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451 crank balancing #3261109 09/30/24 11:28 PM 09/30/24 11:28 PM
Joined: Jan 2013 Posts: 75 norcal J JLaSalle OP member
JLaSalle OP member J Joined: Jan 2013 Posts: 75 norcal	Do these counterweight holes look correct for a 451 with 7.25" diameter counterweghts?I know the rotating assembly is light but didnt expect this much swiss cheese with the counterweghts turned down.I could be wrong lol.Mahle 1.32" pistons,6.76 molnar h beams,.990,2.20. 1967 Coronet R/T 9.83 134mph. 470 cid st.6 heads 10x pro et track champion

Re: 451 crank balancing [Re: JLaSalle] #3261111 09/30/24 11:31 PM 09/30/24 11:31 PM
Joined: Jan 2013 Posts: 75 norcal J JLaSalle OP member
JLaSalle OP member J Joined: Jan 2013 Posts: 75 norcal	Front 1967 Coronet R/T 9.83 134mph. 470 cid st.6 heads 10x pro et track champion

Re: 451 crank balancing [Re: JLaSalle] #3261148 10/01/24 07:56 AM 10/01/24 07:56 AM
Joined: Jan 2003 Posts: 75,353 A gulag near you. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,353 A gulag near you.	The only way to be sure is to have it checked by a competent engine builder , if you bought this stuff second hand assume NOTHING . Mainstream Media is the new Pravda

Re: 451 crank balancing [Re: JLaSalle] #3261183 10/01/24 09:57 AM 10/01/24 09:57 AM
Joined: Jan 2003 Posts: 31,303 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 31,303 Oregon	It all depends on what crank it is. We used to have to do stuff like that 20 or 30 years ago but these days it is very rare. Almost all of the stroker cranks made these days are designed for modern rotating assemblies. That is either an old crank, or a crank that wasn't designed for a stroker engine. It will probably still work fine in a street engine, just looks ugly but nobody will know once you put the oil pan on.

Re: 451 crank balancing [Re: AndyF] #3261193 10/01/24 10:30 AM 10/01/24 10:30 AM
Joined: Jan 2013 Posts: 75 norcal J JLaSalle OP member
JLaSalle OP member J Joined: Jan 2013 Posts: 75 norcal	Andy this a new Ohio Crankshaft. 1967 Coronet R/T 9.83 134mph. 470 cid st.6 heads 10x pro et track champion

Re: 451 crank balancing [Re: JLaSalle] #3261227 10/01/24 12:15 PM 10/01/24 12:15 PM
Joined: Jan 2013 Posts: 75 norcal J JLaSalle OP member
JLaSalle OP member J Joined: Jan 2013 Posts: 75 norcal	A little backstory here...I bought all the rotating assembly parts new and gave them and the block to my machinist to bore/hone and have balanced.His longtime trusted balance shop is no longer doing that,so he went to a different place for balancing.Now there's 2 things about the balancing on the crank that have me asking questions.First was starting to use a bit wider than the counterweight in the 2nd photo...oops.And through my research it seems that a crank for a 451 with counterweights cut down to 7.25" shouldn't need a lot of drilling. My machinist is a decent drive from me and doesn't answer phone calls and the shop that balanced is even farther.Just wanted to get some more info here before I made the trip down and asked about the work. 1967 Coronet R/T 9.83 134mph. 470 cid st.6 heads 10x pro et track champion

Re: 451 crank balancing [Re: JLaSalle] #3261264 10/01/24 02:56 PM 10/01/24 02:56 PM
Joined: Jan 2003 Posts: 31,303 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 31,303 Oregon	I don't think we've ever used a crank from Ohio Crank so I can't tell you if that is a bad job or a normal job. We typically use Molnar cranks and they only require a small amount of touchup to build a 451 or 470 type of engine. I think 440 Source cranks are rough balanced at 2400 or 2500 grams these days and most modern rotating assemblies balance around 2400 grams. If you have the part number for the crank you can call Ohio Crank and see what the rough balance numbers are on the crank. Then you should be able to see from the machine shop info what the bobweight of your assembly was. If the crank is built correctly it usually only takes a small amount of metal removal to balance. Here is the rotating assembly from the last 470 I built. It was a Molnar rotating assembly and I don't recall the balance job taking much time.

Re: 451 crank balancing [Re: AndyF] #3261292 10/01/24 04:45 PM 10/01/24 04:45 PM
Joined: Jan 2013 Posts: 75 norcal J JLaSalle OP member
JLaSalle OP member J Joined: Jan 2013 Posts: 75 norcal	Very helpful info Andy,thank you! 1967 Coronet R/T 9.83 134mph. 470 cid st.6 heads 10x pro et track champion

Re: 451 crank balancing [Re: AndyF] #3261398 10/02/24 09:28 AM 10/02/24 09:28 AM
Joined: Jan 2004 Posts: 8,926 fredericksburg,va C cudaman1969 Itch Nutz
cudaman1969 Itch Nutz C Joined: Jan 2004 Posts: 8,926 fredericksburg,va	Originally Posted by AndyF I don't think we've ever used a crank from Ohio Crank so I can't tell you if that is a bad job or a normal job. We typically use Molnar cranks and they only require a small amount of touchup to build a 451 or 470 type of engine. I think 440 Source cranks are rough balanced at 2400 or 2500 grams these days and most modern rotating assemblies balance around 2400 grams. If you have the part number for the crank you can call Ohio Crank and see what the rough balance numbers are on the crank. Then you should be able to see from the machine shop info what the bobweight of your assembly was. If the crank is built correctly it usually only takes a small amount of metal removal to balance. Here is the rotating assembly from the last 470 I built. It was a Molnar rotating assembly and I don't recall the balance job taking much time. That 2400 is good to know, I have two that will need balancing both have a number close to that, 4.15 and 4.5

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