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Old 03-01-2011, 08:59 AM   #1
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4 in stroke crank in a production 2pc 350 block?

has anybody done it?
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Old 03-01-2011, 10:04 AM   #2
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Re: 4 in stroke crank in a production 2pc 350 block?

..
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Old 03-01-2011, 11:13 AM   #3
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Re: 4 in stroke crank in a production 2pc 350 block?

Yes

It is extremely difficult, to the point of being not worth trying unles you have access to a large pile of blocks to keep trying on until you accidentally fail to scrap one.

About the longest stroke customarily used is 3.875", which is referred to as a 396 when the block is .030" over.
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Old 03-01-2011, 01:12 PM   #4
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Re: 4 in stroke crank in a production 2pc 350 block?

Quote:
Originally Posted by sofakingdom View Post
Yes

It is extremely difficult, to the point of being not worth trying unles you have access to a large pile of blocks to keep trying on until you accidentally fail to scrap one.

About the longest stroke customarily used is 3.875", which is referred to as a 396 when the block is .030" over.
how much clearancing would I would have to do to fit a 3.875 crank? any risk of hitting water? I've heard of people filling the water passages with something to fit stroker cranks any thoughts on this?
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Old 03-01-2011, 05:26 PM   #5
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Re: 4 in stroke crank in a production 2pc 350 block?

Quote:
how much clearancing would I would have to do to fit a 3.875 crank?
ALOT. Exact amount and details would vary according to the rods you use.

Quote:
any risk of hitting water?
Absolutely. That, and the oil pan rails, and the cam.

Quote:
filling the water passages with something to fit stroker cranks any thoughts on this?
Sure.
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Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

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Old 03-01-2011, 06:32 PM   #6
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Re: 4 in stroke crank in a production 2pc 350 block?

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Originally Posted by sofakingdom View Post
ALOT. Exact amount and details would vary according to the rods you use.



Absolutely. That, and the oil pan rails, and the cam.



Sure.
what would I have to use for a cam?
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Old 03-01-2011, 07:12 PM   #7
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Re: 4 in stroke crank in a production 2pc 350 block?

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what would I have to use for a cam?
I had a 400 with a 4" crank in it many years ago. I used a Cam Motion cam, small base circle, which is a must. I used Oliver 6" stroker rods and still had to grind a few of them for cam clearance. The lower part of the block was filled with Hard Block, a filler thats like concrete, that stiffens the cylinders. Also had splayed main caps. It made pretty good power for a 23 degree head engine. Best I can remember it made 670 ish HP on Gene Fultons dyno.
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Old 03-01-2011, 07:17 PM   #8
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Re: 4 in stroke crank in a production 2pc 350 block?

no help as to how its done, but my sbc has a 4" stroke in a late model vortec block, 94 i think? Its a crate engine, came built that way, not sure how it all fits. no block filler or any of that jazz

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Old 03-01-2011, 07:31 PM   #9
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Re: 4 in stroke crank in a production 2pc 350 block?

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no help as to how its done, but my sbc has a 4" stock in a late model vortec block, 94 i think? Its a crate engine, came built that way, not sure how it all fits. no block filler or any of that jazz
Are you sure about that? I thought the big inch gen 1 small block crate engines were the 383 & 400. Both use a 3 3/4" crank. I didn't know GM even had a 4" small block crank, aside from the LS type engines.

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Old 03-01-2011, 07:40 PM   #10
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Re: 4 in stroke crank in a production 2pc 350 block?

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I had a 400 with a 4" crank in it many years ago. I used a Cam Motion cam, small base circle, which is a must. I used Oliver 6" stroker rods and still had to grind a few of them for cam clearance. The lower part of the block was filled with Hard Block, a filler thats like concrete, that stiffens the cylinders. Also had splayed main caps. It made pretty good power for a 23 degree head engine. Best I can remember it made 670 ish HP on Gene Fultons dyno.
I've heard of guys running block filler in street cars without having cooling problems but i'm not so sure. what do think about running a partially filled block on the street? a max effort big inch small block sounds like fun think I want to do one for my next project.
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Old 03-01-2011, 07:48 PM   #11
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Re: 4 in stroke crank in a production 2pc 350 block?

Pushing it to 4" in a stock block is possible but difficult. Clearancing at the bottoms of the cylinders needs to be done. A small base circle cam needs to be used. Special pistons need to be used which moves the wrist pin up into the oil rings and have enough cut away from the bottoms of the pistons to clear the crank weights.

