Camshaft lobes wearing down

S

skully

Daily Driver
Can anyone tell me why my cam lobes are wearing down on my 85 F.I. 1.5 X ? As I am tearing the engine down to replace the leaking head gasket I see that # 1, 2, and 4 exhaust lobes ONLY are badly worn any ideas as to why this would happen ? Thanks
 
Valve lash?

Have you measured the valve lash? It could be the gap is too great and the lobes are "slapping" the cam bucket shims.
 
Actually the cause is usually the opposite, the lash being too tight,lobe runs on the shim without getting a chance to cool and get lube into the non-existent gap... lash clearance doesn't grow with use, it closes up with valve wear and seat recession... "noisy tappets" with too much lash clearance would usually get noticed and prompting action, too tight and the tappets are quiet..prompting inaction...and cam lobe wear.

Or the shim size is so thin that the lobes have caught the edges of the buckets...

Other usual causes are valve spring bind up with a high lift cam.

SteveC
 
I have had 2 late Yugo's with low miles that had a lobe missing from the cam shaft. I always assumed it was a hardening process that was skipped. What ever the reason, you need a new one.
 
Oil Companies bending over to take it from emisions laws

Try some ZDDPlus in your oil. Or Joe Gibbs Driven Oil.
 
Not convinced this is a problem for the valve system used in this Fiat SOHC engine due to the cam lobe area, cam ramp rates and overall design of the valve system.

The vast majority of modern engines have a similar to identical valve-cam system except many use smaller cam lobes, smaller diameter valve buckets and related to reduce cost. If the modern engine of this design is flattening cams, all manufactures involved would have a extremely serious warranty problem.

Under spec valve lash can not only cook a cam, it can cook valves due to the semi closing of valves and not allowing the valves to fully seat for cooling.

If possible, take the defective cam to a machine shop or similar testing facility and have the surface of the cam lobe hardness tested. This will give a better indication of what might have actually happened. Anything less is mostly speculation or conjecture.

What is fact, Fiat's do not have cam-valve system problems unless something is seriously defective.


Bernice




Deane said:
Try some ZDDPlus in your oil. Or Joe Gibbs Driven Oil.
Click to expand...
 
cam lobe wear

O.K. I do believe I seriously overheated this engine and the cam was rusted from sitting in a bag for 10 to 12 years, I am pretty sure that I had the shims within specs but from the outcome I have done something wrong. I just finished replacing the head gasket and it is running but I,m not out of the woods yet. I need a new cam and I am going to have to re shim that mess . Where can I get a new cam ? What cam should I use ? O.H please help me .
 
skully said:
O.K. I do believe I seriously overheated this engine and the cam was rusted from sitting in a bag for 10 to 12 years, I am pretty sure that I had the shims within specs but from the outcome I have done something wrong. I just finished replacing the head gasket and it is running but I,m not out of the woods yet. I need a new cam and I am going to have to re shim that mess . Where can I get a new cam ? What cam should I use ? O.H please help me .
Click to expand...

Matt will have a decent con'd Cam to get you going.

But.

Well not so fast on the conclusion there folks, it would be good to have a little data on the history of the engine itself before asking a blanket question like

"Can anyone tell me why my cam lobes are wearing down on my 85 F.I. 1.5 X ? "

How many miles on the engine?
Has the top end been refurbished at any time with only the shims on those valves changed. (poor material hardness?) Now that you say it may have had surface rust from sittin in a bag is a giveaway, did you have this polished and Nitrided before fitting it?


It would have been nice to have some pictures of the lobe " Toe & Heal". If you had considerable wear on the heel of the lobe, which bad, the " Toe " is likely to be worse.

Questions like , there appears to be metal wiping off the exhaust lobes! would likely lead to suggestions that you might find that the cam bucket shims are failing as well. I would be concerned enough to throw them out with that Cam too.


Lobe wear exisits and why it happens is varied. I heard a new term from Marine Engineer the other day that went into the vocabulary, "it was made from chinesium. " I know that the X1/9 is ltalian, a lot of issues that pop up in other Marques are because of cheap aftermarket parts, but is the valve train ALL Fiat OEM, that includes the shims? There is so much CRAP(Chinese Replacement Auto Parts) around these days its frightening. If its all OEM then it is in all honesty unlikely to be just the camshaft itself. That E1 E2 E4 are worn points to what SteveC suggests. Valve seat recession, have you monitored the lash gap and has it shrunk?

