Vacuum CFM for 2.8L V6

[Barry]

It's not the 2 barrel, its the intake manifold.

Data?

 

[Rockonp04]

I am going off of the restrictive nature of the intake due to smog restrictions and the experience of Jose. I don't have any solid data but I have Offenhauser techs and Jose's experience to rely on and they are all saying the same thing.

Also, the EFI would have to work with the dual-port of the intake manifold. Offenhauser techs were adamant any EFI would have to either be dual-port compatible or an adapter would have to be installed. I am calling Holley about this just to quash my curiosity.

The 2 barrel Offenhauser top does bolt onto the bottom part of the Offenhauser 4 barrel intake but the linkage would be rotated 90 degrees which complicates things. They are also rare. I sourced a few but again the dual-port issue would still have to be rectified.

Perhaps someone should do a build and run some engine dyno tests to know once and for all and run all types of setups. That would be legit but also costly. When I get my raise perhaps.

 

[260Alpine]

I will have a porting setup (flow bench) when I retire. The only emissions on the stock intake is the EGR which would be capped. Check out this pic of Morana's 4 barrel top on the stock intake and the daylight view out the port.

 

[DanR]

Jim, The OFY bottom piece inside routing is near identical to the stock two bbl as I recall.

I have a cut-a-way view in the shop perhaps I can get a pic loaded.....

Perhaps someone should do a build and

I vote for you to be the Guinea Pig

 

[Rockonp04]

I had a long conversation with the Offenhauser tech Vince and he mentioned the EFI would have to be a two-stage EFI, meaning it would have to have one valve open for low to mid-range throttle and then the other valve would have to open at full throttle.

The Offenhauser intake is a 2 stage dual-port system, not a dual plane. I checked with Holley about the 2 barrel EFI and it is not a 2 stage EFI. It is simply a single-stage setup, meaning both flaps open at once. This essentially rules out the Holley EFI working with the Offenhauser.

The only alternative is, using the stock intake manifold which is a single plane intake and would work with the 2 barrel EFI, and make an adapter. The Offenhauser tech said the stock intake isn't a bad manifold. Essentially Ford copied Offenhauser Equa Flow system.

I'm going to continue with the Holley 390 because of the high flow nature of the 4 barrel Offenhauser setup.

 

[DanR]

Like they say, if it aint broke..... Wise choice - 390 4bbl carb IMHO