#13---Big Mouth Heads: Flow #'s & Port Volume

10/11/2013


“Big Mouth” Heads

We have developed some very large port Edelbrock small block heads with greatly increased air flow and port volumes. These heads, called “Big Mouth” are available in both L.A. and Magnum series. Our testing has confirmed that the small blocks need more port volume and airflow. Note our  #19---Smallblock Big Mouth Ports on the Dyno, which demonstrates what increasing the port volume only 11cc, to 206cc, was worth (nearly 30hp) in a milder engine over the 195cc port volume in a highly modified engine with more displacement.
The increased port volume and removal of pushrod pinch area not only increases the port volume and flow, it also makes the port cross-sectional area more consistent which reduces turbulence in the port. This allows more air to be packed into the combustion chambers, and enhances the inertia supercharging effect. All of these features are important to getting the most power from the heads.
In the L.A. heads we have moved the pushrods over .350”. This allows us to achieve 2.57 square inches of cross-sectional area which is the smallest area in the port, and that is at the gasket. The stock port volume is 170cc. our Big Mouth is 225cc. That is a 54cc increase! Either of these heads used in a properly built 408 small block could supply enough air for over 700HP.
When using the L.A. Big Mouth heads, you will need our rocker arm kit P/N 15093. The intake rockers are offset .350” and both intake and exhaust rockers are 1.6:1 ratio. You should be able to use 3/8” diameter pushrods with very little if any clearance problems.

#60779BIGMOUTH
Small Block "LA" Edelbrock Heads
Fully C.N.C. Ported with 2.08" Intake Valves
Intake Port Volume 225cc

Lift Stock Intake CFM CNC'd Intake CFM CFM Gained   Stock Exhaust CFM CNC'd Exhaust CFM CFM Gained
.100 69.5 77.4 +7.9        
.200 135.6 168.1 +32.5   109.0    
.300 189.9 236.4 +46.5   139.2    
.350 214.0 262.1 +48.1   147.6    
.400 228.9 279.0 +50.1   158.6    
.450 234.7 292.4 +57.7   164.6    
.500 241.4 304.8 +63.4   169.9    
.550 249.7 308.4 +58.7   172.1    
.600 255.9 312.3 +56.4   176.1    
.650 255.9 316.2 +60.3   179.9    
.700 261.3 319.9 +58.6   182.3  



On the Magnum heads, the ports, both intake & exhaust are better at their job in stock condition than the L.A. version. Therefore, the results are slightly better. Here we have moved the pushrods over .420” and have a 218cc port volume. And like the L.A., the port has a 2.57 square inches area at the gasket surface.

#61779BIGMOUTH
Edelbrock Small Block RPM Magnum
Fully C.N.C Ported with 2.08" intake valves

Lift Stock Intake CFM CNC'd Intake CFM CFM Gained   Stock Exhaust CFM CNC'd Exhaust CFM CFM Gained
.100 67.6 73.4 +5.8        
.200 125.0 149.7 +24.7   78.1 114.1 +36
.300 180.9 226.6 +45.7   132.9 154.5 +21.6
.350 204.1 257.5 +53.4   147.0 172.6 +25.6
.400 223.9 282.1 +58.2   167.8 185.3 +22.5
.450 236.2 303.8 +67.7   170.2 194.7 +24.5
.500 247.9 314.1 +66.2   180.1 201.0 +20.9
.550 247.8 323.6 +75.8   187.9 206.2 +18.3
.600 245.6 326.9 +81.3   192.1 210.9 +18.8
.650 245.5 331.1 +85.6   196.7 214.0 +17.3


We purchase both of these heads from Edelbrock without pushrod holes and, with no intake bolt pattern in some cases, and these are what we “Big Mouth” for our customers. In cases where the customer wants his existing heads reworked into “Big Mouth” we can plug the original pushrod and intake bolts and reposition them. Currently the best flowing intake manifold for these heads is the INDY 360-I4-3. This manifold is available with either Magnum or W-2 bolt patterns. We are working with Edelbrock intakes to see if there is anything there that we should be offering too.

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