Hello. I have a 1984 E-150 with a 351W H.O. motor. I purchased an older Offy Dual-Port intake and installed it on my otor. Well, after I installed it, I filled the radiator up with fluid and saw that radiator fluid was coming out of four unused holes on the intake manifold.

I did some research and it looks like in 1975 Ford switch from a 16 bolt intake to a 12 bolt intake. I apparently purchased a 16 bolt intake and now it doesn't work on my 12 bolt motor.

Dopes anyone know of a workaround to solve this problem? in other words, does anyone know if it is possible to run a 16 bolt intake on a 12 bolt motor? Or am I sol and did I just waste a bunch of time and money?

 

Okay, I did some checking, and I think I can get away with just tapping and plugging the extra holes.

I would appreciate a second or third head and set of eyes on this problem though.



In this picture, the stock intake is on the bottom, the Edelbrock Performer is in the middle, and the Offy Dual port (which is NOW bolted on the van) is sitting on top. I have circled in red the extra bolt holes in the Offy intake. It is the same on the other side.

The factory intake is water cooled, as are the Eddy and the Offy. The heads have coolant passages front and rear, but the factory intake, and the Eddy and the Offy, only have a cooling passage at the front of the intake. For some reason the gaskets have both front and rear coolant passages, even though only the front is used.

The factory intake has a square coolant passage hole, but the Eddy and Offy both have inverted "L" shaped holes.

I believe that I can tap and plug all four extra bolt holes. The existing intake gasket keeps the coolant flowing where it should, and the bolt holes aren't in the head. Therefore, the only extra holes are in the intake, so I should be able to just tap threads into the aluminum intake and find the right size pipe plugs to fill the holes.

I am going to give it a shot tomorrow.

 

I think you got the most efficient solution to your problem, make sure to use some sealant on whatever you use to plug the holes.

 

What is the advantage of using this manifold?It looks like it would restrict the flow alot

 

Yes, it will restrict the flow at VERY high RPM, but these manifolds are fabulous for street use with the carburetor secondaries set up right.

The separate runners connect to primaries and secondaries in the carb. When the secondaries are not open, the primaries are feeding the intake ports in the head at VERY high velocity due to the small runner size, making REALLY GOOD low speed torque. Once the secondaries kick in, you are using both sets of runners for more flow for higher speed operation.

Don't use one of these on a drag car. It would be like making it breathe through a straw. For a street engine that sees normal, maybe a little spirited street driving, it is GREAT!

In the early seventies I had one of these on a modded 350 SBC in a 40 Ford Coupe. I had to mess with the secondary springs on the Holley to get it to run really right, but once I did that, the width of the power band was nothing short of amazing. It was almost like an electric motor with STRONG torque from idle up to about 6,000 RPM.

 

Yes. I am not drag racing this van, and even with 3.7 rear gears it never gets above 4000 RPM on the highway. I figure this intake should give me better gas mileage. Ultimately I plan on running the Dual=Port intake with a Holley 4360 Economaster carb. Maybe I will throw in an AOD tranny too.

But right now I have to get these ang holes pugged and get the Edelbrock Performer carb tuned for this intake.

 

Did you have much trouble finding this intake? I don't know how long it's been since they stopped making them.

I would love to have one for the 347 that I'm building.

 

I just had to watch eBay closely for a couple months before this one popped up in my price range. They do turn up from time to time. Many people don't know what it is, so you have to do a wider search than "dual port".

I also scored an old Edelbrock SP2P intake for the 318 in my Chrysler 5th Ave. I ave heard good things about these older technology intakes. Again, drag racers hate them for their constricted flow, but I think it should work out great for a daily driver. I hope to swap that one on this weekend.

 

Yes, the SP2P will build LOTS of low speed torque.

I did a little snooping on the Summit site and the Offy Dual Port is still available for the Small Ford. I hadn't heard of them in so long, I had no idea they were still in production.

I know now MUCH more about manifolds than I knew in the early seventies. By doing a little looking I understand that the Dual Port is sort of like two single plane intakes. That would mean that individual runner velocity should be increased, but since all cylinderes feed from the same plenum, the overall volume exposed to the carb venturi will weaken the signal more than I thought.

I do know from using one almost 40 years ago that it will broaden the power band.

 

Thanks for the input. I will be keeping a close eye on my vacuum guage to see how it changes.

 

SUCCESS!!!!



This is what I started with:


There were four of these holes, one at each corner of theintake. This was the easiest one to photograph.

Here is my high-tech, super accurate machining tool:



Yes, a 1/4 drive ratchet and handle attached to a 1/4 inch 8 point socket which fit over my Napa tap. All the stuff on top of the motor made it hard to fit the regular tap handle in there, so I had to improvise. If you are going to be doing any machining, I HIGHLY recommend you use cutting oil. Last night i tried tapping out this hole with just the tap and the regular handle, and it ws so hard to turn that the tap handle stripped. So this morning I made a pilgrimmage to Tacoma Screw (an awesome store: Tacoma Screw Products, Inc. :: Home ) and got the 8 point socket and a tap handle. While there, I picked up a bottle of aluminum cutting oil. MAN, what a difference! I won't say it made it as easy as cutting through butter, but just about. It took me all of about seven minutes to tap all four holes.

i also picked up some replacement plug bolts at Tacoma Screw:



I wrapped them in Teflon Tape and put a ring of high temp RTV gasket maker arounf them:



Then snugged them down in the intake. Tight, but not tight enough to strip the threads:



I started it up and ran it for about 45 minutes, letting it get good and hot. no leaks! YAY!

Now I have to figure out why I can't get the engine to idle below 1000 RPM without retarding the timing to ten ATDC or leaning out the curb idle mix. The throttle linkage is detached and the curb idle screw isn't even touching the throttle linkage. I pull 17 inches of mercury at idle, so I doubt it is a vacuum leak. Maybe I need to lean out that Ededlbrock carb on there. It is running the Edelbrock Performer 600 CFM carb and a cam with a near identical grind to the Edelbrock Performer cam. I am fairly sure I didn't set the distributor up right though. Hmmmmm.

Anyway, the fine tuning is a project for another day. Thanks for the help and the suggestions guys! Now I can move my van back out of the garage until I pull it into the garage for a complete cosmetic makeover. Button-tuck and gorilla fur here I come! :wink:

 

I figured out the idle problem- the nut on the back of the ball stud for the throttle was hitting the curb idle screw. I bent the linkage and everything is fine now. On to the fine tuning.

 

Please keep us posted. I may use an Offy Dual Port on my 347. Let us know your results please.

 

Well, I got the base timing and curb mixture dialed in. Final idle vacuum is 17.5 inches at about 750 RPM in park. Idle is nice and smooth.

I don't have insurance on the van right now, so I took it for just a quick drive around the block. Throttle response is impressive, and definitely better than the Edelbrock Performer intake. An off-idle bog is gone. However, I know I need to recurve the distributor that is in the van right now. That is a different thread though.