Jump to content

IGNORED

Camshaft advice


J Shara

Recommended Posts

Hello everyone. It's been awhile since I've signed on, and to be honest it's been awhile since I've touched my old Z. I was running the car all last summer, and it ran great. It had great power,  and pulled really strong. I'm running ZTherapy rebuilt SU's which I synced and tuned, pertronix ignitor, and just an MSA 6 to 1 header. I rebuilt the engine but had the head sent out to Mancini machine, where I know they re surfaced it, and I can only assume they checked, repaired, and assembled the head correctly, as this was some years ago.  I was driving the car one day and I thought the valve train sounded louder than normal so I preceeded to pop the cover off and check my valve clearances. I found that a few lobes on my cam are black, not shiny like the others. I also noticed that the oil is dark for how new it is. I'm wondering if I ran the valve clearances too tight on these valves and damaged the surface hardening of the cam. I ran Lucas oil stabilizer in this engine when I was driving the car as well. Also used some ethanol fuel treatment in the gastank. Any feed back would be greatly appreciated. 

Link to comment
Share on other sites


Was it a new or reground cam?  What were the clearances on the cam card, what did you adjust them to?  is it an internal oiler cam or do you have a spray bar?  Have you seen oil hitting those black lobes?  You can take the cover off, pull the plugs and spin the motor over to see if it's oiling properly.  Which oil are you running, it may be too thick?

A picture of the lobes and rocker wipe pads would be very helpful.  

Link to comment
Share on other sites

  • 3 months later...

OK so I finally had some time to do some more digging on my Z. It has the original externally oiled camshaft that was in the car when I got it. I set the lash to the spec as per the FSM. I run 10w30 in it with one bottle of Lucas oil stabilizer. I have since taken the plugs out and with the valve cover off cranked the hell out of it. And with the spray bar removed as well I get no oil coming out of the cam towers. But the entire time I was running the car, the oil pressure read fine and the engine never knocked or anything. Is it possible that the oil passages in the head alone could be clogged? Also does the center cam tower supply oil for the entire cam?

Link to comment
Share on other sites

Where are you in MD? Did you set the cold lash? The oil passes from the center right side of the block through a passage into the head. That area could be blocked. But if there's no oil getting to the cam and lobes then I couldn't expect it to run for too long. The lobes will wear and the cam might seize in the towers. I think the end towers supply the oil to the front and back halves of the cam.

Chuck

 

Link to comment
Share on other sites

56 minutes ago, J Shara said:

 But the entire time I was running the car, the oil pressure read fine and the engine never knocked or anything. Is it possible that the oil passages in the head alone could be clogged? Also does the center cam tower supply oil for the entire cam?

Could be that you just need more RPM to get the oil volume up.  Higher oil viscosity will result in lower volume (edit - actually that's a general statement.  The pump likes high viscosity if it has loose clearances.  There's probably an optimum viscosity for max flow).  Start the engine with the valve cover off and see what happens. But a clogged oil restrictor in the block could cut flow also.

The later FSM Lubrication chapters have great pictures and descriptions for the oil spray bar system.  Try 1976 EL-2.

Edited by Zed Head
Link to comment
Share on other sites

I am about 25 mins north east of baltimore in harford county. I also removed the oil filter and blew some compressed air back through the cam towers and the end ones had no back flow of air but the middle one did. I could see it go through to the cam main journal bit it felt different from the other towers. I might try and remove the cam and the middle tower and inspect it but at that point I might as well just pull the head ?. I am gonna order new rocker arms and lash pads, the cam is a given. I wonder if I should get new valve springs as well at least for the affected cylinders, not all the lobes are burnt. This is cyl 1.

IMAG0300.jpg

Edited by J Shara
Link to comment
Share on other sites

Does the oil flow around the cam tower mounting bolt? It would have to right? And what about the mouse trap springs could they get weak with age and cause a problem?

 

Edited by J Shara
Link to comment
Share on other sites

On 2/13/2017 at 4:47 PM, J Shara said:

 I rebuilt the engine but had the head sent out to Mancini machine, where I know they re surfaced it, and I can only assume they checked, repaired, and assembled the head correctly, as this was some years ago.  I was driving the car one day and I thought the valve train sounded louder than normal so I preceeded to pop the cover off and check my valve clearances. I found that a few lobes on my cam are black, not shiny like the others. I also noticed that the oil is dark for how new it is. I'm wondering if I ran the valve clearances too tight on these valves and damaged the surface hardening of the cam. I ran Lucas oil stabilizer in this engine when I was driving the car as well. Also used some ethanol fuel treatment in the gastank. Any feed back would be greatly appreciated. 

They don't look good.  If you had lash set too tight what would happen is that the base circle would get shiny from the rubbing of the rocker arm (the base circle is where the gap or lash is and normally only feels the light pressure of the anti-rattle spring), and you would burn the valves that are set too tight because they wouldn't close completely and would over heat.  As I understand things.

It does look like you just have low volume of oil passing over the lobes, causing overheating.  Lucky that you stopped quickly, the cam looks saveable.

I might check the oil pump.  The way the system is set up the head gets low flow, controlled via a small orifice in a plug in the head's oil passage, and most of the oil is routed to the crankshaft, where the forces are much higher.  That's my guess - oil pump going bad.

Or the orifice in the block itself is clogged.

Actually, I'm going to change my guess to sludge in the spray bar.  The spray bar is a piece of cake to remove.  Maybe you already took it off.  Just noticed that you blew air back in to the cam towers.

Anyway, jumping to "remove head" seems premature.

Edited by Zed Head
Link to comment
Share on other sites

On a side note, just picked up a 79 L28 with matching 5 speed trans lol. Just to have it. ? It's an F54 block and a P79 Head. I've heard different things about the P79 head and when I get around to rebuilding/modifying it, I may just buy a different one.

IMAG0328.jpg

Link to comment
Share on other sites

15 minutes ago, siteunseen said:

The head bolts go through the far left holes in my picture. The cam tower bolts go through the two that are in line with each other. The oil feeds are the smaller holes to the right. Hope you can understand my backwards arse thinking/splainin'. LOL

1496968827774.jpg

I'm mistaken and sorry for that but it's been over my minds time limit. LOL

The head bolts don't go through the towers I don't think, the line up dowels do.

Again I'm sorry but I have early onset of dementia. Too much sun has fried my mind like those eggs on the drug commercials. 

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
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Who's Online   1 Member, 0 Anonymous, 83 Guests (See full list)

×
×
  • 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.