Even though BG's are rated CFM wet flow (air and flowing fuel) and Holley's dry (just air)...which means a 750 BG will outflow a 750 Holley when flow tested dry (again, with just air), you'll be hard pressed to find anybody using a 750cfm anything on a peformance 496.

So....you may be alone, or near alone, on that one.

Hey guys, So i went to the shop and got some more paperwork. I'll post up some specifics when i get the docs out of the car at lunch. Long/short of it is that my carbs are definitely just not efficient, which we already know by the fuel consumption numbers. The shop has a holley 750 which he uses to get a base line then he goes from there with the owner's carbs. Both engines ended up making just about the same power with his carb and my carbs but just my carbs use over 100lbs more fuel per hour to make that power according to the dyno pulls.

So now I'm looking into new carbs for the remainder of this season instead of waiting for offseason, figured they will almost pay for themselves in fuel cost savings. Should I stick with the Holley marine 800? Not knowing much about the internals of carbs I'm curious to know how these carbs can be so "out of whack", is it something that can be fixed or is it a lost cause and just trash them?

Is anybody running dual PV's? I've asked this before without any straight answers. I had a carb built by Pro Systems with dual PV's. I'm running 94 square on the jets and have been going off plug color. I get incredible fuel economy at cruise but wonder if I'm hurting the motor?

Without knowing the application, it is hard to say. Generally dual power valves are used in applications where there is a possibility of going lean when the throttle is hammered. Very common in blower applications.

Only way to know for sure would be with a Wideband O2 for A/F numbers, or possibly a pyrometer to measure EGT's. You could be seeing good plug color at WOT because you have plenty of fuel then, but have a lean spot at the top of your cruising speed, say 3800 RPM.

I don't believe that can be right. If you are making the same power, but using 100lbs/hr (~16.5gallons more) that can't add up. If you're richer you are not going to make the same power. If this was the case you would never have to tune an engine unless you were looking for efficiency.
Ramos I'm not busting on you or your engines. I just think your dyno guy has taken advantage of you and did not do what you expected and paid for.

Smarter members please correct me if i'm wrong.

I'm not smarter and I think you are correct. I wonder if they were actually dynoed... If they were then whoever dynoed them needs to find a different line of work maybe a flower shop or something along those lines.

That's why I scheduled a vacation day to be there for my dyno session - I could see first hand what was being done. Besides, what better way to spend a day than listening to your motor sing?!? :)

Ramos can you get a list number off your carbs? Should be on the choke horn ...let's see what they really are and what came shipped in them from holley

I for sure know at least one was dynoed as I went to the shop during a lunch and saw the pulls. The one I witnessed was the stronger out of the two. I just ran the boat on Sun with 6 on board and 1/4 fuel and magaged to get some more rpms out of them. 4700 stb side and 45 port. Phone gps said 53 mpg but from what i remember the prior year it sure felt faster than 53 so I'll have to get another gps unit to compare.

Carbs don't have choke horns at all so no list number. Then only number I see on the main body is 6R 3767B. Here is a pic of the weaker motor's A/F and so on. The one on left is my carb, on right is first pull with shop carb. I'm currently running 78 primary with 6.5 PV and 92 secondary. Thinking about lowering the secondaries but I'll wait until I get the O2 bungs in my risers for more data.

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