Thanks for the info; I think I understand why the 3310 works on my 331 sbc. I may need to change the vac. secondary spring.
Thanks for watching, there are many simple carb size formulas out there, but most don't allow for different states of tune or much explanation about what state of tune they are for. Hope it helps you out.
Very interesting video! You probably should market the video to Summit, or some of the other carburetor suppliers, as required watching prior to the purchase of a carburetor. One issue that I have observed over the last 50 or so years of working with carburetors, is that about 90 percent of first time carb buyers actually lie to themselves about the state of tune of their engine (always that is stronger than it is) and thus end up buying a carburetor too large for their specific engine. Don't know how you can solve this issue. One very minor criticism: you mention that ALL 4-barrel carbs are rated at 1.5 inches of vacuum. This standard was agreed to by the carburetor companies in 1952, when it became obvious that 3.0 inches (standard for 1 and 2 barrel carbs) was not obtainable by those early 4-barrels; and the 1.5 standard was used up until some time in the 1980's when some enterprising folks found that many newbies bought carbs based on the CFM rating, and the CFM rating could be varying by changing the rated vacuum. One company that "needed" a 600 CFM carb for compe***ion that did not have one, simply took their 625 CFM carb, issued a new part number, and rated it as a 600 CFM! Unfortunate that there are dishonest folks out there. All 4-barrels should be rated at 1.5 inches, but some of them are not. Again, very interesting video. Possibly the moderators could come up with a technical "sticky" for this. Thanks for doing the video, and posting. Oh, and some of us prefer "other makes" to Edelbrock, Holley, and Summit. There are also Autolite, Carter, Rochester, and Stromberg 4 barrels to consider! Jon
Thanks for the kind words. Were in the manifold selling business and it seems like everyone thinks were in the carburetor business which isn't the case. After so many years of trying to explain it to people of all knowledge levels, it became time to try and come up with a better way. It may not be perfect but I figured if we could get people to this level, we could fill in the blanks much quicker.
Rule of thumb I’ve always used… If it’s going down the 1320 on a regular basis then the Holley is the way to go. Size of the carb will depend of a mul***ude of factors. If the majority of time is street driving the the good ole Carter carb is the way to go.
I just got into a which manifold question for a Cleveland headed "race" car. Which head? Which cam? Road/Drag (RPM range)? All things that need to come into the conversation before you know which manifold to start with. The Motorsport A3 aluminum Cleveland heads on my 310" engine loves the 850 Holley @ 8,200.
1.563 venturi it's the Track Warrior based on the 4150 https://www.holley.com/products/fuel_systems/carburetors/street_strip/parts/0-67201BK But for a really big venturi they did run a pair of Dominators on the Boss 302 TransAm cars. The were set up as IR (Individual Runner) with one barrel feeding 1 cylinder with no plenum.
Standard 1.563 large venturi 850 with HP body flows north of 900 cfm. Makes more sense too me now. Cool Boss pic.
IF you do share this with others as suggested, I'd say another video could be the other side of the air pump, the exhaust. It used to be duals were the hot rod step. Then dual 2", then dual 2.5". I've seen some pretty goofy sizes for cars cruising around town and never seeing the high side of 4K RPM. There are restrictions (mufflers) there too, but do you really need 2 " primaries and 4" exhaust for your 350?
Exhaust discussions can get complicated. The biggest thing to remember is that the exhaust is the bridge between the power stroke and the intake stroke, it relieves exhaust g***es on the front end and and helps initiate intake flow on the back end. Most people only view it from one perspective so they miss what someone might be trying too accomplish. A simple answer is that running primary tubes significantly larger than your exhaust valves doesn't do much good on the street.
Determining VE is based off of head CFM as well as velocity through the choke point, (minimum cross sectional area in the port.) So the CFM gives you an idea of what RPM your peak VE will be at, the choke point in the port will give you and idea of how high the velocity or how high the VE will be. This is of course relative to displacement. Intake manifold design will effect VE. Dual plane manifolds will have lower VE because of split Y runner designs. They can make more bottom end power because the the same split Y design can divert reversion away from the carburetor allowing less double fueling. Single planes will usually make more Peak Torque and Power because they have higher reflected strength at the port opening in the plenum and more direct path from carb to valve. It takes high VE to generate high TQ per cu/in. . High HP per cu/in can be attained with decent VE and Rpm.
The Jalopy Journal
