Has anyone went from a sbc to a bbc and slowed down? I have!

Old 06-23-2008, 02:55 PM
  #21  
hammertime
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find a cheap gm crank it'll work great, I had 22 passes or should I say 22 passes 200ft last year losing a motor early sucks !! Good Luck finding parts
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Old 06-24-2008, 05:17 AM
  #22  
3dracing
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Yep, that'll slow it down allright. It's a wonder it cranked when it was hot. I've got a Crower 4 inch stroke crank in the classifieds if you're interested.

Steve
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Old 06-24-2008, 05:43 AM
  #23  
performanceengin
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i have a gm steel crank that is turned .030/.030 fresh. if you want it come and get it. if you need rods i also have a set of gm dimples.as long as it never spun any bearings you'r alright.
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Old 06-24-2008, 09:36 AM
  #24  
I972Nova
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thats the wierd thing is the rod bearings look great. just the mains are thrashed. The bearings didnt spin, the lowers are just destroyed, the uppers dont look anywhere near as bad, but they are into the copper.

This might be the dumb question of the day, but Does the crank need to be balanced to the rods and pistons? I already have external balance flywheel and good external balance balancer...

Performance, where are you located at? Are you saying I can have the crank, or how much do want for it?

Thank You.

Yeah I couldnt understand why this thing was 185 when i got back from a run and hard to cool down, I have never had a bb before so I thought that was normal.
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Old 06-24-2008, 11:49 AM
  #25  
hammertime
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Originally Posted by DragsterJosh
thats the wierd thing is the rod bearings look great. just the mains are thrashed. The bearings didnt spin, the lowers are just destroyed, the uppers dont look anywhere near as bad, but they are into the copper.

This might be the dumb question of the day, but Does the crank need to be balanced to the rods and pistons? I already have external balance flywheel and good external balance balancer...

Performance, where are you located at? Are you saying I can have the crank, or how much do want for it?

Thank You.

Yeah I couldnt understand why this thing was 185 when i got back from a run and hard to cool down, I have never had a bb before so I thought that was normal.
Josh even with a ext balanced flywheel/balancer it still needs balanced. Not a stupid question I didnt have a clue untill last year either.
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Old 06-24-2008, 12:31 PM
  #26  
hollowayshotrods
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Josh,
I wish you luck in getting back to the track soon. Although I do not know you, you seem to be one helluva nice guy! I hate this for you.
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Old 06-24-2008, 12:56 PM
  #27  
olds48
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Man hate to hear about your big block.That sux!!!Hope you get her fixed up cheap...and right
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Old 06-25-2008, 05:37 AM
  #28  
3dracing
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I think it needs to be balanced. I wouldn't put one together without it. It sounds like they didn't clearance the main bearings. It should be put together and plasti guaged first for the clearance. The rods could be ok and the mains too tight.


Steve
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Old 06-25-2008, 08:16 AM
  #29  
itsabird
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josh are the main cap discolored badly? one or just some, think i would have block align-bored or honed, or checked at any rate, good luck man.
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Old 06-25-2008, 10:32 AM
  #30  
zipper06
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Definately needs to have been balanced. All GM's with external balancing have to be balanced when adding after market rods and pistons. The factory rods and pistons will alway be a different weight than after market products.
After market rods are usually matches sets within a couple grams and so are after market pistons. These two added together plus rings and bearings add up to the swing/bob weight that the crank needs to be balanced too, along with the flywheel and balancer. What you have is a classic case of crank harmonics/distoration which beat the mains out. Clearance could have been a little tight on the mains, but non the less it would have still beat the mains out if the crank was not balanced for the proper bob/swing weight. The stock units was meant to run max 4500rpm and factory balanced to run that. but the minute you start running 6500/7000 rpm you are in deep DOO DOO.
As mentioned before, you will have to check the alienment on the blk. now because it may be distorted, i'm a little surprised you didn't spin the bearings with that much heat involved.
I know it's a hard and expensive learned lesson, it's something the person who assembled the engine should have warned you about. I personally would have not assembled the engine for no price for a customer without having it balanced.
But atleast when you're able to get her up and running again you'll have a better engine and a faster one.

Zip.
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