Factory HP ratings: 1967 383 versus 1968/1969 383

[69SportSatellite]

The 1967 383 4V in my Coronet wagon is rated by the factory at 325HP with dual exhaust, which it has. The 1968/1969 383 in the Roadrunner was rated at 335HP, only 10 HP more, even though it had a better cam, better exhaust manifolds, and I would think a more performance oriented carb?

My 1967 383 has the 516 heads, which I understand are less desirable than the 915 heads. Additionally, it does not have the HP exhaust manifolds, which I believe came with the Roadrunner.

So my question is why only a difference of 10HP from 1967 to 1968/1969? Did the 906 heads take away some of the performance gains from the other improvements? If so, how much would an otherwise stock 1968/1969 383 have benefited from the 915 heads? Or, at lower HP levels did the changes/differences not have that much of an impact?

Granted, aluminum heads are definitely the way to go today -- I'm just trying to educate myself.

If this has already been discussed in another thread, feel free to point me in that direction; I looked around quite a bit and didn't find anything that addressed this.

Thanks for any information on this!

Chris
Sacramento, CA

 

[lewtot184]

a loaded question and most mopar people don't want to know the truth. in the October 1967 hot rod magazine vic edelbrock flogged a '67 383. the best he got was around 280hp stock. the magnum heads were added and I think they were only good for about a 4hp gain. the direct connection/mopar performance engine books state that a 383 was only good for about 270-290hp. all the big wedges were over rated from the factory. I think the better heads/cam/exhaust was probably only good for 20hp net at the best. the 383's and 440's were uncompetitive in the classes they ran in.

 

[A383Wing]

68 had a better intake manifold also. Open chamber heads in 68 as well

 

[monaco66coupe]

I read a History of the 383Hp by Bill brownlie, the creator of the 68' charger/superbee, highlighting the turnout of the 68' HP engines, and the engineers were also amazed that the actual Increase was 5 hp, not 10. The 335HP was an advertising plan, but the 67' was a great engine. The 516 was an excellent head for the time. Closed chambered, which helped with compression. the 906 began the drift towards reduced emissions. I would love to find an original 67' HP383 engine. They are hard to find. As far as the manifolds go, the log manifolds are almost as efficient as the rams. it is hard to compare the two engines, they are more different from each other than people realize.

 

[YY1]

Not hijack, but can we backup, and include the 66 383-4?

What differences if any are there between 66 and 67? Are the 4 barrel versions considered "HP" for both years?

There seems to be a fair amount of confusing and/or contradictory info concerning the 66/67 383.

Some sources don't even list a 4 bbl version for one year or another. It doesn't help that the 66 Plymouth FSM has an error.

I think in 66, the 383 was only available as a 10:1 4 bbl motor in B bodies. 2 bbl was only available in trucks and C body cars.

 

[monaco66coupe]

Not hijack, but can we backup, and include the 66 383-4?

What differences if any are there between 66 and 67? Are the 4 barrel versions considered "HP" for both years?

There seems to be a fair amount of confusing and/or contradictory info concerning the 66/67 383.

Some sources don't even list a 4 bbl version for one year or another. It doesn't help that the 66 Plymouth FSM has an error.

I think in 66, the 383 was only available as a 10:1 4 bbl motor in B bodies. 2 bbl was only available in trucks and C body cars.

You could get the 361 V8(F), 383 2bbl, or four barrel. In 66' the 383 Vin# didn't change between two and four barrel. Which is the G.

I'm no expert in the Dyno world, . but I saw a lot of street drag racing back then, and the 383/440 mopars held their own against similar size and weight of the muscle cars of the other brands on the street. If Mopar was down on HP, I suspect all of them were embellishing. My experience was if the car won on the street, sales went up. Most of the guys never really paid a lot of attention to track records, only if the girl was impressed, and you made the other guy look stupid. HA HA

 

[A383Wing]

there is no such thing as a "66 or 67 383HP" engine...they were either 2bbl or 4bbl engine...the "HP" designation did not come into use until 68

 

[Pops1967GTX]

nice article........

I read a article years back on a 1962 383hp rated 343 stocker special used in NHRA..... anyone knows about this? still have a few pics....

[video]http://www.moparts.org/Tech/tech/pages/bigblock.html[/video]


http://books.google.com/books?id=F4...jge#v=onepage&q=1967 mopar engine 383&f=false

 

[monaco66coupe]

I beg to differ that Mopar didn't have a high performance engine in 1967. you couldn't tell that to my brother-in-law, who bought a brand new 67' 383 four barrel coronet. Just because they didn't stamp it HP, Doesn't mean it wasn't. It ate up his 327 Chevy,, and the 67' GTO he got rid of to buy the Coronet. What I want is an original 10:1 compression 66 or 67' 383. The 915 440 heads and good headers turned that engine into a hard runner. (back in 1975) as long as I had 98 octane fuel. Chrysler put The HP stamp was on earlier engines as well, I pulled one from a smashed 65' Plymouth Highway patrol car in 1975. it was Stamped clear as day. Never say never in the mopar world,things happen.

