new to the S2k and the forum. Just reading this morning I found two posts from owners who dropped valves from over reving. Would replacing the stock retainers with titanium retainers be a prudent mod on an 02 with 53K miles?

TIA,

David

 

I don't know which is "harder". I was only reading about the popular prevention/fix on this forum for dropping a valve and it seems to be titanium retainers. Seems to me the lighter weight of the titanium would be advantageous.

More to the point: is there any opinion as to whether changing out the OEM retainers is a worthwhile preventive maintenance procedure?

 

Sounds like your mind is already made up. Let the rest of us know how the Ti retainers work out for you.

 

OEM retainer replacement is a good idea. If you have ever had an over-rev I would DEFINITELY do it. It is a common enough failure mode that I will change mine out. I am tough on my car... I'll probably change mine out around 60-75k.

AP2 retainers are beefier than the AP1, even though the redline was lowered on the AP2. A lot of people just switch to AP2 retainers and call it good.

Titanium belongs on your exhaust.

 

I put the Ti retainers on right after cracked a OEM retainer and droped a valve, i waited 9 months for my engine to get rebuilt...sure wish I wouldn't have raised that redline lol....

 

Titanium retainers are high maintenance. Depending on the manufacturer of the retainer and the machinist you ask, I have the seen recommended replacement intervals range from 10K-25K miles for the Titanium retainers.

 

This is only an advantage when you are running a very big race cam, as it helps to prevent valve float. Their lighter weight also allows the use of weaker springs for a given cam to reduce friction.

There'd be no advantage to using Ti retainers with stock cams.

As already mentioned, Ti retainers need to be changed often, as they are weaker than steel. Ti is mainly for race use where motors are serviced frequently, not for street use.

 

This ("Ti retainers are weaker than steel") is not quite accurate. However, it is accurate that for normal street applications Ti retainers would be a bad choice.

The key is that two different failure modes are involved. For the Ti retainers, the issue is galling between the retainers and the springs. After some period of time the galling will get bad enough that the retainers need to be replaced. This might be as often as once per year in a street driven car.

For the steel retainers, galling is not an issue. The concern there is that in an overrev if the valves "float" then the retainers will get hammered. This exceeds their design strength and causes cracks leading to failure.

For the Ti retainers the same sort of thing can happen, but because of their light weight they don't float as easily. If you use dual valve springs, you can move the "safe" overrev limit up by maybe a 1000 rpm or so. This means you can either raise your redline (if you are using different cams) or you just have more margin in case you overrev.

If you never overrev and you don't raise the redline, going to Ti retainers would be a huge mistake. If you do happen to overrev and you get to, for instance about 11K rpm, that would be in the magic zone where the Ti retainers would not be floating but the steel retainers would be. So in that limited circumstance, going to Ti might save your engine. Unless the car is tracked very frequently as compared to the street miles, this is hugely unlikely.

All that being said, I'm in the process of switching to Ti retainers on my now-to-be "track only" car. But rebuilding/replacing the engine every year or two in a dedicated track car is not especially unlikely. Shit happens.

 

Anyone seen or heard of Ti retainers advertised for sale with a hardened surface to keep the spring form eating into the softer surface of the Ti retainer? It would be great to keep the soft core of Ti for strength and toughness. But we need more hardness on the surface, due to Ti galling where the valve spring and split keepers contact the retainer.

Does anyone know of any common surface hardening treatments, normally used on steel, that will work on Ti? Carburizing, nitriding, shot peening, induction hardening, work hardening, cryogenic treatment?

My second choice would include a replaceable hardened steel wear face (shim-type washer between the spring and retainer). Maybe it could be an interference fit into the retainer then staked on for good measure.

 

If you race your car I would highly recommend the Ti retainers. My f20c engine survived a 11,000rpm overrev when the weld on my gearbox custom bell house came apart on the drag strip 11 months ago. The clutch came apart from the flywheel, the flywheel freespinned all the way to 11000rpm.

Just finally got the car back and checked the valvetrains. They are all A ok. Thanks god for that.