Jump to content

IGNORED

high idle speed issue


Jeff Berk

Recommended Posts

Wasn’t me . I made a thread here many years ago about this subject of dual oiling systems  , but I think it’s lost . 
There’s been man stories of lost cams . With all the variables , it’s hard to attribute a wiper lobe to one thing .

Spray bars -to me - are problems just waiting to happen 

Link to comment
Share on other sites

18 hours ago, siteunseen said:

@Jeff G 78

I think he runs both on his race car? I have not built mine yet but I will use both on my e31 head with a Schneider cam kit. I have turbo pumps on both my Zs and they flood the valvetrain when I spun the pump with a drill before 1st start up. I read a lot of post with people using both with the higher volume pump. Actuall my 9/76 has both on the early n47 head from Nissan. That came looked great in 2011 when I bought the car. That's from '76 to 2011 without the turbo pump. At idle it barely moved the needle on the gauge. With a turbo Melling pump it sits halfway then I installed a new head with just internal oiling cam. Now it's 3/4 gauge at idle. My spray bar 240 with the turbo pump pegs the needle at idle. 

the melling 152 is the turbo pump. Cost me $60 8 years ago from Advance Auto.

 

 

I run only internally oiled on my P79 race car head.  I ran both for a while on one of my motors, but eventually blocked off the tower ports and went with only internally oiled.

  • Thanks 1
Link to comment
Share on other sites

  • 10 months later...

It's been a year and I just completed a valve lash adjustment. It looks like the mechanic did not reinstall the spray bars and only went with the internally oiled cam shaft. One issue I notices was that there was a little damage to the cam on cylinder 5. I'm assuming that since the chip is off to the side, it will not impact anything. 

PXL_20210617_145001511.jpg

Link to comment
Share on other sites

I'd be a bit worried about that chip as it's a few mm into the wipe pattern.  Make sure there are no protrusions around the edges that could eat the rocker.  I'd also be a bit worried that it could propagate across the lobe.  

Link to comment
Share on other sites

On 7/19/2020 at 9:04 AM, Jeff Berk said:

Well I'm back to where I was last year. I got this message from my mechanic when I brought the car back in to have the valves adjusted:

Jeff, For some reason your cam/head has an oiling problem. The same cam lobes that were destroyed on the first cam are bad on the new cam. I have a new cam and rocker arm set coming next week. This cam uses a different oiling system than the original cam.

Followed by:

The new cam will be internally oiled. You can use both the spray bar and internal oiling, the oil pump does not have the volume to do both. I think we should also replace the oil pump with a turboZ oil pump. I have not got the complete cost of the replacement parts yet. I will keep you posted.

Any opinions on this? The mechanic specializes in Japan and British car restoration and races a 510 so he seems to know what he is doing. 

I don't see any holes in the three cam lobes you showed.  The internally oiled cams have those to let the oil out.

Why does he say "new cam" when it looks like you got a used one?  That chip might work but it could also self-destruct rapidly.  Looks like the chip is on the base circle though, where there should be almost no pressure.  Only the anti-rattle springs pressing on it.

Link to comment
Share on other sites

4 minutes ago, Zed Head said:

I don't see any holes in the three cam lobes you showed.  The internally oiled cams have those to let the oil out.

Why does he say "new cam" when it looks like you got a used one?  That chip might work but it could also self-destruct rapidly.  Looks like the chip is on the base circle though, where there should be almost no pressure.  Only the anti-rattle springs pressing on it.

You are right!  I wasn't even looking for the oil holes.  That's an externally oiled cam and I can't tell if it's new, but there is a wipe pattern that wouldn't be there if it was brand new.

Link to comment
Share on other sites

I just sealed the valve cover back up so I can't check if it is contacting the wiper.

Yes, there are spray holes, they just don't show up due to the position of the lobes. 

Yes, it was a new cam shaft (last year).

The mechanic has been non-responsive lately as he's working as a crew on a Miata racing team and doesn't have much time for his shop.

I think I'm going to treat this as a mole on my skin. I'll just keep an eye on it and check to see if there are changes.

Link to comment
Share on other sites

I just looked at the pics of my internally oiled cam and the oil hole is opposite the lobe peak on the base circle.  Zed Head thought that the chip was on the base circle, but I don't think that's the case.  If true, there would be an oil hole visible.  I believe the chip is at the peak of the lobe and it's just hard to see due to the camera angle.  If that's the case, the chip is on the peak of the lobe, not the base circle, though the majority of the chip as on the downslope.  Still, the loads will be high in that section of the lobe.

Link to comment
Share on other sites

The hole position varies.  They just drill in a straight line for some, then another straight line for the others, I think.

