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  #166  
Old 08-10-2012, 01:13 PM
dog ear dog ear is offline
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An informative 340 Engine Buildup from August 69 Hot Rod.

Check out stock horsepower. Might seem low but not surprising. 340s went like hell anyway.
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File Type: jpg 6908 HR 340 Engine Buildup (1).jpg (907.2 KB, 9 views)
File Type: jpg 6908 HR 340 Engine Buildup (2).jpg (862.9 KB, 6 views)
File Type: jpg 6908 HR 340 Engine Buildup (3).jpg (776.3 KB, 19 views)
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  #167  
Old 08-12-2012, 02:37 PM
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Thanks for the info, dog ear. Very interesting. Yes, the Mopar 340 was always one of my favorite (or maybe favorite) small-block engines.

I have that Hot Rod test but I don't have the last article you posted. Thanks for that.
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  #168  
Old 10-20-2013, 11:25 AM
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Quote:
Originally Posted by dog ear View Post
An informative 340 Engine Buildup from August 69 Hot Rod.

Check out stock horsepower. Might seem low but not surprising. 340s went like hell anyway.
At 275 gross horsepower, the 340 may have been the most under-rated engine of the time!
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  #169  
Old 10-20-2013, 07:05 PM
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In reality, the Mopar 340 was honestly rated at 275 (gross) horsepower. Its net rating would have certainly been much less according to the August 1969 Hot Rod Magazine results. In some circles, the generally accepted net ratings would be approximately 20 % less than actual gross figures. If this were taken at face value, the net rating would be somewhere around 235 horsepower.

I am aware that other quoted gross and net horsepower figures were substantially higher; Roger Huntington had predicted 275 ''net'' according to his formula based on personal road tests, and many believe that the 340 actually produced close to 315 gross. If you believe the Huntington figures than the 340 was obviously under-rated by the factory.

When the 340 was newly introduced in the fall of 1967, as a 1968 model option, the NHRA did re-factor the manual transmission equipped engines at 315 horsepower. Manual equipped 340s had a more aggressive camshaft profile that gave higher peak horsepower than the automatic equipped versions. Exactly how much was always debatable. Once again, accepted quotes were around 10-15 horsepower more than the automatic cam 340.

Keep in mind, that the manual cam version was only available for the 1968 model year. Afterwards, ALL 1969-1973 model 340s were apparently factory equipped with the lower lift, smaller duration automatic camshaft, including the vaunted 340 Six Pack with the triple 2 barrel Holley carbs, despite factory brochures and ads stating otherwise.

Refer to attached scan for Gross figure comparison.

I do have net duration figures for both cams but at the moment the net figures elude me.

I have horsepower figures derived from Desktop Dyno 2003 which, I believe were fairly close to real-world actuarial but unfortunately, that program no longer works on my computer. I retain several hundred DYN files with both gross and net camshaft profiles for all of the popular North American engines produced from 1949-1990. However, I cannot open the DYN files.

Around 1970, the NHRA had once again re-factored the 340 to 300 gross horsepower at least for automatic class.

In the 1968-1973 era, several magazines tested 340s and most were said to produce anywhere from 275-290 gross horsepower using factory exhaust manifolds and air cleaner systems. Very close to factory claims. Based on these tests when the engine was new and in current production, the 340 was actually honestly rated by the then current GROSS test standards. It was not under-rated. Another honestly rated engine was the 383 Magnum at 335 gross horsepower. In 1971 it was rated at 250 net horsepower and 300 gross. Since that time, many dyno tests indicated a true 325-335 gross horsepower for the respected 383 Magnum.

If you were to use Hales Formula or Huntington’s to derive gross and net horsepower figures for the various 340 models they tend to fall within the 275-300 horsepower range. A few indicate more than 300 but I believe that those tests are outside the probable area of true factory produced cars and were most likely modified. In the case of the early 68-69 models, I would say that Chrysler probably slipped in a few manual cammed engines for magazine testing, and super tuned them with indexed cam timing, re-curved distributer timing, re-jetted carburetion, and in some cases larger exhaust man folding and piping than otherwise stock production cars off the dealership showrooms provided. These popular ''cheater'' tricks were standard fare from all American manufacturers back then.
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File Type: jpg 68 340 AT & M4 Cam Specs.jpg (148.4 KB, 10 views)
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  #170  
Old 11-02-2013, 02:14 AM
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Quote:
Originally Posted by ricrit View Post
At 275 gross horsepower, the 340 may have been the most under-rated engine of the time!
Yes, the fact that the trap speeds in the 1/4 mile of the 340 in the Dart and Duster of mid-to-high 90s (mph) indicate they were putting out more than 275 hp.
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  #171  
Old 11-02-2013, 02:38 PM
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Since the subject came up, the Oct., 2013 issue of "Hemmings Muscle Machines" has an article on a 1969 Camaro RS COPO 427.

