Offenhauser Intake Manifolds, Opinions Please?

Discussion in '40- & 55-Series Tech' started by cabron, Jul 5, 2005.

  1. cabron

    cabron

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    Summit racing sells these intake manifolds saying 15-30% increase in power, yada, yada, yada. Anyone bought or seen one? Is it a honed factory intake manifold? Here's the ad...

    Offenhauser Dual Port intake manifolds feature completely separate runner systems for the primaries and secondaries. At low-load, the primaries feed the fuel-air charge through the smaller bottom passages at near sonic speed, improving power and efficiency. When the secondaries open, their charge goes through the bigger, cooler upper passages. Then, in turn, it is rammed into the cylinders when it encounters the high-velocity mix from the primaries. The result is better fuel economy and a 15-30 percent power increase across the whole rpm range

    Is it snake oil?
     
    Last edited: Nov 25, 2005
  2. PabloCruise

    PabloCruise SILVER Star

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    Cabron, I left my x-ray vision goggles at home, so I can't see the manifold inside your engine compartment...

    :D

    Nice Cruiser though!

    Is this the intake made for 4 barrels?
     
  3. too tall

    too tall

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    I used one for my last fuel injection system on a 2f It's about the same as far as power goes bit of a pain to install (you have to cut washers in half to space the backside of the exhaust manifold properly for seal) The performance thing might be different though with a 4 barrel carb.
     
  4. Wayneraintree

    Wayneraintree

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    My buddies 2F in his 60 worked well with this intake, he claimed it gave an increase and it felt like it did... I think a larger diameter exhaust in combination with the intake would help the 2F in terms of power.
     
  5. dfmorse

    dfmorse

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    Cabron; had one on my '73 FJ40. Best addition u can have. I think I had a Weber on there too. Stock every thing else except ignition. As soon as the engine rpm hits around 1000-1200 rpm's, it really haulsass; for a FJ40 that is. The real test around here (Denver) is to drive up I-70, a hill called Floyd Hill. Before the manifold, I had to shift to 2nd and go over the top at 40mph. After the conversion, 3rd gear at 55mph and increasing. It was was amazing.

    How much are these now? I'm thinking of putting one my '79 FJ40...

    David in Denver
     
  6. Felix

    Felix

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    I've got an Offenhauser intake and a 4-barrel Carter AFB carb on my 2F, both installed by a PO. It seems to make pretty decent power, but it seems to lag a little bit. You have to git on it a bit before you feel anything. The intake and carb might explain why I get 11 mpg at best.

    Another drawback that I've experienced is in off-camber situations isn't due to the Offy but to the non-Aisin carb - which you'll probably want in order to get full advantage of the intake. Get in a weird angle and my engine sputers, rpms drop, and I smell the gas spilling out of the bowl. There are modifications listed in the tech links that would help. I haven't tried them, yet.

    Felix
     
  7. SpaceGhost

    SpaceGhost

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    The important thing here is the carb. These are made for 4 bbls. The whole dual port concept is smaller longer runners for the primary to increase low end torque, requires a 4bbl to take advantage of this. using a spacer/adapter to get to TBI or a 2bbl aisin defeats this whole premise.

    TBI's are 2 bbl units (ok, not all but 4.3's are). I had a brand new early Offy dual port intake that I passed on using with the TBI.
     
  8. Pin_Head

    Pin_Head

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    Horsepower increase is a matter of burning more air/fuel mix. To the extent that the intake manifold and carb are the bottle neck to moving the air/fuel mix, improving the flow of the manifold and carb will increase horsepower. If the heads/valves/combustion chamber are the bottle neck, then changing the intake and carb won't accomplish much.

    The sure fire way to get more air/fuel mix into the combustion chamber is to turbo/super charge the engine. That way no matter what the bottle neck is, you can be sure that more air/fuel will be burned.
     
  9. cabron

    cabron

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    Might be dumb question but are all Aisin carbs 2bbl? When I do my rebuild I was considering this intake manifold but will be using a rebuilt carb from Marks Off Road probably, Is the consensus that they wont be a good combo?
     
  10. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    " but are all Aisin carbs 2bbl? "


    One barrel or two barrel...the ones we were blessed with from Toyota anyhow....


    " Is the consensus that they wont be a good combo? "


    according to the inforamtion provided above...


    :beer:
     
  11. Mark W

    Mark W

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    If you are not putting a 4 bbl carb on top of it then an Offy Dual port is contr-productive. The Dual Port is actually pretty restrictive. It's only claim to fame if the ability to run a 4bbl and avoid loss of low speed intake charge speed.

    The 4bbl on top of the Offy is a BIG plus IF you also have a cam to let your engine work the midrange and top end better. A good Asian and the separate runner factory intake will actually give most Dual Port/4 bbl setups a run for it's money. If you have increased compression, exhaust flow and cam duration, then the C Series offy is a better choice. Maybe a little less bottom end with the saem carb, but better mid range and top end.


    Mark...
     
  12. BobLablaw

    BobLablaw

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    I run the Offy with a 600 holley (maybey going back to a 465). The head was ported, polished and matched to the intake, a custom ground cam, new harder springs and dual headers. B4 all this was done I tested out the offy with a 465 holley with headers, I noticed my fuel economy improved, more responsive crisper throttle, not to mention easy starts. But its the sum of the parts that makes this intake work the best. I got lucky the intake and headers came with all the other spare parts when I bought the 40. If you decide to get it youll need a 390/465/600 4bl and headers for it to work well.
     
    Last edited: Jul 18, 2007
  13. BobLablaw

    BobLablaw

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    Wow Im such a noob....I need to check the dates more closely.....this thread is OLD! Sorry to wake the dead
     
  14. dfmorse

    dfmorse

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    Ah! But a good wake-up.

    ...
     
  15. kirkagosto

    kirkagosto SILVER Star

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    i had a 77 fj40 desmogged and i put this intake on with the weber carb and headers and i can tell a huge diff in it compared to before and also compared to my 1980 fj40
     
  16. antFJ

    antFJ

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    on summit there is the c series intake and the dual port intake.. which one is the one we are talking about here? i have an intake that came as a spare with my truck and says offenhauser on the top.. how would i know which one it is?
     
  17. Mark W

    Mark W

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    Simplest way to tell the difference between the Dualport and the C series is... Look and see if it says "C series" or "Dualport" on the top. ;)

    The Dualport is really a pretty restrictive design. It makes up for that some by allowing you to run a 4 barrel. The C series is a much freer flowing intake. But you give up a bit of low end flow speed (which translates to slightly worse low end performance).

    There's no point in running either unless you are running a 4 barrel carb. And no point in that unless the engine has seen a few mods to take advantage of it.


    Mark...
     
  18. antFJ

    antFJ

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    alright so now that i've gone back and looked... if i have an intake that just says offenhauser and nothing else... would it be the c-port? i can get a pic in a couple of weeks if that would help
     
  19. Downey

    Downey

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    My guess is that either Landcruiser Offy intake suffers the same problem their mini truck manifolds suffer, reduced plenum chamber/ pratically no plenum chamber!!!!! These manifolds are "minus 20 h.p." on the Pickup 4 cyl. engines, so obviously I never cared to waste money testing them on Landcruiuser engines. To those of you who have found success with an Offy, good for you!!!!! My guess is any performance gains you noticed probably came from improved carburetion, not the Offy.
     
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