I figured it out 1966 block everything else a 71.. question

[brigond]

I just figured out that my 1971 charger SE has a 1966, 383 block. I believe that this 1966 block was a 2 bbl engine.

The intake manifold, exhaust manifold, and the heads are 1971(very likely original to the car). The car originally had a 383 4 bbl, hp engine. These were rated at 300 horsepower.

Currently , my car has 1971 heads, 1971 4bbl intake manifold, and 1971 exhaust manifold sitting on a 1966 block that was originally a 2bbl engine.

The question .......... Have I lost horse power with a 1966 2bbl block instead of my 1971 4 bbl block? I'm not expecting a Definitive answer here. I'm just wondering what is more likely .

The answer here is the difference between a 1966 block 2 bbl And a 1971 block 4 bbl. Is there a difference?
Did one use a different crank than the other? Any thoughts or opinions would be appreciated thank you.

[brigond]

I have done more research since my last post. I looked up some engine specs for both the 1971 and the 1966 engine block. I'm not to we'll versed in the meaning of the specs but I do have a good idea. I'm hoping that when I post the specs here, someone can tell me if I am better off or not (horsepower wise) with the 1966 block or the original 1971 block. (That was unfortunately removed). Here are the specs:

1966-        bore    stroke                   Compression                          Horsepower                                   Torque

                 4.25 / 3.375.           2bbl 9.2:1 / 4bbl 10.0:1.        2bbl 270@4400/ 4bbl 325@4800 rpm      2bbl 390@28
                                                                                                                                                  4bbl 425@2800




1971 -    Bore      Stroke                  Compression                         Horsepower                                    Torque

              4.25 / 3.38.              2bbl 8.5:1 / 4bbl 8.5:1           2bbl 275@4400 / 4bbl 300@4800rpm.     2bbl 375@ 28
                                                                                                                                                   4bbl 410@3400

[brigond]

I have done more research since my last post. I looked up some engine specs for both the 1971 and the 1966 engine block. I'm not to we'll versed in the meaning of the specs but I do have a good idea. I'm hoping that when I post the specs here, someone can tell me if I am better off or not (horsepower wise) with the 1966 block or the original 1971 block. (That was unfortunately removed). Here are the specs:

1966-        bore    stroke                   Compression                          Horsepower                                   Torque

                4.25 / 3.375.           2bbl 9.2:1 / 4bbl 10.0:1.        2bbl 270@4400/ 4bbl 325@4800 rpm      2bbl 390@28
                                                                                                                                                 4bbl 425@2800



1971 -    Bore      Stroke                  Compression                         Horsepower                                    Torque

             4.25 / 3.38.              2bbl 8.5:1 / 4bbl 8.5:1           2bbl 275@4400 / 4bbl 300@4800rpm.     2bbl 375@ 28
                                                                                                                                                  4bbl 410@3400

Please keep in mind that I likely have the 2bbl Version of the 1966 engine. Thanks again.

[XH29N0G]

See what other folks have to say.  My understanding is that the compression will depend on the pistons and the heads (chamber volume).  My understanding is that aside from possible differences that make one bottom end stronger than another, the bottom end is really just the 'pump' that is made to work.  The power and torque will come from the top end (compression, cylinder heads, intake, carburetor, exhaust and cam....). 

[Tilar]

I doubt you lost horsepower with the 66 block, because the heads and manifolds will add or subtract from your horsepower as well as the bore/stroke and pistons in the block. Either way you're probably only talking a small difference if any.

[John_Kunkel]

The '66 383-2 had 9.2 compression with closed-chamber heads, the '71 383-2 had 8.5 compression with open-chamber heads. Putting the '71 open chamber heads on the '66 probably makes the compression about the same so the only difference would be the better flow of the '71 intake and heads so you probably gained a little power.

[mauve66]

assuming it hasn't been rebuilt in the last 40+ years

[brigond]

assuming it hasn't been rebuilt in the last 40+ years

I would assume that it has been rebuilt. I would think that if it was , it would be a positive thing. I'm trying to contact the original owner. I've also been trying to get the classic car dealer to dig up the paper work he said he had from the block change. He said that the top half was rebuilt. I'm thinking of bolting on  headers or may be a performance intake manifold. I found a real good site that shows how the 383 did well with bolt on parts like intake manifold, exhaust manifold and cam.

[brigond]

Hi, any more input on this?  So far Im thinking that I may have gained or there may be little or no difference.  Thanks.

