400 Build Ideas

RockyPat

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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.

Awesome info! Thank you for your comment. I really like the 400 motor. They are very durable.
 

RockyPat

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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 ?

Thanks for the comment!

I agree with you there. I like the idea of a 9ish compression 470 stroker. Good on the street with tons of power.

You think the costs of a stroker build is that similar in price to a stock build?
 

rumblefish360

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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!
I agree with you there. I like the idea of a 9ish compression 470 stroker. Good on the street with tons of power.

You think the costs of a stroker build is that similar in price to a stock build?

You don’t need a stroker for a really nice street bound build. The cost of a stroker, just the short block can be inexpensive. 440 source .com can get you a kit for a very reasonable price. Then, It’s just machining.

By the time your done building a 400, and making sure everything is up to spec with the old parts of purchasing new ones to replace the old ones, the cost savings is small. Hence the crowds opinion to get a stroker.

Go to 440source and price a stroker kit and then for the 400, find pistons and I would say connecting rods since rebuilding OE rods can be as pricey if not more than new ones. Compile prices and see what’s what.

A 400 can have a very good return on a double duty roll. The cam can still be small to retain decent mileage but combined with a good cylinder head and valve lift yet provide good top end up. The stroker enhances all of this through more torque everywhere.

If your just set on a stroker, cool, run with it.
There is no replacement for displacement when it comes to making power. How much power you need for the street is your call.
 

451Mopar

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Thanks for the comment!

I agree with you there. I like the idea of a 9ish compression 470 stroker. Good on the street with tons of power.

You think the costs of a stroker build is that similar in price to a stock build?

There are a bunch of considerations, and some depends on the current condition of the parts you have.
I added up the cost difference some time ago, and I think it was less than $1,000.
Example: Had a cast crank 440, where the main and rods journals were shot. You spend $$$ turning, polishing, and balance the crank, then find the undersized bearings are more expensive or difficult to fine. When your done, you still just have a cast external balance crank that makes it difficult to find performance dampers and torque converters.
On a Stock stroke, Stock rod 400, you also limit yourself to a smaller selection of off the shelf pistons. There are more choices for the stroker engines than the stock stroke stuff.
On the stock rods, First 3/8" rod bolts and press piston pins. Shop charges to R&R the piston pins, install ARP Rod bolts and then re-size the rods.
Stroker kit rods come with larger 7/16" ARP bolts, and the small ends are bushed for floating piston pins so you can R&R the pistons yourself.
The rods are made of stronger steel and are designed (chamfered) to clear the fillets of the stroker crank.
The aftermarket rods use the smaller and lighter GM 0.990" piston pin too. This seems to increase the selection of off the shelf pistons as all the stroker pistons use the smaller piston pin size. Depending the the stroke/rod combination, the large end of the rod may use the smaller GM 2.20" rod bearings. The main advantage is the smaller rod end makes it easier to fit the stroker kit into the lock, but again, also makes a wider selection of rod bearings, and usually less expensive too.
As mentioned, there is a good selection of stroker pistons, and being designed for performance, not stock replacement are much lighter in weight.
In addition, the stroker pistons use a thinner 1/16" ring pack compared to the thicker 5/64" stock thickness rings.
Again, using the more common 1/16" rings gives you more choices to choose from. The stroker kit comes with good Sealed Power file-fit moly ring set.
Taking a look on Summit, Total Seal Classic street and racing 5/64" Ring kit is $203.52 for 4.350" bore, the Total seal Clasic Race 1/16" kit is $123.89 (trying to compare same company/quality)
 

rumblefish360

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I only have to say is the OE rods are plenty strong for the street. Now what are we exactly doing?

Some guys will be happy with 1 or 1.1 hp per cube from the engine. A 400 would be 440hp @ 1.1 hp/per cube. Not a bad thing IMO. Other guys will look for 1.4 out of there 470. That’s north of 650hp.

Each owner considers this a mello streetable HP build.
They look at each other’s engine and think the other is crazy. LMAO! But that’s the truth! What’s yours?

OH! I’m not trying to champion the 400, FWIW, just sayin….
 

RemCharger

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Lots of fellows like the idea of building a $$$ stroker all up :drinks: !!!!!!!!

......and then choke er all back down again with little dual planes and shitty carbs...:(

I agree a 400 with real compression should make in the 440hp range with the right parts. And live forever.
 

rumblefish360

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I like the engine masters Chevy 383 vs the MP 383 shoot out. The interesting thing that surprised me was the crushing incoming torque curve of the short stroke MoPar engine over the long stroke Chevy 383.

The only one place I can find it to watch for free, just get through the BS in the beginning…
 

RockyPat

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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).

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.

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.

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......

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

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.
Cast cranks can handle a good amount of power. No issue going north of 550.

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.

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!

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.

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 ?