For what it's worth, it's better to use an aftermarket block. Raised cam, taller deck etc.
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Old 03-01-2011, 07:52 PM   #12
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Re: 4 in stroke crank in a production 2pc 350 block?

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Originally Posted by WESTOF7 View Post
I've heard of guys running block filler in street cars without having cooling problems but i'm not so sure. what do think about running a partially filled block on the street? a max effort big inch small block sounds like fun think I want to do one for my next project.
Sorry if I misled, this was NOT a street engine. Drag race only.
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Old 03-01-2011, 07:56 PM   #13
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Re: 4 in stroke crank in a production 2pc 350 block?

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Are you sure about that? I thought the big inch gen 1 small block crate engines were the 383 & 400. Both use a 3 3/4" crank. I didn't know GM even had a 4" small block crank, aside fram the LS type engines.
When I was asking my machinist friend about how much stroke a sbc would take he said some 1 piece blocks would take more stroke than a 2 piece. I think I remember seeing 4 inch stroke small block cranks in the 2nd or 3rd edition of the chevrolet power book from the 70's/80's so gm may have made them just not in any production engines.
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Old 03-01-2011, 07:58 PM   #14
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Re: 4 in stroke crank in a production 2pc 350 block?

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Pushing it to 4" in a stock block is possible but difficult. Clearancing at the bottoms of the cylinders needs to be done. A small base circle cam needs to be used. Special pistons need to be used which moves the wrist pin up into the oil rings and have enough cut away from the bottoms of the pistons to clear the crank weights.

For what it's worth, it's better to use an aftermarket block. Raised cam, taller deck etc.
All of what you said. The pistons only had a 1" compression distance. This type of build can get expensive quickly. Mine was somewhat of a budget build and still was not cheap.
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Old 03-01-2011, 08:14 PM   #15
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Re: 4 in stroke crank in a production 2pc 350 block?

Thanks for the replies. I'm going to price out an aftermarket block etc. a big block/LS motor is starting to look better and better for the power levels I'm looking for.
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Old 03-01-2011, 11:27 PM   #16
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Re: 4 in stroke crank in a production 2pc 350 block?

Don't forget that trying to build a big small block runs into other problems. A good set of high flow small block heads can get expensive to feed a big engine while a basic set of BBC 781 heads with a port and polish and bigger valves can do the same thing for a fraction of the cost. The BBC can get more potential with better than stock parts.
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Old 03-02-2011, 10:17 AM   #17
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Re: 4 in stroke crank in a production 2pc 350 block?

Bottom line is, if you want a 400-inch SBC, go to the junkyard and get a 400. Cheeeeeeeeeepest and eeeeeeeeeeeziest way to get there, by far.
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Old 03-02-2011, 01:18 PM   #18
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Re: 4 in stroke crank in a production 2pc 350 block?

Think I'm gonna go for a big block. Is there a serpentine setup for a big block that will fit in these cars? will I need a cowl hood? I would really like to keep the stock hood if possible. it looks like an hei is'nt gonna fit am I correct about this? can I make one fit? can I use a tall deck block?
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Old 03-02-2011, 07:41 PM   #19
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Re: 4 in stroke crank in a production 2pc 350 block?

Tall deck block has a lot of clearance issues.

HEI will fit with no problems. I ran one for a few years. The back of the block is the same distance away from the firewall as a SBC. The extra length of the block goes forward.

Unless you use a real low profile intake manifold which will hurt performance and use a drop base air filter, you're going to need some sort of cowl for clearance.

Finding a 400 SBC in the junkyard is getting hard. There hasn't been one made since 1979 so finding a 70's vehicle with one in it is getting harder and harder.

There were no serpentine belts for the BBC, or at least no reverse rotation water pump systems until 1991 when they switched to the Gen V engine but there are plenty of aftermarket systems that will work. My 91 454SS uses a serpentine belt system.
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Old 03-02-2011, 08:05 PM   #20
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Re: 4 in stroke crank in a production 2pc 350 block?

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Originally Posted by DeanJ View Post
Are you sure about that? I thought the big inch gen 1 small block crate engines were the 383 & 400. Both use a 3 3/4" crank. I didn't know GM even had a 4" small block crank, aside from the LS type engines.
i had a typo that i fixed, may have confused people. Its not STOCK, it was meant to be STROKE, but my fingers got ahead of me.

my 408 is a 350 vortec block with a 4" stroke, crank and rods are K1, mahle pistons
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