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Old 10-27-2009, 12:33 AM
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400 sbc crank in a 350 block

i have a 350 sbc motor broken down to the short block and im considering swapping crankshafts... i know i can purchase a 400 crank to make it a stroker motor or so ive been told.... what all do i have to change if i swap crankshafts... sorry if this is a rookie question but hey...im a rookie! thanks in advance

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Old 10-27-2009, 12:54 AM
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Cheapest/best way out in my opinion is Scat 9000 series cast STEEL crank. You can buy the unlightened, external balance crank for 189 bucks. Get a 400 balancer/damper for 90 bucks and a 400 flexplate for 40/50 bucks off ebay and you're good.
Here's the crank....
http://www.summitracing.com/parts/SCA-910375/
Rebuilt balancer/damper from Damper Doctor...
http://www.damperdoctor.com/Merchant...egory_Code=CHE

This assumes you have a 2-piece seal block and don't want to spend the extra dough to internally balance the rotating assembly.

You have your choice of using stock length 5.7" 350 rods or aftermarket 6" rods, depending on the piston you use. I like the shorter rod because the 6" rod puts the wrist pin up into the oil ring. Maybe no big deal, I just don't like it. I like these rods for a street or mild street/strip motor...they're clearanced to prevent cam lobe interference with a standard base circle diameter cam...
http://www.summitracing.com/parts/SCA-25700P/

Last edited by techinspector1; 10-27-2009 at 12:59 AM.
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Old 10-27-2009, 06:25 AM
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You can't just put a "stock" 400 crank in a 350 block. You need to have the main journals ground down because the 350 uses 2.449" and 400 uses 2.649" main journal sizes. But like tech suggested you can get aftermarket cranks that are designed to fit into 350 blocks with no machining.

Secondly you have to consider your stack height.

If you put a 3.75" stroke crank in a 350 with 5.7" rods and a stock 1.560" compression height piston from a 350, the piston will be .11" inches above the deck.(Assuming you have a stock deck height of 9.025")

Another option If this were a strict budget build would be to use the stock 5.565" rods from the 400 and then you can use the stock 350 pistons and your stack will come in at 9"

IMO If you are replacing the pistons go with 5.7" rods and find a piston with the correct compression height. If you go to summit they have complete rotating kits for the CID you are after. You can get them balanced internally or externally. Hope this helps
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Old 10-27-2009, 09:00 AM
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scat 9000 crank

I have talk to people who have claimed that the scat 9000 crank sometimes needs 3 pieces mallory to balance making it more expensive than the forged unit.Anybody else had this problem?
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Old 10-27-2009, 09:33 AM
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Quote:
Originally Posted by SDLuck
I have talk to people who have claimed that the scat 9000 crank sometimes needs 3 pieces mallory to balance making it more expensive than the forged unit.Anybody else had this problem?
You may have to do that with anybody's crank, depending on the weight of the piston, rings, wrist pin and rod. If you use heavier than stock components, you must expect to equalize those weights at the crank counterweights. I don't think it's fair to make a blanket statement about anybody's crank. Not taking up an argument for Scat, just stating what's real.
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Old 10-27-2009, 09:51 AM
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So if i go with a scat crank and stock components with flat top pistons (4 valve reliefs), and stock rods should I need something else to help balance the motor or just the harmonic balancer recommended?
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Old 10-27-2009, 10:13 AM
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Crank

I understand your answer,but that doesn't answer my question.I am not attacking scat . I have used there parts many times and have had good luck with them,but i haven't used their cast stuff.We have a crank grinder who will not do their crank balancing because of this,I just wondered if anybody else has had this problem and what parts were used.
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Old 10-27-2009, 10:50 AM
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http://www.speedwaymotors.com/Econom...mbly,3176.html
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Old 10-27-2009, 03:33 PM
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Well to let you know I have bought two scat 3.480 crankshafts that where both cast steel and the same rods as stated above by techinspector and one set was with forged pistons and the other was hypereutectic pistons and the machine shop did not have to hardly do anything to the crank just a little drilling and that was about all. Yes my crank was the 3.48 internal balance but compared too the 3.750 external balance unit it should not make that much of a difference to a degree. My one cranks was for a one piece rear main seal block and the other a two piece rear main seal. Machine shop said my rods and crank where spot on for the specs. Hope that might ease your worring.
Eric
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Old 10-29-2009, 08:13 PM
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Eagle internal balance crank in my 406,eagle rods 5.7" and kb pistons. minor grinding on roads and very minor drilling on crank.
Shane
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Old 11-04-2009, 06:53 PM
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Hey NTX Gearhead.......

Whynot....with all the stuff out of the engine....get the Scat crank and ALL the related movung parts balanced at a machineshop? Problem solved for around $75.00/100.00. When swapping in new...used...aftermarket...modified..etc. etc.parts into one moving assembly....really ruins your day when you fire it up and it shakes itself to death. When you coulda spent alittle more and not hafta re-do your work. My oppinion.
6sally6
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Old 10-04-2010, 07:31 AM
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Balance question

Quote:
Originally Posted by zildjian4life218
You can't just put a "stock" 400 crank in a 350 block. You need to have the main journals ground down because the 350 uses 2.449" and 400 uses 2.649" main journal sizes. But like tech suggested you can get aftermarket cranks that are designed to fit into 350 blocks with no machining.

Secondly you have to consider your stack height.

If you put a 3.75" stroke crank in a 350 with 5.7" rods and a stock 1.560" compression height piston from a 350, the piston will be .11" inches above the deck.(Assuming you have a stock deck height of 9.025")

Another option If this were a strict budget build would be to use the stock 5.565" rods from the 400 and then you can use the stock 350 pistons and your stack will come in at 9"

IMO If you are replacing the pistons go with 5.7" rods and find a piston with the correct compression height. If you go to summit they have complete rotating kits for the CID you are after. You can get them balanced internally or externally. Hope this helps
Any real critical difference between internal vs external balance on the crank for building a sreet/strip enngine? Worth the extra $$ or not?
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