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what size carb?

  
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what size carb?

 
freddiejip freddiejip
New User | Posts: 25 | Joined: 10/12
Posted: 03/17/13
12:54 PM

355 sbc, 230cc heads, .597 lift, 13.5:1 compression. Looking to run 7,500-8,000 rpm's  

68scott385 68scott385
Guru | Posts: 1990 | Joined: 10/09
Posted: 03/17/13
02:35 PM

800-850  
68scott385 68scott385 68scott385

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/17/13
03:20 PM

Freddie

If your duration is in the .240's @ .050  you can maybe pull to 7700.

7000 RPM 709 CFM

7500 RPM 760 CFM

8000 RPM 810 CFM

8500 RPM 861 CFM

Your cam will limit the upper end.

Bob  

freddiejip freddiejip
New User | Posts: 25 | Joined: 10/12
Posted: 03/17/13
04:40 PM

Duration is 267 @.050  

68scott385 68scott385
Guru | Posts: 1990 | Joined: 10/09
Posted: 03/17/13
07:11 PM

CFM=(CIDxRPMxVE)/3456
cid = cubic inch displacement
rpm = max rpm expected to turn
ve = volumetric efficiency

rarely do naturally aspirated engines achieve 100% volumetric efficiency but in some instances one will in a small rpm range when all breathing components are matched correctly

the cam determines at what rpm the engine breathes best

the carb determines how much it is allowed to breath...all it wants...or gasping for air...you have to choose a carb that allows your combination to breathe what it wants at the rpm it wants it without being too big causing a poor signal to the venturis  
68scott385 68scott385 68scott385

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/18/13
07:53 AM

freddiejip.

Most carburetors will flow more then they specify. Thats why when NASCAR was running carbs. They had gauges for every part of it. So there was little risk of Cheating...LOL... The new Holley Fuel injection from what I understand is all sealed with the techs Name, and flow rates from the factory, for NASCAR...

Drag racers for years have used a 750 CFM body with an 800 CFM or 850 CFM base to get them to flow mare, and it works. You need to know what your doing like anything else....

I have No Idea what your course of action is for your engine. With a 13:5:1 compression ratio, and a fairly big stick. I would feel safe to say its a weekend warrior.

Give us the following?

1.What type of Cam are you running?
  A.Hydraulic Flat Tappet
  B.Hydraulic Roller
  C.Solid (Mechanical) Flat Tappet
  D.Or an all out Solid Roller

2.Cylinder Heads who's heads, or Home Grown. Do you know what they flow. @ .500, .600 and .700 lift
  A.230 CFM intake runner will flow with with big valves.

3.Is your Cam .597 the lift on both IN/Ex. I'll tell you why in my next post. I have some ideas for you.

4.Type of intake

5.Automatic, or Manual trans. If an Automatic the type and stall speedopen plenum or a 180* divided

Bob  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/18/13
07:53 AM

freddiejip.

  Most carburetors will flow more then they specify. Thats why when NASCAR was running carbs. They had gauges for every part of it. So there was little risk of Cheating...LOL... The new Holley Fuel injection from what I understand is all sealed with the techs Name, and flow rates from the factory, for NASCAR...
  Drag racers for years have used a 750 CFM body with an 800 CFM or 850 CFM base to get them to flow rates, and it works. You need to know what your doing like with anything else....Don't do something you don't understand...
  I have No Idea what your course of action is for your engine. With a 13:5:1 compression ratio, and a fairly big stick. I would feel safe to say its a weekend warrior.

  Give us the following?
1.What type of Cam are you running?
  A.Hydraulic Flat Tappet
  B.Hydraulic Roller
  C.Solid (Mechanical) Flat Tappet
  D.Or an all out Solid Roller
2.Cylinder Heads who's heads, or Home Grown. Do you know what they flow. @ .500, .600 and .700 lift
  A.230 CFM intake runner will flow with with big valves.
3.Is your Cam .597 the lift on both IN/Ex. I'll tell you why in my next post. I have some ideas for you.
4.Type of intake
5.Automatic, or Manual trans. If an Automatic the type and stall speedopen plenum or a 180* divided Grin  Cool

Bob  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/18/13
09:39 AM

freddiejip

I have to ask with the 13:5:1 compression engine, fairly big stick, and your looking for a carb to get you to 7,500 RPM to 8,000 RPM is this a weekend warrior?

  Fill in these blanks
1.Rear Gear Ratio
2.How Tall are your Rear Tires
3.Transmission type, an Automatic or Manual
4.If an Automatic what stall speed convertor are you using
  I am guessing that your cam whatever the type is .597 In/Ex now the duration is .267* @ .050.