[bsakal]

My '66 Newport 383 2bbl has the small chamber 516 heads, with a 1.60 exhaust valve, and dished pistons from the factory. I doubt the compression is close to 9.2 as listed, especially with the dished pistons. I believe it's between 8.5:1 to 9:1, at the most. The only mod is a '69 4bbl cast iron manifold, Carter AVS, and dual exhaust. The factory cam has .425 intake / .435 exhaust lift at the valve. Putting open chamber heads on the '66 2bbl engine would drop the compression, unless it was rebuilt and had flat-tops installed at the least.

I have a 71 HP block that's .040 over, the pistons are way down in the hole at TDC. That engine would benefit from the small chamber '66 head.

Both engines have forged steel crankshafts from the factory. 

[brigond]

My '66 Newport 383 2bbl has the small chamber 516 heads, with a 1.60 exhaust valve, and dished pistons from the factory. I doubt the compression is close to 9.2 as listed, especially with the dished pistons. I believe it's between 8.5:1 to 9:1, at the most. The only mod is a '69 4bbl cast iron manifold, Carter AVS, and dual exhaust. The factory cam has .425 intake / .435 exhaust lift at the valve. Putting open chamber heads on the '66 2bbl engine would drop the compression, unless it was rebuilt and had flat-tops installed at the least.

I have a 71 HP block that's .040 over, the pistons are way down in the hole at TDC. That engine would benefit from the small chamber '66 head.

Both engines have forged steel crankshafts from the factory. 

So it's likely that  I lost compression  with the 1971  heads . especially if  the original dished pistons are still there . this would mean loss of power . if the engine was rebuilt with flat top pistons , I may have lost some  compression with the 1971 open chamber heads.  How am I doin.  so you believe I lost. Horsepower?

[71 SE3834V]

Ok, time to get an education. What's the difference between open & closed chambered heads?

[Ghoste]

Open chamber features a large dish shaped combustion chamber in the head and closed has none or just enough to hold the valves.

[Cooter]

Ok, time to get an education. What's the difference between open & closed chambered heads?

About a half point in compression. Sure, there are those that will tell you that the open chamber heads have better ports, larger valves, etc. IMO, All that CAN BE ADDED to closed chamber heads which have way better quench. NOWHERE can one gain 1/2 point compression free.

[71 SE3834V]

Ok, makes sense now. If you put an open chamber head on where a closed one was before you have increased the volume therefore dropping the compression ratio a bit. Does that help you understand brigond? Did me, learning more everyday.
From what I'm reading, whether it hurts or helps (due to larger valves etc.) is up for speculation and my guess is it might take a dyno to tell the difference and probably wouldn't be noticed in the seat of your pants. 

Hey brigond, you might look into getting ahold of one of those "Led" cameras to look in the combustion chamber to see if you can tell if the pistons are dished.

[John_Kunkel]

I've never seen a "dished" piston in a BB, they just reduced the pin height to lower compression.

All factory CR numbers can be expected to be a half-point lower than the advertised spec so comparing early/late gets the same result.

[brigond]

Yes 383se 4v, I got it. I was thinking about that led camera trick also.  John says he's never seen dished pistons in a BB. I'll research that too. I did read that closed chambered is better because it creates more compression but is not as clean. This is why they moved away from closed chamber. Like you said it seems to be up for debate from what I've been reading.

My 383 was originally an 4 bbl  HP engine making 300 HP when it sat on its original block. Now the same upper half sits on a 1966 2bbl block. Is it likely I'm still making 300 or less?


The previous years made 325- 335 horse power. They had higher compression .What made this difference? The earler cranks were forged and in 71 they went to cast.

[bsakal]

John Kunkel, were the engines you looked at mostly 4bbl engines? Or later year 2bbl engines? The 1966 383 2bbl engine with the 516 head has a shallow dished piston. My own car has them, and it is factory. There is another '66 Newport in a yard near me with a 383-2bbl engine, and it has 516 heads with shallow dished pistons. It's also been discussed on other forums over the years. I am not sure about the later years with a 2bbl and the 906 head.  

[brigond]

Yup bsakal , I also read  other forums  refer to 66 pistons with the two barrel having dished heads.

[Cooter]

My 383 was originally an 4 bbl  HP engine making 300 HP when it sat on its original block. Now the same upper half sits on a 1966 2bbl block. Is it likely I'm still making 300 or less? I too have never seen a "dished" piston from the factory. I HAVE however, seen a rebuilders piston that has a Slight "ring" about a 1/4" from outside but is in no way a "dish" to lower compression.


