400 Build Ideas

RockyPat

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Hello everyone,

I am in the process of sourcing a 400 engine.

The car already has a 8 3/4 489 Suregrip. It is an original big block car.

I am thinking about different build ideas.

2 main options:

1. 400 with 383 crank and a mildly supped-up build.
2. 470 stroker from 440 source.

Is it a bad idea to use the stock 400 crank for builds over 400+hp?

Thank you!
 

slepr1

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IMO if you are looking for lots of torque then you won't be happy until you get the stroker. I guess it all depends on your budget. As far as the stock crank, others may chime in but I know if I was building a stroker I'd go aftermarket forged crank and aluminum heads. I always look for the weakest link and even though they may still be good, they are old technology. I've upgraded my cars engines for 30+ years and if I could start all over again I'd upgrade them all at once and change out all the older tech. It would've been far cheaper to do it once and not multiple times. I'm very happy with my current build (440ci, 500 hp).
 
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440Coronet500

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Aftermarket aluminum crankshaft? Never seen one of those. 440'
 

66Satellite47

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Hello everyone,

I am in the process of sourcing a 400 engine.

The car already has a 8 3/4 489 Suregrip. It is an original big block car.

I am thinking about different build ideas.

2 main options:

1. 400 with 383 crank and a mildly supped-up build.
2. 470 stroker from 440 source.

Is it a bad idea to use the stock 400 crank for builds over 400+hp?

Thank you!

What car is it, what will it be used for? With the parts available today, the stroker kits are attractive. Use of any of the OEM cranks is based on the RPM it will see, in my opinion. The Source 470 kit looks interesting.
 

440Coronet500

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If money weren't a consideration I'd definitely do a stroker 471 with aluminium heads etc. A well built 400 with stock crank and some higher compression pistons can run strong. 400 hp won't be an issue for a stock crankshaft. 440'
 

PRHeads

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400hp isn’t an issue at all for the stock crank.
Or the rods either for that matter.
Or the stock hardware(rod bolts, main bolts, head bolts).

If you decide to do a stroker, I’d skip right past the 470 and go right to the 511.
 

yella71

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400hp isn’t an issue at all for the stock crank.
Or the rods either for that matter.
Or the stock hardware(rod bolts, main bolts, head bolts).

If you decide to do a stroker, I’d skip right past the 470 and go right to the 511.
this...
 

hunt2elk

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Go with a stroker kit with a new crank from 440 source along with some aluminum heads. And most importantly, find a builder who knows what they are doing and listens to what you want out of the motor. Unlike the last fiasco I am still fighting with......
 

ckessel

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You can do a cost comparison between using what you have on the short block, crank/rods using replacement 400 pistons and rings etc to going with a stroker reciprocating assembly. Add in the potential cost of getting your oe crank ground, rods resized too. With that, the cost of balancing your oe reciprocating assembly. Going stroker may be less money
 

Outsider

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So I recently put together a 400 with cast Crank motor. Only reason I used cast Crank is that it was new, as I still had a crate motor that I bought for my truck about 40 years ago that I never used. Bought stock bore higher comp pistons because the stock were about 0.100" in the hole. Did some adjustments with the piston wt and checked the running balance with my Bently Nevada set up and it was actually some significant mills less at 6k than a good running internal balanced reference 440 motor that I have in a car. Bottom line, if you have the dough, buy the stroker kit, if not, and the rest is good, just buy some KB OS 400 pistons, have your shop make some adjustments and don't worry about the crank.
 

JedIEG

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Subscibed... Basically considering the exact same thing. From what I have read 440 source uses a really short rod (6.535) with their 470 kit, which I am not a fan of. I would rather have a shorter piston with a 6.700+ rod to build a 470 to reduce side loading friction and reciprocating weight. The 500" option seems like a better assembly from 440 Source. Any experience there?
The 400 option is also there. Better economy 500hp within reason, cheaper, the satisfaction of giving old pars new life...
my third option is a LA based stroker in the 400" range but we need not discuss that here.
 

Xp29h

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Hello everyone,

I am in the process of sourcing a 400 engine.

The car already has a 8 3/4 489 Suregrip. It is an original big block car.

I am thinking about different build ideas.

2 main options:

1. 400 with 383 crank and a mildly supped-up build.
2. 470 stroker from 440 source.

Is it a bad idea to use the stock 400 crank for builds over 400+hp?

Thank you!
If you go stroker route, the kits are the same price, go 512! Keep CR around 10 and it will be a good strong street car and have all the HP you need. Bring the quench up close to the deck and that’ll get you great power!

My thought was if I’m going to spend the money to stoke a 400, why leave HP on the table? Mine is really only a street car and dome pistons, lots of quench and 9.7:1CR and used pump gas at 93 octane.
Good luck!
 

RockyPat

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What car is it, what will it be used for? With the parts available today, the stroker kits are attractive. Use of any of the OEM cranks is based on the RPM it will see, in my opinion. The Source 470 kit looks interesting.

The car is a 1973 Roadrunner 400. It will be used for street driving. Thank you for the information and help!
 

RockyPat

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So far, some good advice here, but... what is your intent for the car ?

I have indeed!
I want the car to have good power on the street. Nothing insane, but lots of fun to drive! I want to avoid having to replace parts because they can’t handle the power numbers the engine puts out.
 

Cranky

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Mom's cast cranks were pretty good and do not have a history of breaking like some of the other manufacturers did but if I had a forged 383 crank laying around, I'd use it. Will probably have to balance it for the combo since it's heavier and that's the only down side I see. And lighter weight engine assemblies spool up faster. As for torque, the 400 still makes decent torque even with a stock stroke......
 

66Satellite47

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The car is a 1973 Roadrunner 400. It will be used for street driving. Thank you for the information and help!
All depends on how much you want to spend. A relatively stock 400 will give you a lot of usable power. I would expect the stock 400 cast crank is good with over 400 HP, but RPM is the key. The 383 crank may a bit better. The 400 rods are just fine. I'd polish them & use top quality rod bolts. Shot peen them for added insurance. A lite piston is a big advantage with a selected CR. For a street car the most important part is the combination of cam and the heads. Iron OEM heads can make very good power. Modern aluminum heads will flow more than mildly ported OEM heads and will be better on today's gas at 10+ CR. I built two 400 blocks for my drag car, each with 440 steel cranks. One with the low deck rods & one with 440 LY rods. The short rod motor saw 7200 RPM all the time. But the 440 steel crank was only good for 350 or 400 runs. That same motor on the street at 6000-6500 RPM would last for ever, of course with a smaller cam.
 

451Mopar

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The cost per performance of a stroker kit is actually a pretty good value.
By performance, I mean more displacement and stronger parts.
You can get good HP with the stock 400", but at higher RPM, and loss of low end torque.
Just depends on what you want. The money saved? (if any) on the stock stroke build might need to be spent on a higher stall torque converter ?
 
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