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#21
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The Following User Says Thank You to mgarblik For This Useful Post: | ||
#22
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The Following User Says Thank You to PAUL K For This Useful Post: | ||
#23
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I'm hoping the information will be archived here and help other folks in the future. I probably should've posted it in the "street section" as they are the guys most likely to benefit from this information. However, I figured we wouldn't get input from guys that have had success using a factory crank and making relatively "big" power. Most of the folks I work with have some kind of budget and are always curious as to "how much" something costs. The part I have a hard time understanding, is upgrading to a forged crank "just incase". As most of us know there are no guarantees, but to me it seems like an expensive insurance policy for a 550 horsepower build. I also feel since most engine projects have some type of budget, the money could be spent more wisely elsewhere. Something I'm sure you can relate to: many years ago I ported a pair of SBF Ford heads for a guy. I charged him $650 and he wasn't really sure if he should be sending that much money for "porting" in his quest for a quick street/strip Mustang. But he proudly showed me his $300 Billet valve covers when he picked up his heads.... It just didn't make sense to me. I'm not suggesting folks don't have the right to spend their own money how they want. Also with the supply of good 455 blocks and cranks this thread is probably a few years to late. But if you have a nice 455 block and crank most of the time you will be money ahead by using it and with the dough you save a really nice pair of Billet valve covers can be purchased. |
The Following 5 Users Say Thank You to PAUL K For This Useful Post: | ||
#24
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I'm always curious what "caused" the failure. Not long ago, I took in an engine from another shop that did everything but complete engine builds. They gave me a freshly ground .020/.020 455 crank and the journals had no radius whatsoever. Zero, it looked like they deliberately ground the crank to make it a sharp 90°. I'm pretty sure the crank would've failed in short order and most folks not knowing the story would just blame the factory crankshaft as being weak. It's great have choices between factory and 16 month wait Billets at $4k a piece. I recall many years ago, Dave Johnson's White Warrior (RIP) hunting down a 990 crank and bending it almost immediately. Last edited by PAUL K; 01-13-2023 at 12:08 PM. |
The Following User Says Thank You to PAUL K For This Useful Post: | ||
#25
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Cast iron is very strong but somewhat brittle. Brittle material is very susceptible to stress concentrations in corners...big fillets are a huge benefit! Brittle material is very susceptible to impact loads.....aluminum rods add some important cushioning effect. Forged/billet steel is more ductile and therefore more forgiving of stress concentrations, impact loading and random abuse. Eric
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"Everybody has a plan until they get punched in the mouth" noted philosopher Mike Tyson Life begins at the end of your comfort zone. “The mind, once stretched by a new idea, never returns to its original dimensions.” |
The Following 3 Users Say Thank You to Elarson For This Useful Post: | ||
#26
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#27
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Others' experience can help you bound the risk but compare your apple to someone else's, not to their orange. The more detail, the better you can judge.
IMO, once you exceed factory stress levels and usage models (load, rpm, time) you are rolling the dice. I expect Pontiac engineers kept the max stress below the fatigue (endurance) limit of the material, effectively eliminating risk for fatigue failure. They could even have had the luxury of adding a safety factor. But once you push the stress above that endurance limit by raising the HP, modifying the piston/rod weights, or exceeding the max rated rpm, the crank will eventually fail. Like HIS shared, how long it takes depends on cumulative history of time and stress levels (Goodman diagram). So when you share your broken crank experience, the more detail about the application and use history, the better others can compare. |
The Following User Says Thank You to Shiny For This Useful Post: | ||
#28
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Someone may have mentioned this above and I missed it but Pontiac/Olds cranks were way over engineered. FE Ford cranks have 2 3/4" mains.