The previous years made 325- 335 horse power. They had higher compression .What made this difference? The earler cranks were forged and in 71 they went to cast.I wouldn't believe the hype about factory HP ratings. Recently we did a 440 "Magnum" engine to factory sepcs without ANY High Perf. enhancements and it only made 360 HP with manifolds, stock compression(9.5:1) and stock "Magnum" cam. Not quite the 375 HP rating.

[brigond]

pgrading The 383 Magnum AVS Carb - 383-Resto To Rad
Bolt-Ons Add 117 Horsepower To A Stock 383
From the September, 2002 issue of Mopar Muscle
By Steve Dulcich
Photography by Steve Dulcich

1  

Last month we built this conspicuously...
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Last month we bolted together a 383, built as true to original 383 Magnum/Commando specs as practical. Inside, our 383 benefited from Jim Grubbs' blueprint-quality machining, moly rings for increased bore life and seal, and modern KB hypereutectic pistons. The block was milled for "zero deck," which will eventually give us an ideal quench clearance if aftermarket closed-chamber heads are employed.

The stock #906 heads were milled .020-inches to compensate for the thicker replacement head gasket, thereby reducing chamber volume from the stock 87 cc to 83 cc. The deep valve notches in the KB pistons (6 cc) required to run long-duration high-lift cams, coupled with the 84cc open-chamber heads and the 383's short stroke, gave us a compression ratio of 9.2:1. This compares to 9.7:1, which would have been achieved with stock-style flat-top pistons with no valve reliefs.


For our baseline runs, the...
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Such minor modifications aside, this was a 383 just like Chrysler used to build. We gathered up an original 383 Magnum AVS carb, the correct PN 666 iron intake manifold, a real set of factory high-performance exhaust manifolds, and slid in a reproduction 383 "Road Runner" cam. A PAW SuperStock crank kit supplied the usual rebuild parts, as well as a crank and rods ordered as a balanced assembly to replace our too-far-gone originals. Overlooking the Mopar electronic ignition distributor-installed more for reliability than performance-the 383 on the engine stand was like an artifact from the past. We had only one question: How much power would it make?

From 1968-1970, the 383 Magnum was rated at 335 hp, although Mopar fans who remember these free-revving engines would compare seat-of-the-pants pull to the 440. Sporting the same heads and cam as the 440, but with a smaller displacement, the 383 certainly could be wound tighter. Was it good for its advertised 335 horsepower? A visit to the friendly dyno operators at Westech would give us the answer.


With our baseline numbers...
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It was no secret that a 383 was responsive to traditional hot rod mods. Some may even argue that modified 383 cars played the key role in establishing Mopars' legendary reputation for performance. The 383 B-Bodies in particular were everywhere, while the Hemis were feared but seldom seen. The 383 cars were performance machines for the regular guy, and were used, abused, modified, torn-up, and sadly, often thrown away. The 383s fought it out in the trenches, simply because they worked. People weren't afraid to modify their 383s, and we weren't going to be shy about souping-up ours. We had a program of bolt-on parts waiting to prove their worth, with the dyno being the final yardstick.

Truth or Lies
Much has been said of the horsepower numbers game in the musclecar era. Sometimes the claim is made that the gross ratings were wildly optimistic. In some cases the assertion is that certain engines were "seriously underrated." We've been here before, testing a stock 340 and a stock 440, and generally found that Chrysler was fairly accurate in its ratings compared to dyno numbers we've seen on other stock engines. We dutifully loaded our stock 383 onto the SuperFlow dyno at Westech to see how many of the 335 horses were real, and how many imagined. The 383 sparked instantly to life, and we were struck by how mellow it sounded through the factory manifolds compared to the open-header, big-cammed beasts we had been testing lately.

After the customary break-in cycle, we let the 383 fly. The readout at the end of the pull showed 335.2 hp at 5,000 rpm, and 392 lb-ft at 3,600 rpm. We adjusted the timing from 35 degrees total to 38, and ran a couple of backup pulls. The 383 responded with 338 hp at 5,000 rpm and 394.6 lb-ft at 3,600 rpm. No, Ma Mopar wasn't lying when she hung the numbers on the high performance 383.


