1973 360

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65 Cuda 340 said:
yes the low compression made them turds. I can remember when I was a kid nobody wanted them. Then everyone realized the cubic inches made them worthwhile...All part of growing pains.
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Ok, so Jeff you can't be referring to the 74 360 Hi Po they are talking about. I'm almost certain you never rode a 74 A-body with the 360. They were super rare and definitely not Turds. In fact, they were as fast as the early 340 cars, and faster than the 72-73 340 A-bodies
 
65 Cuda 340 said:
I've seen that, but it makes no sense that a 71 340 would make five less net hp than a low compression 72 340.
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No argument. Plus the different RPM peaks makes me thing something is going on, as I mentioned.

Could be they rated it after the peak when it was dropping so the '71 340 in effect made 275@5000 but 285@4800 (the same peak as the later low comp motors). So maybe the net rating at 5000 is 5 hp less than the '72 340, but the actual peak is at 4800 where it makes 10 more? And because they listed the gross peak at 5000 RPM for the '71 340, they had to stick to that RPM for the net rating?

200 RPM difference seems awfully small of an window to drop 10 hp, but maybe?
 
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Dan the man said:
Do you remember the specs for the cam that you used?
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It's the Mopar Performance 761 cam, gross duration is 270/272, lift is .450/.455. I've seen strange figures for the lift at fifty for MP cams, because MP just muliplied the gross duration by .85 to get a duration at .050. I think the real duration at fifty is something like 222 on the intake and 224 on the exhaust. That cam is no longer produced.

I put it in my 360 back in 1991 to replace the so-called Hemi grind cam that was a dog in my low compression 360 which at the time had factory heads, factory 340 exhaust manifolds, stock torque converter, a Torker intake and 3.23 gears. Switching to the milder 761 cam and an MP dual plane intake got me down from 14.50 to 14 flat. Then a Performer RPM intake and Turbo Action 11 inch converter got me down to 13.70s. Left it that way for years, then switched to TTI step headers, their 2.5 inch X-pipe exhaust, Indy LAX heads, an air gap intake, and 3.55 gears. The 62 CC LAX heads and thin gaskets bumped my CR to about 9.5 to one if my calculations are correct. All that knocked off another 3/4 second. At this point, it could use more cam. And better pistons, too, even though the CR isn't half bad, it's not a quench motor. The short block is just a backyard rebuild; the block has not been decked at all, cast pistons, factory rods, the rotating assembly has not been balanced, and I'm not sure I even degreed the cam.
 
TF360 said:
Ok, so Jeff you can't be referring to the 74 360 Hi Po they are talking about. I'm almost certain you never rode a 74 A-body with the 360. They were super rare and definitely not Turds. In fact, they were as fast as the early 340 cars, and faster than the 72-73 340 A-bodies
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do you have a source on this?

the reason i'm asking is that it's common knowledge that the later cars were heavier than the earlier stuff. so i'm kinda wondering how say a 74 dart sport with a 360 would be faster than 72 340 dart when it weighs 5~700lb more.
 
junkyardhero said:
do you have a source on this?

the reason i'm asking is that it's common knowledge that the later cars were heavier than the earlier stuff. so i'm kinda wondering how say a 74 dart sport with a 360 would be faster than 72 340 dart when it weighs 5~700lb more.
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They didn't weigh as much as a new Challenger. The '74 with a shock mount bumper was certainly heavier than a '72, but not by that much. The only other thing I can think of that added weight were door bars. Maybe 100#, at most? And the later '74 Duster 360's didn't even have the shock mount bumpers.
 
TF360 said:
Ok, so Jeff you can't be referring to the 74 360 Hi Po they are talking about. I'm almost certain you never rode a 74 A-body with the 360. They were super rare and definitely not Turds. In fact, they were as fast as the early 340 cars, and faster than the 72-73 340 A-bodies
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I agree, but would point out that the comment you are replying to is not mine.

