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Old 06-28-2008, 08:09 AM
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Offenhauser intake question w/pics

I have an Offenshauser intake for my 173 ci 60*V6 build.

I don't know the date of manufacture, but it is very nice and is a model used for racing so far as I can tell.

So here is my problem. Which side do the Primaries go on?

One side has the pipes straight through and the other side a shelf.

In theory I think the primaries should go to the longer runners for good low end torque, but I don't know for certain. Can anybody help?

Thanks,

Arn
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Old 06-28-2008, 08:43 AM
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Quote:
Originally Posted by Arns85GT
I have an Offenshauser intake for my 173 ci 60*V6 build.

I don't know the date of manufacture, but it is very nice and is a model used for racing so far as I can tell.

So here is my problem. Which side do the Primaries go on?

One side has the pipes straight through and the other side a shelf.

In theory I think the primaries should go to the longer runners for good low end torque, but I don't know for certain. Can anybody help?

Thanks,

Arn
I assume you are asking where the primaries of the carb should be in relation to the intake.

The intake will install on the engine only one way.

The carb throttle linkage is on the drivers side of the carb when looking at the carb from the front. Installing the carb in this configuration will place the primaries over the front two openings of the intake. Some dual carb intakes will cause the carbs to be mounted sideways placing the carb linkage 90 degrees from this position and would require special linkage.

The photos you show of the intake appear to have an adapter plate installed to enable you to install a square flange carb i.e. Edelbrock, Holley, etc.
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Old 06-28-2008, 09:06 AM
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one more question

Thanks Frisco,

The top of the intake is concentric and installs in both directions the same. The vacuum port is on one side only, and if I install it so the vacuum port is on the passenger side (standard side on my vehicle), and the carb linkage on the drivers side (standard position) then the primaries will feed into the main opening which will give the primaries the widest and shortest runner length, with the secondaries having long narrow runners.

This is the reason for the question. I don't understand using a short runner for the primaries. Everything I have read suggests you want the long narrow runners on the primary side.

I hope my question is a little clearer.

Arn
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Old 06-28-2008, 11:14 PM
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Offenhauser Dual-Port

The theory behind the Dual-Port is this, by making the Primary (upper) runners smaller it speeds up velocity "to the speed of sound" thereby keeping the fuel atomization at low speeds more efficent from a torque and mileage standpoint,when the carbs secondaries open this velocity picks up the secondary runners and increasing their flow.These manifolds were developed in the 70's as an answer to the Jimmy Carter "fuel crisis" and may help even today,tuning them is a problem for most because they don't understand the theory and why you will find threads badmouthing this intake.By increasing velocity you require less fuel so going down on jetting is first,stepping down on power valves helps also(Holleys) NEVER use an adapter!! this disrupts flow of the Dual-Port,there were two kinds made, one for straight bore and one for and spreadbore carbs,Use the right carb.You will also find in some cases that the carb works better by use of an adjustable fuel pressure regulator.There was some testing that showed a 20-25% decrease in emissions using these intakes.
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Old 06-29-2008, 06:10 AM
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So is this the correct answer?

Do the primaries belong over the shelf and the secondaries on the straight bore?

In the pic, the shelf is toward the back of the engine and can be turned around without any problem to be at the front so the primaries will be over it.

Arn
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Old 06-29-2008, 12:00 PM
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Quote:
Originally Posted by Arns85GT
Do the primaries belong over the shelf and the secondaries on the straight bore?

In the pic, the shelf is toward the back of the engine and can be turned around without any problem to be at the front so the primaries will be over it.

Arn
Go to the HAMB website,click on Alliance Vendors,click on Exeter Auto Supply they are the largest, most knowledgable,Offenhauser dealer there is.
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Old 06-29-2008, 06:29 PM
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Quote:
Originally Posted by Arns85GT
I have an Offenshauser intake for my 173 ci 60*V6 build.

I don't know the date of manufacture, but it is very nice and is a model used for racing so far as I can tell.

So here is my problem. Which side do the Primaries go on?

One side has the pipes straight through and the other side a shelf.

In theory I think the primaries should go to the longer runners for good low end torque, but I don't know for certain. Can anybody help?

Thanks,

Arn
I've run a couple of these on a SBC and SBF in both cases the primarys ran off the bottom which was actually the larger passage, go figure? Not a manifold that will endear itself to ya.

Bogie
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Old 06-29-2008, 06:47 PM
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another question

Thanks JeffB I'll go looking.

Bogey, can you explain a bit more? This is a v6 application and I am wondering about the characteristics that might apply in common with the SBC unit.

It is not too late for me to change it out if it has a fatal flaw.

Arn
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Old 06-30-2008, 09:33 AM
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Thanks JeffB

Quote:
Originally Posted by JeffB
Go to the HAMB website,click on Alliance Vendors,click on Exeter Auto Supply they are the largest, most knowledgable,Offenhauser dealer there is.
I found the Exeter website and it linked to this page

http://www.who-sells-it.com/cy/exete...27/page-6.html

Turns out it is a Dual PORT intake (Oops ) Very good info and thanks again.

Arn

Last edited by Arns85GT; 07-01-2008 at 10:34 AM. Reason: typo
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