The old AVS perched atop our...
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Steve Brule, Westech dyno...
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We elected to go to a Mopar...
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Power Mods
While 338 hp for any stock engine is respectable, we wanted to explore the power-producing potential of the 383. This time around we would keep the basic 383 long-block package stock, but shake out some of the hidden power with basic bolt-ons. Our first target was the same chosen by countless thousands of 383 owners over the years-adding a set of tube headers. We pulled down the Magnum manifolds and replaced them with a set of Hooker PN 5101-1 HKR metallic-ceramic coated 1 7/8-inch four-into-one headers. Was there much to be gained over the sleek high-performance manifolds? The 383 definitely thought so, posting 358.3 hp at 5,400 rpm, and 413.7 lb-ft at 3,500 rpm. The headers added a solid 15-25 lb-ft of torque across the full rpm range. That's added power you'd definitely feel.


The big Demon actually boosted...
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Next, we set our sights on the original AVS carb. With only a guesstimated 600 cfm at hand, and the dyno recording over 1.8 inches Hg. of vacuum at wide open throttle, it was clearly short on airflow and costing some power. We went straight to the kill here with an 850 Demon carb. The 850 may be considered too much at this mild state of tune, but with our subsequent modification plan, it would be just enough.

Even though at this stage of the game we would be over-carbureting the 383 with the big Demon, we were confident it wouldn't be a detriment on the dyno. On the street, however, it may be a bit much for a stock 383 with headers. The added airflow was a definite improvement, with the 383 now edging up to 367.2 at 5,100 rpm, and 434 lb-ft at 3,600 rpm. Contrary to conventional wisdom, we found the big carb actually added substantially to torque in the low- to mid-range-as much as 25 lb-ft. Although the top-end numbers also climbed, the gains weren't as dramatic as lower in the rpm range.

The Demon carb was clearly doing a better job of mixing the air and fuel than the AVS. We knew exactly what was holding the 383 back at higher rpm-that heavy chunk of cast iron sitting under the carb.


We opened the engine, liberally...
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Our next mod, naturally, was to swap the stock iron intake for a modern performance piece in an effort to unlock the 383's breathing efficiency. Since we eventually intend to create a high-rpm screamer from our 383, we opted for a single-plane intake. Since Mopar Performance's M-1 has been the best low-deck street/strip single-plane intake we've used to date, it was pressed into service on our 383. With the intake change, the visual character of our 383 was transformed, finally looking like a performance mill. Our next pull showed that the looks were more than skin deep, with the dyno numbers now catapulting to 406 hp at 5,400 rpm, and 433 lb-ft at 4,000 rpm. True to form, we lost a handful of torque down low while going from a dual-plane to a single-plane, but we gained huge up top. The M-1 really unlocked the breathing of the engine, giving us a remarkable 400-plus hp with a stock-cammed, stock-headed 383. Yes, 383s can make power, and make it cheaply. We had a rebuilt stock engine, with headers, carb, and intake, and were churning better than 400 hp.


The Demon carb certainly looked...
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Our final mod this time around...
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Comp recommends their dual...
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We just bolted the stock valvetrain...
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Our final mod, not surprisingly, was a good old-fashioned cam swap. There was, however, nothing old-fashioned about the grind. Competition Cams has recently introduced a line of Mopar-specific grinds which take advantage of the Mopar engine's .904-inch tappet diameter. Mopars have a tappet diameter of .904 inches, while Fords measure .875 inches, and Chevys .842 inches. Why is this significant? The larger tappet raises the limit on the possible cam velocity in a flat tappet cam. This allows the cam designer to develop more aggressive profiles, giving a faster rate of lift. More lift means more open area at the valve, and typically more power than a lower lift cam of the same duration. Most cam profiles are simply designed to be compatible with .842-inch tappets, since it is the lowest common denominator, and will work with that tappet size or larger.


Wi

I didnt know how to add a link so i copied and pasted this pretty interesting article

[brigond]

If i can figure out how to add a link I will post it so you all can read the full article.

[ACUDANUT]

Demon cabs are just Holley's that look aerodynamic.

[brigond]

In the end of the article , after the addition of a new cam, they made 450 HP. 

[Cooter]

 I'M sure all the factory, Mass production 383's got "Blueprint Quality" machine work with zero deck blocks. I'm all but positive every single 383 came out the factory making exactly the same 335 HP.

