avis au gars de mopar question sur 383 2 bbl et magnum

ma question est la suivante :

Moi mon auto est sorti 383 2 BBL.

J'aimerais savoir

1. le bloc 383 2bbl et le bloc du 383 magnum est t il le meme?
2. peut on prendre mon bloc 383 2bbl et le remonter en 383 magnum ?
3. les differences entre les 2 moteurs sont quoi a part la carburation? cam?piston?tete?valve?

voici un article du net sur les difference mais je ne suis pas sur de leur exactitude.If one is talking a 383 Magnum (1968-1971) versus a 400 Magnum (1972-1978, though 1974 was the last year they were un-choked by catalytic converters, etc..), the differences are few but significant. Both are Chrysler "B" engines, sharing a 3.38" stroke and related connecting rods. The Magnum versions (Not just a Four Barrel engine but a true "Magnum") will have a windage tray, the Magnum camshaft (Pirated from the 440 Magnum), a double roller timing chain (Though, this is an area of some contention), and heavy duty valve springs with surge dampers. Both engines even had a "fresh air" option during their careers (The Roadrunner & Super Bee 383's all had the option, same with the Challengers & 'Cudas, and the 1971 (Only) Charger Super Bee had a "Ram-Charger" system. The 400 Magnum only had the option in the 1972 Roadrunner with "Air Grabber"; I haven't seen any Charger Rallye (1972-1974) with anything besides the power-bulge hood.). Both engines share similar heads with 2.08" intake valves & 1.74" exhaust valves... (Arguments can form as to whether the 1970 "906" heads are best... etc.. 400's did get the hardened exhaust seats starting in 1973, though..)

Differences:

Bore: the 383 Magnum has a 4.25" bore; the 400 as a 4.34" bore (Even larger than the 4.32" bore of a 440).

Compression ratio: the 383 Magnum from 1968-1969 has a 10:1 ratio; I believe the 1970 had a 9.5:1 ratio (need to verify) and the last year of the 383 Magnum, 1971, had a 8.5:1 ratio. All 400 Magnums had an 8.2:1 compression ratio.

Horsepower ratings (A bit of an apples to pumpkins comparison). The 383 Magnum from 1968-1970 was rated at 335 Gross horsepower. In 1971 it dropped, with the compression ratio change, to 300 gross horsepower and factory literature noted a 250 SAE Net horsepower rating. All 400's were rated in terms of SAE Net Horsepower with ratings as high as 260 horsepower and others ranging from 245-255 horsepower. So, the low compression 383 Magnum was edged out power-wise by the 400 Magnum (Which all else being somewhat equal, it should have). The high ratio 383 was probably 15-20 horsepower stronger than the NHRA rating of 310 for the 400 Magnum...

Manifolds: Intake: the 383 Magnums were all set up for 'square bore' carburetors (Carter AVS; some 383's had Holleys but I'd have to research to see if it came on the Magnums... and that would have only been 1971, I think..). Oddly enough, the 1971 intake came with the infamous 666 in the casting numbers. All 400's with a 4 barrel came set up for a Carter Thermo-Quad (850 CFM) spread-bore carburetor. Considering that folks in the "know" in the late '60s & early '70s, recognized that the 383 was under-carbureted with its piddly 600-660 cfm carb (Big bore, short stroke engines like air flow more so than their longer stroke brethren and routinely put the larger 750 cfm AVS from the 440 on them ~ for a sizable degree of top end power... The 400 had a substantially better induction system. Direct Connection/MoPar Performance actually recommended retro-fitting the 400 Intake & Thermo-Quad on to 383's for a power boost! I'd say the change was worth 10 horsepower or more.

Exhaust: The '68-'70 383 Magnums (And 440's) had the best exhaust manifolds for a Big Block MoPar since the Max Wedge 413/426 of '62-'64. 1971 is dubious as to what it came with... some say "yea"; some say "nay". I've got a 1971 Polara with a 383 Magnum and its got "the good ones"... but that doesn't mean that the B-Bodies got them. Anyhow, none of the 400's got the really good "Magnum Manifolds". I don't know what the difference is, power-wise, but I suspect that its worth around 5-10 horsepower, if that... I always noticed that MoPar Big Blocks love headers ~ even if they came with the good manifolds to start.

Crankshafts: All 383's, except the 1971 383 2 barrel, came with forged steel crankshafts. All 400's came with cast cranks, except the '72 - '74 400s that came in a Roadrunner or Charger with a 4 speed manual transmission.

Blocks: Very, very similar but the 400 is a special thin-wall casting to allow for the 4.34" bore size. The average 383 block cannot withstand the .090" over-bore to become a 400.