Stroker crank questions
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Drifting
Joined: Nov 2004
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2020 C3 of the Year Finalist - Modified
just for your info:
I have a lightweight cast crank from scat.....ext balanced....I bought me a new ext balanced balancer and flexplate......should've been ok right?.....brought it to the machine shop anyways to have the bottom end balanced cause of the clearancing I did to the 5.7" rods.....the guy put it on the machine and he said his machine was shaking pretty bad at around 1500 rpms....he said it was one of the worst he's seen, so he went to drilling/balancing....built the motor and the car runs freakin awesome!
take that as you want it, it's just my experience.....I'd have a trusting shop check the bottom end no matter what I buy.....I just don't trust them....I miked all the journals on the crank, my block, rods, etc...
I have a lightweight cast crank from scat.....ext balanced....I bought me a new ext balanced balancer and flexplate......should've been ok right?.....brought it to the machine shop anyways to have the bottom end balanced cause of the clearancing I did to the 5.7" rods.....the guy put it on the machine and he said his machine was shaking pretty bad at around 1500 rpms....he said it was one of the worst he's seen, so he went to drilling/balancing....built the motor and the car runs freakin awesome!
take that as you want it, it's just my experience.....I'd have a trusting shop check the bottom end no matter what I buy.....I just don't trust them....I miked all the journals on the crank, my block, rods, etc...
Racer
Joined: Jan 2006
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From: Orange massachusettes
Lars thanks for jumping in! With your experience, there is No doubt that you know what your talking about. Many poeple like to hear your take on things, myself included. At what RPM do you step up to forged PISTONS and forged CRANK? Again, I apologize to a Oldguard 7 for stepping on his thread. 
If for whatever reason there are no responses to this question, I will start new thread, and stop highjacking Oldguards. As 63Mako has posted, even an L82 has a forged rotating assembly. Many other high performance engines from the 60's and early 70's, also had forged components and had redlines AT OR LOWER than 6500 rpm. With todays modern head designs and newer cam profiles, its not that hard to match or exceed many of the old muscle car engines HP/rpm levels. If GM and (and other manufacturers) engineers saw a need to put the more expensive/stronger components in the high performance engines, as we duplicate or exceed there outputs, shouldn't we do the same? No disrespect intended to you in these questions. I will be the FIRST to admit that you have a FAR GREATER amount of experience than I do. Just looking for an honest answer/personal opinion on the subject. Thanks in advance.
If for whatever reason there are no responses to this question, I will start new thread, and stop highjacking Oldguards. As 63Mako has posted, even an L82 has a forged rotating assembly. Many other high performance engines from the 60's and early 70's, also had forged components and had redlines AT OR LOWER than 6500 rpm. With todays modern head designs and newer cam profiles, its not that hard to match or exceed many of the old muscle car engines HP/rpm levels. If GM and (and other manufacturers) engineers saw a need to put the more expensive/stronger components in the high performance engines, as we duplicate or exceed there outputs, shouldn't we do the same? No disrespect intended to you in these questions. I will be the FIRST to admit that you have a FAR GREATER amount of experience than I do. Just looking for an honest answer/personal opinion on the subject. Thanks in advance.
Last edited by 72 LT1; Mar 18, 2007 at 03:21 PM.
Race Director
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From: Millington Illinois
St. Jude Donor '08-'09
Check these engine specs.http://www.corvetteforum.net/c3/vette73/compair.htm. General motors decided to go to a forged bottom end and 4 bolt mains @ 250 net HP@ 5200 rpm, 285 ft lbs of torque@ 4000 rpm and a 5600 RPM redline. A stroker crank puts more stress on the internals. For the price difference and the stroker cranks being chinese castings, I don't see any logic in going with less that the GM engineers would have given a similar or upgraded build. I know there are a lot that have gone with cast cranks and pistons and 2 bolt mains at double these power numbers and had them live but not me. Figure Zora might have had a reason for doing this and don't want to find out the hard way what it is. BTW The 73 is the highest HP L82 ever made. They went down in power from that point to a low of 205 HP in 1975 and GM still stayed with the forged bottom end and 4 bolt mains. If the cast cranks, pistons and 2 bolt mains would have been sufficiant they would have used them. Just my .02.
Last edited by 63mako; Mar 18, 2007 at 11:06 AM. Reason: added information
NCM Grand Opening Veteran
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From: South of giving a damn
St. Jude Donor '11, '17
Most stroker cranks are internally balanced these days. If given choice, forget about external balancing. Also, more good news. The newer stroker cranks require less if any block clearancing. Cast is fine for the street up to 6500 RPM and even more. But in a stroker, I'd definetely machine for four bolt mains and use studs. Fairly cheap insurance.
Good luck!
Good luck!
This is my 396 block with the latest Eagle forged kit. This was a ZZ4 block that had the pan rails clearanced by GM, but you can clearly see the extra clearance needed for the rods. It is true that the Eagle stroker rods will clear a std base circle cam. This engine now contains main ARP studs, instead of the bolts. This is also a good thing.
http://forums.corvetteforum.com/atta...1&d=1174229661
clear11.gifhttp://forums.corvetteforum.com/attachment.php?attachmentid=47605820&stc =1&d=1174229661
clear12.gifhttp://forums.corvetteforum.com/attachment.php?attachmentid=47605821&stc =1&d=1174229661
clear13.gifhttp://forums.corvetteforum.com/attachment.php?attachmentid=47605822&stc =1&d=1174229661
clear14.gif
Last edited by ratflinger; Dec 21, 2010 at 11:54 PM.
