Carb for 383 on. 411 s3 from 72

[Ed.bass416]

I put a stock Edelbrock performer 1406 on and whilst it’s ok for regular low rev driving, there is no real power or acceleration. Do I change the jets and rods to align. With a 1405, or replace with. A 1405. If I do that, do I change the manual choke to automatic? Or should I go bigger or switch to a Holley?
What. Have you guys done?
1972 411 s3 - not sure of the compression?

[Geoff Kingston]

1406 is a 600 cfm carb, for a 383 you need a 750 cfm unit if you are going to get the performance you are after, fitted one on my 411/3 and found it did everything I wanted and with manual choke and facet electric pump no starting problems hot or cold.

[Ed.bass416]

Thanks Geoff

[David C]

Here is a really good video where different size carbs are compared on a 383 using a dyno:

https://www.youtube.com/watch?v=tjbUd5mrmWg

What I take away from it is that if you are starting from scratch or replacing a worn out carb then the 750 that Geoff suggests is your best bet. However, there is probably little or no difference between that and the unit you already have below 4500RPM and you may well only see an improvement of around 2% in power by going larger.

[dezelsky]

On my 1975 Series 4, with 400ci engine, I initially replaced the original Carter with an Edelbrock Performer 750cfm, with electronic choke. It worked well out of the box and better with some rolling road adjustment. The car is mostly for long distance touring, not pedal to the metal, but plenty of fast motorway type cruising and I would say very satisfactory. On a long run returning 17-18mpg, with good acceleration and torque through the range. The car is also fitted with longer 603 rear axle.

I then switched to the Edelbrock 1902 AVS2 650cfm with electronic choke, because I read that it has a more sophisticated jetting system, and also was persuaded by comments that perhaps 750cfm is over-carbed for this engine. In practice the difference in driving is not noticeable at all. Similar torque and acceleration through the range. The 650cfm actually returned slightly lower mpg at 15-16 over a long run. I did not test either at the extremes of torque or revs (are any V8 Bristols are driven on the limit?), but pretty happy with both overall. I will probably switch back to the 750cfm unit for next long trip.

It might not be the same for your 383, which I think has slightly higher compression, but suspect it will not be a lot different. Also I doubt there is a lot of difference between equivalent Holley and Edelbrock units). From some other threads, it seems that to make bigger steps in performance/efficiency you should consider efi options, but this needs more complex setup and installation.