You're the man. Thanks.

There is no difference between the Thunderbird and passenger car intake flow cfm.  The manifolds have changed flow a very minor amount over the years but not significant.  After porting, the Mummert comes out the best for maximum flow in my experience.  I have a couple of the dual plane intakes flowing over 340 cfm average through all 8 ports, and just barely over 330 cfm with the BT.  Still Ted made 585 hp with my ported BT on a 375 CI engine in Y block Magazine several years ago.  Just typical clean up of the ports will net 300-305 cfm for your average performance build.  Here are the BT and Mummert side by side with flow figures as cast.  Joe-JDC

JDC

Thanks, Joe. What are the numbers for the out-of-the-box Mummert dual plane? Have you tested both versions (Tbird vs other)? Just wondering how much is lost with the height difference. 

I use a SF-600 flow bench that I have owned since 1994.  I have had it rewired once per Super Flow Technical bulletin, and replaced the motors at least 3 times.  It has 8 vacuum motors and they get really hot flowing the exhaust ports if you don't have an airconditioned shop.  I keep my shop at 71* year round just for that reason.  Removing the four holes and opening up the plenum to dual ovals really allows the fuel/air to turn more quickly into the runners, and there is about 15 cfm gain average.  Removing the sharp corners or rounding them as much as possible helps the air turn into the ports better and increases the flow.  I usually have to flow an intake at least 5 or 6 times after each rework of the ports to get the flow to balance between runners.  Some dual plane intakes make that nearly impossible, but if you take the best flowing port and bring the others up to that one, then the fuel distribution and carburetor jetting is much easier allowing the engine to make best torque and horsepower.  I don't know many folks who will take the time to balance the runners to equalize the flow, but I have done it for over 30 years for the hundreds of intakes I have ported for folks.  I made my own adapters for each engine family and head port size.  Joe-JDC

JDC

Joe, how much of an improvement have you seen when the ECZ-B intake carburetor base/plenum has been opened up to two ovals, runners blended into the plenum, and removal of any casting flash/irregularities but no extensive porting? Surely you've tested in stages to determine what modifications return the greatest improvement.         

Just looking at John Muumert's Y-block Porting chart, the stock ECZ-B intake will outflow stock ECZ-G heads. However, once the heads have been worked on, the stock, non-ported ECZ-B intake could be a restriction. 

Hi Joe, you always do a better job that anyone else can. what flow bench do you use? mine is a JKM 600 (old)

I ported my ECZ-B iron intake for testing for the 304CI Y that Ted and I took to EMC.  We tested several intakes and 3 sets of heads before finalizing the engine for EMC.  The ECZ--B made 437 hp and my ported Mummert dual plane made 454 hp.  It took a lot of time, effort to get the ECZ-B to respond to porting but can be made quite good.  As cast it only flows ~189 cfm and the new aluminum intake that I flowed for Ted flows ~184 cfm IIRC.  Here are a couple of pictures of the ECZ-B after port work.  Joe-JDC

JDC

Yes a little, but nothing that I could not fix, most problems is with the rear ports, they get thin at the bolt hole. These manifolds are cheap, they are not better than stock, I spend about 1 1/2 hours on each one.

Cliff have you come across core shift that could be problematic, or is it just more metal inside to remove?
Seth

That's funny, considering that the OEM cast-iron intake manifolds weigh 31 pounds. The aluminum intake, according to John Mummert, weighs 14 pounds.Unless you're into serious 1/4-mile racing, I wouldn't be concerned about the weight difference.