Anyone have actual data re: carbs?

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Posts: 33
Joined: Wed Aug 23, 2017 5:49 pm
Your car is a: 1979 Spider

Anyone have actual data re: carbs?

Postby Slartibartfaster » Wed Sep 27, 2017 2:23 pm

I'm looking for help to find dyno or other data regarding my carburetor options. I've had lots of recommendations and I think I at least know what to eliminate (e.g. I'm not a dual IDF level player yet.) But I can't find actual data to support one carb over another. I know a lot of you have been through this already; can anyone show me what actually changed with their upgraded carb?

I'm replacing the original dog on my '79 with a single carb. My 1800 manifold is on the way, I have a non-CA car that already has a 4-2-1 exhaust so I'll keep that. I do not plan to replace cams, head or pistons. I'm in Ohio so no emissions testing worries. Looking at 34ADF, 32/36DFEV (Weber and EMPI), 38/38DGES. Missing any obvious choice?

How can I use data to aid this decision? Before vs after swap (and tuning) dyno runs? Even if it's a different car or setup I'm only concerned about what changed due to a carb swap. Too many variables? What about CFM through the carb...does this data exist and what would it tell me? How else is carb performance measured?
'79 Spider
'15 Tesla Model S85D
'14 Santa Fe
'17 Civic

Posts: 987
Joined: Tue Mar 17, 2009 9:25 pm
Your car is a: 1972 124 Sport Coupe

Re: Anyone have actual data re: carbs?

Postby sptcoupe » Wed Sep 27, 2017 7:13 pm

I don't have actual data, but if the build doesn't include cams, CR bump bigger valves (optional), I would stay with a single carb (32/36 or 34 ADF) on a single plane manifold. With the header, that will get you a noticeable performance gain for a lot less money any save you from having to set up the throttle linkage, etc, for dual carbs.

In 1972 I was living in Spain and had factory dual IDF 1608 124 coupe. As I recall, the single carb version had 98hp, and mine had 108hp (both euro cars). Assuming my memory isn't terrible and those are the numbers (or close to them), you will get half that 10hp difference with the header, a bigger carb and better manifold.

Posts: 156
Joined: Mon May 25, 2015 11:14 am
Your car is a: 1979 Spider

Re: Anyone have actual data re: carbs?

Postby bluespider262 » Thu Sep 28, 2017 5:00 pm

No data, but you are just gonna have to trust me when I say its night and day. Just the 32/36 and single plane - no other changes. But if your stock setup works and you are happy with it, not sure I'd bother until I had a problem because it is a bit of work that easily leads to "while I'm at it" type of stuff. The ADHA is a time bomb in my opinion though. If you tear a diaphragm, for example, I'm not sure you'd have a real easy time finding a reasonably priced replacement.

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