250GT Connecting Rod

[John Vardanian]

If anyone can help, I need a used 250GT connecting rod. The cap on one of my rods has crack. Thanks in advance.

john

[zac]

John,

I have several sets sitting around but may I ask why you are re-using the rods instead of buying a new set? If budget is the issue I completely understand but I would suggest you thoroughly check the old rods and at a bare minimum replace the rod bolts and nuts. Not to get on a soap box but saving money on the Ferrari motor can come back to haunt you in the future, a con rod failure will potentially destroy the block so he $1500 bucks saved on the new set of rods could end up costing 30-50k in a replacement block not to mention the down time of doing the motor again. Reconditioned rods on a cast iron Ford or Chevy motor no problem but I would be extra cautious on a Ferrari or other irreplaceable motor, so if your machine shop has magnafluxed the rods and all checks out than your probably O.K. but I was just putting my opinion out there.

If you want I will trade you a used rod for your cracked one, I have been saving the old ones I have for years to someday make some office furniture or something cool out of them.

Zac

[John Vardanian]

Hi Zac, thanks. I will send you a PM.

The reason I am using the old rods is because they were made at Ferrari. That's it.

john

[Hein]

Hello!

I would need two rods for my engine #1897GT too. They are horizontaly cut and marked 504 gramms. A friend of mine needs one with 508gramms. I would like to have original ones in my car.

Regards

Hein

[zac]

John, e-mail sent

Hein, rods I have in front of me are from 1891GT so 3 cars away from yours and more than likely the motors were built right next to each other at the factory, what is your internal number? Like the deal with John, I am happy to trade old part for old part or if you are missing two rods I am sure we could work something out.

Zac

[tyang]

A question to those with engineering degrees. With forged steel (which am I'm assuming what a Ferrari connecting rod is made of), if it checks out with magnafluxing (sp?) and is shot peened, should it not perform in a stock application? Does age affect the performance life of a connecting rod?

I asked Francois his opinion on reusing connecting rods, and he has only seen one rod failure that was directly associated with the rod, and the conditions were suspect. Other rods have failed due to other other failures in pistons and dropped valves. His feeling is if the rod is properly checked, treated, and balanced, it should be fine in a street engine. If he was building a race engine, then by all means, new everything. My initial question is whether his experience can change from the age of the components. As these parts reach 50+ years old, can this factor into the mix?

Cornelis is always inserting pictures to threads, so here's one for this thread:

connectingrod3.jpg (143.73 KiB) Viewed 10280 times

Both of these are from Ferraris. Any guesses? (hint: note their factory polished surfaces)

[zac]

Like I said Tom the old rods can certainly be re-used but why would you if you don't have to?? Metallurgicaly speaking all parts half a life expectancy that can be calculated under normal operating conditions but a used ferrari part that is 50 years old with potentially unlimited stories how can you possibly know everything that has happened over the course of the engines life up till now. How many times has the car been over heated??? was it run low on oil or any other number of variables that can't be accounted for. l think after thousands of heat cycles and the forces put on the rod from the piston trying to tear it apart every time the engine cycles. Certainly at the very least the rod is more brittle after 50 years of life and unless you were to perform destructive testing on hundreds of old rods and compare the internal crystalline structure to the original metal than how can any one say with 100% certainty that it will not fail. Bottom line is I am 99% sure a new Carrilo H-Beam rod is going to perform for the next 25-50 years of engine use and I would not be as confident that the already 50 year old part would do the same.


John, Hein here is the old set of 250 rods for 1891GT. If I remember correctly one is bent but I would have to check them to remember which one. The car sat in a swamp for who knows how long a couple pistons needed a little extra assistance to come out of the liner

Zac

[Hein]

Hello!

My internal number is 354F. My engine #1897 is a collection of part which I got over the last years via Ebay, Ferrarichat, some of my customers ,parts markets and some other parts dealers around the world. I was very lucky to get a very good engine block and matching timing chain cover last year here in Germany from somebody who had it for years. The rods I got from Belgium with some other parts. I have 10 good rods and 1 broken one. See the photos. Beside that I am looking for 1 cylinderhead with 16 studs for the cam cover. I have two very good( 84mm and 83,8mm ) later heads with 14 studs from a later car.For #1897 there should be the early heads. The engine is for my GTE 3905GT, but I have an early 330GT engine which is completly restored and ready to mount. ( Maybe there will be one day a PF Coupe resto project without engine fo sale.)

