MoparTrucker
Active Member
I tried to search it but I couldn't find it everywhere I searched, The 400 V8: Final Mopar Big Block Engine they tell you net horsepower but what was the gross HP and Torque ratings for it?
400 Gross power?
- Thread starter MoparTrucker
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There were no gross HP ratings given. Not since 1972.
MoparTrucker
Active Member
Yeah, just if anyone here knows its gross that have dynoed it
Unless someone has dynoes a stone stock 400, it would only be a guess. What was the net rating?
Generally, you can add "in the neighborhood" of 100 horse power going from net to gross. One example is the small block 400 Chevy. The highest HP rating stock was 265 (gross) the lowest was 150 (net). There were several other versions made, but that's the best comparison with a same displacement engine between net and gross.
Another comparison is the Ford 400. The 1971 model year was 260 HP. Both the Chevy and Ford engines could be better comparisons, but IMO are the closest to compare to. The Chevy has a tiny bore size (4.125) compared to the Chrysler 400 (4.342) and a longer stroke (3.75) VS the Chrysler 400 of 3.375. The Ford has a 4.00 bore and a 4.00 stroke (really a 402) so neither engine is what I would call a "great comparison". I think it's safe to say the Chrysler 400 was somewhere a little north of both the Ford and the Chevy 400s, simply because of its huge bore size. Now torque, is another story. IMO the Ford wins out with its 4" stroke.
If I had to "guess" I'd say the 400 Chrysler was probably around 275 HP in gross trim.
Another comparison is the Ford 400. The 1971 model year was 260 HP. Both the Chevy and Ford engines could be better comparisons, but IMO are the closest to compare to. The Chevy has a tiny bore size (4.125) compared to the Chrysler 400 (4.342) and a longer stroke (3.75) VS the Chrysler 400 of 3.375. The Ford has a 4.00 bore and a 4.00 stroke (really a 402) so neither engine is what I would call a "great comparison". I think it's safe to say the Chrysler 400 was somewhere a little north of both the Ford and the Chevy 400s, simply because of its huge bore size. Now torque, is another story. IMO the Ford wins out with its 4" stroke.
If I had to "guess" I'd say the 400 Chrysler was probably around 275 HP in gross trim.
@RustyRatRod besides the compression ratio of the 400 dropping and the bigger bore, did the big block change much during the smog years in the major parts vs the earlier 383? Things like valve sizes and camshaft?
you can also look at the 71 and 72 440 and 360
look at the compression ratio difference between the two years, and keep that in mind when comparing the 1971 (gross) and 1972 (net) HP
in general, IIRC, there is about a 20% reduction from gross to net rating
apply that and note any design differences as above and you will be close
also note that subtracting 20% from gross and adding 20% to net do NOT come up with the same numbers
look at the compression ratio difference between the two years, and keep that in mind when comparing the 1971 (gross) and 1972 (net) HP
in general, IIRC, there is about a 20% reduction from gross to net rating
apply that and note any design differences as above and you will be close
also note that subtracting 20% from gross and adding 20% to net do NOT come up with the same numbers
Not to my knowledge. Once they got the open chamber head, I think that's all they pretty much needed for emissions as far as hard engine parts.
I think my estimate was probably pretty close. I love that torque though. lol
stroked340
Well-Known Member
Not much..those 400's were DOGS from the factory..now when you stroke them...
I fixed it for you.
stroked340
Well-Known Member
PRH
Well-Known Member
I’d say in 100% stock form, with the correct ex manifolds, stock earlier TQ(non-lean burn), driving the water pump and alternator, air cleaner in place...... 280-300hp “STP” corrected hp should be in the ball park.
Finding another 100hp with typical hot rod upgrades would be no problem.
Finding another 100hp with typical hot rod upgrades would be no problem.
I took my ‘78 - 400 and added;
Open air cleaner
Electric choke (small TQ)
Holley Street Dominator
Hedman headers into 2-1/2 exhaust
Aero Chamber mufflers
MP chrome box ignition w/upgraded MP distributor
Not very fast but a reasonable return for a mill that mic’d at 7.8-1. I would have like to installed closed chambered heads and a small cam. I had a handle on the MP 272/.455 stick.
PRH
Well-Known Member
In the late 80’s i re-ringed a couple of 100,000 mile 400’s that got to see some bracket race use.
One got bowl blended 346’s put on it, a swap meet dp4b, swap meet 3310, used white box special cam(same as Lunati .480 bracketmaster), PAW re-ring kit for the bottom end.
Cleaned everything really well, deglazed the bores, slapped it back together.
Went 12’s in a Duster with 4.10’s and a GER 10” converter.
The other one got some bowl blended 516’s, new SD intake, new 650dp carb, new MP484 cam...... same PAW re-ring kit and lower end prep.
That went into a 71 Charger with 4.10’s and another GER 10” converter.
Mid-13’s from that one, and it stayed in the car and was street driven and bracket raced quite a bit until 2004 or 2005, when it got replaced by a 446.
It was still running as good as ever and got sold.
One got bowl blended 346’s put on it, a swap meet dp4b, swap meet 3310, used white box special cam(same as Lunati .480 bracketmaster), PAW re-ring kit for the bottom end.
Cleaned everything really well, deglazed the bores, slapped it back together.
Went 12’s in a Duster with 4.10’s and a GER 10” converter.
The other one got some bowl blended 516’s, new SD intake, new 650dp carb, new MP484 cam...... same PAW re-ring kit and lower end prep.
That went into a 71 Charger with 4.10’s and another GER 10” converter.
Mid-13’s from that one, and it stayed in the car and was street driven and bracket raced quite a bit until 2004 or 2005, when it got replaced by a 446.
It was still running as good as ever and got sold.
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