360 vs 383

[318willrun]

If using a 904 is an option, in the mildly hopped up scenario I might say its a tie or down to personal preference. I'm not sure if the lighter transmission and reduction in drivetrain losses completely make up for 23 extra cubic inches, but the extra room in the engine compartment will sway plenty to opt for the small block vs the big block. I would still go big block lol, but not for objective reasons.

904 will handle big horsepower. It's also lighter for the human to handle. It is generally safer than a 727 unless a billet ($$$) piece is used in the 727. This is along with the other benefits from my previous post.
In fairness, as built from the factory, the 727 will obviously take much more abuse than a 904.

 

[66fs]

Not sure if this was directed at me but if it was, I did clearly say in one of my posts that I have not driven a big block A body so no, I do not have any direct experience with it. However, it seems to be long-standing, common knowledge in Mopar world that was indeed the case with those cars. Take that for what it's worth I guess.

You can't get around the fact that there is a decent amount of extra weight in front with a BB over a SB. The surrounding parts that support the BB also add some amount of heft (t bars for example) so it's not just the engine itself, it's more unsprung weight all around. Trying to get a heavier car with poor front-to-rear weight balance to handle is an uphill battle. That's a fact.

The guy that thought up the 383 A body was Mr. Norm. Mr. Norm was not an engineer, he was a salesman. Did he prove it could be done? Sure. Were they the terrors that he thought they would be? I don't think so since only a couple thousand BB A bodies were produced between 1967-69. From either an engineering or sales standpoint, they don't make as much sense as a hi-po small block, at least for a normal street driven application. BB A bodies were heavier, more expensive to insure, don't handle as well, got less MPG and ultimately they cost more to buy because of all the special equipment. Not hard to see why they didn't sell that well. I'll take a 340 Dart over a 383 Dart 10x out of 10x.

Also, in regards to the rpms of the 383 - I tried to get mine to rev over 4,500 just about every time I was in the car. What can I say? It just wouldn't do it. Seriously, it would barely break the tires loose unless it was on gravel. I'll reiterate that the engine was likely worn out to an extent but despite that, I know for a fact it ran about as well as it could have - it had good compression, plenty of timing and it was EFI so the fuel was pretty well managed. It really just had no stones. Nothing to do with a poor converter either since it was a 4 speed. 3.23 gears didn't help but that's what gears were in those cars when they were new. Maybe if it had bias tires it would have been easier. It cruised OK but that's about it. Like I said, pretty much a station wagon engine. The 5.7 Hemi (345 c.i.) in my 2017 Ram is a noticeably better performing engine because it gets my heavier truck moving faster than the 383 did in the lighter car.

Prior to owning my Coronet, I'd driven a few other 383-equipped cars over the years and was underwhelmed those times as well. In general, factory-spec'd hydraulic cams are not great performers no matter what engine they're in. Obviously a cam and gear swap would have woken things up but I never got around to those things before I sold the car.

Conversely, I had a '71 Dart with the original, bone-stock 318 2bbl and 2.94 gears (open) with 14" radials that would roast the tires at will. Is what it is.

Where to start... It was a general statement why I would pick a 383 over a 360 having daily driven Factory A-Bodies with a 383 and a 340. The "seems to be a long-standing, common knowledge in a Mopar world" is actually a long standing common misconception. As for the extra weight it really seems to be a non issue. What is the weight difference between a 7/8 torsion bar and a 15/16 torsion bar? Same for the 7/8 vs 15/16 front sway bar. Everything else is the same, only the engine weighs more. My early 68 Formula S does not have A/C or power steering and was a pleasure to drive with no handling issues. The extra weight of a 383 is easily offset by the intake flow of the heads. Maybe 190 cfm for the 360 vs 230 cfm for a 383. At 2 x intake airflow = hp that is 80 hp. 360 torque runs about 360 ft lb vs 425 ft lb for the 383. Have you heard the exhaust sound from a healthy 383, even through factory A-Body exhaust manifolds?

As for the 383 being a dog, just ask anyone who owned a 68-71 Road Runner. I worked with a guy who had a "68" 4 speed Road Runner, he had it for years. It was stock and would occasionally break into the 12's at 75-80 Drag Strip in MD. All he did was mill the heads, richen up the metering rods in the carb, add headers, gears and slicks. He never even changed the cam. It did not stop pulling at 4,000 to 4,500 rpm. Oh and yes, that was his baby. He probably tuned it for years to get it to that level. The 383 in my 68 Barracuda ran 906 heads, a Comp Cams 268 high energy cam, stock red HP valve springs, a 400 HP TQ, 3.23 sure grip, and a stock 727 5.0 kick down arm and a 340 torque convertor would spin the rear tires and move the rear sideways a foot or two before it straightened up at the 1st to 2nd shift. It also would get 16-18 mpg steady highway cruising in the midwest, up hill or down hill. Just because you would not, or could not, get any performance from your 383, does not mean someone else could not. It is not hard.

