Any one ever come across a dual port intake?? To make a long story short, I had a whistle in my carb area since I bought my truck 4 months ago. At part throttle the noise would start and the engine would stumble. Repaired all the vacuum leaks I could find(lots), no change. I replaced the carb because it was too big any way, no change. I had a spare 4 barrel intake swapped it out today.Noise gone, stumble gone, also off idle stumble gone. This Offy intake is called a dual port and the runners are divided into 1/3 for primary side and 2/3 for secondary. Strangest this Ive ever seen It is a dual plane but the primary and secondarys are also divided at the carb mount.

 

Sounds like your intake was cracked...

 

Or warped....

 

I agree that your manifold might be cracked. Dual plane manifolds were what was used for street applications. Single plane (tunnel ram) were used for racing.

 

The only other thing I can think of I was using a open carb spacer for carb clearance and it looks like it should be divided into four so the primary and secondary runners stay seperated. I wonder if it was just air turbulance at the spacer.It was loud enuf to hear from another vehicle on the road with the window closed.

 

A dual PORT is different than a dual PLANE intake. Chilako has a dual PORT intake which were popular for a while in the 70's. He never said what engine this was on but they were available for several applications.

A dual PORT or PLANE manifold should be used with a 4 hole or divided carb spacer to preserve the low end advantages. Sometimes an open spacer is used to enhance upper RPM performance but again low end performance is compromised. Some dual plane and dual port manifolds had a notch in the divider to improve high RPM performance. The notch was carefully designed to provide enhancement without losing too much low end performance.

 

Which one of these do you have ?


http://store.summitracing.com/egnsea...2&autoview=sku

 

This should be what I have but the pic is wrong.
http://store.summitracing.com/egnsea...5&autoview=sku
This is like mine but for a 351W not a 400
http://cgi.ebay.com/ebaymotors/OFFEN...48640601QQrdZ1

Notice how the sections are divided. I might have been able to solve my problems now that I have seen the intake off with the right carb spacer??

 

I once had a whistling noise at a certain throttle position. Turns out that the throttle shaft bore was shot. Would only whistle at certain positions, though. But if the carb swap didn't help then that rules it out. Must have been the intake.

 

i have an offenhauser dual port hi rise intake too. it is on a fe390 engine i ran back in the early 90's.it worked fine for my engine.i liked it.