How to achieve 425 HP and 500 TQ from a 400 cubic in engine?

[Fisher]

I am in the process of negotiating on a 72 charger. The car is a bit of a Frankenstein, at the same time it has a lot of potential. The car currently comes with a 400 / 727 combo with 3.91 diffy.

The goal is to make 425 hp/500 tq on pump gas. I also want to run a therm-quad as well as HP exhaust manifolds., this will be a daily driver sort of deal. I am going to swap the rear gears to a 3.23 sure grip.

I would like to hit 9.5-1 compression, not sure if i could get away with warmed over cast heads, or if 440 source aluminum heads would be better. I want the engine to look stock from the outside. As far as the cam goes? Will a cam under .500 lift get the job done.

If not, then i am not apposed to making it a 451 cubic inch with the same concept. Should be easier to hit the numbers with a larger engine.

Please post some combos etc to point me in the right direction, I have had performance builds in the past that were a pain to deal with and live with on the street. I am 62 yrs old now and just want a nice car that will dance when i stab the gas on the highway to pass someone. lol

 

[rmchrgr]

If it's a stock 400, you will definitely need pistons to make any sort of power so if you have to spend money already just go right to a stroker. And why limit yourself to 451"? A low deck 400 can be stroked to over 500" for similar money. The Thermoquad and exhaust manifolds will work fine. Stealth heads will also be a much better deal than wasting money on refurbishing a set of stock iron boat anchors. Stealth heads will help increase compression and will tolerate it better than iron heads since they are aluminum. Go with a hydraulic roller cam in the 230/235 @ .050" range and you will achieve your goal easily with good street manners.

 

[Fisher]

Can you run a hydraulic roller with Stock shaft rockers? i want factory valve covers etc. My last set of comp roller rockers for a mopar were $700.00, i am not looking to build a huge money motor.

 

[496 polara]

The better the cyl head the easier it is to make power. A good set of heads with something like the comp XE274 or similar would work.

A hyd flat tappet with the same figures will get you there with stock rockers and valve covers.

 

[qkcuda]

I made 415 HP and 450 TQ from a stock stroke 400 with about 9:1 compression. I had ported stock heads which flowed about the same as the Stealths . It used a 222/234 cam. More cam would up the horsepower but not necessarily the torque. The stock exhaust manifolds and 3.23 gears are not going to work well with that combination. A 451 will get you to your torque goal with less cam and will work better with your intended combination.

 

[PRHeads]

500tq from a “mild” stock stroke 400 BBM with ex manifolds isn’t gonna happen.

Save for a stroker……… or just build it with the stock stroke for what the intent of the vehicle is……..and be happy with whatever it makes.

 

[Pecos Bill]

I was going to suggest a 392 gen 3 hemi

 

[rmchrgr]

Can you run a hydraulic roller with Stock shaft rockers?

I imagine there is someone out that's done it or at least tried but the problem is there's no adjustment with stock, stamped-steel rockers. With the stock parts, lifter preload is set by torquing the shafts to spec. which is the limiting factor in how big you can go.

Personally, I would not run a hydraulic flat tappet cam in anything these days.

i want factory valve covers etc. My last set of comp roller rockers for a mopar were $700.00, i am not looking to build a huge money motor.

Roller rockers generally fit under stock valve covers. You don't necessarily need rollers. As an alternative, you can try to find a set of old factory or Crane iron adjustable ones, they're usually not too expensive.

Even basic engine builds are expensive these days. Budget builds are fine but like PRH said, you just have to be realistic about it especially when you put limitations on what you're willing to do/spend.

I was going to suggest a 392 gen 3 hemi

Retrofitting a late Hemi into anything from the '60s-'70s is an expensive and involved endeavor.

 

[rickseeman]

I think you can get close enough to make you happy doing what you said you are willing to do. 451 flat top stroker from 440 Source, ported Stealth heads, 440 Source can probably tell you which of their cams to use with stock rockers. (I hate stock rockers, but I guess they will work for you.) Hopefully you will at least put an aftermarket intake on it like a Street Dominator. I don't see you being unhappy with your build.