As for other engines they are not relevant in this thread.

 

[rmchrgr]

OK, here is some real world data essentially proving that the 383 is not a great or even good performance engine. The data below is from the Pure Stock Muscle Car Drag Race page where you can find the results of their meets going back 25 years. I didn't go through every single year but below was pretty much the only recent incidence I could even find of both subject engines as being entered and competing at the same meet.

To be clear, neither the 360 or 383 shows up on any of their all-time best lists but that makes sense since neither engine was ever considered to be in the same class as the big dog 400+ c.i. engines even when new.

The PSMCDR class rules are pretty strict so I'd say the results are valid. In essence, there are no internal engine modifications allowed and all the original equipment has to be in place including the OE tires. The E.T.s are commensurate with old magazine tests so I don't see anything being fudged to the extent that you'd be skeptical of the performance. Cheating defeats the purpose of the class and is generally frowned on within it's ranks so these guys just don't do it. That's what F.A.S.T. is for and the E.T.s in that class prove that out in spades.

Anyway, below are two entries' (one 360, one 383) results from the same day (9/23/23) to compare. (both cars are 727s.)

1971 Dodge Challenger 383/335, 3,780#, 3.23
15.578 90.97
15.398 91.84
15.993 90.57
15.398 91.78
15.460 91.84

1974 Plymouth Duster 360/245, 3,555#, 3.55
13.677 100.91
13.677 101.29
13.815 99.83
13.754 99.70
13.736 99.44

Based on those results, the 360 Duster was nearly 2 seconds and 10mph better than the 383 Challenger. That's a huge margin.The difference in MPH alone is astounding. For compariosn sake, 340 cars are usually a couple 10ths quicker and usually get down to the 13.2s. 440 cars are usually mid to high 14 second ETs with the Six Pack cars being the exceptions.

The two obvious caveats to the above results are that the Duster weighs 225 lbs less than the Challenger and has a 10% increase in rear gear ratio. It's slight but let's say the Duster has a .025-.030 inherent advantage at the line. Clearly though, that is not worth nearly 2 seconds and 10mph of ET, no way no how.

The factory C.R. for a '74 360 is probably somewhere between 8.4-8.7:1 and came with a Thermoquad. For a '71 383 C.R. is listed at 10:1 but in reality is probably closer to 9.25:1 ith dished pistons. I believe a '71 383 would have had a Holley but don't quote me on that. But even at the lower end of the C.R. ratings, the 383 still has significantly more squeeze. It would be interesting to know where the drivers shifted but it's probably safe to bet that neither engine was run much past 5,500 rpm.

Yes, I 'found this info on the internet' but I trust it to be valid as it's put up by a well-known racing organization for public consumption. There would be no reason to fake this stuff anyway since again, the whole point of the series is to see how fast bone stock cars are in the 1/4 mile.

Discuss.

 

[rumblefish360]

WOW! Both cars are heavy!

 

[Icetech]

I think decades change peoples memories about how fast stock stuff actually was...

 

[RustyRatRod]

904 will handle big horsepower. It's also lighter for the human to handle. It is generally safer than a 727 unless a billet ($$$) piece is used in the 727. This is along with the other benefits from my previous post.
In fairness, as built from the factory, the 727 will obviously take much more abuse than a 904.

This is simple. Four speed, beeotch. lol

 

[Icetech]

This is simple. Four speed, beeotch. lol

Always one bad shift away from a new engine

 

[rumblefish360]

I think the 383 has the goods over the 360 to be a more powerful engine and a better street or strip performer. Weight of the power plant is of some concern if the OE must be retained. Once the OE heavy iron is dumped for the aftermarket performance parts, it’s the big block.

What would 225lbs. weight reduction and 3.55’s do for the challenger’s 15.46 ET? The power plant remains the same.

 

[Jim Lusk]

In the real world with similar builds the performance will probably be similar. There's no real 383 vs. 360 performance tests from the 1960s, but there is 340 vs. 383 and they ran similar numbers with the 340 maybe being a little quicker.

