Cast Cranks(again) Wednesday, 31-Jan-01 17:13:03 126.96.36.199 writes: I have an offer for a Scat 69mm C/W crank,i haven't seen it but it is quite cheap, so i suspect it is one of the infamous cast cranks. Is there any way of knowing for sure without seeing it,any special markings etc.. Would it be OK in a mild 1776,w-110, std.heads, double 36idf's. TIA, Rune Rune
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How Cheap?-think about this ......more..... ( James2) (31-Jan-01 17:51:40) Cranks, Solid Info without Flames, A cast Crank has a very thin "Parting line where it came out of the mold, A Forged crank has a 1/4 inch wide parting line !! -->> ( Old Fart) (01-Feb-01 00:10:22) The easiest way to tell the differance between is with a box end wrench. Dont laugh.(hehe) take the wrench and tap lightly once on a unimportant part (ex counter weight) and the sound you hear will tell you which is what. The cast will have a dull sound. The forged will give off a pleasing ring. Cheapest way I know how to tell the diff. (n/t) ( Gary Cooper) (31-Jan-01 19:29:25) the only way to be 100% sure is to have it maged! any machine shop with a mag machine can do it. shouldnt be over $20. if the guy your buying it from says its ok have him pay for the mag. DONT GET BURNED!! (n/t) (bergboy) (31-Jan-01 19:45:46) Just touch it lightly with a grinder (Bruce Tweddle) (31-Jan-01 22:00:42) Bruce, you make an extremely valid point, but most of the people here are going to subject the engine to far more stress than the engine was originally designed for. For that reason only, I give the advice that a cast crank is not the recommended part to use. Otherwise, they do exactly what they were intended to do. (n/t) (bugly) (31-Jan-01 23:38:55) I absolutely concer with Bruce. I run a cast crank in my Notch and have zero worries about its life span. I limit my car to 5k in rpm due to the heads anyway. And, I run a slightly less stickly tire incase I do spin the wheels. Since the car won't ever see a hard launch... (n/t) (Brian) (01-Feb-01 11:23:38) I first ran a 78 cast crank, now an 82. Rev limiter is set to 6200, and is hit many times every time the car is driven. It comes out for the quarter, shifting is at 7000, and at the lights its at around 7500 in 3rd. (Bruce Tweddle) (01-Feb-01 13:13:50) you guys are totally missing the point (dan) (01-Feb-01 16:15:40) fill us in on the 4 types of casting processes, Dan (Bruce Tweddle) (02-Feb-01 00:31:50) HEY Thanks a lot for all this very valuable info, summing all your answers up (n/t) (01-Feb-01 16:35:05) HEY Thanks a lot for all this very valuable info, summing all your answers up i think i'm going to get my stock crank 8-dowelled and balanced and let my wife drive it like that! (n/t) (Rune) (01-Feb-01 16:37:23)
you can get a good forged crank for under 150.
So if this crank was $30, you would save 120 bucks. Now I'm not saying 120 bucks is not a lot of money, because it is, to me anyways.
Now lets say you are getting a deal on everything, and the motor is costing 1200 to build. what is 120 bucks? 10% of 1200.
So the real qusetion is, would you spend 10% more for a crank that is twice as strong?
Chances are you could run it and have no problems, 100s have. But think about the 1 out of 100 that did bend/break a cast crank. 120 bucks is cheap insurance. JMHO
And yes a cast crank rings with a thud and a forged unit rings like a chime ! If you have a used forged crank and it don't ring with a nice chime, it's CRACKED !
Cast iron gives off orange sparks, and steel gives off yellow sparks. Have a piece of steel ready to compare with. If you only touch it for a fraction of a second you won't remove enough material to affect its balance.
IMO, cast cranks get a bad name from people who misuse them. They run them with slicks and they break. If you're just after a mild daily driver that won't go down the track, then put it in. In that application it would probably outlive most other engine parts.
