The problem you run into with the smaller bore of the 396 when switching to larger intake valves is that the cylinder wall actually starts to shroud the valve which hurts flow. 2.25" intake valves on a 396 is definitely way too much valve for the motor. 2.19" intake valves would be about as big as you want to go with a 396 motor.
Full Answer
What is the intake valve angle of a Chevy big block head?
Production big-block Chevy heads all came with 26-degree intake valve angles, and that dimension was standard throughout the first two decades of competition cylinder head development, both by Chevrolet and the performance aftermarket.
What size are the intake valves on a BMF head?
All BMF heads feature 24.5-degree intake valve angles and intake valve sizes from 2.250 to 2.325 inches, with chamber volumes of 114 to 124 cc. Exhaust valves are 1.880 inches and they accommodate standard Rat motor exhaust headers. Brodix 383 Head Hunter head with large oval intake ports.
How many CC are the intake ports on a BB head?
Brodix BB-4 and BB-5 series 24-degree heads feature traditional rectangular intake ports from 340 to 390 cc, but they are raised approximately .400 inch for a better intake flow path and improved short turn radius from the ports into the valve bowls.
What are the different types of intake heads?
Factory heads are classified as either high-performance (rectangular port) or standard passenger car (oval ports). Latemodel trucks feature an even smaller oval intake port, frequently referred to as the “peanut” port, on heads that appear to be nearly round at the port entrance.
What is intake valve diameter?
Calculate intake and exhaust valve sizes For example, a 1,588 cc engine (bore of 79.5 mm and stroke of 80 mm) and a rev limit of 6,000 RPM should have a 36.4 mm intake valve and a 31 mm exhaust valve. This calculator uses the following formula: Valve diameter = √((rpm × stroke × bore²) ÷ 2,286,000)
Is the intake valve bigger or smaller?
Therefore, the intake valve is generally designed to be larger than the exhaust valve to reduce the difficulty of intake and increase the amount of intake air.
How do you measure intake valves?
1:023:22Measuring valves and valve guides - YouTubeYouTubeStart of suggested clipEnd of suggested clipYou. Take it out and then you use a micrometer to measure. What the diameter of the guide is.MoreYou. Take it out and then you use a micrometer to measure. What the diameter of the guide is.
Which valves are bigger exhaust or intake?
End of dialog window. The intake valves are larger because the air and fuel volume taken in by the engine is greater than the exhaust volume. The intake valves are larger because the air and fuel volume taken in by the engine is greater than the exhaust volume.
Do bigger valves make more power?
Answer: It depends on the type of cylinder head. Generally, if the cylinder head was designed for street applications larger valves will not improve air flow. Often tines, large valves will actually decrease air flow.
What is the valve clearance of intake valve?
Opinions may vary between piston and valve manufacturers, but a popular consensus is a minimum clearance of . 080-inch for the intake and . 100-inch for the exhaust. The exhaust valve expands more due to heat from combustion, and therefore needs additional clearance.
Why is inlet valve bigger in diameter?
The inlet valves have larger diameters to allow the largest volume of air for the engine cylinders. But some engines have 2 or 3 intake valves with slightly larger diameters than the exhaust valves. Equalizing the inlet and exhaust valve diameters reduces the volume of air to the cylinders ..
How do you measure valve stem diameter?
0:172:28Valve Measurement - YouTubeYouTubeStart of suggested clipEnd of suggested clipDown a little ways so there's not going to be anywhere above where the valve spring is but you'llMoreDown a little ways so there's not going to be anywhere above where the valve spring is but you'll see it mostly where the valve sits in the valve guide. And that's typically got some wear marks on it.
How do I know what size cylinder head to buy?
There are many factors involved in choosing the optimum cylinder heads for a specific application, including:Engine displacement.Type of vehicle.Intended use.Desired compression ratio.Gear size.Other performance modifications.
What will be the harmful effect of too small valve clearance?
If there's too little valve clearance, the valves won't fully close, causing excessive heat, and the engine will lose power.
What happens when valves are to tight?
