actually be checked without a spring, retainer, etc even installed.

[2eighTZ4me]

Did you even bother looking at the pictures? You can clearly see the difference in spring height, AND you can see that the factory retainer is thicker than the Racer Brown retainer - causing more pressure on the spring, and it DID change the installed height. Look at the pics. They're right there side by side.

[1 fast z]

Yes I did look at the pics. Let me state it once again. ALL PADS NEED/HAVE to be resting ON TOP of the actuall valve, therefore the difference in retainers has NOTHING to do with wipe patterns. You are bringing in spring assembled height to this sittuation, which has NOTHING at all to do with wipe patterns. You probably had a short valve stem to keeper groove dimension and had the lash pad sitting on the retainer rather than the valve. And if this is the case you will pop off the keepers and drop a valve.

[2eighTZ4me]

The whole problem is that he's got zero lash because his spring installed height is too tall. He can't even get a rocker under the cam without removing the lash pad completely. That's my point. The retainers are from a different cam setup and the installed spring height is taller than what it's supposed to be.

 

My head was done by a competent machine shop. All valves were new and sized properly. The pad was not sitting on the keepers. I changed retainers across multiple valves, all with the same result Lash pad was on the valve tip - not the keepers. I've run the piss out of my motor and haven't dropped a valve. I know it's right. I guess I'll go slink into my corner - I obviously can't get my point across clearly enough to be understood as being pertinent to this thread.

[Babalouie]

Have you tried any thinner lash pads in your engine yet? And have you tried the rest of the valve train to see if the problem is with all the rockers?

 

Yes I did...borrowed some stock 2.5mm lash pads (vs 5.0mm that I had) and gave it a whirl:

 

No dice though, even with the pedestal turned as high as it could go (zero lash) the rocker still seems to be "reaching up" to the valve and doesn't look like it sits on the lash pad properly. Also even if I back the pedestal down all the way, there is still zero lash.

 

 

It goes back to an earlier question I asked, were all the old pads the same thickness for that old cam? It may have been a case that the valve seats were machined too deep by the machinist but a mock up with the old cam, rockers, valves and lash pads worked out ok with a suitable rocker arm wipe pattern and it was left at that, deemed acceptable. This, rather than valve seat recession is what I'm thinking.

 

Yes all the lash pads were the same 5.0mm.

 

From what I can tell, the head's had quite a bit of work done to it in Japan. The ports are quite huge and it seems to have a lot of compression.

 

 

So the most likely scenario is that the builder in Japan installed some aftermarket, or maybe valves from a small block Chevy (or something) that were a bigger diameter...but a taller stem. But instead of machining down the stem and machining a new groove for the retainer, they used a cam with a dramatically smaller base circle to allow the rocker to lift up high enough to get on top of those valves.

 

..at this point it's only a theory, but we'll know soon enough.

 

Trying to put in a new cam with less material ground off it manifests itself with the problems your having. Bite the bullet and take the head off OR put the old cam back in, build a new head on the bench and swap them in one go. Is it a stock head on there ie no porting etc as far as you know? That would make it a much easier (and less expensive) decision IMO.

 

Good luck mate.

 

Great minds think alike! The engine now looks like this:

 

The head's coming off, and will be sent to a pro, and we'll do and re-do what's needed to get this all 110%. It'll be very interesting to see what it looks like on the other side...

[Babalouie]

The whole problem is that he's got zero lash because his spring installed height is too tall. He can't even get a rocker under the cam without removing the lash pad completely. That's my point. The retainers are from a different cam setup and the installed spring height is taller than what it's supposed to be.

 

I know what you're saying...maybe it's just a tall retainer (ie ignoring that the valve tip inside the retainer is at the same height as normal) that's in the way of the rocker, right? When I looked at your pics I thought the same thing, but I don't think that's the case with my head...the raised collar on the retainer is quite low on mine (not like your Racer Brown ones) and I don't think the rocker is fouling the retainer.

 

Anyway, head's coming off, we'll have some proper answers soon.

[naviathan]

I can't see the pics in this thread because of network restrictions at the office, but the first question I have after reading through the thread is, what head is this? If it's a P series head and someone put N series valves in it that would make the valve stem longer in relation to the head than stock and it's not unheard of.

[johnc]

1fast Z and 2eighTZ4me,

 

You guys are arguing about two different things (valve stem height and spring installed height). Agree on one and the continue your discussion.

[Babalouie]

I can't see the pics in this thread because of network restrictions at the office, but the first question I have after reading through the thread is, what head is this? If it's a P series head and someone put N series valves in it that would make the valve stem longer in relation to the head than stock and it's not unheard of.

 

The spot where the head code is cast has been sanded down. I think it's a not-uncommon practice in Japan to disguise the fact that you increased your capacity (which normally means you pay more road tax). But rather bizarrely, anyone can see plain as day that the engine number begins with L28....

