Intake Velocity Speed of 565 CID w/850 Holley?

-

70DusterBob

Well-Known Member
Joined
Feb 20, 2016
Messages
781
Reaction score
148
Location
Texas
I have been tinkering around with increasing vaporization of fuel for some time now and found someone willing to test one of my protos on his 565 CID w/850 Holley that he runs at 6500 RPM as a max. I'm not sure what type of intake he is using, but I need to know about what speed the intake will be flowing through the carb. at 6500 RPM.

His car runs 6.65 in the 1/8th.

I have made a proto for a 360 CID with only a performer intake and took it up to 4300 RPM with no restriction what so ever. But I am going to have to do a re-design to reach 6500 with no restriction, so I need some idea of either how much more air/fuel mix flow will be passing through the carb on his engine compared to mine, or have some idea of how much air/fuel mix will be flowing through his carb at max RPM in some way that I can understand how much air/fuel mix will be flowing or at what wind speed it will be flowing. Basically I don't know how much velocity I am dealing with and I need some idea to design the proto correctly.

Any help is appreciated...
 
It will be no more than 850 CFM.
 
Also that engine is choked off big time by that tiny carb. I personally don't think it will be good test bed for ur product. Kim
 
I don't think anyone here, has access to those resources..for free. "Knowledge and research"cost money.... Nothing worth while,is for free......
 
Should be able to get close on one of those Wallace calculators. The speed of the air going in is measured in CFM, so, plug the cubic inch and given RPM in and you should get close.......of course things like camshaft, head flow and the like will be variables, but you should get in the ballpark.
 
Should be able to get close on one of those Wallace calculators. The speed of the air going in is measured in CFM, so, plug the cubic inch and given RPM in and you should get close.......of course things like camshaft, head flow and the like will be variables, but you should get in the ballpark.

Please correct me if I'm wrong, but with an 850 Carb, that is close to 900 cubic "feet" of air per minute. So if you divide 900 CFM by 3 you get 300 Cubic "yards" of air per minute right? So that would be "close" to 1 foot ball field by 1 foot ball field by 1 foot ball field of air going into his engine per minute, right?

I am a rookie when it comes to calculations, and I have dyslexia, but is that right?

Thanks
 
Please correct me if I'm wrong, but with an 850 Carb, that is close to 900 cubic "feet" of air per minute. So if you divide 900 CFM by 3 you get 300 Cubic "yards" of air per minute right? So that would be "close" to 1 foot ball field by 1 foot ball field by 1 foot ball field of air going into his engine per minute, right?

I am a rookie when it comes to calculations, and I have dyslexia, but is that right?

Thanks

I believe your calculations are correct. Yes.
 
Damn, that's a lot of air. I will have to make it strong enough to hold up in a hurricane, or more, of air.

You have been very helpful.
 
Should be able to get close on one of those Wallace calculators. The speed of the air going in is measured in CFM, so, plug the cubic inch and given RPM in and you should get close.......of course things like camshaft, head flow and the like will be variables, but you should get in the ballpark.

Would you explain how the air speed is measured in cfm's?
 
6.6's in the 1/8th with a 565..... do you have a better description of this combo?
 
Would you explain how the air speed is measured in cfm's?

It's self explanatory. CFM= cubic feet per minute. If an engine moves 800 CFM of air, there's your air air speed. 800 cubic feet per minute.
 
It's self explanatory. CFM= cubic feet per minute. If an engine moves 800 CFM of air, there's your air air speed. 800 cubic feet per minute.


CFM has zero to do with speed. I can have a port that flows 300 CFM with an average speed of 280 feet per second and another port that flows 300 CFM with an average speed of 320 feet per second.

In that same port you can have 10 different velocities. So CFM is not air speed.
 
Alright. Then please carry on without me. Thank you drive through.
 
CFM has zero to do with speed. I can have a port that flows 300 CFM with an average speed of 280 feet per second and another port that flows 300 CFM with an average speed of 320 feet per second.

In that same port you can have 10 different velocities. So CFM is not air speed.

^^This^^ CFM is a volume measurement.

At cruise an engine may be using a steady 100 CFM of air/fuel mix but the air speed from the carb to the cylinder may change several times before it dumps into the cylinder.
 
^^This^^ CFM is a volume measurement.

At cruise an engine may be using a steady 100 CFM of air/fuel mix but the air speed from the carb to the cylinder may change several times before it dumps into the cylinder.
think about this: larger ports will flow more air at a certain speed, but a smaller port will generally have higher intake speed . read hughs porting tech pages . on heads and intakes. that is one reason I didn`t go full max wedge on my cnc`d raisd port heads. the intakes are a diff animal tho.
 
think about this: larger ports will flow more air at a certain speed, but a smaller port will generally have higher intake speed(BETTER CARB SIGNAL) . read hughs porting tech pages . on heads and intakes. that is one reason I didn`t go full max wedge on my cnc`d raisEd port heads. the intakes are a diff animal tho.
 
I'm just curious.......so humor me. Why is it important to know the speed of the air going into the engine? Not like you can influence it much. Seems pretty combo dependent.
 
CFM has zero to do with speed. I can have a port that flows 300 CFM with an average speed of 280 feet per second and another port that flows 300 CFM with an average speed of 320 feet per second.

In that same port you can have 10 different velocities. So CFM is not air speed.

If you take CFM and take into account the RPM of the engine - you get volume/time = speed...

Speed is volume over time...

Similar to torque and horsepower... Horsepower is torque/time...
 
I'm just curious.......so humor me. Why is it important to know the speed of the air going into the engine? Not like you can influence it much. Seems pretty combo dependent.


Not much time with a flow bench?

You MUST control air speed. It's more important than CFM ever was, or ever will be. Most Pcar heads can only take 260 FPS of air speed without issue. A well prepped Pcar head may get close to 300 FPS but you will have spent a bunch of time and effort for not much gain.

You can do many things to control air speed. If all you do is make the hole bigger...anyone can do that. You have to control air speed. You also have to learn that less CFM can and will make more power. Especially if you work with your flow bench. At other than 28 inches of depression. And flow the ports backwards.

Air speed management makes horsepower.
 
Nope. I know somebody with one, but I've never operated one, or professed to have.
 
LOL...... this thread is pretty funny. Want a bunch of air speed? put 318 heads on a stout built 360 block. That there air will move real quickly through them ports :D
You want volume? put some W2's on that same 360.
 
-
Back
Top