[mauve66]

I'M sure all the factory, Mass production 383's got "Blueprint Quality" machine work with zero deck blocks. I'm all but positive every single 383 came out the factory making exactly the same 335 HP.

i agree, didn't they have ISO 6625-6626 specs back then
my car was made 2 days before xmas, i bet it didn't make the published HP rating either

[brigond]

Here is thOur final mod, not surprisingly, was a good old-fashioned cam swap. There was, however, nothing old-fashioned about the grind. Competition Cams has recently introduced a line of Mopar-specific grinds which take advantage of the Mopar engine's .904-inch tappet diameter. Mopars have a tappet diameter of .904 inches, while Fords measure .875 inches, and Chevys .842 inches. Why is this significant? The larger tappet raises the limit on the possible cam velocity in a flat tappet cam. This allows the cam designer to develop more aggressive profiles, giving a faster rate of lift. More lift means more open area at the valve, and typically more power than a lower lift cam of the same duration. Most cam profiles are simply designed to be compatible with .842-inch tappets, since it is the lowest common denominator, and will work with that tappet size or larger.


With the new cam, the engine...
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We were eager to try one of the new Comp grinds, and ordered up an XE285HL-10. This is a fairly serious hydraulic profile, rated at 285/297 degrees gross duration and spec'ing out at 241/247 degrees duration at .050 inches, with .545/.545-inch lift on a 110-degree lobe separation. The cam was degree'd in at four degrees advance and topped with a set of matching Comp lifters. We were still budget-conscious with this engine and elected to retain the stock 383's valvetrain. Unlike some competitive brands of engines, the big-block Mopar hydraulic shaft-mount system is rugged. We upped the valvesprings at the same time to Comp's PN 924 dual-spring assemblies since the high lift cam requires more spring than the stock 383 cam. We used an on-the-head spring compressor from Powerhouse to make quick work of the job.

Back up and running, with the big stick, the 383 had a weightier thump. With the stock heads, the cam would likely not realize its full potential with our present combo, but we still expected a gain and expected to pull higher rpm. With that in mind, the dyno controls were reset to 6,200 rpm, and we opened up the 383 once again. It pulled cleanly through the revs and we now had a 455 hp 383. Peak power was actually 454.9 hp at 6,000 rpm, and 456.6 lb-ft of torque at 4,800 rpm. With the big cam we lost 5-10 hp at the bottom of our test range, but from the mid-range up the big stick just pulled away like a freight train for a gain of nearly 50 hp. The useable rpm range of the engine was extended by better than 500 rpm in the bargain.

We were impressed with the 383. Stock with the exception of the headers, cam, intake, and carb, we were solidly over 450 hp. That's dollar value per horsepower.

Is that the end for this 383? We'll likely revisit it a few issues down the line, looking to increase the head flow capacity and compression ratio. We can handle that in one swap. Maybe a solid lifter cam to up the rpm range, and who knows how far the under appreciated 383 can go.

Dyno Results
Tested at Westech Performance Group on a Superflow 901 Dyno

Torque
RPM   STK   HDRS   CARB   INTKE   CAM
3000   382.7   406.3   427.1   405.5   394.2
3200   388.1   406.6   422.6   410.9   400.0
3400   388.3   412.6   431.9   421.2   414.7
3600   394.6   411.2   433.7   426.1   431.5
3800   392.4   408.3   430.8   430.0   435.5
4000   387.2   401.3   424.6   433.0   446.5
4200   377.8   396.2   416.4   430.1   451.5
4400   371.4   390.2   409.7   430.1   451.8
4600   367.8   384.6   402.0   427.8   454.2
4800   361.6   379.5   398.5   424.3   456.6
5000   355.1   373.4   385.6   421.3   450.3
5200   337.2   357.8   368.1   407.7   449.1
5400   322.8   348.5   351.4   395.1   435.8
5600       417.0
5800   407.6
6000   398.2
Horsepower
RPM   STK   HDRS   CARB   INTKE   CAM
3000   218.6   232.1   244.0   231.6   225.2
3200   236.5   247.7   257.5   250.3   243.7
3400   251.4   267.1   279.6   272.7   268.5
3600   270.5   281.9   297.3   292.1   295.8
3800   283.9   295.4   311.7   311.1   315.1
4000   294.9   305.6   323.4   329.8   340.0
4200   302.1   316.8   333.0   343.9   361.1
4400   311.1   326.9   343.2   360.4   378.5
4600   322.2   336.8   352.1   374.7   397.8
4800   330.5   346.8   364.2   387.8   417.3
5000   338.0   355.5   367.1   401.1   428.7
5200   333.9   354.2   364.5   403.7   444.6
5400   331.9   358.3   361.3   406.3   448.1
5600       444.6
5800   450.1
6000   454.9


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