The factory rating for this engine was 425 gross hp @ 5600 rpm, even though it was quite a bit different than the other 427 Chevy engines. One example being that it had a cam with a lift of .520/.520.

Anyway, the engine was rebuilt to correct specs and put on a dyno. It put out 497 hp and "was still pulling hard when it was shut down at 6,000 rpm." So figure 500 or more horsepower.

So why was it rated at only 425? Because "425 hp" sounds much better to an insurance company than 500 hp!
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  #172  
Old 11-03-2013, 02:34 PM
dog ear dog ear is offline
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We can quote horsepower ratings all day but in the final analysis what really matters is how much power you can put down at the wheels on the street or track depending where you are at the time.

http://www.ultimatecarpage.com/forum...7&d=1344629542

If you refer to my post #166, in this thread you will see that the 340 did not make much more than 275 (stock) horsepower on the dyno according to the August 1969 Hot Rod magazine article. Those dyno figures are in gross measurements back in the day when the 340 was new.

That particular test even used advnced total timing. If you were to use a net rating with a 20% less figure you would have approximately 240, still more than what the engine would be rated at today.

Even though net ratings have been around since 1971 (standard in 1972 OEM specs) the acturial measurements have been tightened up since then resulting in at least another 5% power loss.

http://www.ultimatecarpage.com/forum...9&d=1331617679

http://www.ultimatecarpage.com/forum...0&d=1331617791

http://www.ultimatecarpage.com/forum...1&d=1331617829

As for the COPO Camaro with the L-72 427-425 hp engine it never made anymore power than the later 1970 high compression 454-450 hp LS-6. Both used same cam, but the later 454 engine used better breathing heads with slightly larger valves, and a low profile aluminum intake instead of the vaunted high rise unit on previous big block incarnations of the fabled 396 - 427 rat. Refer to my post # and you will see a dyno sheet for the LS6 which made a net 380 hp with all factory equipment installed. Gross figures equalled the stock rating of 450. Again, honestly rated for the times. However, this very engine would not be rated so high today. It would make somewhere around 340-350 net hp at the flywheel, perhaps less.

Point is that we tend to lose sight of reality when talking about these iconic musclecars and their engines, and their attendent power making capabilities. I grew up in that era and many cars barely made it out of the 15s when bought straight off of the dealership lot. Contrary to popular opinion, most people did not tune their cars and modifiy them like we might believe. It's the same thing today. I see lots of new musclecars prowling around the streets and most are in fact left stock. It takes money to make power and most people are satisfied with what they purchase.

Unlike today, where factory cars are fairly close in tune to each other, because of computers, emissions, and such, older musclecars had wider variences between like models and engines. Of course, there are always exceptions to the rule. Some cars are just faster than others but they are an exception.

It was not uncommom for someone to buy a new muscelcar and be stuck solidly in the low 15-sec bracket without tuning tweaks to engine and suspension. Tires were capable of getting many cars into the mid-high 13s once they were properly sorted out. That usually meant timing and carburetion recalibration. Sometimes headers and intake mods.

340 Dusters and Darts were cheap, commom and effective to modifiy so many people bought them. I knew quite a few guys that did exaxtly that and I can tell you that they were running mid-high 13s with those cars. Popular engine mods were headers (pick your choice) Edelbrock LD-340 intake and a complimentary 650-780 Holley carb. Ignition and timing mods were made by those more enterprising and better results were seen. Still the average guy on the street never got his hands much dirtier than that. Traction bars, larger Firestone, and Goodyears were usually installed. Soe used Tiger Paws. Mid to later seventies saw Mickey Thompson tires as well. G-60-14 and G-70-14s were generally thumbs up. Thats what I recall anyway.
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Last edited by dog ear; 11-03-2013 at 02:40 PM.
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  #173  
Old 11-03-2013, 07:21 PM
ricrit ricrit is offline
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340 Gross and Net

The Dodge Net rating for the 340 was 235 hp (see attached).
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File Type: pdf 1971 Mopar Gross Net Horsepower.pdf (388.6 KB, 7 views)
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  #174  
Old 11-03-2013, 08:01 PM
dog ear dog ear is offline
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Net and gross horsepower figures were published in 1971 by Chrysler and GM. Some Mopar publications quoted the 340 at 240 net hp instead of 235. Go figure!

It is interesting to note that the 1972-73 340 was also specified as having 235 net horsepower, even with a lower compression ratio. In reality the 68-71versions had to have more horsepower then the later low compression, small valve heads but, just how much is debatable.

In fact, the 1971 models would have had the most horsepower of all 340s, because Chrysler outfitted those versions with the larger 800 cfm Carter Thermoquad four barrel, which outflowed the early models by approximately 200 cfm.