The Duster 360 I got the motor and trans out of for my 67 Barracuda to replace its slant six should never have been junked. It had a good, solid, straight body and was all there before a fellow North Ga Mopar club member got its 3.21 sure grip rear end. He told me about it, so I snatched the motor and trans. I'm sure the Duster 360's body got scrapped a long time ago.
 
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DionR said:
This lists curb weight for a '70 340 Duster as 3275#

The 1970 Hamtramck Registry - 1970 AMA Specifications - Valiant & Duster

'74 Duster 360 - 3395#

The 1970 Hamtramck Registry - 1974 AMA Specifications - Valiant

And just for comarpision sake;

'73 Duster 340 - 3220#

The 1970 Hamtramck Registry - 1973 AMA Specifications - Valiant

'71 and '72 specs aren't listed.
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i didn't see one for dart, but it lists the valiant (so close enough) at under 3K

so that's still 250+ all day without the nitty-gritty of 4spd v automatic, undcoating (+30 lb!!) or powersteering, etc.
 
junkyardhero said:
i didn't see one for dart, but it lists the valiant (so close enough) at under 3K

so that's still 250+ all day without the nitty-gritty of 4spd v automatic, undcoating (+30 lb!!) or powersteering, etc.
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Sounds like a /6 model? I was comparing V8 to V8.
 
I see 2930# for a 1970 /6 Duster compared to 3055# for a 1974 /6 Duster, a difference of 125#. Virtually the same difference between a 1970 Duster 340 and a 1974 Duster 360 at 120#. Before all the nitty-gritty of 4spd v automatic, undcoating (+30 lb!!) or powersteering, etc.

I would have looked at a 2 door sedan /6 car, but they don't list a 2 door Valiant with a /6 in 1970 so I figured the Duster was as close to apple to apples as I could get. I haven't looked, but makes me think they didn't offer a 2 door Valiant in 1970 outside of the Duster. And yes I know the 1970 Duster is badged as a Valiant, I just figured they still had a 2 door sedan Valiant still available in 1970.

Wish they had the Dodge AMA specs, but they don't show them.
 
DionR said:
I see 2930# for a 1970 /6 Duster compared to 3055# for a 1974 /6 Duster, a difference of 125#. Virtually the same difference between a 1970 Duster 340 and a 1974 Duster 360 at 120#. Before all the nitty-gritty of 4spd v automatic, undcoating (+30 lb!!) or powersteering, etc.

I would have looked at a 2 door sedan /6 car, but they don't list a 2 door Valiant with a /6 in 1970 so I figured the Duster was as close to apple to apples as I could get. I haven't looked, but makes me think they didn't offer a 2 door Valiant in 1970 outside of the Duster. And yes I know the 1970 Duster is badged as a Valiant, I just figured they still had a 2 door sedan Valiant still available in 1970.

Wish they had the Dodge AMA specs, but they don't show them.
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i think it was 70 that they didn't make the val in a 2dr?

i'm not much of a betting man, but i'd go a slice of ham that a 70 dart is several hundred lbs lighter than a 74 duster/dart sport

having driven and ridden in both an early 340/727 dart and a later 360/727 dart sport, the earlier car was noticeably faster. not run away and hide levels or anything, but the difference was there. and both cars were fairly similar in build, so neither had an up on the other.

not saying the 360 cars were turds, but they certainly weren't as fast as the early 340 cars.

(and to your earlier point, i'd brook no argument that the challenger was a porker)
 
junkyardhero said:
i'm not much of a betting man, but i'd go a slice of ham that a 70 dart is several hundred lbs lighter than a 74 duster/dart sport
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Very well could be. The AMA specs list the curb weight for a 1974 Scamp with a 318 at 3190#. That's 205# lighter than the '74 Duster 360. Now, the Duster came with HD suspension (+20?) so maybe 180# more?

Add the 120# difference based on MY and you are at potentially a 300# difference between a 1970 Dart 340 and a 1974 Duster 340.

BTW, this makes it look like a 1974 Dart Sport 360 was 15# heavier than a 1974 Duster 360?

https://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1974/74_Dart (23).jpg

Didn't realize there was that much difference between a Dart and a Duster. Doesn't feel like an apples to apples comparison to me though if looking at the 360 vs 340 alone.

