400"SBC stroked to a 420"? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-15-2010, 03:53 PM
4bnbad
 
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400"SBC stroked to a 420"?

I'm sure some readers are about ready to hurl at my questions. I notice PAW
offers a SCAT ROTATING ASSEMBLY TO MAKE A 420" OUT OF A 400"
.030 OVER BORE AND 3.875 STROKE USING 6.0 RODS. I CALLED THEIR CUSTOMER SERVICE, and inquired why their 426" rotating assembly was no longer offered. Too many problems. Here is the question, is the extra 14" worth the risk of a shortened life or should I stick with plan A .030 over bore and 6" long rods with SCAT 3.750 stroke? that's it Help please.

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Old 06-15-2010, 03:59 PM
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Hummmmm!!!!!!!!! How can you achive a 420 with a .030 bore?


Cole

Last edited by eloc431962; 06-15-2010 at 04:14 PM.
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Old 06-15-2010, 04:14 PM
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No but with the stroke increased from 3.750 to 3.875 you do

The 400 block is bored .030 and crank stroked to 3.875 from 3.750= 420"
I've never heard of anyone running this combination which makes a man wonder why not?
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Old 06-15-2010, 04:38 PM
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Couldn't find the rotating assy. (maybe that's why nobody's buying it?), but found the block-kit. Online catalog though...I don't have a hard-copy.
https://secure.pawengineparts.com/420_426_4B_Chevy.html
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Old 06-15-2010, 04:41 PM
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yes the super gorilla is the one I refer to 426 no longer made

What say you? As Bill O'eilly would say.
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Old 06-15-2010, 04:53 PM
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Hell for a all out race engine, hell yeah go 4 it, id like to hear more about it!!!!!!!!!
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Old 06-15-2010, 04:55 PM
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Quote:
Originally Posted by 4BNBAD
The 400 block is bored .030 and crank stroked to 3.875 from 3.750= 420"
I've never heard of anyone running this combination which makes a man wonder why not?
It is more commonly referred to as a 421(420.33 rounded up), common for a lot of Open Modified circle track racers. The reason you may not have heard much about them is that in the past it cost more to build than the horsepower it returned for that added cost, compared to a 406. It only really made a difference to mid range torque, needed off the corner in circle track. Didn't make much sense for a street or strip engine, cost didn't equal output.

It also requires more clearancing of the block, a small base circle cam for clearance and clearance grinding on most of the common performance rods, and a stroker clearance oil pan.

Stroker cranks and pistons are now much more affordable, so more of these are coming out to play. 23 Heads big enough to feed these big SBC's are also more affordable and available today, didn't used to be that way, you needed 18 heads ($$$) to make these big engines shine in the past.

For a street, or street/strip engine, I still don't beleive it returns additional power proportional to the cost of all the stroker specific parts and clearncing needed when compared to a 406, IMO.

I've tried every which way with Dyno programs and can't make the small amount of power gained(25-ish on a 600 hp engine) to equal the added cost of the parts. The added cubes seems to only be good for bragging rights on the street.

Makes more sense to use the 3.875" crank in a 350 block, especially a later roller cam block which has more clearance already, to make a 396 SBC.
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Old 06-15-2010, 04:57 PM
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Do you have the link for the rotating assy?
That block kit is over $3000...and it's on special now...whoa.
Quote:
Originally Posted by ericnova72
Makes more sense to use the 3.875" crank in a 350 block, especially a later roller cam block which has more clearance already, to make a 396 SBC.
Now that sounds interesting...
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Old 06-15-2010, 05:02 PM
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I don't like being the pioneer you end up with arrows in your back

Has anyone on this board heard of this combination being used for a street strip truck? and if yes how was the survivability? I'd like my efforts and money to last more than a few drag races.
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Old 06-15-2010, 05:08 PM
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Quote:
Originally Posted by 4BNBAD
Has anyone on this board heard of this combination being used for a street strip truck? and if yes how was the survivability? I'd like my efforts and money to last more than a few drag races.
Nothing basic wrong with it, built with good decent parts it is no more likely to have problems than any other stroker, just costs more for the maybe 20-ish HP more you will get from it. It is a much bigger headache to clearance everything however, takes more time.

Will likely need small journal rods and the rod pins on the crank sized to match, to help with cam to rod and rod to block clearance, and a more expensive oil pan. All that i have been around are this way. You will have to take into account if the pan will fit the chassis you are using, if this is for an S-10 clearance WILL be a problem with the pan.
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Old 06-15-2010, 05:18 PM
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http://www.worldcastings.com/product...et-engine.html
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Old 06-15-2010, 05:20 PM
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A-1 Ss

I see your point and I'm in complete agreement 14" not worth the $3K right on
tell me about this sbc 396" I've never heard about such a thing. What's the point if you already have a good 400" block?
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Old 06-15-2010, 05:29 PM
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Quote:
Originally Posted by 4BNBAD
I see your point and I'm in complete agreement 14" not worth the $3K right on
tell me about this sbc 396" I've never heard about such a thing. What's the point if you already have a good 400" block?
No point if you have a good 400 block, but not alot of those around anymore. Roller 350 block is still an easy find. I was just pointing out a more likely place for the use of a 3.875" stroke crank.

Myself, the only place I would try the 3.875" with a factory block is a roller 350 block. I'd only do it in the bigger bore 400 block if it was a Dart or similar aftermarket block. Wouldn't want to do all that work and have the stock 400 block go "poof!"
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Old 06-15-2010, 05:45 PM
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redsdad

The link to 650 HP LS/1 427" I know it is dumb to ask what that brute costs because I know it's out of my price range. Pretty amazing however.
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Old 06-15-2010, 05:45 PM
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Ok i see how it's done now. I am running a 408 in my 67 camaro man i love that thing. I like what Eric said about the 350 roller block also 406 is a sweet engine too. JMO



Cole
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