TRD Crankshaft Good or Bad?

[quartzracer]

Bought a Toyota 4age Club motor from a reputable builder (name with-held) with many national wins. Upon tear down we found that the crankshaft's rod journals had been turned down to 0.020 (twenty under). The crank also has been cross drilled (ala Porshe 944 turbo mod) for oiling. Anyone have any problem using a crank with these specs? (Stan, Ren, ???).

[Stan Clayton]

Bought a Toyota 4age Club motor from a reputable builder (name with-held) with many national wins. Upon tear down we found that the crankshaft's rod journals had been turned down to 0.020 (twenty under). The crank also has been cross drilled (ala Porshe 944 turbo mod) for oiling. Anyone have any problem using a crank with these specs? (Stan, Ren, ???).

What you describe sounds very similar to our bespoke (non-TRD) lightened crank. I think it uses a bespoke rod, as well, and small diameter rod bearings from a Honda Civic to minimize bearing drag. Rennie wails on it to 10-grand-plus with no problems...

Edit: Oops! I just realized that you specified a TRD crank. Let me look at my Loyning-prepared spare tomorrow and I'll get back to you.

[quartzracer]

Stan thanks for the reply. When we looked at the internals we thought GREAT (throw away piece). I don't know what specs are workable for guys like Hasselgren and Jennings, however I thought they would use a crank with these specs as a boat anchor.

[Stan Clayton]

I would not be too quick to toss the piece (unless it's in my direction... ). Arne once told me that the TRD bottom end was bullet proof for club racing, as it was designed for 9000-RPM standing starts in the pro series. I would call whomever built your engine and talk with them about it.

[Brian]

I'm really curious as to why you would consider a 20 thou under crank to be bad practice? You can get a good radius on the corners, and loss of strength in the webs would be low, maybe even none considering the radius on the journals. Cross drilling I've always thought was a great idea. I'm hearing more of people modifying cranks to run smaller journals than that these days. The only concern I would have is wondering why it had to go .020" under. If it was just scuffed journals, that's one thing, a burnt journal from a lost bearing would make me wonder. Always want to learn new things

Cheers, Brian

[Paul LeCain]

In one of our engines I have a -.010 TRD crank that's been in it for four years. It regurlarly sees 10,400 with no problems so far.

[quartzracer]

Brian,

The reason that I thought the crank was no good was the following: I bought a used crank from a pro team that was touted to be "low mileage," the crank was sent to a reputable builder of these motors to install into a short block. The builder called me and told me that the crank had one journal at 0.020 and the rest were 0.010. He told me that he did not want to turn the other journals to 0.020 and stated that the crank was "junk." I believed this and bought a new TRD crank. I 'am interested in your statement that others have been turning their journals even smaller. What would be the theory behind that? I am a dumb blonde when it comes to motors. Thanks for the the insight (everyone).

[Brian]

first off, I'm no expert on high output high rpm engines, I mostly build vintage Ford and BMC stuff. Stan referred to the idea of using smaller journal diameters in his note where he had a engine that uses Honda size bearings which I understand are smaller in diameter. I'm hearing the same thing is or was used in Nascar engines. The idea is less weight in the crank, less weight in the rod, lower friction in the bearing.

To me, the thing about an undersize crank is why was it turned. If one journal is undersize, what happened to it? A scuffed journal from a little dirty oil is one thing, a spun bearing is another! I find it hard to believe that taking 5 thou off the radius of a journal makes a difference in strength per se. But how you do it makes a difference. you need to put the right radius on the corners, you may need to re-heat treat since you have ground through the surface hardening, you may want to shot-peen the corners, you will need to have it straightened after all of that. Still cheaper than a new crank since new cranks have all that done to them anyway.

With some engines where you start with a stock piece rather than a race billet or forging, one of the first steps is grinding the crank to get the throws exactly right and put the proper radius on. Anyway, like I said I'm trying to learn this stuff, not educate, because I'm really not an expert on this stuff.

Brian

[quartzracer]

Brian,

Actually you probably do qualify as an expert. The crank in question had exactly what you describe performed to it. Its hard to read the build sheet, but I can make out shot peening, and hardened with the letters nitr???? after it. Its amazing what you can learn on this forum! Its also funny how tempermental each specific builder is towards anothers work. I don't mean in a disrespectful way however they certainly have far different standards.

Thanks For The Replies,

Quartzracer

[quickmag]

QR:

The "nitr???" you can't make out on the spec sheet probably said "nitrided". This is a surface hardening (10-15 thou deep) process that can be applied to certian types of steel (ie. EN40). This has been around for decades. It was stock in 1969 on my Cooper S.

Brian S
81 F/A Magnum (basket case)
86 F/C Reynard (back marker)

[Brian]

Thinking about this and chatting about similar stuff with a well known engine builder (I build maybe five or six engines a year, my partner is the real engine guy). And he points out the obvious - when a serious, top level engine builder takes 10 or 15 grand or more to build you a race motor, it comes with a real or implied warranty of correctness. It's understandable that they will say that if they don't know why the crank got turned, who did it, etc, that the crank is "suspect". And they won't put suspect parts in a customer engine because they can't "warranty" them. My engines are warrantied till they come off the dyno - I can't be responsible for what the customer does with the install, the tuning that they might do, the conditions that they race it under. But I still stand behind the work that I do and the parts that I put in - I feel it's right that I do so.

So what I'm saying is that a pro engine builder may take a crank that they've known from new, turn it to .020 under for some completely legitimate reason and say it's good - and another builder will say no way because it turned up in a used engine that they don't know from Adam. And you, as a guy who owns a crank, have to decide to take the risk or not, based on all of the parameters discussed so far.

Cheers, brian

[quartzracer]

Brian,

That sounds feasable, the motor with the .020 crank has always been maintained at the same shop. The history of the internals was a known factor. I have also found that some builders are indeed turning the rod journals down for less friction as stated by Stan. I don't know if the gain is worth the sacrafice, but who knows.