Not saying the 360 is all that either. I have what I have and it isn't stock so I don't really care how fast they were when new.
 
junkyardhero said:
having driven and ridden in both an early 340/727 dart and a later 360/727 dart sport, the earlier car was noticeably faster. not run away and hide levels or anything, but the difference was there. and both cars were fairly similar in build, so neither had an up on the other.
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Rear axle ratios the same?

3.91 was available in 1970 while 3.55 was the highest available ratio in 1974. And it looks like the standard ratio for 1970 was 3.23 while in 1974 it was 2.94.

I think the 240# weight difference is enough for what you describe to make sense, just curious if there were other differences as well.

And the Dart Sport didn't have AC, right? That added over 100#!
 
A average 70' 340 Duster ran about 97mph in the qtr. at 3300 lbs with driver. A well tuned stock 74' 360 Duster ran about 95mph at 3550 lbs with the same driver. That equates to around 235 net horsepower for both.

Considering the lower comp. and 1.88 intakes for the 360, i'd say both engines were pretty evenly matched. The T/Q int. and carb were a plus for the 360.

Talking showroom type cars here...
 
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DionR said:
Rear axle ratios the same?

3.91 was available in 1970 while 3.55 was the highest available ratio in 1974. And it looks like the standard ratio for 1970 was 3.23 while in 1974 it was 2.94.

I think the 240# weight difference is enough for what you describe to make sense, just curious if there were other differences as well.

And the Dart Sport didn't have AC, right? That added over 100#!
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they were both strippers: manual steering/brakes. both had 3.23's SG's at the time, the dart sport now has 2.71 for road tripping purposes (along with a borgeson upgrade). i've worked on both cars a fair amount over the last 10+ years, so i'm confident in saying that they're a pretty fair comparison to each other. no flim-flammery or sandbagging, both motors are a about the same spec, carbs are close enough, manifolds and duals. the 340 shines it everywhere. it's not night and day, but enough to notice.
 
TF360 said:
Ok, so Jeff you can't be referring to the 74 360 Hi Po they are talking about. I'm almost certain you never rode a 74 A-body with the 360. They were super rare and definitely not Turds. In fact, they were as fast as the early 340 cars, and faster than the 72-73 340 A-bodies
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I had a low-mileage one in 78, and I concur; there was nothing turdy about the 74 Dart Sport 360/4-speed/3.55s. I think tho, that they were lighter than they looked.
I sold that car in 80 right after my first baby was born, used the money to buy a 76 Volare station Wagon. 318 with air conditioning.
 
Best test shown on a factory '74 Duster 360 4bbl back then I seen was 14.6's in the 1/4 mile. Not too shabby for a '74.
 
In about 71/72, I weighed my 70 Swinger 340/4speed at the track, with me in it, it was 3330. I was 140. so 3190 to the Dart with a lil less than half a tank of gas, and the steel slapper bars.
She had P/S, PDB, no radio but did have an 8-track and 4 speakers. Yes the jack was still in the trunk, and IIRC so was the spare.
IIRC they plugged me into G-stock, and I won a trophy that day, for what I don't remember cuz the car only went [email protected] I was the only G-stock car there that day, lol. Those E70-14s were horrible tires. but they looked pretty racy compared to the bias-plys that preceded them.
 
65 Cuda 340 said:
I think the real duration at fifty is something like 222 on the intake and 224 on the exhaust. That cam is no longer produced
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I’ve got a similar cam in a stock compression 1973 340, 4-speed. Z and O heads. LD340. HFT. 273 rockers.

Runs pretty good with 3.21 but definitely wants 3.55’s. It really wants some compression and cylinder head work.


IMG_1041.jpeg
 
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With different compression ratios being brought up, what would be a good dynamic compression ratio for the 360 with a 4 barrel carburetor? It will be a daily driver and will need to be pump gas friendly. Cam, I don't know how to match that with the dynamic compression ratio.
 
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