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#29
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The Following User Says Thank You to PAUL K For This Useful Post: | ||
#30
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"It's great have choices between factory and 16 month wait Billets at $4k a piece. I recall many years ago, Dave Johnson's White Warrior (RIP) hunting down a 990 crank and bending it almost immediately. " Paul K
Many years ago, probably late 1990's, we had the opportunity to buy a 990 crankshaft. It was raced by Hubert Platt? (SP). Arnie Beswick tracked it down for us and we bought it. It magged OK and looked to be in good shape. We put maybe 20 passes on it in the Grocery Getter no issues. During a routine re-fresh I magged it expecting to find nothing. But It had developed multiple cracks radiating from the fillet area inward on several crank throws. We retired it at that point and sold it for a couple hundred bucks as a conversation piece. It was an expensive lesson in using 50 year old race parts. As much as I hate using Chinese parts, having a source for NEW forged crankshafts is a wonderful thing. IMO, the best of both worlds is a Chinese crankshaft raw forging, inspected and finished by a reliable and trustworthy company like Molnar. Other than a billet at 3X the cost, I don't think you can do better than that right now. |
The Following User Says Thank You to mgarblik For This Useful Post: | ||
#31
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I ran a factory 103 N crank in my 740 hp 482 for years and at least 1000 passes. It was done decades ago by Crankshaft Specialist. It's offset ground to 4.250 with 2.200 RJ. When I parked the car in 2011 the engine went on a stand. Last year the same shortblock, with fresh bearings went into my friends bracket car where it's still being raced but in a detuned state. That's one example out of a few, but I've never had any issue with any other cast cranks.
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Jack Ferris RestoRacing LLC www.restoracing.com Sandy, UT --------------------------------------------------- |
The Following User Says Thank You to Jack Ferris For This Useful Post: | ||
#32
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Crankshaft Specialists was an excellent shop and we had a few cranks worked on there with great results. Finding a competent crankshaft grinder who can even get the correct diameters on the journals is nearly impossible now. The 2 shops I used the last 30+ years are closed, and the experts retired. I do not have a crankshaft grinder available nor the skills to operate it. It's one of the few things I have so farm out. In the entire State of OH, there is only 1 reputable source. That is Shaft Tech in Northern, OH. About a 3 hour drive but you do what you have to do. The only other shop I know is really good is Mile High Crankshaft, in Denver. Dave is just fantastic. The work is 110%. But $300.00 shipping round trip from OH. So for basic re-grind for a street engine, awfully expensive. Proper crankshaft grinding by a skilled professional is a lost art. Right now I have a cast crankshaft for a student's 400 Pontiac at a local shop. They tried 3 times to just do a simple re-grind on it. They finally ruined it and it is a throw away. He has crankshaft #2 now. Simply want the crank ground to a specific dimension for proper bearing oil clearance, straight and round. Seems to be beyond their capability. Fingers crossed.
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The Following User Says Thank You to mgarblik For This Useful Post: | ||
#33
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We had a 455 years ago in a dirt track stock car turning 5 to 6000 for 1 season, on a dry track it would hit 6500 at the end of the straight. It thru 3 rods in a race midway into the next season. I watched it run 3 laps like that on a 3/4 mile track before he drove it on the trailer. I thought for sure it was toast. Not sure how he could hold on to the steering wheel with it missing 3 slugs, it had to be vibrating violently. We tore it down and mag’d the crank and it wasn’t broke, so we had it reground and ran in again. It went in 2 more engines, eventually cut down to 3” mains and bbc journals. We eventually decided it had enough and took it out of service.