 

[Pops1967GTX]

Class-Racer has a great thread on the 383HP 343..And great photo’s.......


http://classracer.com/classforum/showthread.php?t=37998

 

[69Coronetrt]

there is no such thing as a "66 or 67 383HP" engine...they were either 2bbl or 4bbl engine...the "HP" designation did not come into use until 68

What changed was the use and context of the word "high performance" There are numerous references to the 67 383-4bbl engine as 'High performance".

http://www.hamtramck-historical.com...DataBook/1967/67_Plymouth_Engineering0009.jpg

In 67 and earlier and in 71, the 383-4bbl was called High Performance as compared to the 383-2bbl version. From 68-70, the 335 horse variant was the 'high performace' engine.

It is proper to call the '67 383-4bbl 'high performance' as that's what the factory called them. The 330 horse 383-4 in the fall of '68 was not called 'high performance'; the 335 horse was. It's just a matter of year and context.

 

[A383Wing]

only because it was a 4bbl motor..there were no "HP" stamps at all in 66 or 67 for these motors...

and your brothers 67 383 Coronet was just a 383 4bbl motor, nothing special about it...

 

[monaco66coupe]

That is totally untrue. If that were the case, then every 68-69 charger or Sport satellite with the "H" designation for 383 Four Barrel was nothing special, as they weren't stamped HP either. But they had the same compression,Pistons, heads. Intake, and exhaust of the Superbee and RR. Why is that? Advertising.
There is plenty of documentation showing the 66 and 67 as a high performance car. There were a lot of differences between the two and four barrel 383 those two years. But They saw no point in putting an HP on every 10:1 Improved engine, the service manual even shows the differences. The Springs and cam was different, and you couldn't get duals on a two Barrel. Did the 68 up have more stuff? Yes. I stood in front of those salesman then, and the Coronet 383 four barrel was advertised as the high performance option available for that year.That HP stamp means squat. My 69' CUDA 383 doesn't even have the stamp.
High performance cars weren't first Invented in 1968 with that HP stamp. Read the books and advertising, Chrysler chose to apply that stamp to sell cars. In 1967 Chrysler had their engine, and in 68' they had another. It's as simple as that. You had to be old enough to be there.

 

[69SportSatellite]

"Strictly a high performance option".... I like that - especially since I have a stock 1967 383 4V!

What started my whole thought process (and this thread) regarding the factory ratings was the "stock" 383 Magnum rebuild in the Mopar Muscle Mopar Tech Guide (Fall 2003) "383 Resto to Rad" which resulted in a "stock spec" (their words) 383 with 906 heads generating 335 HP, exactly in line with the factory rating, and probably on lower octane fuel. Given that manufacturers were admittedly all over the map (under/over) on HP ratings, I figured they'd be somewhat consistent in their ratings from year to year.

In my mind, it would stand to reason that if any HP inflation were involved, it would be with the introduction of the Road Runner, not with the 1967 383's. And, since the 1968 RR383 had several new or HP deemed parts, I was surprised to find the factory rating from 1967 to 1968 only +10.

Either way, I have learned a great deal from this thread; working hard to educate myself and I appreciate everyone's opinion and knowledge on this subject - thanks.

Chris
Sacramento, CA

 

[69Coronetrt]

only because it was a 4bbl motor..there were no "HP" stamps at all in 66 or 67 for these motors...

and your brothers 67 383 Coronet was just a 383 4bbl motor, nothing special about it...

What would be the reason to stamp them?
What was the reason for the stamp from 68-70?

 

[monaco66coupe]

You are riding down the right track! The 67' was a great engine, and the 68' got better. The people that made the Roadrunner said the same thing: only 10HP? Look up Paul Herd. His book is great reading, and will better explain what Chrysler wanted to do.

 

[440 Cuda]

1967

The 383/325 was the base 4-Barrel Performance Engine.

Though rated at 325 HP, Mopar clearly over-rated the HP, as most agreed it was closer
to 290 HP.

This 383, when placed in an A-Body {Barracuda 383-S and Dart GTS 383} was correctly rated at 280 HP, due to restrictions in the Exhaust System.

 

[monaco66coupe]

My doubts about the validity of the claim of being over-rated horsepower rating is if the four barrel is only 280, what would the two barrel actually be? That A body manifold sucked, and the later A body manifolds were better. I own and have driven both 383 engines, and the difference is day and night. The 360 is rated at 255, and my polara 383 2 bbl would blow the doors off my1972 360 Polara. It doesn't make sense, and those over-rated 383 engines back then, at least on the street ran with the other brands, and frequently came out ahead. I take with a grain of salt these reports, mainly after I read a dyno report in the 90's in a magazine that suggested the 340 V8 was closer to 330HP, not 275. I own two of those, and that is definitely a stretch. I submit if mopar over-rated their engines, all the brands are guilty as well.

 

[440 Cuda]

On the 383,

1966, I saw enough of them run in C/S and C/SA {9.50 to 10.59 Wt/HP} at the Drag Strip.

The Plymouth Belvedere and Dodge Coronet were clobbered.

The Satellite and Coronet 500 were slightly heavier, and fell into D/S and D/SA {10.60 to 11.29 Wt/HP}
where they faired much better.

 

[440 Cuda]

In 1966, I saw many of the 383/325 HP classed in C/S and C/SA {9.50 to 10.59 Wt/HP}.

The Belvedere and Coronet were over-matched at the Drag Strip.

* 10.0 - 1 Compression
* Mild Camshaft > .425"/.437" Lift ~ 256*/260* Duration ~ 32* Overlap