I say rpms don't hurt a cast crank, its impact loads like wheel hop that breaks them. CV cages too.
there are 4 different methods for making cast cranks, and they all vary in strength. i bet none of you have a clue which procedure was used to make your cast crank, so you really don't know what the strength limits are... therefore, those overall generalizations and comparisons regarding cast cranks are highly suspect... forging is a much more uniform process, as compared to casting.
what everyone has failed to mention here is that cast cranks in general will always flex more than forged cranks. that flexing will pound out the center main bearing saddle much quicker than if a forged crank is used... yes your cast crank may not have broken, but you have needlessly compromised your case life by not bothering to use cheap and widely available forged cranks.
Most of the nay-sayers I have met have never used a cast crank, and say they will fall apart in a few hundred miles. This is simply not true. Cast cranks in general aren't bad. Other car makers install millions of cast cranks.
If cast iron does flex more than steel, then will a counterweighted cast crank flex more than an uncounterweighted steel crank?
Cast stroker cranks are a cheap alternative to forged. I found my last 82mm crank at a swap meet for $140 with matched flywheel and clearanced rods. Forged would probably run you $500 and up with FW and rods.
Be carefull when you say "reduced case life". Some may read that as meaning will only last 10k miles or some other rediculously low figure. Give us your estimate on how much % less.
I junked my last case at 180,000 miles on it.
I may be hypocritical, cause I'm going to a steel crank now--got slicks!
junk internet engines Friday, 02-Feb-01 07:35:50 188.8.131.52 writes: >>>>fill us in on the 4 types of casting processes, Dan<<<< forging is the process of forming metal parts by the use of extreme heat and pressure. this procedure develops a grain structure in the metal, which makes it stronger in the direction that it has been stretched. Forging is done with a tool and die procedure. to put it very simply, casting is done by pouring hot metal into a mold, and with automotive cranks we are talking about a malleable cast iron or a ductile cast iron... the former uses gray iron, which comes from pig iron, and it's cheap... ductile(nodular) cast iron cranks are definitely stronger, but that is also affected by the heat treating used during the manufacturing process... ductile metallurgy and heat treating costs more. it doesn't take a rocket scientist to see which crank you should be basing your engine on. be careful, bruce, about coming out on a performance forum and spouting off about how good cast cranks are: "...my cast crank broke in less than one full season despite being always run well below an installed 6400 rev limiter, which echoes the experiences of others that have catastrophically lost motors at well below 6400. BUT, until a rule change occurs that would allow us the option of using a reliable steel crankshaft, we must figure out how to make cast iron crankshafts live." http://www.asedan.com/1996.htm dan http://www.oceanstreetvideo.com dan
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Cast - Forged, parts to get & parts to Forget !! -->>>> ( Old Fart) (02-Feb-01 11:21:19) I can see why you hate cast units...real life! My real life experience has been nothing but success with them. Ihave a 76mm cast unit in my current motor, It was about 13k on it know, and the last cast crank I had outlasted the 3 cars the engine was in. Granted $$$ had everything to do with my purchase decision, but it is one I have had no regrets about. No flame here, just the other side. I have wondered though, how many folks here have used a cast crank and had it fail or how many have used one and had no problems. That survey would give use some usable info! (n/t) (Brian) (02-Feb-01 12:08:16) lotta good feedback in this thread... cast cranks flex so much that even in a stock v-8 application the iron block sometimes needs align-boring, just like a vw case. (n/t) (dan) (02-Feb-01 14:18:55) I ran a cast crank in a engine it started to knock took it apart crank was in two pieces and it still ran before I took it apart this was 15 years ago. (n/t) (don) (02-Feb-01 12:14:02) Don, same thng happened to me in my bus years ago...lost oil pressure, and had some noise. Drove it home (about 12 miles!) and tore it down. Crank in 2 pieces! In the cranks defense though..I drove that bus HARD all the time. (n/t) (Dave Buckholts) (02-Feb-01 12:32:46) Don't Knock Cast Cranks (Tony) (02-Feb-01 13:59:49) Re: Don't Knock Cast Cranks - "OK" Let me BACK UP & EXPLAIN MORE-->> (Old Fart) (02-Feb-01 19:46:12) Re: Dan ,I`m not advocating cast cranks but rev limiters can cause cranks to break ...more>> ( Mark H) (03-Feb-01 00:48:14) if he broke the crank in the sand, all bets are off :-0 (dan) (03-Feb-01 01:47:33) That was an excelent article, Dan (Bruce Tweddle) (03-Feb-01 00:50:07) Re:hey bruce,you going to put the slicks to good use this year ? (hans k.) (03-Feb-01 01:54:05) Its not the phone, I'm just not at home---spend too much time here:-) (n/t) (Bruce Tweddle) (03-Feb-01 02:32:24) Re:sorry- ph.#>>>>im up (hans k.) (03-Feb-01 02:50:12)
The reason cast cranks work in some engines is due to the fact that the case/block is rigid, like the american V8s with the soft VW case that case flexes, it's soft and only "Right on" when new, a forged crank in a VW engine is more rigid than the case and can bend with high RPMS ( Non counterweighted) and that poinds out the center main web of the soft case, Counterweights or not if you spin up a cast crank in a VW engine is soon breaks, a casting can't take the flex, plain & simple a casting in this engine is crap and you are asking for failure, have had two Cast cranks fail in VW Bus engines in a year, a bus engine turns 4000 RPMs at 62 Mph and this is a stock application and not Hot rodded at all. Please no flames as I'am only relaying honest info for you to make the right decision !
