400 SBC crankshaft

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Jdme
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400 SBC crankshaft

Post by Jdme » Sun Oct 15, 2017 5:05 pm

I have a 400 Chevy cast block bored to 4.185, I was wondering if I could run a stroker crank, either 4.0 to make a 440 or 3.875 to make 426. Any advise would help.

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Re: 400 SBC crankshaft

Post by DaveMcLain » Sun Oct 15, 2017 5:56 pm

Jdme wrote:
Sun Oct 15, 2017 5:05 pm
I have a 400 Chevy cast block bored to 4.185, I was wondering if I could run a stroker crank, either 4.0 to make a 440 or 3.875 to make 426. Any advise would help.
Why not? Clearing the cam is the biggest hurdle and your choice of connecting rods will make or break you in this area. A .900 base circle cam will also be mandatory to get it to work. I've done 4.185 bore 4.125 stroke for 454 cubic inches.

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Re: 400 SBC crankshaft

Post by Jdme » Sun Oct 15, 2017 7:06 pm

What connecting rod would you recommend?

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Re: 400 SBC crankshaft

Post by DaveMcLain » Sun Oct 15, 2017 7:47 pm

I like the Scat I beam rod with the 7/16 bolts for this sort of thing. They are about the best when it comes to clearing the cam.

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Re: 400 SBC crankshaft

Post by mark_follweiler » Wed Oct 18, 2017 1:59 pm

is this a stock 400 block or aftermarket?

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Re: 400 SBC crankshaft

Post by cpmotors » Wed Oct 18, 2017 2:19 pm

Stock block I would stick with 3.75" or 3.875" at most. The extra work to make a 4" crank fit isn't worth the hassle, I'd rather spin a few hundred more rpm to make up for it. Not to mention the heads needed to feed a 4" crank, it all exceeds the limits of a stock block anyway.
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Re: 400 SBC crankshaft

Post by prairiehotrodder » Wed Oct 18, 2017 2:55 pm

Ive had some experience with 400 blocks and i think you are allready past the limit of bore size. I would consider .030 max. I'd try and stay .020 if i could. You are in aftermarket block territory. A 383 with a 3.75" crank and a .580 lift hyd roller needs grinding on those scat I-beam rods. Stock base circle.
I'm not a pro but this is what i have seen.
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Re: 400 SBC crankshaft

Post by mark_follweiler » Wed Oct 18, 2017 4:47 pm

yea, that is why I was asking. 4.185 and 4.00 stroke is not going to work in a stock block. plus WHY? 600 HP is about max on stock block......

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Re: 400 SBC crankshaft

Post by Jdme » Wed Oct 18, 2017 6:37 pm

Yes it is a stock block, it is already bore to 4.185 and I think everything is cast, so I'm looking to go with forged components that is why I was thinking about changing the stroke. The motor is in a 79 Camaro I just purchased a few months back, now it was at it last show for the year so I'm going to start my rebuild.

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Re: 400 SBC crankshaft

Post by mark_follweiler » Wed Oct 18, 2017 7:41 pm

GOOD LUCK!

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Re: 400 SBC crankshaft

Post by GARY C » Wed Oct 18, 2017 8:36 pm

Jdme wrote:
Wed Oct 18, 2017 6:37 pm
Yes it is a stock block, it is already bore to 4.185 and I think everything is cast, so I'm looking to go with forged components that is why I was thinking about changing the stroke. The motor is in a 79 Camaro I just purchased a few months back, now it was at it last show for the year so I'm going to start my rebuild.
The stock 400 crank will most likely out last the block even on nitrous. I would not build anything on it without having it sonic tested for cylinder wall thickness. Hopefully others will chime in on what they feel minimum should be but after going through 3 that appeared perfect at .40 over I don't think I would build much more than a mild performance street engine on a stock block.

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Re: 400 SBC crankshaft

Post by rfoll » Wed Oct 18, 2017 8:57 pm

I ran a .060 over 400 block for several years. I knew it to be strong enough because the previous owner destroyed some pistons using nitrous, and the block held up. Some blocks are OK for this others will have problems. Be reasonable with your expectations. I got to low 11s @120 in a 3200 lb. car with mine, but I started worrying about driving over the crank at that speed. Get your block decked square and honed with a plate to give yourself a chance of a good seal. Thin rings will help seal the thin bore. Don't put any exotic parts in it in case the block fails. I used the standard Scat rods and KB pistons and never had any problems. 412 inches will make plenty of power even if you only spin it to 6000 or so.
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Re: 400 SBC crankshaft

Post by 68post » Thu Oct 19, 2017 1:24 am

rfoll wrote:
Wed Oct 18, 2017 8:57 pm
I ran a .060 over 400 block for several years. I knew it to be strong enough because the previous owner destroyed some pistons using nitrous, and the block held up. Some blocks are OK for this others will have problems. Be reasonable with your expectations. I got to low 11s @120 in a 3200 lb. car with mine, but I started worrying about driving over the crank at that speed. Get your block decked square and honed with a plate to give yourself a chance of a good seal. Thin rings will help seal the thin bore. Don't put any exotic parts in it in case the block fails. I used the standard Scat rods and KB pistons and never had any problems. 412 inches will make plenty of power even if you only spin it to 6000 or so.
They like a lot of cyl head at 412 and 6,000. What were you using ?

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Re: 400 SBC crankshaft

Post by mag2555 » Thu Oct 19, 2017 7:00 am

If your looking to to stroke it and make over 550 hp long term I hope your starting with a 2 bolt block because they are the best ones to convert over to 4 bolt mains , and if it where me I would want 4 bolt mains even if just running the motors stock stroke!
And while we are at it let's toss in a 1/2 fill in the block too!

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Re: 400 SBC crankshaft

Post by rfoll » Thu Oct 19, 2017 9:41 am

68post wrote:
Thu Oct 19, 2017 1:24 am
rfoll wrote:
Wed Oct 18, 2017 8:57 pm
I ran a .060 over 400 block for several years. I knew it to be strong enough because the previous owner destroyed some pistons using nitrous, and the block held up. Some blocks are OK for this others will have problems. Be reasonable with your expectations. I got to low 11s @120 in a 3200 lb. car with mine, but I started worrying about driving over the crank at that speed. Get your block decked square and honed with a plate to give yourself a chance of a good seal. Thin rings will help seal the thin bore. Don't put any exotic parts in it in case the block fails. I used the standard Scat rods and KB pistons and never had any problems. 412 inches will make plenty of power even if you only spin it to 6000 or so.
They like a lot of cyl head at 412 and 6,000. What were you using ?
I'm using Track 1 Spec heads. I got them really cheap bare and added my own components. They were big enough for 6500 rpm or so, but they will get retired soon. The block fill is a very good idea.
So much to do, so little time...

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