I am yet to see a OEM EURO cast iron flat tappet camshaft that had a single ( or in this case 3 of 8) soft lobe. Camshaft cast cores are made in a casting foundry, all the lobes are flame hardened at the same time. That process hardens all the lobes to a depth below the barrel of the core. That depth of hardness allows the finish cam grinder to finish grind the cam lobes with a generally accepted hardness on a finished cast cam. After that Nitriding etc only adds a depth of roughly 0.010 of an inch. Once you eat through all of that its a death march for the Cam, speed of demise is relative.

Many other reasons, or a combination of factors can cause camshaft lobes to fail.

Here are some possible causes.


Lets get the ones that are improbable out of the way for this Fiat lumpy stick.

Bent cam
In this engine design hit by a rotating part such as a reciprocal piston/rod, in this instance impossible but, the cam will usually break in more than two-pieces. Sometimes the camshaft will break in two pieces after a short time of use because of a crack or fracture in the cam due to rough handling during shipping, or really poor storage. The best place for a SOHC is in the cam carrier, if a cam becomes cracked or fractured due to rough handling, it will generally not be straight.

Generally, if you can install the cam in the engine and just install the timing gear, the cam should turn freely with pressure of just your thumb and fore finger. Be aware that the heat generated at the cam during the failure of the cam lobe, and/or lifter, has the ability to distort the cam and cause it not to be straight any more.

Camshaft end play.
Some engines have a thrust plate to control the for & aft movement of the cam. These types of engines have many factors which cause this end play to change. If the end play is excessive, it will cause the cam to move causing the side of the lobe to contact an adjacent lifter. Not a Fiat issue.

So now some possibles

Spring pressure.
Normal recommended spring seat pressure for most mild street-type flat tappet cams is between 85 to 105 lbs. Fiat use valve spring seat pressure over that but the lobes are wider to accommodate it. But be sure to run enough oil to avoid the lack of oil splash onto the cam at low speed running to help cool the cam and lubricate the valve buckets. Once the oil shears at the lobe/shim interface its metal to metal time, bad ju ju!.

Higher than spec spring pressure causes the heat created in the cam to breakdown the material, resulting in its early failure. Any springs that may be used must be assembled to the manufacturer’s recommended height. Never install springs without verifying the correct assembled height and pressures, checking for coil bind is critical.

Increased spring presure from a spring change and/or increased valve lift can hinder lifter rotation during cam break-in wiping off the hardened layer. Just for info I have used lower spring pressure during the break-in period on a French engine by decreasing the thickness of the spring seat shim washer. This can be accomplished on a Fiat removing the inner spring, during the cam break-in time ONLY, because dual springs are being used.

Mechanical interference.
Spring coil bind, when all of the coils of the spring (outside, inside) contact each other before the full lift of the valve. The spring you are using be capable of traveling at least .060″ more than the valve lift of the cam from its assembled height.

I have seen poorly installed valve guides just high enough to limit the full compression on the valve train once the head was 'at speed', installer missed it as the heights of the spring were measured in a spring compression rig and not checked once in the head. Retainer to seal/ valve guide boss interference. You need at least .060″ clearance between the bottom of the retainer and the seal or the top of the valve guide when the valve is at full lift.

Valve to shim bucket interference, this occurs when valve seat recession is enough to cause this mechanical interference. Also increased valve size, surfacing the cam box tec may cause this problem. This is a probable cause for your exhaust valve cam lobe failure.

What folks fail to do on rebuild

Lobe wear.
Incorrect break-in lubricant. Use only the moly lube that is included with the camshaft from the manufacturer. This moly paste must be applied to every cam lobe surface, and to the bottom of every lifter face of all flat tappet cams. I also, apply the moly paste to the distributor gears where a cam drives a distributor or pump. For extra protection, an anti-wear additive should be added, such as Crane Super Lube.

Synthetic oil.
Do not use synthetic oil during the break-in period, running in oil + an ZDDP additive is the way to go.
It is not recommended to use any type of oil restrictors to the lifter galley, or use sump windage trays, baffles,or plug any oil return holes in the head.

Oil has a two-fold purpose, not only to lubricate, but also to draw the heat away from whatever it comes in contact with. The crankshaft needs oil splash from the crankcase and oil run-back from the top of the engine to help draw the heat away. Without this oil flow, all the heat generated at the camshaft is transferred to the shims, which can contribute to its early demise.


Correct break-in procedure.
After the correct break-in lubricant is applied to the cam and lifters, fill the crankcase with fresh non-synthetic oil. Prime the oil system so that all oil passages and the oil filter are full of oil. Preset the ignition timing and prime the fuel system. Fill the cooling system.

Start the engine. The engine should start quickly and run between 1,500 and 3,000 rpm. If the engine will not start, don’t continue to crank for long periods, as that is very detrimental to the life of the cam. Check for the cause of the failure to fire and correct it. The engine should quickly start and be run between 1,500 to 3,000 rpm. Vary the rpm up and down in this rpm range during the first 15 to 20 minutes, (do not run the engine at a steady rpm).

