high idle speed issue

[Patcon]

31 minutes ago, Zed Head said:

The fragments would get splattered up to the valve cover and around up top but once they get to the pan they have to go back through the filter before reaching a bearing.  Might be interesting to split the filter open.

unless the filter was bypassing due to loss of filtration capacity.

28 minutes ago, Dave WM said:

I run high zinc oil, have read that is important with flat tappet valve train. Modern engines use roller bearings. I wonder if the camshaft can be saved? weld on some new metal and re grind.

You might could build it back up but it would have to be hardened again and would be cost prohibitive.

[Jeff Berk]

The SU whisperer pointed to several potential contributing factors. The performance cam was milled from a CWC core. Apparently, CWC has a bad reputation. That engine should of had an internal oiler, but the cam shaft did not have provisions for that so an external oiling tube was installed. Since exhaust cams for 1, 2, and 3 cylinders were worn out, perhaps, the front half of the oiler tube became clogged.  

 

[AK260]

This clearly left an impression on me - I was dreaming about it for most of the night!! ;)

Glad you have some ideas about root causes.now comes the fun bit, going shopping, improving, enhancing etc

[Jeff Berk]

I just got word from the shop:

"I’ve been talking to my camshaft contact. He grinds a slightly less aggressive cam for your car. The cam itself will cost around $450. We will also need new rockers and lash pads. They cost between $400 and $500 depending on what thickness pads are required. I’m looking at around 10 hours labor to remove and replace, and setup the geometry of the new cam. I will also change the oil & filter when I’m finished. So your looking at $1800 to $2000 if no problems show up after the cam is removed."

I ask that he try to avoid having to do a valve job if at all possible since I'd be looking at an additional $500 or more.

[siteunseen]

I sent Schneider Cams an original Nissan cam that has "JAPAN" stamped on it after reading about the failures of those CWC cams they will send you if you let them.

You might look at Schneider or isky's web site.  They have a few different profiles for our cars at a lot better price, send your rockers to Delta Cams for resurfacing.  Cost $50, $3 per - $36 plus $14 shipping.

 

[Jeff Berk]

siteunseen... Thanks for the suggestion.

[Jeff Berk]

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. 

[Mark Maras]

 "For some reason" isn't good enough for me. I'd want to know what specifically went wrong. Was the oil flow satisfactory when the cam was installed? I doubt it. The external oiler system works quite well if the tubes have not come loose from the mounting blocks or the oil holes haven't become restricted due to build-up of ? Tubes can be resoldered and the holes cleaned with a torch tip files.

[siteunseen]

@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.

 

 

[jonbill]

does the cam have much lift?
I damaged my cam last year. Based on what I learned here https://forums.hybridz.org/topic/130549-valve-spring-seat-pressure/

I concluded the cause was idling below 1000.

[Zed Head]

Sometimes they flatten a lobe even if everything is done right.  @madkaw knows, if I remember right.

Who is the camshaft shop that he uses?  

[Jeff Berk]

Would using the turbo Z pump be strong enough to pump oil through both the internal oiler and spray arms? Is there a way to check how well it's working?