Lancia Beta Forum

I purchased a couple of camshaft oil seals for the 1979 Beta Coupe from a local (Australian) engine rebuild supplier as part of an order for some other non Beta related items to have on hand for a future timing belt change. The ones I purchased came in an "Elring" branded box, although the seals are "Made in Italy" so may actually be a different brand to fill out the Elring range as it were like bearing companies tend to do ( the box is still sealed). The size is 30 x 52 x 7 which I think is correct.  

The box sticker makes reference to "B F RD NBR" which did not mean much to me until I did a bit of comparative reading.

I came across this description of an alternative Beta camshaft seal:

"High Quality - High Performance Corteco camshaft /auxiliary shaft seal (Poly-Acrylic) suit DOHC and SOHC Fiat.

52 x 30 x 7 seal size. Made from Poly-Acrylic rubber which will handle higher temperatures (+ 150 c) and rotational speeds (22m/sec) than regular Nitrilic rubber(120c and 12m/sec)"

Which suggests that not all camshaft seals were created equally! Does this mean that the "Poly-Acrylic" rubber seal is the preferred choice for a better seal with longer service life, less prone to leakage and failure? By inference are the NBR seals that I bought junk and not fit for purpose in a Beta? Or are they perfectly adequate for the task? The "NBR" code on my seal box apparently refers to Nitrile Butadiene Rubber:

"NBR is the abbreviation for nitrile butadiene rubber. This is a synthetic rubber that was developed during the 1930s. It is fabricated through the co-polymerization of acrylonitrile (ACN) (polar building block) and 1.3-butadine (nonpolar building block). Its attributes mainly depend on its ACN content.

Nitrile rubber exhibits superior mechanical strength with high elasticity as well as good deformation behavior in a temperature range between -30 °C and 100 °C. Its relatively low heat resistance can be traced to the presence of reactive double bonds. It is used for oil- and fuel-resistant seals such as Simmerrings, O-rings and frame seals. The use of NBR marked the arrival of elastomers as a sealing material particularly in general industry. It is also employed in the auto industry."

https://www.fst.com/materials/nbr/ (https://www.fst.com/materials/nbr/)

This SKF link does confirm the differences between NBR rubber having an absolute operating temperature limit of 120 degrees C and polyacrylate elastomer rubber being able to operate at temperatures up to 150 degrees C:

"Polyacrylate elastomer

Polyacrylate elastomers are more heat resistant than nitrile rubber or SKF Duralip. The operating temperature range for polyacrylate elastomers lies between –40 and +150 °C (–40 and +300 °F) and in some fluids the upper limit may be extended to 175 °C (345 °F). Seals of polyacrylate are resistant to ageing and ozone and are also suitable for use with lubricants containing EP additives. They should not be used to seal water, acids or alkalis etc. Dry running should be avoided."

https://www.skf.com/au/products/industrial-seals/materials/elastomers (https://www.skf.com/au/products/industrial-seals/materials/elastomers)

So is a polyacrylate elastomer camshaft oil seal the holy grail of camshaft oil seals and should they be the preferred choice of seal for Beta owners? If yes, is there a preferred brand, part number etc?  Presumably Cortico make them. Or are there other reasons not to specify this material?

Here is a list of some 30x52x7 seals:

https://size.name/en/catalog/salnik?in_dia=30&out_dia=52&b_width=7 (https://size.name/en/catalog/salnik?in_dia=30&out_dia=52&b_width=7)

I guess that it would be helpful to know the Lancia OEM part number and work back from there to get the best camshaft seal match materials and or brand wise?

This is a bit of a techno overload I know. Interested in other forum members experiences with camshaft seals and some technical clarification as to how much seal elastomer material choice really matters for this application. I remember the mechanic who used to work on my HPE used to say that if the camshaft seal is not leaking, don`t touch it regardless of whether you are changing the belt or not. Because it might start leaking if you do change the seals! A very Italian position on the problem or solution depending on your perspective!

Andrew
 

Hi Andrew

I will not respond on seal material. However Later OE Fiat seals were upgraded with full coverage of material and mini fins on the edges to provide a better seal. Seals of this kind have a 10 -15 year service life before they harden and leak. But the original kind need some RTV sealant on the edge before fitting. Also look out for grooves worn in the cams and expect to scotch bright clean the cams then clean with brake cleaner before building. GC used to take the spring seal off and shorten it slightly if dealing with cams with wear grooves.

Eric

Just revisited this thread. Thanks Eric. Very useful advice.

Andrew

This thread piqued my interest and I decided to do a little Googling and came upon this quite detaikled write-up about ACM and its pros and cons compared to other synthetic rubber seals:

https://nh-oring.de/en/acm-o-rings-materials-simply-explained/ (https://nh-oring.de/en/acm-o-rings-materials-simply-explained/)

From everything I can see, ACM works well up to a point but it would appear that in just about every metric FKM (Viton) is a superior, if more expensive, material.