Thanks

Hein

[tyang]

Like I said Tom the old rods can certainly be re-used but why would you if you don't have to?? Metallurgicaly speaking all parts half a life expectancy that can be calculated under normal operating conditions but a used ferrari part that is 50 years old with potentially unlimited stories how can you possibly know everything that has happened over the course of the engines life up till now. How many times has the car been over heated??? was it run low on oil or any other number of variables that can't be accounted for. l think after thousands of heat cycles and the forces put on the rod from the piston trying to tear it apart every time the engine cycles. Certainly at the very least the rod is more brittle after 50 years of life and unless you were to perform destructive testing on hundreds of old rods and compare the internal crystalline structure to the original metal than how can any one say with 100% certainty that it will not fail. Bottom line is I am 99% sure a new Carrilo H-Beam rod is going to perform for the next 25-50 years of engine use and I would not be as confident that the already 50 year old part would do the same.


John, Hein here is the old set of 250 rods for 1891GT. If I remember correctly one is bent but I would have to check them to remember which one. The car sat in a swamp for who knows how long a couple pistons needed a little extra assistance to come out of the liner

Zac

Hi Zac,

All really good points and things I would pose to the customer when making decisions. My discussion with Francois brought up the same points about age. His experience is with these engines over the last 50 years, and is worth considering, but as these engines go into 2nd and third rebuilds, other factors come into play.

Thanks for your thoughts.

Tom

O.K. for the one or two people in the world who care, the connecting rod on the right is for a 250LM, and the one on the left is from a four cylinder 5 liter Testarossa engine. Yes, a five liter four cylinder monster, same displacement as the Admiral's Mondial. (actually I was wrong, 2 liter displacement)

[Admiral Goodwrench]

Dear Tom,

Not to start with a disagreement but the Testa Rossa (two words) (TR 500) tipo 131C motor was a two liter motor and that rod certainly looks like mine.

See attached.

Best regards,

Robert

[tyang]

I stand corrected. 2 liter, but still a monster connecting rod compared to the V-12s!

Thanks for keeping me honest, Admiral!

Tom

[Admiral Goodwrench]

Dear Tom,

The really monster comparison in my mind is the dramatic difference in pistons. The diameter of my pistons shown below is over 3.5 inches and for a really big piston check out the size of the ones in the 860 Monzas at 4 inches.

Best regards,

Robert

[kare]

Fatigue does not generally occur in steel under 18MPa or 180 kg/cm2 or 2600 lbs /sq.inch (if I calculate correctly), so ways to damage a rod in normal engine use are very limited. So check them for cracks and don't keep them in your attic for 10'000'000 years, or the heat tratment will wear off!

Best wishes, Kare

[John Vardanian]

Are you serious, Kare, the heat treatment will wear off? Is this a premature April Fools' post?

john

[kare]

When studying metallurgy I think my material science professor said that thermodynamic calculations show many heat treted phases in steel really to be meta-stabile with a half life of a few million years. So yes, maybe we should replace the conrods every 10 million years or so. In real life this means that unless a macroscopic defect (a crack) can be detected by using a NDT-method (non-destructive testing), a 50 year old conrod is probably as good as it ever was.

New conrods can also fail, so chancing is not really eliminating the risk, it is replacing it with a smaller or greater one depending on the quality of the rods in question.

One should also known that fracturing is a three stage process. 1) formation of a starting point for a crack 2) crack propagation 3) separation (brittle). Stage 1 cannot be detected (unless there is a clear notch in the contour), but existing starting points can be deleted by polishing. Stage 2 can be detected by applying penetrating fluid. Time window for discovering a crack is usually much longer than one would think; easily years and years. Bridges and aeroplanes serve us with detected (and monitored) cracks. Stage 3 occurs in a fraction of a second; once the fracture reaches the critical size, it runs over the structure at the speed of sound. Critical size for a crack in MD80 wing structure is 1,5", if I recall right. The monitored cracks must be repaired before they reach 1". I choose not to think about that when flying.

Summasummaarum: tested rods are very unlikely to fail, but many engine builders choose to replace them anyway. They don't get their mark-up by reusing old parts.