Racer
Joined: Jan 2006
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From: Orange massachusettes
If the cast cranks, pistons and 2 bolt mains would have been sufficiant they would have used them. Just my .02.
Pretty much what I'm thinking. I'm NOT a professional engine builder, just a mechanic trying finish my winter projects, so I can drive the vette in the spring. Right now I have a lot of faith in Zora Duntov's decisions, althou, I learn something new on this forum all the time. I hope Lars and/or other experienced engine builders will chime in on this subject.
Last edited by 72 LT1; Mar 18, 2007 at 05:06 PM.
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
You don't need a forged bottom end for mild small block buildup used on the street, get one of the Eagle or Scat cast kits and save yourself some money 
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
I don't see any logic in going with less that the GM engineers would have given a similar or upgraded build. I know there are a lot that have gone with cast cranks and pistons and 2 bolt mains at double these power numbers and had them live but not me. Figure Zora might have had a reason for doing this and don't want to find out the hard way what it is.
Last edited by 63mako; Mar 18, 2007 at 02:08 PM.
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Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
I'm looking for a stroker crank for my 383 build this spring. I have narrowed it down to two brands Eagle or Scat. My question is do these cranks have the 3.75 stroke and 350 main journels? Are they internally balanced? If not does anyone make internally balanaced stroker cranks?
Racer
Joined: Jan 2006
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From: Orange massachusettes
MotorHead, if you are using or are going to use a forged crank, how high an RPM are you looking to turn w/it? Also, are you going to use Cast/ Hyper, or Forged pistons?
Last edited by 72 LT1; Mar 18, 2007 at 05:20 PM.
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,337
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From: Norfolk VA
Lars thanks for jumping in! With your experience, there is No doubt that you know what your talking about. Many poeple like to hear your take on things, myself included. At what RPM do you step up to forged PISTONS and forged CRANK? Again, I apologize to a Oldguard 7 for stepping on his thread. If for whatever reason there are no responses to this question, I will start new thread, and stop highjacking Oldguards. As 63Mako has posted, even an L82 has a forged rotating assembly. Many other high performance engines from the 60's and early 70's, also had forged components and had redlines AT OR LOWER than 6500 rpm. With todays modern head designs and newer cam profiles, its not that hard to match or exceed many of the old muscle car engines HP/rpm levels. If GM and (and other manufacturers) engineers saw a need to put the more expensive/stronger components in the high performance engines, as we duplicate or exceed there outputs, shouldn't we do the same? No disrespect intended to you in these questions. I will be the FIRST to admit that you have a FAR GREATER amount of experience than I do. Just looking for an honest answer/personal opinion on the subject. Thanks in advance.
If for whatever reason there are no responses to this question, I will start new thread, and stop highjacking Oldguards. As 63Mako has posted, even an L82 has a forged rotating assembly. Many other high performance engines from the 60's and early 70's, also had forged components and had redlines AT OR LOWER than 6500 rpm. With todays modern head designs and newer cam profiles, its not that hard to match or exceed many of the old muscle car engines HP/rpm levels. If GM and (and other manufacturers) engineers saw a need to put the more expensive/stronger components in the high performance engines, as we duplicate or exceed there outputs, shouldn't we do the same? No disrespect intended to you in these questions. I will be the FIRST to admit that you have a FAR GREATER amount of experience than I do. Just looking for an honest answer/personal opinion on the subject. Thanks in advance.I do not plan to run this engine past 6500 any way.
Thread Starter
Melting Slicks
Joined: Apr 2002
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From: Norfolk VA
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Last edited by 63mako; Mar 18, 2007 at 09:38 PM.
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
If you are building a high RPM boat motor or circle track or whatever track racer that sees high sustained RPM's then you need a forged bottom end. Most of us don't need it.
MY new motor ( 427ci ) is going all forged including pistons, this motor will be built for 600HP/600TQ + and will see 7000 RPM
Burning Brakes
Joined: Sep 2005
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From: Iowa
Just as a point; our hobby stock engines turn 7300rpm all day long with the original gm cast crank that is only balanced. From my experience cranks die from tq, rods from rpm. 500-600 ft/lbs is where it starts to become a real decision on changing over. The best example I have for you is a 406ci engine that we ran in a camero that we drag raced. It saw 6700rpm all day long with a cast crank and rods while hitting in the high 11's and did not expire on us over the course of two years. Is that the limit that we will run in that app, sure, but it illustrates the fact that a large portion of the hot rod community run parts that their engine and environment does not warrant. That's not a problem and it sure does reduce failures, but it should not be mistaken is what is required. If we were building the engine and it was clear that it was not going to be a starting platform for a semi-serious effort we would run a cast crank. Now if you have plans....that is a different story entirely!
Racer
Joined: Jan 2006
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From: Orange massachusettes
From my experience cranks die from tq, rods from rpm. 500-600 ft/lbs is where it starts to become a real decision on changing over
Racer
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From: Orange massachusettes
Here is my take on it and also the take of a very experienced engine builder who has built 1000+ race engines. For street / strip applications a good cast crank will work up to the 550HP. The main reason is this, the RPM's that the motor will see are very low
MY new motor ( 427ci ) is going all forged including pistons, this motor will be built for 600HP/600TQ + and will see 7000 RPM