  Just hear me out because if you want to get more Horse Power, you can try a few changes, really without much money and a little work on your end. Well here are my thoughts and you can do what you want. But I'm an old Gear Head and I see maybe some potential, for more Horse Power.

1.If you have the "PISTON TO VALVE CLEARANCE" by increasing the Rocker Arm Ratio from 1.5 to 1.6 you can pick up another you can increase it to .675. Thats providing your valve springs, and the remainder of your valve train can handle the increase in lift. The increase in duration would be marginal.
2. For a Steel Rod Engine you need a required minimum of .080 Intake valve and .100 Exhaust valve clearance using clay in a plastic bag.
  A.These clearances should be measured with a head gasket in place and torqued to specs. (Use an Old Head Gasket).
  B.Measure the Piston Dome to the Head Clearance using (Play Doh) clay in a plastic bag.
  C.This is Providing you have "NO VALVE FLOAT".
3.For an Aluminum Rod Engine you need a  required minimum  of .100 Intake valve and .120 Exhaust valve clearances. Measured with clay (Play DOH) in a plastic bag
  A.These clearances should be measured with a head gasket in place and torqued to specs. (Use and old head gasket).
  B.Measure the piston dome to head clearance
  C.This is providing you have "NO VALVE FLOAT".
4.From a performance stand point you can install the a 1.6 rocker arm on the exhast valve side, and then try them on the intake valve side. You may find that the exhaust side will respond more, with the 1.6 rocker arms.

Bob  

freddiejip freddiejip
New User | Posts: 25 | Joined: 10/12
Posted: 03/18/13
02:43 PM

.597 with 1.6 ratio figured in if i figured right. Box says .555
Duration is @.050
procomp aluminum heads with 2.05 intake valve
solid flat tappet at the moment
Victor jr. Intake
steel hbeam rods
14cc dome pistons
.041 mls head gasket
6.68 tranny gear, 4.10 rear gear
31in 15.50 15 bkt tracmaster tires and will also run 33 14 15 boggers
6,200lb 2wd super stock pull truck  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/18/13
11:09 PM

Freddie were we working on a project approx 5-6 months ago?

Okay thats what I needed to know. The .597 is with a 1.6 rocker ratio.

I thought if you could pump a little more air into the engine, bur if your using a 1.6 rocker already.

So your pretty much at the maximum now.

You have enough Rear Gear, just keep an eye on the solid flat tappet.Just a little FYI: If the engine is going to lay dorment for a couple month's, release the valve spring tension. It takes the pressure off the valve train, and I believe it helps the save valve train life.
  I always took the tension off the valve train. I ran Solid Rollers with .800+ lift and a lot of valve spring pressure. Just something I believe in...

Bob  

skyeking skyeking
Addict | Posts: 2738 | Joined: 08/09
Posted: 03/19/13
04:04 PM

Hi Bob,
Why not try a 830 annular Holley.??  
skyeking

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/19/13
07:08 PM

HI Noel:
I was talking about you my friend....
An annular discharge 830 would work, I don't know if there is enough Cam and Cylinder head to support a carb that big. we played around with them on the Dyno. There are still some old school things that still work, and I enjoyed working with them.
 
  I had a friend back in the day (He was 12 years older then myself). He taught me things about the old Mechaical Hillborn Injection you can't just learn from a book. You remember the old pill boxes, and fuel pumps driven off the crank, and the throttle plates if they were off .0005 and it threw the system off. But when they were on, look out buddy....You know we spent more time tuning the little 301. There was these (2) brother's that looked as if they took an engine from the bone yard and stuffed it in the rails. There was grease and dirt just an all around nasty looking engine. They ran well every weekend.

Bob  

freddiejip freddiejip
New User | Posts: 25 | Joined: 10/12
Posted: 03/21/13
02:06 PM

Just made a purchase. Barry grant race demon 825  

Dave632 Dave632
Addict | Posts: 2225 | Joined: 07/08
Posted: 03/21/13
04:26 PM

I had good luck with the King Demon RS I had on my 68 Camaro. They are the only company that makes provisions for idle air control with a high performance cam. Using the adjustment under the air cleaner stud to control this setting.  
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freddiejip freddiejip
New User | Posts: 25 | Joined: 10/12
Posted: 03/21/13
06:09 PM

This motor will only be used for a year or 2. If the big block rule doesnt stay i am thinking about making the virgin 4 bolt i have into a 396 small block  

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