Can you Straighten bent Titanium valves ??

[Shane Noone]

Hey Guys,

As the subject says really. It may be a dumb question but several people mentioned to me that this may be possible by " freezing " ? I have no idea but I do have a set of Ti 38mm exhaust valves that were over revved and suffered some degree of bending. To be honest they don't look that bad, I can only see one obvious bent one by eye but I was told by my engine builder they were bent and a new set required  I have some stainless in there now as a new set but would be nice to know whether the Ti's could be re-used before they go in the bin as they weren't exactly cheap 

Let me hear your thoughts please

Cheers Shane.

[Fastbrit]

If only one is bent, why not just buy a single replacement? Ii remember hitting a Ti valve with a hammer once (as you do when you're bored) and it had little effect. A more progressive application of pressure may be a different thing!

Be worth putting them in a lathe, or some other fixture, and checking them with a dial-gauge. In my experience, it's very unusual to bend a Ti valve unless it's hit something. Did you float the valves enough for them all to hit pistons? Again, that's not easy with Ti valves unless deck height is minimal.

Bottom line – you shouldn't have to bin them. But I'd be interested to hear from anyone with hands-on experience with successfully straightening Ti valves.

[Fastbrit]

OK, just found this in relation to a patent for a fixture to straighten bent valves:

"Titanium alloys have long been used to fabricate engine valves for racing and other high performance engines. More recently, titanium aluminides, titanium borides and other titanium intermetallic compounds (TICs) have been used to make engine valves. Titanium is particularly well suited to such applications because of its high strength-to-weight ratio. However, the relatively high cost of titanium has been a deterrent to its use for valves in higher volume passenger car applications where steel remains the valve material of choice. Nevertheless, the performance advantages that can be realized with titanium valves recommend them as an increasingly attractive alternative for passenger car engines.

Aside from the higher material cost of titanium relative to steel, a significant reason for the higher cost of titanium valves is the processing required with traditional fabrication techniques. Titanium alloys used to make engine valves require heat treatments that cause the stem of the valve blank to distort or warp. Although this same problem arises when steel engine valves are heat treated, the distortion of steel valves can be fairly easily removed by mechanical straightening at room or elevated temperature. In the case of titanium alloy valves, the high ratio of titanium's strength to elastic modulus makes this solution impractical. The technique typically utilized with titanium valves is to restrain them from distorting during thermal processing. Such restraint is conventionally provided by suspending the valve on a latticework rack with the stem extending downwardly. Loading such racks is generally done manually and is very time consuming. Moreover, the racks themselves are expensive and tend to warp after several uses due to the elevated temperatures to which they are exposed. Once the racks warp, they no longer provide the intended support, and therefore they must be continually monitored, repaired and/or replaced.

The brittle nature of TICs at room temperature make mechanical straightening impossible...... The currently employed solution is to use oversize blanks with the excess material being machined or ground to the desired envelope."

[Fastbrit]

Double post!

[Shane Noone]

Hi Keith,

Thanks for the double post and all that info. So at first glance it's a "no" to straightening Ti valves so what I was told must be stuff of rumour and legend 

You have a very good point in asking, why wasn't just one or two Ti valves replaced rather than effectively scrap the whole set.

The bigger question is why didn't my engine builder ( and I know you know who that is !! ) suggest to me that maybe only one or two be replaced...... I can only presume that he put them in a lathe and checked for distortion across all 8 exhaust valves ?!!?  I was told it would be a replacement set of 8 from CB.
All I can say is to the eye with the valves sat on a flat shelf in my garage, I can only see one that is bent with the naked eye. The engine over revved due to a mechanical fault and no limiter fitted to somewhere between 8 -10 000 rpm at a guess( going by tacho reading on shutdown ) There were more obvious bent cro-moly HD manton pushrods, that's for sure. I had one cracked 94B Mahle piston from the wrist pin up the side of the skirt.

I guess I will have to get the Ti valves in a lather for myself as you suggest to see if any are salvagable as it's a wrench to have to ditch what could be reusable based mainly on what they cost versus Stainless ......

By the way I was hanging out with Tony for a bit recently and he said you had a good laugh at the 80's styling of his 67 looker    It should look good when he gets it re-styled and has that 2332IDA motor nestling in the back huh 

Cheers, Shane.

[Fasterbrit]

Shane, if your engine builder spec'd your engine with Ti valves, you probably need to stay with Ti. The reason being your valve springs will be matched and will therefore be underspec'd for heavy stainless. The likelihood of repeated valve float is increased exponentially.

[Shane Noone]

Shane, if your engine builder spec'd your engine with Ti valves, you probably need to stay with Ti. The reason being your valve springs will be matched and will therefore be underspec'd for heavy stainless. The likelihood of repeated valve float is increased exponentially.

Hi Matt, Good point that. The engine was rebuilt by same builder who replaced the Ti set with the stainless set that originally came with the heads from CB.He also replaced the valve springs. I can't remember which type were used with the Ti but was told that I now have CB racemaster ? on the exhaust. I think the heads originally came with K800's but don't think they were used at all....?

But thanks for raising that point.

Cheers, Shane.

[leec]

That may explain the slight power drop you experienced. If the motor was dyno'd with ti valves surely the lightervalve train would have released more power?

Lee

[richie]

That may explain the slight power drop you experienced. If the motor was dyno'd with ti valves surely the lightervalve train would have released more power?

Lee

If the heads dont flow enough or the cam isnt big enough or exhaust to small etc,etc then the extra RPM that the ti valves might allow would be wasted and no hP gain


Shane,if i built your engine and I was 100s of miles away I would have swapped them out for new valves for sure,if it was my own engine I would have tried to re use as many as I could and just changed the one or two needed,its very difficult when it is a customer engine to re use parts that may fail


cheers richie

[Shane Noone]

That may explain the slight power drop you experienced. If the motor was dyno'd with ti valves surely the lightervalve train would have released more power?

Lee

If the heads dont flow enough or the cam isnt big enough or exhaust to small etc,etc then the extra RPM that the ti valves might allow would be wasted and no hP gain


Shane,if i built your engine and I was 100s of miles away I would have swapped them out for new valves for sure,if it was my own engine I would have tried to re use as many as I could and just changed the one or two needed,its very difficult when it is a customer engine to re use parts that may fail


cheers richie

Hi Richie,

Yeah I take your point on whether you yourself are building motors or you are in fact paying someone else too and that's a fair comment. I only mentioned this after Keith raised the question to me in his reply anyway. Don't want to get political about it or anything or for anyone to take things the wrong way and get p*ssed off with me. Been there done that with forums / email where it's taken up all wrong or out of context ! So no slaggings I can assure anyone. Just points of interest for discussion 

The bottom line is I have a set of Ti valves that weren't cheap so the original question was can I get them straightened to re-use if they are bent or simply throw away.. I think the answer seems to be to throw away unless anyone is interested in buying 38mm Ti valves from CB off me, to use a s spares or whatever 

Cheers, Shane.

[Fasterbrit]

Pm sent Shane