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Clifford vs Offenhauser intakes

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frank b
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Clifford vs Offenhauser intakes

Post #1 by frank b » Tue Nov 22, 2005 5:07 pm

I did a search but couldn't find the answer.

Which would be better for the street? A Clifford single plane, or the Offenhauser dual plane.
It's going on a "mule" that would be hauling and towing.

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StrangeRanger
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Post #2 by StrangeRanger » Tue Nov 22, 2005 6:07 pm

The Offy is not a dual plane, it's a dualport. All 6 head ports are connected to both primaries and through another passage in the manifold to both secondaries.

The Offy DP is intended to be used on a dead stock engine with a small 4V like a Holley 390. It is intended to provide more power for towing or hauling. The DP is reported to have some fuel distribution issues.

The Clifford and the Offy C are both intended for use with either a small to medium 4V or a large 2V on moderately built up engines. In practice they seem to work every bit as well as the DP for building a 4 wheeled mule without the distribution issues and without the funny sideways mounted carburetor that the DP requires.

frank b
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mild

Post #3 by frank b » Tue Nov 22, 2005 7:09 pm

"The Clifford and the Offy C are both intended for use with either a small to medium 4V or a large 2V on moderately built up engines"

What would you consider a moderate build up? A cam and headers with the intake?

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StrangeRanger
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Post #4 by StrangeRanger » Tue Nov 22, 2005 7:41 pm

That's pretty moderate, asuming it's not an insane cam

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shmoozo
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Re: Clifford vs Offenhauser intakes

Post #5 by shmoozo » Tue Nov 22, 2005 7:55 pm

frank b wrote:I did a search but couldn't find the answer.

Which would be better for the street? A Clifford single plane, or the Offenhauser dual plane.
It's going on a "mule" that would be hauling and towing.


The four barrel Clifford manifold has a "water heated" feature which seems to be a really good idea for folks living in colder areas. It costs significantly more, however, and also requires an adapter plate for whatever kind of carb you want to use. They do sell adapter plates both for four barrel carbs as well as for several types of two barrel carbs.

Clifflord also sells manifolds that allow you to run dual or even triple carbs, but they seem to be mainly used by guys who are building engines for racing or for use in hot rods. Dual four barrel carbs on an inline six might be a bit much for anything but a racing application, but dual or even triple two barrel carbs (depending on how large they are and how they are configured) might be more reasonable.

:)

Needless to say, however, the single four barrel setup is the one most guys seem to go to when they want a bit more punch out of their 300's. A single two barrel carb is probably the next most popular choice. Between them those two options probably account for at least 95% of the market for carbed inline 6 intake upgrades if the talk in this forum is any indication of the market as a whole.

:)

The Offenhauser "C" manifold is similar to the Clifford four barrel manifold except that it is set up to use a four barrel carb without an adapter plate and it lacks the water heated feature of the Clifford. If you live in a warmer climate that might not matter much. To use a two barrel carb on the Offy "C" you'll need to buy a two barrel to four barrel adapter, but I'm pretty sure that would still be less expensive than the Clifford setup for a single two barrel carb would be.

:)

The Offenhauser "DP" (dual port) manifold is a whole different kind of critter. From what people in here say it seems to be a fairly good choice for somebody with an engine that is going to remain internally stock but which will have the "EFI" exhaust manifolds to improve breathing on that side. If you're also thinking of upgrading the cam or doing any other internal mods to boost power then one of the other manifolds might be a better choice in the long run. If you want to go with the Offy DP the carb that seems to get the most kudos here for that setup is the Holley 390.

:)

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Post #6 by Luckyman » Wed Nov 23, 2005 11:09 am

StrangeRanger wrote:The Offy DP is intended to be used on a dead stock engine with a small 4V like a Holley 390. It is intended to provide more power for towing or hauling. The DP is reported to have some fuel distribution issues.


Would you please elaborate on the fuel distribution issues of the DP, or point me in the direction of some discussion or documentation of those issues. I have been thinking about trying out the DP on my truck, but I like to get all the info I can on something before I make a decision.

Thanks for your help.

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Post #7 by StrangeRanger » Wed Nov 23, 2005 12:34 pm

About 6 posts doewn in this forum
http://fordsix.com/forum/viewtopic.php?t=29363

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Fred
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Post #8 by Fred » Wed Nov 23, 2005 1:46 pm

You can convert an Offy C or a Clifford single four into a dual plane. You mill a groove into the manifold so it divides the chamber into 1-3 and 4-6 cylinders. Make a divider out of aluminum (I used 1/2 in plate) and mount your carburetor sideways. Low end torque is great. Someone else on this forum has done this too and it worked well for him also. I advocate this instead of the dual port manifold.
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