offenhauser intake
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Junior User
Joined: Nov 2012
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From: Raleigh N.C.
offenhauser intake
im putting an offenhauser intak on with a holly carb. its dual port and from what i understand the primarise are supposed to be on the right and secondaries on the left putting the throttle on the back but some of the pics ive seen show it on the right side or even on the front. the other issue im having is that i need a way to mount the trottle cablei was just gonna cut the factory mount shoter and tack it to the valuve cover but i wanna make sure i have the acerb right first.
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I could be wrong because I have never had my hands on one of these but I reason the top side of the intake tubes are feed by two carb holes on the driver side and two holes on the passenger side feed the bottom of the intake tubes.
Though you could mount the carb four different ways, the concept of the dual plane is that the primary half of the carb would feed the hot plane which is the bottom side closest to the exhaust manifold. The cool plane would be the top side and supplied by the secondaries.
Having said all that, you should still confirm which plane is going to be heated by the heater hose hook-ups. The main thing is that the hot plane is the primary plane.
So where ever your throttle linkage ends up when you align the primary to the hot plane ends up being the correct place. Then you can figure out how to hook it up.
Though you could mount the carb four different ways, the concept of the dual plane is that the primary half of the carb would feed the hot plane which is the bottom side closest to the exhaust manifold. The cool plane would be the top side and supplied by the secondaries.
Having said all that, you should still confirm which plane is going to be heated by the heater hose hook-ups. The main thing is that the hot plane is the primary plane.
So where ever your throttle linkage ends up when you align the primary to the hot plane ends up being the correct place. Then you can figure out how to hook it up.
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Junior User
Joined: Nov 2012
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From: Raleigh N.C.
Ok that sound exactly like how I've hooked it up. However i don't have a spacer with heater hose hookups. Is that necessary? I live in NC so it rarly gets cold enough to make starting hard. And if i do need a heater hose hooked up which of the 2 should i use? I also have hedman headers on this truck so the heating tubes from the manifold are gone.
Thanks for the help!!
Thanks for the help!!
Fleet Mechanic
Joined: Jul 2011
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Plenty of info on this in the Ford Six forums and on our inline-6 forums here on FTE.
Primaries towards the valve cover and secondaries towards the fender. It's necessary for even fuel distribution.
Heating the bottom of the intake is done to keep fuel from puddling on the intake plenum regardless of the ambient temperatures.
You'll notice a strong difference between a non-heated intake and a heated intake on a street driven 300.
I recommend a 390 to 500 CFM 4bbl. Save the 600 for the C-series.
If using a 2bbl, trade in the dual plane for a C-series and run an adapter.
Primaries towards the valve cover and secondaries towards the fender. It's necessary for even fuel distribution.
Heating the bottom of the intake is done to keep fuel from puddling on the intake plenum regardless of the ambient temperatures.
You'll notice a strong difference between a non-heated intake and a heated intake on a street driven 300.
I recommend a 390 to 500 CFM 4bbl. Save the 600 for the C-series.
If using a 2bbl, trade in the dual plane for a C-series and run an adapter.
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Junior User
Joined: Nov 2012
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From: Raleigh N.C.
so when installing that bracket how did you seal the intake where you bolted the bracket under the spacer? itd have to leave a gap the thickness of the metal on the fourth side with no netal there or am i looking at it wrong? 
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Elder User
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It sits on top of the spacer, not between the spacer and the manifold. I used linger studs to bolt the spacer to the manifold to accommodate it.
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Junior User
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From: Raleigh N.C.
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From: Raleigh N.C.
Fleet Mechanic
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so that means that the heat from the headers wont be enough and i need a spacer with a heater hose attachment? im young so this is kind of new to me ive always been told cold air!! cold air!! cold air!! but thats with efi vehicles. if thats what i need where do i get it?
It'll take an 1/8'' or so of plate steel, a couple pipe fittings, some solder, a few marked holes, bolt it on, and T- it into t he heater hose for the header.
Cold air is good for racing where there are high RPM applications. A street motor that won't see over 6000 rpm has no use for a setup like a race vehicle. Drive-ability, fuel atomization, and gas mileage are your prime concerns.
The heating plate goes where the stock exhaust bolted together. Ford bolted the manifolds together right at the carb to provide heat to the intake and the carburetor (which also turned into a prime location for the EGR when the emissions era hit).
V8's even have heated intakes, but they're built in.
The reason the intakes are heated is so the fuel won't puddle and get drawn in as a liquid, which creates incomplete combustion as liquid won't burn as well as vapor. When the fuel is boiled, it vaporizes.
https://www.ford-trucks.com/forums/1...eat-plate.html
Here's an example.
Elder User
Joined: Sep 2012
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ive got plenty of stud length. So does that mean its still under the carb? the onlu way i could see it working is on the carb, under the bolts that normally hold just the carb... on top of everything. but i feel like if you did that the bracket would have to be more elaborate to go around the parts of the carb. at least it would be for my holly 390 cfm.
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Junior User
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From: Raleigh N.C.
i just dont like the idea of welding to the valuve cover.
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Junior User
Joined: Nov 2012
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From: Raleigh N.C.
i cant really visulize where your trying to say it goes.
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Junior User
Joined: Nov 2012
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From: Raleigh N.C.
do you mean instead of where the manifold mounted you mounted the heating plate. if thats it that wont work for me i had to grind that level edge down on the engine side to fit the offenhauser with my headers.