0:272:07Common Problems - Tight Exhaust Valve Clearances | Honda S2000YouTubeStart of suggested clipEnd of suggested clipNow the reason why this is a problem is because tight exhaust valve clearances can lead to burnMoreNow the reason why this is a problem is because tight exhaust valve clearances can lead to burn exhaust valves and burn exhaust valves will lead to misfires. And loss of compression.
Are stainless steel valves better?
Because valves are meant to open and close, corrosion can cause big issues. If there is too much corrosion, this may cause a Ball Valve to break or become unable to move. Stainless Steel Ball Valves will hold up much better to harsher water types. This will ensure a longer lasting valve.
What is the L89 head?
The L89 head is a 842 casting, the 840 head smokes them due to the dog leg in the port (842). Believe it or not a 840 head with a good valve job will go over 330 CFM @ 28 inches at higher lifts, but the port is big. I love L78s!:yes:
Does an L78 need a bigger valve?
From my experience an L78 doesn't need bigger valves as much as it needs a much bigger cam to get lots of air flowing through those big ports so that the engine can actually make decent power. Extra cubic inches as with a 427 displacement makes a big difference. Again more air travelling through those big ports.
What size valvestems are used on aftermarket heads?
Aftermarket heads typically come with 11/32-inch-diameter valvestems, and frequently use longer than stock valve lengths that allow installation of taller valvesprings that are better suited for use with high-lift camshafts.
What is the valve angle of a rat motor?
The original head design is often referred to as having a 26-degree valve angle, although this intake valve angle of inclination is only one of four angles needed to numerically describe ...
How many bolts are in a big block?
Because the big-block has six head bolts around each bore (if you count the hidden bolt bosses on the bottom of two of the intake ports), and that dictates where the intake ports must be placed.
Why are spread port cylinder heads longer than conventional cylinder heads?
Also, when comparing port volume of spread port cylinder heads, remember that because these heads have raised runner locations , they are longer than conventional cylinder head intake ports, and the port volume is greater due to the extra length.
How much horsepower does an oval port head have?
When reworked by someone who really knows what to do, oval port heads are capable of providing very good performance up to 600 or more horsepower. However, most high-performance street and full-race big-blocks can still take advantage of larger rectangular port heads.
When did the Big Block head come out?
Big-block heads all had closed combustion chambers, or bathtub-shaped chambers, when the engine was introduced in the mid 1960s. In 1969 the open combustion chamber was introduced and it offered better air/fuel flow and a better combustion burn in the chamber.
Do spread port Chevy heads need shaft rockers?
All spread port big-block Chevy heads require shaft rocker arms because the pushrods must be relocated around the revised intake port location, and the large amount of rocker arm offset eliminates the use of traditional stud-mount rockers.
BBC intake valve length
I have two questions, needing the opinions and thoughts of the pros here. To save everyone a little time, I'll just ask both questions in one post. Question 1: I had my heads "professionally" ported.....full job, intake exhaust and chambers....BBC heads. Both intake and exhaust valves were replaced.
Re: BBC intake valve length
The seats may not have to be redone if you are going to hone another couple thou out of the guides. Just check runout after opening the guides. What are the spring pressures on intake and exhaust? That's the number you should be concerned with instead of absolute installed height.
Re: BBC intake valve length
Thanks for your response Monty. That'd be wonderful if I don't have to re-do the seats. I haven't as of yet settled on a spring. I'd like to run the isky tool room at something like 250 seat/570 open. My biggest concern, though, is in the huge difference between the intake and exhaust installed height, as they set right now with no shims.
Re: BBC intake valve length
First of all is are you measuring the spring installed heights with the retainer you plan to run in the engine??
Re: BBC intake valve length
Thanks for your reply, propower. The -.050 locks hadn't dawned on me. I'm measuring the installed height right now with the original retainers, and od locator. My cam is a 31* lobe with .680 gross lift, solid street roller.
Re: BBC intake valve length
The installed height you are workin with are not uncommon. I am in the middle of a sm blk and have 2.050 installed heights for a solid roller set up.I do not recall seeing what the stem size you are working with.
