variable intake runners on 4.0 SOHC?

[ThunderB]

I was reading an old '96 issue of Motor Trend and they tested the then new '97 Explorer with the SOHC 4.0. The article said the SOHC had variable intake runners that popped open by a vacuum valve at 4000 RPM to give good low RPM torque and high RPM HP. Has anyone seen this valving on their intake? I looked at mine and at pictures of other disassembled SOHC intakes and haven't seen anything resembling it. I 'm wondering if this made it into production. it would certainly explain part of the 40 HP difference between the OHV and SOHC.

B

 

[ThunderB]

Anyone? Someone out there has to know.

B

 

[scottyb]

Now I know why my 98 Limited has that big funky intake. I believe you're right because there is a vac operated valve right in the center that I didn't underatand what it was for.

Mine also makes so much noise (hissing type sound) that I swear it has a vacuum leak. I have searched and searched, but could not find any leak. The engine runs like a champ and has no symptoms of a vac leak. Does yours seem loud as well?

 

[Eneurb]

Every engine with a plastic intake makes alot of noise. Ford tried in the past to install an intake air straightener, which was a throttle body gasket with a comb on part of the top half to try and quiet it down, but didn't really do much. The SOHC motor in Explorers does not have variable intake runners. The valve you see on top of the intake is the IAC.

 

[aldive]

Now I know why my 98 Limited has that big funky intake. I believe you're right because there is a vac operated valve right in the center that I didn't underatand what it was for.

I think you are describing the IAC.

 

[scottyb]

After taking a closer look again, I have to agree it's not a variable runner intake.

The valve I'm talking about is not the IAC. It's behind the IAC and closer to the firewall and is vacuum operated. It appears to be a flapper between the 2 "banks" of the intake. Now I'm curious as to what it is for.