During this break-in time, it would be great to verify that the lifters are also rotating, a permanent marker on the circumfrance of the buckets and shims and lifting the Cam cover to check when shut down helps. If the lifters don’t rotate, the cam lobe and lifter will fail. Sometimes you may need to help spin the bucket to start the rotation process during this break -in procedure. Lifter rotation is created by a taper ground on the cam lobe and/or the convex shape of the face of the flat tappet lifter/shim. In some cases (like the French XU9 series engine ), the lobe is slightly offset from the center of the lifter bore in the head/Cam carrier. If the linear spacing of the lifter bores in the head is not to the correct specifications, or the angle of the lifter bore is not 90 degrees to the centerline of the cam, the lifter may not rotate.

Even if the engine you’re rebuilding had 100,000 miles on it and the cam you removed had no badly worn lobes, this still doesn’t mean that your carrier is made correctly. It just means that the break in procedure caused everything to work correctly. Be careful to watch the shims during break in to verify lifter rotation. Don’t assume everything will work correctly the second time around.

Always use new lifters on a new flat tappet cam. If you are removing a good used flat tappet cam and lifters and are planning to use them again in the same (or another) engine, you must keep the lifters in order as to what lobe of the cam they were on. The lifter breaks-in to the specific lobe it is mated with and it can’t be changed. If the used lifters get mixed up, you should discard them and install a new set of lifters and break the cam in again as you would on a new cam and lifters. You can use new lifters on a good used cam, but never try to use used lifters/shims on a new cam.

I'll leave you with this.

"Nitriding is recognized by metallurgists worldwide as one of the most effective ways to increase the case hardness and lobe surface lubricity of flat tappet cams."

http://www.compcams.com/Base/pd/FlatTappetCamTechBulletin.pdf

What oil are you using ( Weight and brand ). There has been a lot of controversy over new " Eco " oils that have lowered Zinc and Phosphate levels to allow manufacturers to make cheaper Catalytic convertors. Engine manufacturers/Gov't requested oil manufactures to reduce Zinc and phosphorous levels so that they could make cheaper converters with reduced Platinum content. IMHO contrary to popular belief the higher ( actually NORMAL ) levels of ZN/PH in older motors does not adversely affect Catalytic converters because of the following reasons.

1: The older Catalytic convertors ( such as on a 2003 car ) were designed to be used with the higher levels of ZN/PH. More platinum was used in coating the honeycomb matrix as the levels of platinum degrade over time. That also costs more money these days as Platinum is darn expensive.

2: The EPA requirements were less stringent in previous years. Catalytic convertors had to pass a 100,000 mile No Fail test. That has been increased to ( I believe ) 150,000 miles with the latest regulations. ( Not 100% sure on the mileage figure. Might be 160,000 miles )

However, Zinc and phosphates are extreme pressure additives necessary for extreme load conditions. Camshaft to valve bucket shim interface is the highest load area in any engine. Increasing the lift as seen on many camshafts only makes this worse.

Please be aware that 'ZDDP overload' is just as bad as the additive can actually cause blocking of other important friction modifiers or detergent agent additives. So dosing at every oil change is unwise unless the ZDDP level is carefully specified and blended to the correct concentrations required.

Just for giggles follow the link to the VW forum where the 'Superior German Engineering" is discussed. Will make Bernice chuckle I guess. We had a little experience with the old Punpe Duse engine which we moved on and bought newer one equiped with one of those dirty new common rail engines. I know its not as clean as advertised but we have an acronym down under DILLIGAF, I'm not really worried.

http://www.myturbodiesel.com/wiki/camshaft-lobe-wear-inspection-and-replacement-on-tdi-pd-engine/

Low Zinc and phosphorous levels works fine with new motors designed with roller lifters or followers, but the general increases wear on flat tappet and bucket cam engines is an industry wide debate. Most consumers don't care or notice as 1. not a gearhead 2. will dispose of the car long before these issues become problematic.


Rotella T6 I read has reduced the Zinc/Phos levels. For all my old flat tappet engines I use zddp additives. ESPECIALLy during a rebuild where new parts are concerned, running in oil and use brake in lube.

Here is an article showing Phosphate and zinc levels.

https://www.amsoil.com/techservicesbulletin/MotorOil/TSB MO-2007-08-08 Flat Tappet.pdf


A short spreadsheet listing Phosphate and zinc levels

https://docs.google.com/spreadsheet...sHUacyZz8hvvwBSBIblxnuALfc/edit#gid=0&vpid=A2
 
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