 

[jeepthrills01]

Again...look to the brains of our forefathers....heres a good starting point...
Dyno a 7.5:1 400? Sure, why not?

 

[Fisher]

Thanks for the replies.

 

[YY1]

What's your budget?

...and how does it run now?

I had a stock 400-2 from a '77 van that ran like a scalded dog.

Pistons to get 9:1 (true) for a 400 are expensive.

Lay out your costs vs the stroker kit and machine work.

451 should be plenty, but a good 400 can also get you there.

Depends on "the math".

 

[Fisher]

I am still waiting to hear back from the owner about the purchase. I have not heard it run yet. At this time i am just trying to get a recipe together. My last motor for my duster was a 383/426 stroker. 9.89-1 compression Eddy rpm performer heads and intake, Lunati solid lifter cam, 750 carb and TTi 1-3/4 headers. made 525 HP and 550 tq.

My thought is, I can build a pump gas 400 that should make 425 HP and 500 or worst case build a 451 stroker. The power is in the compression, heads and cam. 9.5to 10.0 compression and aluminum heads should not detonate with 32 degrees total timing cam in the [email protected] range. I don't want a real lumpy cam.An old street master intake which will support a TQ carb. The 3.23 gears would be plenty, as this is a hwy car, not a drag car. so 2500 rpm at 60 mph is where i want to be. Like i said i want it to be as stock as possible, no headers, no roller rockers, no bling.

 

[toolmanmike]

The power is in the heads but don't overlook the compression. 9.5/1 is pump gas friendly with iron heads if you don't push the timing too far. A point more compression with alloy heads works. They have good chambers, big valves, and decent ports. A friend built a mild cammed 440 with some mildly ported iron heads and it spun 500/500 on the dyno

 

[rmchrgr]

If all you want is a street/highway cruiser don't put a number on it. No matter what, a 400 will need pistons which is where it starts to get expensive. Also, it makes little sense to spend a grand+ on pistons etc. if you're going to handicap the rest of the combo. The 400's best attribute is it's potential to make power in stroker form. Conversely, a basic, iron head 440 with a mild cam will do what you want all day.

Speaking from direct experience, stock 400s do actually suck. I had one in my old '76 D100 truck that the previous owner 'built.' It mostly drank gas and could not get out of it's own way. It had 452 heads which are what 88-90cc? so it was probably around 7.5:1.

Regardless, the P.O. decided a Mopar .484" cam was the hot ticket for it... but hey, it had headers, an Edelbrock RPM intake and a Holley 3310 so maybe it looked sorta cool? Truth is I've had faster 4 cylinder cars!

 

[lilcuda]

Build a mild stroker. Also, call Bullet Cams for a custom grind. Avoid Comp Cams like the plague.

 

[fishmens67]

I'd do a 451 using the stealth heads, any larger displacement would require Trick flow heads or a well ported Edelbrock head.
A good valve job and port cleanup of the stealth heads would be required to achieve an honest 500 tq/425 hp.

 

[fishmens67]

but a good 400 can also get you there

Yes but it wouldn't be very street friendly, it would take compression, decent heads and a camshaft in the range of the Mopar 590.

 

[furious70]

Perfect place for boost.
I think that street master intake was near the bottom of the famous intake comparo.
Spend the money on the rpm performer intake or even just a performer

 

[rmchrgr]

I'd do a 451 using the stealth heads, any larger displacement would require Trick flow heads or a well ported Edelbrock head.
A good valve job and port cleanup of the stealth heads would be required to achieve an honest 500 tq/425 hp.

Sorry, that's just not true. I built a 383/438" 9.3:1 stroker for a friend with untouched "OOTB" Stealth heads that made around 450hp/475lb ft of torque with a relatively mild Hughes cam. Headers, Performer RPM intake, 750 DP carb. OK, it had Comp Magnum roller rockers... "Mineshaft" air that day, the dyno actually took away some power. Hydraulic roller would probably be another 25 hp...

This engine went in a 100% street/highway cruiser C body and the guy loves it. It's the most power he's ever had under his right foot.