From my experience, I have over 80,000 miles on a 74mm "cast" crank.If you build it right for the use intended...they will work If you use it as a shortcut(save a buck)for a racing application it will cost you more in the long run. The compression was set at 9 to 1 and a stock flywheel. If you want to go FAst, the old saying right...You need to spend the money!!!
In the old days those 74 & 76MM cranks were a much better quality, I agree, as they lasted, what I did not want to state that most failures today, including mine have been with Scat Cranks, one was so poorly made that it hit the center web and required case trimming, I never like to blast anyones product but you guys are to important to the VW Brotherhood to not be told the TRUTH, so in closing I will just say that those Scat Cast Cranks, like their Lifters just plain suck !
I know that high compression and or pinging and high rpms can take their toll on crankshafts ,cast or forged. But I never thought about how a rev limiter could break a crank untill it happened to me and someone suggested that the limiter had something to do with it. I put together a 2180 for a guy that had previously been assembled and driven on the street. It was going into a sand rail and it had 12 to 1 compression and reved to about 7000. I had the crank magnafluxed before assembly and checked everything else as well. The motor lasted two outtings before it broke the crank! I`ve never had anyone break a crank and I`ve never broke one myself. I thought how could this happen. I knew the guy drove like a lunatic and I know he had been "running" the motor on the limiter. He would hit it every gear and hold it there sometimes.
I thought about what I`d been told about limiters breaking cranks and it did make sence.
The crank is being violently loaded and unloaded when its on the limiter. I think this could definately break the crank. I use limiters myself for safty purposes but I know the trend in drag racing is to use a two step for lunching but I don`t think its such a good idea anymore. I launch my car the old fashoned way :-)
Anyway if you were using the limiter alot then maybe that contributed to the early destruction of your crank.
sand guys work hard at getting air, and that is the ultimate load/unload situation... usually it's the trans that goes.
i could see how some rev limiters would be a problem, but not all of 'em work alike, right? did his cut all the spark, every other spark, or was it a computer f.i. rev limiter that works with fuel? some rev limiters are easier on parts than others, but driving on the limiter is asking for trouble!!
Apples and oranges
I do NOT recommend cast cranks for racing purposes. Rune's original question was about a 1776, with 36 IDFs, W110, and stock valve DP heads for his wife to drive. An engine like this will have a natural rev limit of 5000 rpm. This engine might make 75-80 hp, and it would be fine with a cast crank. IMO, the only purpose to use a cast crank is the money. If you can't afford a forged, then go with the cast. VW is building 3500 Beetles each month right now with cast iron cranks. If they were as delicate as many say, they would be swamped with warranty claims. They're not. When I got my first cast crank, it was Darren K. that said it would be fine, just don't put slicks on it. I have stuck with this advice and had good success, but I now have slicks, so I'm stepping up to a forged crank.
We've seen Tom Leib and Rick Tomlinson on this forum, what do they have to say in the matter.
No flames, just a discussion.