Cobra Engineering Secondary tensioner

[cpask8]

Does anyone know if the cobra engineering secondary tensioner bodies are made of steel or aluminum? Having a little discussion, and was led to believe that they were made from aluminum and that because the piston is in fact steel, that there will be a large oil pressure leak from the tensioners as the aluminum body heats up and expands faster than the steel piston inside the tensioner.

Looking on their website, the tensioner body looks to be steel, but I could be wrong as it does not say in the description. I sent an email to them, but have not heard back yet. Thanks

[Tbird]

It's steel.
I installed one of these for a month ago.
Really good craftmanship of the tensioner.

[cobraracer46]

In the Video below, Accufab warns about using an aluminum bodied secondary timing chain tensioner due to the thermal expansion that will essentially cause an oil leak.

https://www.youtube.com/watch?v=Z8I5xEsMNbg&t=5s

[eschaider]

John's video was quite good, Jan. The points he made about his oiling modification and the foot separating from the moving plunger used to tension the chains were both quite good. Although I would not want to use aluminum for the main body of the plunger my reasoning would be somewhat different. The increase in diameter due to thermal expansion is minimal on an item that approximates 0.5" in diameter.

What is not minimal is the effect the cast iron sealing ring has at the bottom of the tensioning plunger shaft. In an untreated aluminum bore, I believe it would fairly quickly wear the plunger bore substantially reducing the usefulness of the tensioner. The increased wear the cylinder would experience is the reason Ford went to the PTWA surface finish for the engine cylinder bores after they stopped using cast in place sleeves.

Although two steps have long been popular ways to duplicate starting line launches they are none the less quite damaging to the entire valvetrain drive mechanism. The two step can damage the tensioner but it also does substantial physical damage to drive chains and sprockets. Generally speaking the racing use of a two step mandates a more frequent maintenance regimen for the cam drive chains and sprockets if you want to prevent premature failure.

However, John's pieces are definitely nice no matter how you look at them.


Ed

[stellaa9x]

hello, in my opinion: It's steel.

[eschaider]

Does anyone know if the cobra engineering secondary tensioner bodies are made of steel or aluminum? Having a little discussion, and was led to believe that they were made from aluminum and that because the piston is in fact steel, that there will be a large oil pressure leak from the tensioners as the aluminum body heats up and expands faster than the steel piston inside the tensioner.

Looking on their website, the tensioner body looks to be steel, but I could be wrong as it does not say in the description. I sent an email to them, but have not heard back yet. Thanks

The Cobra Engineering secondary tensioners are made from steel billet. Whoever informed you they were not, is himself uninformed.


Ed

[Edmisten1]

The Cobra Engineering secondary tensioners are made from steel billet. Whoever informed you they were not, is himself uninformed.


Ed

Ed - when did Cobra Engineering start making these out of steel?? I know when we went thru my engine in 2015, I bought one of these....and it was made out of aluminum.

[eschaider]

You may have gotten a very early aluminum unit, Jeff. I was talking with James about using Steel instead of Aluminum. He elected to change to steel. I have a relatively recent (~2 or 3 years old) one that I used and it is made out of steel.

Ed

[JamesHell]

That is steel. It just isn't black oxide treated. They do have to be steel in order for the piston not to wear into it.
Only early test runs were in aluminum. And all of those were cut open for testing the oiling passages.

[eschaider]

There you go, straight from the horse's mouth


Ed

[Edmisten1]

That is steel. It just isn't black oxide treated. They do have to be steel in order for the piston not to wear into it.
Only early test runs were in aluminum. And all of those were cut open for testing the oiling passages.

Very good....thanks James. Been a while now since I had my hands on it but I would have sworn it was AL. Thanks for the reply.