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.