Re: BBC intake valve length
The original valves that came out of the heads were 11/32, the new valves are .3413 (but seem to fatten up in the muddle to .3415), I'm not sure of the conversion there. I'm ok with the exhaust at 2.046, it's the 2.128 of the intakethats bugging me.
When did big block engines start?
Big-block heads all had closed combustion chambers, or bathtub-shaped chambers, when the engine was introduced in the mid 1960s. In 1969 the open combustion chamber was introduced and it offered better air/fuel flow and a better combustion burn in the chamber. The only drawback to the new chamber design was that it was large, around 118 cc compared to closed chamber heads, which had about 101 to 109 cc, so highdome pistons were needed to achieve the same compression ratios as the closed chamber heads. Note that domed pistons designed for open chamber cylinder heads do not work with closed chamber heads due to insufficient clearance. While introduced on high-performance rectangular port heads, the open combustion chamber was soon being used in common oval port heads to lower the compression ratio for use with unleaded gasoline, and the reduced quench area was found to be helpful in reducing exhaust emissions.
How wide should an exhaust valve seat be?
Typical widths are .100 inch for the exhaust seat and .040 to .060 inch for the intake. Remember that these specifications are minimums, and the cylinder head specialist of your choice may have his own pet set of dimensions that he has found to work best with his combination.
What are AFR big block heads?
AFR offers a tremendous selection of traditional big-block replacement aluminum heads designed to fit within the stock architecture siamesed ports with traditional valve locations and open combustion chambers. Their eminently logical approach to marketing big-block heads consists of offering all of their heads with either as-cast ports and chambers, or CNC machine ported for a slight increase in port volume plus consistency in port-to-port and chamber-to-chamber dimensions. All AFR big-block heads feature “rolled-over” valve angles, which are listed as 24/4 degrees (intake) and 15/4 degrees (exhaust); 3/4-inch-thick deck surfaces for brute strength; and 3/8-inchraised exhaust ports.
What is a big block Chevy?
The big-block Chevy’s canted valve heads are largely responsible for the tremendous power capability of the Rat motor and its continued popularity. The original head design is often referred to as having a 26-degree valve angle, although this intake valve angle of inclination is only one of four angles needed to numerically describe the big-block’s valve angles. The exhaust is tilted 17 degrees relative to the deck surface, and both are inclined 4 degrees laterally. This compound arrangement of valve angles gives the big-block head its characteristic “valves pointing everywhere” appearance when the valve covers are removed and is responsible for the early “porcupine head” nickname when the big-block made its debut in the mid 1960s.
What is Edelbrock big block?
One of the oldest and most respected names in the high-performance and racing parts business, Edelbrock offers big-block cylinder heads in a variety of configurations specifically designed for the application , whether it is a modest street performance vehicle, a street and strip/weekend warrior, or all-out competition car. Most are traditional siamesed port heads, but the Big Victor is an 18-degree spread port design with several unique features not found in similar heads.
What is the poppet valve?
With the poppet valves currently used in all automotive four-stroke engines, it has been shown that the valve bowl, or area of the port directly under the valve seat (viewed from the combustion chamber), is critical in setting up the flow around the perimeter of the valve as it opens . As a result, there is a bend in the port as it makes the transition from the entry corridor to the valve bowl, and that bend must be carefully shaped to reduce the air/fuel flow as little as possible while maintaining a homogenous air/fuel mixture. If the turn is too abrupt, the fuel tends to separate from the mixture and pool into large droplets that do not burn completely in the combustion chamber. The port floor at this bend is referred to as the short turn radius, while the roof is called the long turn radius. Because the airflow path is shorter at the short turn radius, flow velocity tends to increase, just as it does over the curved surface of an airplane wing, and many cylinder head specialists widen the port floor at that point to equalize the flow along the short and long turns.
What is the PN 12363408?
PN 12363408 is an NHRA-legal replacement for the L88 aluminum head used on 1968–1971 Corvettes and 1969 Camaros (original PN 14011076). The same GMPP heads used on the 572 crate engines can be yours by ordering PN 12499255 (hydraulic roller lifter valvesprings) or PN 88961160 (mechanical roller lifter valvesprings).