I would like to thank all of you for the great advice. I am currently strongly considering a stroker kit. I am thinking about purchasing a 400 runner that I can use while I accumulate parts for a proper rebuild. I am excited to use a 400, as I have read that it is the strongest big block Mopar ever casted!
 

RockyPat

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You don’t need a stroker for a really nice street bound build. The cost of a stroker, just the short block can be inexpensive. 440 source .com can get you a kit for a very reasonable price. Then, It’s just machining.

By the time your done building a 400, and making sure everything is up to spec with the old parts of purchasing new ones to replace the old ones, the cost savings is small. Hence the crowds opinion to get a stroker.

Go to 440source and price a stroker kit and then for the 400, find pistons and I would say connecting rods since rebuilding OE rods can be as pricey if not more than new ones. Compile prices and see what’s what.

A 400 can have a very good return on a double duty roll. The cam can still be small to retain decent mileage but combined with a good cylinder head and valve lift yet provide good top end up. The stroker enhances all of this through more torque everywhere.

If your just set on a stroker, cool, run with it.
There is no replacement for displacement when it comes to making power. How much power you need for the street is your call.

Thank you for your input. I completely agree. I am trying to be efficient with my money, and the most efficient option may be a stroker kit because of the gained displacement. Considering a marginal increase in costs possibly.
 

RockyPat

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There are a bunch of considerations, and some depends on the current condition of the parts you have.
I added up the cost difference some time ago, and I think it was less than $1,000.
Example: Had a cast crank 440, where the main and rods journals were shot. You spend $$$ turning, polishing, and balance the crank, then find the undersized bearings are more expensive or difficult to fine. When your done, you still just have a cast external balance crank that makes it difficult to find performance dampers and torque converters.
On a Stock stroke, Stock rod 400, you also limit yourself to a smaller selection of off the shelf pistons. There are more choices for the stroker engines than the stock stroke stuff.
On the stock rods, First 3/8" rod bolts and press piston pins. Shop charges to R&R the piston pins, install ARP Rod bolts and then re-size the rods.
Stroker kit rods come with larger 7/16" ARP bolts, and the small ends are bushed for floating piston pins so you can R&R the pistons yourself.
The rods are made of stronger steel and are designed (chamfered) to clear the fillets of the stroker crank.
The aftermarket rods use the smaller and lighter GM 0.990" piston pin too. This seems to increase the selection of off the shelf pistons as all the stroker pistons use the smaller piston pin size. Depending the the stroke/rod combination, the large end of the rod may use the smaller GM 2.20" rod bearings. The main advantage is the smaller rod end makes it easier to fit the stroker kit into the lock, but again, also makes a wider selection of rod bearings, and usually less expensive too.
As mentioned, there is a good selection of stroker pistons, and being designed for performance, not stock replacement are much lighter in weight.
In addition, the stroker pistons use a thinner 1/16" ring pack compared to the thicker 5/64" stock thickness rings.
Again, using the more common 1/16" rings gives you more choices to choose from. The stroker kit comes with good Sealed Power file-fit moly ring set.
Taking a look on Summit, Total Seal Classic street and racing 5/64" Ring kit is $203.52 for 4.350" bore, the Total seal Clasic Race 1/16" kit is $123.89 (trying to compare same company/quality)

Yes, you have given me some great food for thought. I do not want to have to scavenge for parts when trying to build a motor. Less than a $1000 difference is not bad at all considering you get all new pieces. Plus all the performance parts that would become available like you are mentioning.

Does the stroker kit require a balancer, or is the kit internally balanced?

Thank you!
 

RockyPat

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I like the engine masters Chevy 383 vs the MP 383 shoot out. The interesting thing that surprised me was the crushing incoming torque curve of the short stroke MoPar engine over the long stroke Chevy 383.

The only one place I can find it to watch for free, just get through the BS in the beginning…


That torque curve is insane! Instant power. I like that a lot! Thank you for posting this video!
 

IQ52

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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 if you wanted to be very conservative with a 400 build? I mean 512 inches could be fun.....and 112 inches less could still be.....
https://www.forabodiesonly.com/mopar/threads/dyno-a-7-5-1-400-sure-why-not.293381/
 

slepr1

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I would highly recommend a Hughes cam. I had some Mopar cams in the past and the Hughes cam I have now is just awesome. They are a sponsor here too.
 

451Mopar

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Yes, you have given me some great food for thought. I do not want to have to scavenge for parts when trying to build a motor. Less than a $1000 difference is not bad at all considering you get all new pieces. Plus all the performance parts that would become available like you are mentioning.

Does the stroker kit require a balancer, or is the kit internally balanced?

Thank you!
Kit is internally balanced, so it would require a neutral balance balancer and torque converter/flywheel.
Usually the original 50 year old balancer needs replaced anyway.

Rebuilding with stock parts is a bit easier because they all worked together before.
The stroker kits, everything is new, so everything needs to be inspected and checked, and all clearances verified.

