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Rapid stainless valve wear.


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Anyone had a similar problem as shown below?

Replaced a fully rebuilt 6 cyl head all new valves guides rockers etc onto rebuilt block. After approx 1000 miles following rebuild, (just after 2nd lockdown) on removing rocker cover to check tappet clearances, found brown "greasy" deposits on some rocker / valve stem areas. On removing rocker assembly all the inlet valve stems and rocker arm pads were showing signs of damage / wear. and were coated with the deposits. Whilst none of the exhausts showed any signs of wear, as would be expected at this mileage.

The deposits appeared to be wear debris mixed with lubricant. The stainless exhaust valves came from Rimmers and had no wear, whilst the inlets, also Stainless, came from a smaller Triumph Specialist and unlike the exhausts were stated to have Stelite tips.  I returned the damaged valves on the understanding that they would be returned to the manufacturers for examination. The supplier advised that lack of lubrication was the cause and proceeded to have the valve tips ground to remove the damaged surface. the supplier could not explain how this had only affected the inlets he had supplied, and not the exhausts. I therefore declined to reuse the valves and have rebuilt the head with standard material inlets.

the first photo shows the middle two inlet rockers with wear and deposits whist the outer two are exhausts and completely unaffected. the second shows the exhaust stems at the extreme top and bottom of the pic. The centre pair are the inlets with wear and signs of the deposits on the valve caps.

Anyone have an explanation for this ???

 

Paul B

rockers.JPG

ex valve stems.JPG

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Had similar on a couple of valves supplied by one of the smaller TR suppliers. Duff batch perhaps. 

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How much was taken off the head surface when machined  ? and was the block top machined also ? did you adjust the pushrods for length or use spacers underneth the rocker pillars ?

Was the camshaft used a standard spec camshaft ? or did it have different lifts inlet to exhaust ?

Mick Richards

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If the oil contains decent level  of ZDDP it wont be lubrication at fault. Although the ivs run colder than evs the anti-scuff tribofilm will still form well at the lower temperatures. Peter

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Thanks all,  for replies.

Tim.  Supplier "Never had any problems with these valves"  !!!

Mick. minimum off head to clean up. nil off block. cr checked, close to standard. (this was reason for swapping head) I am not a fan of spacers under rockers, probably would have used shortened pushrods if neccesary

Piper cam,same lift inlet & exhaust. rocker orientation checked. spring clearances checked at full lift,etc etc ????

NTC. Yes bronze guides, by supplier of damaged valves.

Peter. oil Valvoline VR1. 20,50

Thanks

Paul

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"oil Valvoline VR1. 20,50"

Unless you managed to get US spec VR1 the European spec VR1 has Zinc in ZDDP has been "optimised" (reduced so the oil can be used with cats on the engine) unlikely to have enough zinc in it.

Mick Richards 

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When I stripped the head to replace the inlets all the valve stem to guides seemed fine. in fact the only problem was with the inlet valve to rocker pad wear. I took the oppertunity to check the condition of the (new) cam followers and was pleased to see they were bedding in and showed signs of them rotating. Ther seems to be plenty of lubrication for everything else, but the inlet valves?

P

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Hi Paul,

I don’t think ZDDP level has much effect on this type of wear. I more suspect the material of inlet valve or guide since exhausts are fine Were all 12 guides from same manufacturer and all had the same color (as a simple check for brass versus bronze)?

Waldi

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NTC. I dont want to name supplier on this forum.However I shalll not be using them in the future due to their respons to this.

Waldi. All the guides were from the same supplier, no problem with the guides or valve stems. The wear on the stem tips and rockers of only the inlets  was the issue..

Z320.The springs were also from this supplier.chosen to give sensible spring rate. the cam was from Piper with lift simlar to standard 150 cam .

Thanks for all your comments.

Paul

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1 hour ago, paul bond said:

 

Waldi. All the guides were from the same supplier, no problem with the guides or valve stems. The wear on the stem tips and rockers of only the inlets  was the issue..

 

Paul

Sorry Paul,

I now see what you wrote.

So most likely an inlet-valve issue, not a guide issue. SS is much softer compared to alloyed steel. I assume this is why the tips on SS valves are stellited. 
I agree, disappointing response from the supplier. A hardness test of the tips could reveal the cause. Grinding the tips (why would you??) will not solve low hardness.

Cheers,

Waldi

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  • 2 months later...
On 3/29/2021 at 8:30 PM, Motorsport Mickey said:

. oil Valvoline VR1. 20,50"

Unless you managed to get US spec VR1 the European spec VR1 has Zinc in ZDDP has been "optimised" (reduced so the oil can be used with cats on the engine) unlikely to have enough zinc in it.

Mick Richards 

Hi Mick there should be no compromise in the ZDDP  additive technology all of the oil Majors use different antiwear and anti scuff additive for use in CAT's so unless the the ant wear  additive has been substituted  reducing the ZDDP would mean the oil would unlikely to meet the API or ACEA requirement .Most of the formulations which meet API and ACEA specs will also  have an FZG  rating, with good oils meeting of 11-12,  which at those figures  will do the job ..Oils with and FZG 12 are absolutely fine in gear boxes . The balance is to ensure that the oil  protects the valve train with out bore glazing  and the detergency cleans the engine and the dispersants hold the insolubles in suspension. The area  that has a question mark is the quality of base oils used and their performance at extreme temperatures. Most independent oil blenders use preparatory additive packs  from suppliers  such as Lubrizol , Infinium  and Parimins.its possible to blend additives as a small supplier but specific approval are costly  for example i see many oil which have "Meets" or "Exceeds" on the can but few approved to..

I have seem similar  issues which turn out to be coating  of components, poor base oils which caused varnishing or inferior additive packs ..If Paul sends me the details on the oil used i can advise. If you have valve train wear  it is normally  an indication of oil starvation or as Mick suggest a additive pack that is not up ton the job, either way i would  strip the rocker shaft and just make sure the oil is clean   finally did you use any grease on the valves heads 

cheers steve

 

 

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