Wanted Offy DP intake
- Thread starter Craigwell
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Ford Straight 6 Manifold for Sale in Temecula, CA - OfferUp
Open Box (never used), Used in excellent condition. Offenhauser aluminum Manifold 690, Model 6019. For Ford Straight 6 Motors. 240, 300. I have Ford truck parts for sale. 67-86 . Leave number to talk and send pictures if interested. Bronco WHEELS and tires. $750. Make an offer!;
offerup.com
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If I swap to v8 I’ll let you know I have what you need. It’s a offy C though. I’m in NFLD. Do YOU have any parts? Haha
Yeah, it got mounted. But wasn't used much, or the secondary runner would be carboned up.
Thank you... I ordered a new one from Summit yesterday - ouch! - I don't have much else yet, other than my decent core. Found the machine shop today in Bridgewater that I'm going to deal with... now it's time to spec this build!!
I have a couple sets of EFI exhaust manifolds, and a spare carb head (pedestal).
Good deal! What carb are you intending to use with the DP?
In the adds description, it reads as being- used in excellent condition
Perhaps installed but did not run. The price looked better than the $600 plus at Summit; if some really wanted it
I would be interested in the C manifold.
The long standing default was to start with a Holley 390, but I'm trying to get up to date on some of the newer options. There's a good chance I'll also grab a Cliffy intake to try.
I'm cluing in a bit more, I see someone else chimed in about the C above, but I too would be interested if that doesn't work out.
This is your post sir. I'll stand second in line for you to obtain it. Did you decide against the DP?
I appreciate the courtesy. I have ordered a new DP from Summit, should be in my hands next week.
I may have been ahead of myself a bit - I've had Offy DP on the to do list in the back of my brain for nearly 20 years. Ordered it in a moment of "holy crap I have to get moving on this" the other night.
After now researching a bit more and trying to get current on options and tech, (Aussietech wasn't an option I recall being aware of in 2009 for example, when I was last working incrementally with any seriousness on project 300s), I'm seeing it may not have been the best choice.
I don't mind having options, but I will want to be more shrewd and focused going forward, or it will be a gong show, I appreciate.
Cliffy C with water heating provision seems prudent for performance, and streetability in winter.
Craigwell, I have probably the most experience with this intake, been running one 10 years, 80,000 miles on a '90 f150 daily driver. The reason I asked about the carb is, remember it must be oriented with the front of the carb facing the valve cover. This causes many carbs to be less desirable based on fuel bowl design, including Holley. . . I'll have to finish this later, something's come up, have to report to work.
Since you've just bought a DP, I highly recommend this thread.
Offenhauser Dual Port (DP) Intake Manifold
Thank you! I will keep reading !
I don't know of any water heating provisions on either the C or DP manifolds. They are made to be able to attach to your factory exhaust manifold for heat to help with fuel pooling in the bottom of the intake, also helping with winter warm-up in cooler climates. If you use EFI manifolds or headers, you lose this ability. Some guys have made a water manifold that will attach to the bottom to compensate to alleviate some of the aforementioned issues. RASO enterprises also make this hot water adaptation to add to these Offy intakes. If you haven't received the DP yet it may be worthwhile to kill the order and get the C to get away from some of the carburation fitment and performance issues.
If you're using the DP as it's engineered, the carb faces the engine (with 4-hole isolated-runner gaskets). This affects carb selection, since most are engineered with the assumption they will face forward, V8 style. The 90* orientation affects Holley carbs and others with a similar bowl design the most, since the long axis of the fuel bowls are now parallel to the direction of acceleration and braking forces, which will pile the fuel up on one side of the bowl. The 390 has the fuel inlet on the linkage side, what now becomes the rear of the carb on the DP. The float is hung on that corner of the bowl. Under acceleration, the fuel will move out from under the outer part of the float, toward the needle, allowing the float to drop, potentially overfilling the bowl- a rich condition. The reverse happens on braking. Also, if the fuel level in the bowl is not horizontally flat, each of the two jets will pull a different quantity of fuel. During hard acceleration, the front primary throttle is leaner than the rear throttle. All of this may be so minor as to be ignored in a normal street driver vehicle, I can't say personally. Also, the PCV valve port is on the rear of the 390, and many other carbs. Using this for PCV will result in an oily residue build up in the entire secondary tract, since it is 100% static unless the secondaries are open. This is the wrong place for inhaling crankcase vapors on the DP. The 2 vacuum ports cast into the intake are also in the secondary runner. Unless the selected carb has the PCV port in the primary side, there is no good place to connect PCV.
The best carb for the DP based on physical design is the Carter AFB/Edelbrock, bar none. The 90* orientation actually reduces the accel/decel slosh in the bowls over it's forward facing orientation, since the long axis of the fuel bowls is perpendicular to this force. The bowl is very narrow on the parallel plane of acceleration, and the net force on the float is zero, since what small amount of slosh occurs is spread evenly over the length of the float. Both primary jets draw equal fuel at all times, since they each have a separate bowl, all inertia effects have the same affect on each jet in it's own closed system. The PCV port is under the primary side of this carb. Besides being the "right" port for this, the plumbing is short and tidy as well. The AFB has a very small footprint relative to the Holley, which has the primary fuel bowl hanging over the hot exhaust ports. On the down side, 500 cfm is too big for a mild 300. The primary jetting will be too rich in "stock", out of box tune, so a retune is required for optimal performance and economy on a DP. And the power circuit cut-in vacuum usually needs retuning also. This retune may apply to any carb on the DP, because of the narrow primary runners.
Attachments
I was referring to the Clifford with the water jacket.. https://cliffordperformance.net/store/ols/products/43-4502wh
This is great insight, thank you. I am not beholden to Holley in any sense. The AFB is going on my tentative list. I'll continue researching other setups as well - I gotta think about the Sniper, for example.
Yes, Sniper would be great. The only drawback to them, cost aside, is they are all too large. This won't affect mixture, it compensates for that. But it does affect the "feel" of the accelerator pedal action. It will be very sensitive, with a very quick (too quick) response off-idle, then after 1/3 throttle it does very little. I'm basing this on a first-hand example, my son has 4V Sniper on a stock 318, '77 Plymouth van 727 auto trans and 2.73 gears. At WOT the display shows the EFI is operating at 28%. He's going to a 2V intake and 2V Sniper, not an option for DP in it's intended configuration.
I'm not recommending anything, everyone has their preference. So I'll say what I plan to do with my DP, and leave it at that.
When I transfer this intake to another truck, I'm removing a portion of the dividing plenum below the carb- (it's now no longer DP). I'm purchasing a new E'brock AVS-2 carb with the annular boosters, and the jet kit, mounting it in the correct 90* position, tuning it up, and away we go.
It is good to hear about the real world experience of your son and yourself. I'll keep tabs on your progress with the AVS-2!
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