Change the cam or leave it alone?

[Inspector71]

The car is a 66 Plymouth Sport Fury with a 1979 440, very low miles. The owner put a .477 lift comp cam in the engine. I am adding a new 4bbl and aluminum intake. I was wondering, since I have some of it apart, would a .484 lift cam make any noticeable difference, felt or real, in performance to be worth changing out the 477? It has a .323 sure grip with dual exhaust but no headers yet. They are on the list. For now, it is the cam profile I am interested in. Thanks everyone.

 

[The Horvaths]

I wouldn't take the effort to do so, seeing how you're not taking it all apart.

 

[66Newyorker]

I would leave the cam set up alone. Just don't put too big a carburetor.

 

[Inspector71]

Thanks folks. Would a 650 Edlebrock be too large a carb? I have 2 66 Sport Furys and this one is going to a younger brother and I am keeping the second for myself. Number two is getting a 413 from a 65 New Yorker and I'll save the hotter cam for that.

 

[Ripinator]

The car is a 66 Plymouth Sport Fury with a 1979 440, very low miles. The owner put a .477 lift comp cam in the engine. I am adding a new 4bbl and aluminum intake. I was wondering, since I have some of it apart, would a .484 lift cam make any noticeable difference, felt or real, in performance to be worth changing out the 477? It has a .323 sure grip with dual exhaust but no headers yet. They are on the list. For now, it is the cam profile I am interested in. Thanks everyone.

How did the car run with the cam that is already installed ?

 

[Polara_500]

I wouldn't use the 650, I stuck an 800 Thunder series on my slightly warmed 383 and it's been great.

 

[Inspector71]

Good question. I am not sure how it ran as the previous owner, a good friend, was running two 4 bbls on it and that proved too much. Might be a good idea for me to put the new intake and single carb on and see how it runs. I need to change the water pump and housing unit anyway so maybe less work.

 

[The Horvaths]

My 383 with 650 runs like a raped ape.

 

[66Newyorker]

I would leave the cam set up alone. Just don't put too big a carburetor.

I have a 440 in my car with a Street Demon 625 cfm. Had a richen it up from stock.

http://www.carburetion.com/Calc.asp

Do the math you would be surprised just how small a carburetor it takes. You may have to do some tuning.

 

[Ripinator]

Good question. I am not sure how it ran as the previous owner, a good friend, was running two 4 bbls on it and that proved too much. Might be a good idea for me to put the new intake and single carb on and see how it runs. I need to change the water pump and housing unit anyway so maybe less work.

I think that 650 carb is gonna be plenty of carburetor for you. . .

 

[Inspector71]

I really do appreciate your advice. All of you. I noticed Edlebrock's AVS goes from 650 to 800 with no 750, if I read the catalogue right, but they do have a 750 in AFB. Not sure which is better for this application. My brother will cruise around in the car and maybe take it to shows. Same for me but I have this 413 that has been in my garage forever which I want to put in the sister car. I have more time than money but I hope to get at least one done late summer.

 

[65Fury440]

The 650 is going to have better response.
http://www.summitracing.com/expertadviceandnews/calcsandtools/cfm-calculator

 

[70bigblockdodge]

If you are planning headers you should have at least a 750, a 800 AVS thunder series is better because of the spring tension available air valve secondary adjustment is better than a afb and the drilling counterweighs.

 

[Xenon]

Why people insist on using a larger carb is wayyy beyond me...
Bigger is not always better...
However with that said...
Do the math and use the CORRECT size carb...
For a normally aspirated engine:

CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456

Any ordinary stock engine will have a volumetric efficiency of about 80%.
Most rebuilt street engines with average bolt-ons have a volumetric efficiency of about 85%

What is your max USUABLE RPM ... Lets say 5500 rpm ...

• 
  
  
  • Using a 355 CID engine x 5,500 max rpm = 1,952,500
  • Take 1,952,500 x .85 = 1,659,625
  • Then 1,659,625 ÷ 3456 = 480 CFM

 

[70bigblockdodge]

Why people insist on using a larger carb is wayyy beyond me...
Bigger is not always better...
However with that said...
Do the math and use the CORRECT size carb...
For a normally aspirated engine:

CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456

Any ordinary stock engine will have a volumetric efficiency of about 80%.
Most rebuilt street engines with average bolt-ons have a volumetric efficiency of about 85%

What is your max USUABLE RPM ... Lets say 5500 rpm ...

• 
  
  
  • Using a 355 CID engine x 5,500 max rpm = 1,952,500
  • Take 1,952,500 x .85 = 1,659,625
  • Then 1,659,625 ÷ 3456 = 480 CFM

3 reasons I suggested a 800 thunder series
1. Air valve secondary is very fine tunable
2. He mentioned headers and can swap so if he waits to do it later he will have a capable carb for it.
3. If you put a 650 carb on a 440 with manifolds and and run it to 5500 you are coming to the limit add headers and can and turn it to 6000 now your choking it. The only things you gain with a small carb is low speed drivability and better cold weather tolerance, and who is driving these cars much below 40°.

 

[Inspector71]

Thanks everyone. If I know my brother, he will want to swap the 323 sure grip for a 354/355 unit and to with the TTI headers (expensive but work). And he will want the 484 cam. As to the math, I'll have to take your word for it as I am a product of the Philadelphia school (sic) system. But all the responses have been a real help. Now I have something to go on and a bit of research to do. This is a great forum.

 

[65Fury440]

3. If you put a 650 carb on a 440 with manifolds and and run it to 5500 you are coming to the limit add headers and can and turn it to 6000 now your choking it. The only things you gain with a small carb is low speed drivability and better cold weather tolerance, and who is driving these cars much below 40°.

My engine is similar to his but with a .509 and headers. The PO had a 600 Edelbrock on it. It would fall on it's face at about 5500. With an 850 it winds past 6200 where I shift now, but, it is softer down low.
A good 750 would probably be perfect for OP's application, but, I have had 2 750 AFBs, they were hard to tune/problematic.
For the record, this would get my vote.
Demon 1904 750 CFM Street Demon Carburetor - Holley Performance Products

 

[70bigblockdodge]

The AFB style Eddy's seem to have that flop in them when on a engine with any decent can which I'm guessing is a result of the counterweights. That new Demon carb based off the thermoquad should be a good piece, if I cannot get the thermoquad I have to work the way I want on my Charger I will be ordering a street demon.

 

[hotrodharley66]

Carbs are a thing of the past. With the price of a throttle body efi kit why bother with a carb..? This kit is $895 with a $100 rebate. I bought it and will have it up and running soon. http://www.summitracing.com/int/parts/fif-30002

 

[65Fury440]

Yea that EFI system is sweet, and would handle a majority of applications. Not a bad price at all, but still a big bite out of a build budget.

The last 2 carbs I bought were a Mighty Demon 850, for $200 new never used(Craigslist), and a refurbished Demon/Thermoquadish 625 cfm,direct from Holley for $219.00

I agree though, if a guy had to spend $600 on a new carb, the difference isn't much.
Thanks for the heads up!