I have gotten a kit where the rod bearing notch in the rod was machined in the wrong place and it moved the bearing too close the the crank fillet. Showed up as tight rod side clearance. Engine was pretty much together at that point, so I just chamfered that rod bearing a small amount. Has not been a problem, but now I know to check the bearing fit when I get the rods in case I need to return them.
 

rumblefish360

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I would like to thank all of you for the great advice. I am currently strongly considering a stroker kit. I am thinking about purchasing a 400 runner that I can use while I accumulate parts for a proper rebuild. I am excited to use a 400, as I have read that it is the strongest big block Mopar ever casted!
I don’t know about that. Prehaps the “230” casting number has the edge but as far as something head and shoulders above another block, I am unaware.
Thank you for your input. I completely agree. I am trying to be efficient with my money, and the most efficient option may be a stroker kit because of the gained displacement. Considering a marginal increase in costs possibly.
Well, efficient now through cubes can be a MPG draw back later due to the extra cubes. A lot of this is dependent on what your power needs are and any mileage concerns if any exist.
That torque curve is insane! Instant power. I like that a lot! Thank you for posting this video!
Exactly. Read on below.
What if you wanted to be very conservative with a 400 build? I mean 512 inches could be fun.....and 112 inches less could still be.....
https://www.forabodiesonly.com/mopar/threads/dyno-a-7-5-1-400-sure-why-not.293381/
Thank you!

Yes, a stroker is a barrel and a half of monkeys, is it needed. I’ve noticed that a well done set of heads can carry a camshafts supposed listed rpm band even further out and continue to make very good HP.

I think the first time this became evident to me is when I payed attention to Dodges return in NASCAR truck series when I heard they were regulated to a 9.0-1 compression ratio. I said to myself how the heck are you supposed to make HP with just a 9.0-1 ratio?

Ahhhhh the things we learn paying attention to the smart people running and gunning there rides with there talent, brains & mechanical abilities being pushed.

How does a limited small cubic inch small block & compression ratio limited small block engine at that make over 700hp? LMAO! Well, now it’s history you can look up and ask them about.


Like I said rocky pat, build what ya want.
For a fun street car, IMO, huge cubes need not apply when you’ll just be blowing the bologna skins off the rims.

I don’t how easy it is to invest in a OD trans or the big blocks, but I’d look there as well.

Also, I hope you get to dyno the engine. Pay attention to the exhaust. There is a lot of power there left behind when people don’t pay attention and they just throw on exhaust pipes when they get home.
 

66Satellite47

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Rocky, keep in mind all strokers do add torque. The rest of the car needs to be able to handle the added torque. The stroker kits available with all the new parts are very attractive. Rumble makes a very good point, do a good exhaust system.
 

rumblefish360

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Rocky, keep in mind all strokers do add torque. The rest of the car needs to be able to handle the added torque. The stroker kits available with all the new parts are very attractive. Rumble makes a very good point, do a good exhaust system.
Thanks. We have all heard the old racers trick with the header collector and a crayon or paint…. Of course!
Well, on the dyno, you can make a few low rpm pulls and find your best length. The length of pipe should be the same diameter of the header collector.

Alwo while that stroker adds torque by the pay loader bucket load, if you can’t get it to the ground in a effective manor, what’s the point? Get that suspension working for you. No matter what engine size and power output.
 

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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!

I would do a 400 with the cast crank and focus most (money wise) on the stock heads (346/902/452 etc. castings). If the bores/pistons are good enough for a re-ring, mill the heads .060" on the deck and .072" on the intake face, so the manifold will line up. If you need a bore-job, go straight to flat-top KB pistons or the ICON forged units, for valve reliefs and compression WITHOUT the excessive head milling. Do all the factory tricks like a windage tray and baffled oil pan, add a HV oil pump and fully grooved main bearings. A killer camshaft if you want a great sound at idle and great driveability, is the Comp Cams 275DEH, #21-406-5. It works with #911 drop in Comp springs or equivalent and stock rocker gear. If you can find/afford a Edelbrock RPM or DP4B/ Performer 383 or Weiand 8008 intake get it, or use the stock intake which isn't as bad as people think. A 750 carb and HP exhaust manifolds or headers and 2.5" exhaust with straight through (Salute, FlowFX, Dynomax UltraFlo, Pypes RacePro, etc.) mufflers and you're set. This setup responds to a 727/318 torque converter, with the wide ring gear (11" unit) and 3.23-3.55 gears. I had this setup (with the milled heads and original OEM pistons) in a '70 Challenger R/T with 3.23 gears and it was a handful, while beeing really docile and MPG friendly (for a BB MoPar)!! Your friend may think you have a 451!!
 

RockyPat

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I would highly recommend a Hughes cam. I had some Mopar cams in the past and the Hughes cam I have now is just awesome. They are a sponsor here too.
Thanks for the advice. Hughes cams seem to be solid options, especially for low compression engines.
 

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