 

[273]

Plus were talking 70's tire technology. What does it matter what they ran stock 50 years ago.

 

[273]

If you build them similar there gonna perform similar, it's just the 383 has a decent amount of advantages so if you built them similar you would of have to held the 383 back one way or another.

 

[Icetech]

If you build them similar there gonna perform similar, it's just the 383 has a decent amount of advantages so if you built them similar you would of have to held the 383 back one way or another.

But which is cooler?

 

[RustyRatRod]

Always one bad shift away from a new engine

Dang skippy.

 

[rumblefish360]

Holy crap!!!!!!!!! Built similar but held back.

What a crock of ****!
I’m freaking believable.
What a pile!

Back on ignore. The only one ever to make the grade out of stupidity & consistently consistent with it.

 

[rmchrgr]

WOW! Both cars are heavy!

Yep. E bodies are crazy heavy, hard to figure. By '74 A bodies had all the 5mph crash stuff saddled on them so it makes sense that one is as porky as it is.

I think the 383 has the goods over the 360 to be a more powerful engine and a better street or strip performer. Weight of the power plant is of some concern if the OE must be retained. Once the OE heavy iron is dumped for the aftermarket performance parts, it’s the big block.

What would 225lbs. weight reduction and 3.55’s do for the challenger’s 15.46 ET? The power plant remains the same.

Maybe a 1/10th? It's only a 10% difference between the two gear ratios so I doubt the 3.55 would amount to much.

Plus were talking 70's tire technology. What does it matter what they ran stock 50 years ago.

Those are the historical benchmarks, have to start somewhere. Radials may not slip as much but the stiffer sidewall does not allow as much of a contact area. 6 of one, 1/2 dozen of the other.

The PSMCDR results I posted above were on the OE tires so the 2023 performance is still essentially the same as it was when the cars were new. Not sure if a '74 Duster would have had belted radials or not but the Challenger would definitely have been on bias ply Polyglas GTs. Some of the quicker F.A.S.T. guys are basically in the 8's on bald Polyglas tires so the tires may not be as big of a factor as you'd think.

 

[69conv]

So I have a factory 360 roller cam from a ramcharger in a 69 Barracuda and a 69 Dart GT with a warmed up 400. I have never had the chance to race myself. Both cars make about 425hp and the torque developes at the bottom end for the big block and at the top end for the small block. Both have 3.55 gears and a converter designed for the engine. The small block has bigger tires because of the bigger wheel wells, the big block uses 14" vs 15" which effectively raises the ratio in comparison. The small block leaves the line better but the big block finishes way better. You decide.

 

[rumblefish360]

Yep. E bodies are crazy heavy, hard to figure. By '74 A bodies had all the 5mph crash stuff saddled on them so it makes sense that one is as porky as it is.


Maybe a 1/10th? It's only a 10% difference between the two gear ratios so I doubt the 3.55 would amount to much.

Yeaaaaa, I own one. (E body)

 

[rmchrgr]

Holy crap!!!!!!!!! Built similar but held back.

What a crock of ****!

Yeah, that makes no sense to me either. Clutching at straws maybe?

I stand by the fact that 383s are pretty much useless. An oversquare engine should be able to rev like crazy but the factory 383 redline is like 5,200.

What's funny about that though is the '74 360 redline is probably even lower. Without looking it up I'd bet it's 4,500 at the most.

Both are pathetic in factory form. That's not necessarily the engine itself but the restrictions that were placed on them for normal people that don't care about max performance. Factory hydraulic cams are the antithesis of performance.

 

[DionR]

1974 Plymouth Duster 360/245, 3,555#, 3.55
13.677 100.91
13.677 101.29
13.815 99.83
13.754 99.70
13.736 99.44

I wonder if you snagged results from @Seth Jones car

 

[Charlie_es_cool]

OK, here is some real world data essentially proving that the 383 is not a great or even good performance engine. The data below is from the Pure Stock Muscle Car Drag Race page where you can find the results of their meets going back 25 years. I didn't go through every single year but below was pretty much the only recent incidence I could even find of both subject engines as being entered and competing at the same meet.

To be clear, neither the 360 or 383 shows up on any of their all-time best lists but that makes sense since neither engine was ever considered to be in the same class as the big dog 400+ c.i. engines even when new.

