Carb for a street/strip stroked 440

[68-500]

Well obviously a lot of people with way more experience than I have regarding carbs and camshafts. Seems some say the AVS will be OK, others say it will be worse or no different. Some say "just change the cam", well easier said than done, that's what I have to work with, no plans or ability to change it any time soon. No PB, no vacuum advance, so vacuum not really an issue.

I didn't say anything was running poorly (that I can tell by seat of the pants), although the car is a bit hesitant out of the hole (I probably suck as a driver), could be a number of reasons. But then the car screams all the way to close to 6 grand. I doubt I will race it at the track anytime soon (only Brainard is near me, 2 hours drive). I have read in several places that running a double pumper on the street is not good due to too much gas off idle which can wash down the cylinder walls and create damage over time. Sure call me an idiot of that's not true, but I have read it in several places.

Maybe I just don't like Hollys as I don't race.

You didn’t mention that the engine has no vacuum advance. You don’t want to change the cam I can understand that. But you might be able to tune up some street manors with a vacuum advance hooked to a manifold source. Ask around I’ll bet money there’s somebody nearby that can tune that Holley up as well. I really think its probably the best carb for your current setup. I hope you get it all tuned up nicely.

 

[Geoff 2]

This^^^^^^^^^^^^^^^^^^^^^^^^

 

[JARRETT LYNCH]

This^^^^^^^^^^^^^^^^^^^^^^^^

View attachment 1921815

View attachment 1921816

View attachment 1921817

View attachment 1921818

Ported vacuum advances timing when you hit the accelerator and manifold vacuum does the exact opposite, it will retard the timing when you hit the accelerator. You have to decide which works best for you. I find ported works much better when driving around town for my engine than manifold. With a big cam manifold may be better for you. Each engine will be different on which one it likes. This debate goes on and on and on..................

 

[gtxrt]

Ported vacuum advances timing when you hit the accelerator and manifold vacuum does the exact opposite, it will retard the timing when you hit the accelerator. You have to decide which works best for you. I find ported works much better when driving around town for my engine than manifold. With a big cam manifold may be better for you. Each engine will be different on which one it likes. This debate goes on and on and on..................

if you go WOT off the line or to WOT while cruising they both go to zero advance.

 

[JARRETT LYNCH]

if you go WOT off the line or to WOT while cruising they both go to zero advance.

Exactly and what are you doing more when your every day driving? WOT or part throttle/cruising?

 

[BSB67]

Exactly and what are you doing more when your every day driving? WOT or part throttle/cruising?

On a good day, about half and half

 

[not so famous bob]

What places did you read this? Please share the sources.

Can you describe why a double pumper gives too much gas off idle?

I ran an 800 d.pumper on my 406 SBC , didnt have a bit of trouble washing down the walls ...sounds like b.s. to me ///

 

[JARRETT LYNCH]

I ran an 800 d.pumper on my 406 SBC , didnt have a bit of trouble washing down the walls ...sounds like b.s. to me ///

The only people washing down walls are people that don't know what they are doing.

 

[BSB67]

The only people washing down walls are people that don't know what they are doing.

And, generally not a function of the carb itself.

 

[JARRETT LYNCH]

And, generally not a function of the carb itself.

Its a result of an improperly set up carb- float bowls too high, fuel pressure way to high, jetting way too rich , dirty needle and seat, etc etc.

 

[BSB67]

I don’t want to paint with too wide of a brush. I’ve come across a couple carbs that are pretty fat out of the box, but the 4781 isn’t one of them. I find them pretty versatile in big block performance applications.

And certainly saying that DP carbs by definition wash down cylinder walls is silly.

 

[JARRETT LYNCH]

I don’t want to paint with too wide of a brush. I’ve come across a couple carbs that are pretty fat out of the box, but the 4781 isn’t one of them. I find them pretty versatile in big block performance applications.

And certainly saying that DP carbs by definition wash down cylinder walls is silly.

The new RVS double pumpers are so nice. I have one and love it. Start right up every time, ran great right out of the box, part throttle around town driving is perfect, no hesitations and the tuning is limitless with this carb. Everyone I have talked to and read that has one has the same experience.