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Discussion Starter #1
question if you have a externaly ballaced rotating assy and you wanted to swap over to internaly ballaced what is needed a flywheel crank and ballancer or the whole rotating assy i have a motor i broke a crank in and it is externaly ballanced or if i buy a ballanced crank flywheel and ballancer would i need to have it ballanced with my rods and pistons
 

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Yes you would.
Take the whole assembly including the rings and bearings crank spacer etc. to the machine shop. Ask them what they balance it to. My machine shop balances it to 1 to 2 grams.
The factory considers 16 grams or less to be in balance. Most race shops consider anything below 8 grams to be in balance.
The closest to zero grams you can get the better.
Greg
 

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Discussion Starter #3
thanks for your response i did contact clegg engine where i purchased my rotating assy and they are going to set me up with a ballanced forged crank with my "bob wieght" but now that i am going to internal ballance with a 871 what is the correct stack up on the snout crank timing gear non wiehgted spacer ballancer blower hub and blower pulley or do i leave the nuetral ballance harmonic ballancer off
 

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Sub a non weighted spacer for the hatchet and retain your neutral balance Damper.


SJ
used2b RHP

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Discussion Starter #5
okay after speaking with clegg engine and them talking with scat they will set me up with a ballanced forged steel crankshaft to 2 or less grams to my bob weight they currently have on file,it will come with king bearings on the mains, and king H type on the rods and a flexplate for intenal ballance for around 1500.00 i all ready have all the gaskets and a new timing cover coming tomarrow i will scope the cylinders and check the valves.
 

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Discussion Starter #7
okay i recieved the FORGED PRO SERIES CRANK lol and removed the motor, put it on the stand, and dissasembled it, bad news is valves are bent slightly just enough they dont fully close, so mo $$ i orderd a set of swirl polished 2.19 and 1.71 stainless steel 1 piece valves, guess ill be doing some valve work also, lifters are fine roller rockers are fine i still need to check the push rods no divits in the pistons just little smudge marks GOT LUCKY, i installed the crank on king bearings with royal purple assy lube and tourqed it down to 102 and it rotates very nice, next is droppin in the rods/pistons back in, i will say when i took the old crank out the bearings looked the same as if i just put them in, i will get some pics and put them up.
 

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Discussion Starter #8
ok crank is in and tourqed to 102 and the rods and pistons are back in and tourqed to 65 break away is 20 and the end play on the new crank with the king bearings is 5 thousands spec i believe it 4 to 8 everything went together with royal purple assy lube and molly here are some pics the head pic shows the slight valve bend and piston contact new valves coming
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92478
 

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I think I would go ahead and order a new set of pistons. You are going to have quite a bit of money in your engine and a set of pistons arn't going to be that much more.
I just would not feel confident running those pistons on a blower moter.
I would more then likely use them in a NA motor after having them checked but not with the increased pressure you will be running with a blower.
Greg
 

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Discussion Starter #10
i think what i am going to do is at least have them checked these are around 800.00 for pistons and go off of the information i get that is happining now as we speak dropped them off this morning i know the shop pretty well and they will get them back t me or a recomendatin early this coming week i think they will be fine i have seen worse or mayby ill only need to replace 1 or 2 half to wait and see
 

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I think I would go ahead and order a new set of pistons. You are going to have quite a bit of money in your engine and a set of pistons arn't going to be that much more.
I just would not feel confident running those pistons on a blower moter.
I would more then likely use them in a NA motor after having them checked but not with the increased pressure you will be running with a blower.
Greg
What do you see in that photo that makes you nervous?
 

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What do you see in that photo that makes you nervous?
My concern with the piston shown is internal cracks from the valve impact on the piston. I know that forged are plastic in nature and dont shatter like cast pistons will and will return to the shape they were forged at.
On a NA engine I would just dress up the damage to keep down any detonation but with a boosted engine I would be very concerned with that piston. I would at least replace that one.
I am may be a little to concerned but with my past experience with the same issue I found it is better to spend a little more money then planned now then have to rebuild the engine again.
Greg
 
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