The PSMCDR class rules are pretty strict so I'd say the results are valid. In essence, there are no internal engine modifications allowed and all the original equipment has to be in place including the OE tires. The E.T.s are commensurate with old magazine tests so I don't see anything being fudged to the extent that you'd be skeptical of the performance. Cheating defeats the purpose of the class and is generally frowned on within it's ranks so these guys just don't do it. That's what F.A.S.T. is for and the E.T.s in that class prove that out in spades.

Anyway, below are two entries' (one 360, one 383) results from the same day (9/23/23) to compare. (both cars are 727s.)

1971 Dodge Challenger 383/335, 3,780#, 3.23
15.578 90.97
15.398 91.84
15.993 90.57
15.398 91.78
15.460 91.84

1974 Plymouth Duster 360/245, 3,555#, 3.55
13.677 100.91
13.677 101.29
13.815 99.83
13.754 99.70
13.736 99.44

Based on those results, the 360 Duster was nearly 2 seconds and 10mph better than the 383 Challenger. That's a huge margin.The difference in MPH alone is astounding. For compariosn sake, 340 cars are usually a couple 10ths quicker and usually get down to the 13.2s. 440 cars are usually mid to high 14 second ETs with the Six Pack cars being the exceptions.

The two obvious caveats to the above results are that the Duster weighs 225 lbs less than the Challenger and has a 10% increase in rear gear ratio. It's slight but let's say the Duster has a .025-.030 inherent advantage at the line. Clearly though, that is not worth nearly 2 seconds and 10mph of ET, no way no how.

The factory C.R. for a '74 360 is probably somewhere between 8.4-8.7:1 and came with a Thermoquad. For a '71 383 C.R. is listed at 10:1 but in reality is probably closer to 9.25:1 ith dished pistons. I believe a '71 383 would have had a Holley but don't quote me on that. But even at the lower end of the C.R. ratings, the 383 still has significantly more squeeze. It would be interesting to know where the drivers shifted but it's probably safe to bet that neither engine was run much past 5,500 rpm.

Yes, I 'found this info on the internet' but I trust it to be valid as it's put up by a well-known racing organization for public consumption. There would be no reason to fake this stuff anyway since again, the whole point of the series is to see how fast bone stock cars are in the 1/4 mile.

Discuss.

I think the last year for the 383/335 was 1970. By 1971 Chrysler dropped it to an advertised 8.7:1 comp ratio, and was rated at 300 gross/250 net horsepower. Makes sense that a heavier car, with less gear and just 5 extra horsepower is the slower of the two. Converter stall also plays a role here. A smog 383 with a 11.75" converter doesn't seem like a combo that would launch better than a smog 360 with the smaller 10.75". But....... This doesn't completely account for the huge difference in ET.

I would say the driver and tune play the biggest role in the ET/mph discrepancy. An inferior driver in a car that still needs bugs figured out is the only explanation for a full 2 seconds and 10mph difference at the finish line.

I don't think this makes a case for 383 being doorstops.

 

[273]

Yeah, that makes no sense to me either. Clutching at straws maybe?

Eg.. A decent out of the box average available heads for 360 is SM, Eddy, Trick Flow, to build a 383 similarly would have to use similar hp capable heads as these which you can easily exceed with average available bbm ootb heads.

 

[DionR]

What's funny about that though is the '74 360 redline is probably even lower. Without looking it up I'd bet it's 4,500 at the most.

'74 factory cam was the 340 cam (268/276), and rated HP peak was at 4800 rpm. At least per the AMA spec on the Hamtramck historical site.

The 1970 Hamtramck Registry - 1974 AMA Specifications - Barracuda

 

[318willrun]

Both are pathetic in factory form. That's not necessarily the engine itself but the restrictions that were placed on them for normal people that don't care about max performance. Factory hydraulic cams are the antithesis of performance.

Yes, very common in the C-bodies to find a 4500 lbs car with 2.76 gears and a 15" tire. Single exhaust, tight converter, and really never given a chance. But when given a "semi" chance to perform, they ran right with the crowd of that era.

 

[RustyRatRod]

I wonder if you snagged results from @Seth Jones car

That was badass.

 

[318willrun]

Yes, very common in the C-bodies to find a 4500 lbs car with 2.76 gears and a 15" tire. Single exhaust, tight converter, and really never given a chance. But when given a "semi" chance to perform, they ran right with the crowd of that era.

Actually, it's amazing how many famous "muscle cars" ran mid 14's to even low 15's. I think many versions of a 383 car, and 360 vehicles too, were well into the 14's in the 1/4 mile. Just not in C-bodies with 2.76 gears and single exhaust... LOL. I think they were on par for the era.