Steve C has broke 2 cranks. One is Crower billet broke in the fixture like you said Paul. The other was a cut down 455N crank that had the thrust welded. I think the N broke in a couple places and mortally wounded the block. If I recall right it was still running fine and they caught that on a tear down inspection. Jim Hand had a lot of passes and street driving on the one he broke, most of the time it was running 13s to low 12s in his wagon. It was before he was running 11s if I recall correct, if he was in the 11s when it broke it was just starting to run there. It was also in one of his brothers cars for a short time before that with a small shot of NOS. Can’t remember for sure, but seems like it was in a Can Am then? There are threads for the other couple I mentioned, Mchell’s wasn’t that long ago. I will look and see if I can find links, they are in the street section. I thought the most insane failure was the one that sent the dampener, and front of the block into the road ditch with the front of the crank attached yet. I can’t remember who’s engine that was though. With moderate power, forged cranks seem like they will run with cracks for a while. A Billet crank will allow more twisting yet, but have a shorter fatigue life than a forged. Cast cranks with good metallurgy can darn near take the abuse of a forged crank when new. Those examples like the grocery getter and those other big HP engines reinforce that. But comparatively, they probably won’t last as long as a forged because can’t take the twisting like a forged or a Billet. Last edited by Jay S; 01-13-2023 at 02:13 PM. |
The Following User Says Thank You to Jay S For This Useful Post: | ||
#34
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I have a 455 crank reground by CS, in Memphis, done in 1988, everything was dead nuts on when I measured it. the finishes were as close to perfect as you'd ever want them to be. At that time I sent it by Greyhound, and it still was fairly expensive, but worth what I spent when I got the finished product, and everything was correct. I didn't have to swap bearings etc. to get the clearances right, standard .020 rods, and .010 mains fit perfectly. What a shame that they're still not in business.
I still have the engine assembled in my garage, and I'm goin to pull the pan, and check the bottom end before I put it into my next street car. When I built it in 1988 it was a standard bore with low miles, so it still has cast OEM pistons, and stock rods in it. Basically a stock bottom end with that really nice crank in it, and ported 5C heads, mild camshaft. |
The Following User Says Thank You to Sirrotica For This Useful Post: | ||
#35
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Hmmmm, the PMD 455 N crank may fail MAG due to cracks found in the rod journal armpit, yet I only seen broken cranks at the #2 Main. Usually due to a loose Damper.
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#36
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I have some definitive disagreements with some of what’s been posted and or alluded to hear in this string.
1) a Billet has a long way to go before it’s as strong and as durable as a non twisted forging, since a billet does not have grain running the optimal way through out its make up . 2) besides the crank being far less likely to crack when a nice radius is ground from a journal to the cheek, the proper phasing of the weights on the crank can reduce loads by thousands of pounds which is critical to the life of 2 and 4 main . |
#37
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“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
#38
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If you ever do break a crank. Don’t reuse the harmonic balancer.
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#39
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"Steve C has broke 2 cranks. One is Crower billet broke in the fixture like you said Paul. The other was a cut down 455N crank that had the thrust welded. I think the N broke in a couple places and mortally wounded the block. If I recall right it was still running fine and they caught that on a tear down inspection."
Jay is correct. The first was a 455 crank modified for my original '70 400 block. It went into service in Feb 1998 (626 hp at 6400 rpm). The engine was running at the time we found the damaged crank and damaged block. The second was a custom Crower 4.250" billet crank made for my current 505. Its first dyno session was in March of 2007. In April of 2018 we had to tear down the engine for an bearing issue and found the crank bent. When the machine shop tried to straighten it the crank broke. It was replaced with a SCAT 4.250" forged crank that I bought from Paul. .
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE Last edited by Steve C.; 01-13-2023 at 06:18 PM. |
The Following User Says Thank You to Steve C. For This Useful Post: | ||
#40
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When racing the Boss Bird Nitro engine, we ran Crower 4.25" stroke Billets. When trying to sort out the main bearing issues and oiling system in general, we bent the heck out of those poor cranks, especially the nose. We had bends at times in various locations of nearly .020"! We had those cranks straightened at least 3-4 times each, and right back in the engine for some more abuse. Never a crack. We simply couldn't afford to replace them. We were bending them every time out for a couple years. When we finally got the oiling system sorted out, no more bending. I guess I am surprised to hear of a billet breaking like that. Not questioning it happened, just surprised. The billet cranks seem to have a memory as well. Once bent, they seemed to bend easier the next time, until they were happy in the engine. In our case with the nitro engine that meant .0065" main clearance and 140-160 PSI oil pressure through the entire run. 43 GPM oil pump.
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