 

It has: round inlet ports (with injector notches), square exhaust ports, non-hydraulic lifters. It was suggested in the head thread that it could be an N42 or a P90A. But it's a JDM head so maybe it's something else altogether, that's possible too.

[2eighTZ4me]

Like I said Jon - I'm out. Ya'll take it from here.

[naviathan]

A P90 maybe, but most P90A heads are hydrolic. Honestly, I think you may have a P90 with N42 valves. If what you're dealing with is a long valve stem then I would give that the safe bet. Aftermarket valves for the N series heads are abundant, but not for the P series so the proper thing to do is use N series valves and have them cut down to size. Maybe someone didn't do this (or know this)?

[Babalouie]

A P90 maybe, but most P90A heads are hydrolic. Honestly, I think you may have a P90 with N42 valves. If what you're dealing with is a long valve stem then I would give that the safe bet. Aftermarket valves for the N series heads are abundant, but not for the P series so the proper thing to do is use N series valves and have them cut down to size. Maybe someone didn't do this (or know this)?

That makes sense...is there a lot of length difference between the P and N valves? Like maybe 1/8th of an inch?

 

The cam that was in the head had a very small base circle (there is a pic on the first page). I suppose it's possible that in Japan there's a school of thought that says: run the N valves in a P90 head, and instead of cutting down the valves, use a smaller base circle cam.

 

When it was running, the valvetrain was noisy as hell (and the engine didn't make much power) so I'm quite happy to explore alternative routes here

[naviathan]

That makes sense...is there a lot of length difference between the P and N valves? Like maybe 1/8th of an inch?

 

The cam that was in the head had a very small base circle (there is a pic on the first page). I suppose it's possible that in Japan there's a school of thought that says: run the N valves in a P90 head, and instead of cutting down the valves, use a smaller base circle cam.

 

When it was running, the valvetrain was noisy as hell (and the engine didn't make much power) so I'm quite happy to explore alternative routes here

That's about right. When I meaasured them up it was roughly an 1/8th of an inch difference.

[Babalouie]

Dang....well there you go. Well, there's no turning back now, I guess we'll know for sure what sort of head it is when we get to have a look at the combustion chamber.

[1 fast z]

This disscussion in this thread is pertaining to lash, not spring pressures, therefore that is all I am discussing in this thread. z4me brought up difference in retainers, makes a difference in wipe patterns, to where it does not.

[TimZ]

Maybe I missed it in the previous posts, but from the 1st pic in the first post, are you saying that the original cam with the smaller base circle and 0.200" lash pads worked properly in this same head with no other changes?

 

If this is the case, then you can figure out what your new lash pad thickness needs to be by subtracting half of the difference in base circles between the two cams from 0.200" . Seeing as how the difference in base circles appears to be readily visible in the 1st pic, I would think that you would need to go considerably thinner than 0.180". Stock lash pads were 0.120", as I recall.

[Tony D]

Not all P90A Heads hydraulic, but the valves are a different length, but that's a stretch.

[Babalouie]

More food for thought. After a recent valve job, I could not get enough lash on several valves. I'm using Schneider's cam, springs and retainers, The billet was new when I first installed it. Then I discovered that several rockers were touching the retainers on the outer edge and were actually pivoting on the retainer and not on the valve stem. The solution was easy. By sanding/smoothing off the underside of the rockers, I was able to get the proper lash. Several of the rockers had small "nicks" on them, indication to me that they had been touching the retainers before I refreshed to top end.

 

Maybe I missed it in the previous posts, but from the 1st pic in the first post, are you saying that the original cam with the smaller base circle and 0.200" lash pads worked properly in this same head with no other changes?

 

If this is the case, then you can figure out what your new lash pad thickness needs to be by subtracting half of the difference in base circles between the two cams from 0.200" . Seeing as how the difference in base circles appears to be readily visible in the 1st pic, I would think that you would need to go considerably thinner than 0.180". Stock lash pads were 0.120", as I recall.

 

Thanks guys. Old cam had a base circle 200 thou smaller than the new cam, so a lash pad of 100 thou less shoulda done the trick. Original cam used 200 thou lash pads, and the ones I was experimenting with last night were 120 thou. So the new lash pads should have been more or less on the money.

 

So this morning I had another go (I admit I was probably a little pissed with the car last night so didn't have a proper look) and reinstalled one of the rockers:

 

Like Mayolives, my rockers are fouling on the retainer. I don't think sanding it is going to do any good though, I need to more like file a notch in there!

 

To the extent that it's not allowing the nose of the rocker to slip into the lash pad at all....it's fouling at this point, where my finger is:

 

So that's what's been going on all along! With the old cam, the thicker lash pad meant that the rocker was spaced further out from the retainer and so this wasn't an issue before.

 

I suppose it still doesn't change anything: even if I am just going to swap to a different type of retainer the head's still coming off...Do my retainers look like the stock type?