Another interesting point to ponder is the 1974 low compression 360 Magnum high performance engine. It was rated at 245 net using the same cam, heads, intake setup, and exhausts as the discontinued 1973 340 engine. It's net horsepower rating is even more than the 1971 high compression 340. LOL!

I vividly remember the 1972 340 models hitting the streets in GTA. A friend had just purchased a new 72 Scamp with the vaunted 340 and was very disappointed in it's performance compared to the early cars. Both of his brother-in-laws still owned modified 340 cars; 1968 Barracuda Formula S and 1971 Duster respectively. They ate the small 72 for breakfast. Even after the 72 was 'done up' with headers, intake and tuned, it was not as quick as a good running stock 68-71 (tuned) version.
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  #175  
Old 11-04-2013, 03:19 PM
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Mopar Muscle magazine put a 340 on a dyno and got some interesting results.

It was built "as close as possible to stock specs."
With the original carb which obviously need some work (the jets were said to be frozen), the 340 put out 281.3 hp and 328 lbs-ft torque.

They then put on an 800 cfm Edelbrock carb. With just that one addition, hp increased to 316.9 @ 5200 rpm and torque was 351.3 @ 4000 rpm.

Which does show that a 340 engine, in good condition and in good tune, will produce more than its advertised hp.

Later in the test, they also bolted on a set of headers. Horsepower output was 330.4 @ 5500 rpm and torque checked in at 369 lbs-ft @ 3900 rpm.

http://www.moparmusclemagazine.com/t...nce_mill_dyno/

http://www.moparmusclemagazine.com/t...e_headers.html
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  #176  
Old 11-15-2013, 08:03 AM
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Wow! now that takes me back, I can remember when I could buy HOT ROD magazine for under a dollar. I would always buy the magazine with my allowance every month, mainly for the great pictures of all those cars from the day.
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  #177  
Old 12-17-2013, 08:36 AM
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How Much Horsepower Did They Really Make?

I thought I would share some research that has been done on the old nostalgic musclecar engines. Hope this helps sate some curiosities.
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File Type: pdf EVALUATION OF NOSTALGIC MUSCLECAR ENGINES-Rev1.pdf (29.7 KB, 5 views)
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  #178  
Old 12-17-2013, 07:37 PM
dog ear dog ear is offline
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Quote:
Originally Posted by Fleet 500 View Post
Mopar Muscle magazine put a 340 on a dyno and got some interesting results.

http://www.moparmusclemagazine.com/t...nce_mill_dyno/

http://www.moparmusclemagazine.com/t...e_headers.html
Mopar Muscle magazine has many reliable and honest articles online and most are very informative. The 340 dyno article is another good indicator of actuarial 340 performance. Their numbers closely coincide with the 1969 Hot Rod Magazine article I had posted earlier in this thread. Differences in horsepower numbers in the MMM dyno session reflect new (modern) technologies through the years with the result of better numbers.

Again, a good well-tuned stock 340 only makes slightly more horsepower than the original factory quote of 275. This is clearly shown in the magazine articles already posted. Like I stated, a supertuned 340 with headers, larger carb, and an aftermarket intake will produce 325-350 (gross) horsepower and that is with a ''good'' engine.

One thing I do wonder about in the Mopar Muscle article is the heads on that 340; are they actually stock - meaning no modified valves and seats, performance oriented multi-angle valvejob, intake and exhaust porting or gasket matching, and engine blueprinting. This is important information that is lacking in the (posted) February 2001 article. I know that the article states that the 340 is in stock condition but oftentimes it is in fact modified.

I looked online and could not find the indicated January 2001 article with the attendent specs for that particular engine rebuild. Most of these so-called original heads are in need of valve seat reconditioning and it is popular for most rebuilders to perform multi-angle valvejobs and seat mods that will surely enhance horsepower ratings beyond factory specs; even more so with aftermarket intake and exhaust mods. Modern carb and intake / exhaust manifoldiing tech will outmatch most any old-style 60s / 70s peformance stuff by a wide margin. Just sayin'.
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  #179  
Old 12-18-2013, 09:54 AM
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340 crate engines

If you look at the way the engines were tested, they were actually generating a "net" bhp figure in some cases. So the 275 bhp gross advertised number was probably more like the actual net bhp for the 1968-71 engines.

Last edited by RealityCheck; 12-19-2013 at 07:46 AM. Reason: new evaluation of data
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  #180  
Old 11-18-2014, 05:12 PM
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An update:

I saw on eBay, and won, the 1970 and 1/2 Supercars Annual. I should have all of them, now. From what I've read, they were only printed for the 1969-'72 muscle car models.

Here are two photos. I am eager to see the actual specs, especially the 454 Chevelle, the Hemi-'Cuda and the Buick GS 455. I should receive this magazine later this week, possibly by Friday.
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File Type: jpg annualucp.JPG (394.8 KB, 7 views)
File Type: jpg annualucp2.JPG (361.4 KB, 8 views)
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