Those lobes would be for the same cylinder.  That looks like a very wide lobe separation angle if that chip is at the top of the lobe.

I'd keep an ear on it, then an eye.

http://datnissparts.com/new-oe-l6-camshaft-datsun-240z-260z-280z-l24-l26-l28-13001-e4182/

image.png

Link to comment
Share on other sites

I pulled the valve cover off this morning to get a closer look at the rocker arm. I see something that worries me but what do I know. Keep in mind that the chip in the lobe is to the rear of the car when inspecting the photos. That would be the side marked "S" on the rocker.

PXL_20210618_135208925.jpg

PXL_20210618_135218858.jpg

PXL_20210618_135200037.jpg

Link to comment
Share on other sites

Jeff G 78, 

I looked at the Aug 2020 receipt and the rockers were shown as being replaced. That was 400 miles ago. (I need to get this out on the road more)

The fractures on the "S" side of the rocker running parallel with the face don't bother you?

Jeff

Link to comment
Share on other sites

51 minutes ago, Jeff Berk said:

Jeff G 78, 

I looked at the Aug 2020 receipt and the rockers were shown as being replaced. That was 400 miles ago. (I need to get this out on the road more)

The fractures on the "S" side of the rocker running parallel with the face don't bother you?

Jeff

Those sure don't look new to me.  I could be wrong, but they look like they have old oil residue on them.  What do the lash pad ends look like?

As for the S side, I can't tell what's going on there.  I have never seen a pad split, so I assumed it was just a debris line.  I thought you were referring to the chip in the edge which I've also never seen.  I'd probably have a machine shop magnaflux that and see if it's really a crack.  You might even be able to tap on a good rocker and then tap on that and listen for a different tone.  It should thud if it's cracked.

Was the shop that did this work reputable?  I would not be comfortable with what I'm seeing.

Link to comment
Share on other sites

3 minutes ago, Zed Head said:

Do you know how the cam lobe got chipped?  How many miles or minutes have you put on it so far?

What if it chucked a rocker?  The chip on the rocker and the chip on the lobe could have been done together?  I've chucked rockers on the track with no damage, but I guess it could happen.

Link to comment
Share on other sites

Jeff G, what does it mean to chuck a rocker. The lash pads look ok to my untrained eye. I'll clean the rocker in an ultrasonic cleaner, stain it with ink, and see if the apparent cracks are still there.

ZH, There's 395 miles on it. I'm assuming the chip on the lobe occurred during the machining as it's not very noticeable. I'm not familiar with (or know) the machine shop and relied on the mechanic to select one he was familiar with. 

What I think might be happening is the lobe got chipped possibly due to a defect during machining. The rocker was chattering due to the uneven surface and created the cracks.

Possible solution? I was thinking that I'd replace the rocker (they are inexpensive) and grind away just enough on the trailing edge to miss the chipped area of the lobe. Then I'd protect the area around the cam shaft with rags and smooth out the lobe chip with a small grinder to lessen the potential for propagation of the damage.

I'm waiting for the mechanic to get back to me with his suggestion(s).

This is my third shaft in 2 years. 

Jeff

Edited by Jeff Berk
Link to comment
Share on other sites

Chucking a rocker refers to a rocker coming dislodged from it's position.  This can happen due to it being adjusted too loose, over-rev, or weak springs.  If it partially dislodged, it could have caught the edge of the lobe.  In your case, the rocker could have pivoted rearward.  By the time the cam rotated back around, it was BARELY over the lobe.  With the rocker pivoted, I'll bet that the chip in the rocker lines up with the chip in the lobe.  The other possibility for the lobe damage is that it's in the rear of the lobe which could get damaged during assembly in the head.  The cam is slid through the towers and if it wasn't carefully lined up, I suppose it could have caught a tower just right to chip it.

As for the rocker, I'd sure verify that the pad isn't split.  If it sheers, it will destroy the cam and then send metal throughout the engine.

  • Like 2
Link to comment
Share on other sites

I chucked one right after a rebuild. I was breaking the motor in and heard a god awful tick from the valve train. Jeff told me the easy way to fix it and I've not had an issue since. 

@Jeff G 78 got instant hero status and respect from this guy. If you're ever in Alabama dinner and drinks are on me.

LOL

 

 

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

6 minutes ago, siteunseen said:

I chucked one right after a rebuild. I was breaking the motor in and heard a god awful tick from the valve train. Jeff told me the easy way to fix it and I've not had an issue since. 

@Jeff G 78 got instant hero status and respect from this guy. If you're ever in Alabama dinner and drinks are on me.

LOL

 

 

I went from MI to AZ, so I think I'm just as far away from you as I was before.  Same goes to you Cliff.  If you ever make it to the desert, let me know.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.