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Projects Hilborn mix up

Discussion in 'Traditional Hot Rods' started by ManualOldsOnly, Mar 21, 2021.

  1. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    Hey so I just got this sweet deal on a hilborn set up and traded some parts but now that i have received the set up I'm noticing that it does not fit..

    I was told this was for a 394 olds but it is very clearly not fitting. So any advice on fab? Or anyone got a set actually for an olds they'd trade for these? I'm guessing these are for a Pontiac.

    Casting number: 347-p-8a
    Gasket on bottom is what came off the hilborn and gasket on top is the old one off the olds
     

    Attached Files:

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  2. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,799

    jimmy six
    ALLIANCE MEMBER

    I’ll bet it’s a 57 Pontiac 347 ....Hilborn cast in numbers were by the engine cubic of the manufacturer. The typical SBC you see starts with 327
     
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  3. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    Yeah I figured it was Pontiac. That's sucks. Itd probably fit 50s olds with a little modification.
     
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  4. Pete1
    Joined: Aug 23, 2004
    Posts: 2,253

    Pete1
    Member
    from Wa.

    If you could find an Olds base plate you could adapt it ok.
    I adapt several late V8 ones to flathead Fords.
     
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  5. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    Yeah I was thinkkng about that I would still have to cut and drill the hilborn at the very minimum even in trying to adapt it. I'm concerned however about going from that small of a intake bore on the hilborn to the mammoth intake ports of the olds. I don't know if it would work like a venturi or just have really crap flow!
     
    Last edited: Mar 21, 2021
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  6. Pete1
    Joined: Aug 23, 2004
    Posts: 2,253

    Pete1
    Member
    from Wa.

    Venturi ports have been used for many years on race engines. It is nothing new.
    I have made several adapter plates by hand but it is much faster with a CNC mill.
     
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  7. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    I would probably make one by hand just cause that's what I have access to tool wise. I don't know if the olds hilborn set up uses a larger butterfly or if it's the same 1 7/8"

    If its the same I see no problem in adapting it. If the olds is larger then I'm concerned about starving the engine and being unable to give it the appropriate cfm.
     
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  8. Pete1
    Joined: Aug 23, 2004
    Posts: 2,253

    Pete1
    Member
    from Wa.

    If the SMALLEST part of the finished port is smaller than the butterfly, it will work. The other way around not so much.
    Example. The smallest FINISHED port diameter in an all out flathead Ford V8 is about 1.380. The injectors I have been using are either 2.4375 or 2.5.
     
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  9. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    So I did some digging it looks like the butterflies on the 394 setups are about 2 1/16" so I have a feeling on my #23 heads that this Pontiac setup is gonna be too small. I'm gonna call alkdigger/hilborn/and Ross and see what they all say
     
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  10. Russco
    Joined: Nov 27, 2005
    Posts: 4,327

    Russco
    Member
    from Central IL

    Someone like Tim Engler could make the correct bases you’re needing I bet.
     
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  11. 1934coupe
    Joined: Feb 22, 2007
    Posts: 5,051

    1934coupe
    Member

    If you have the ability to make adapters you will be fine. Start off with a 1" to 2" thick aluminum plate a little bit bigger than the size of the intake gasket and have at it. Alky Digger is very good resource, depending how much you have invested you might want to sell the Pontiac and buy the correct Olds unit. My brother had the same exact problem but was able to return the Pontiac unit and got an Olds unit. Good Luck.

    Where are you located?

    Pat
     
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  12. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    I'm not sure who Tim Engler is.

    Alkydigger is great I'm hoping they can help I might try to bore my unit and make it a 2in if I do go the route of adapting.
    I was thinking 1/2 to 1" thick aluminum plate for the adapter.

    The butterflies are 1 7/8" and my intake valves are the same size. So I might just be barely ok for running this system but I'm still waiting to hear back from alky before I decide.

    I'm definitely open to selling and or swaping the unit! It definitely would make feel less guilty about cutting it up and drilling it out! But I have been unable to find anyone that even has the olds unit so far.

    Also I'm in Nashville, Tn
     
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  13. Pete1
    Joined: Aug 23, 2004
    Posts: 2,253

    Pete1
    Member
    from Wa.

    3 inch MINIMUM for the adapter plate.
    1 7/8 is way too small anyway. Move on.
     
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  14. 1934coupe
    Joined: Feb 22, 2007
    Posts: 5,051

    1934coupe
    Member

    YOU SHOULD NOT TRY TO HOG OUT WHAT YOU HAVE. IT WOULD RENDER THAT MANIFOLD USELESS. According to your theory all the early SBC 283, 301, 327, and 350 should not have run well because the largest intake valve they had was 2.02 and the Hilborns at that time were
    1-15/16" or 1-7/8" like mine is and I made over 450HP. Don't over think this.

    Pat
     
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  15. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    Well it's not my theory. I'm not sure of the math to be honest hence why I've been trying to get hold of alky or Holley.

    And I certainly would not "hog" anything out. If i increased the butterfly size I would machine it out to 2in just like I've done with motorcycle carbs. It wouldn't render the manifold useless. But it would increase my cfm. I just wanna make sure I don't wind up with less cfm per cylinder then I would with the stock 4bbl 4GC

    Also 3in minimum?? That seems rather excessive just for a plate to adapt intake ports. The mounting holes are close enough I could stretch the hole to make work. Then the parts of the hilborn that would cover the water parts would just be cut off. The adapter plate would cover the rear water ports, and the front water ports would just use an offenhauser water cross over. They're being remade and are cheap enough to not have to worry about trying to make my own.
     
  16. Budget36
    Joined: Nov 29, 2014
    Posts: 13,174

    Budget36
    Member

    I don’t know a thing about this stuff, but would encourage you to listen to the replies from those who have run the setups before.
    As an aside, do you know what the diameters are that was made for your engine?
     
  17. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    Yeah I mean that's why I'm definitely asking for input. I will also say that I'm going to convert the unit to EFI.

    The hilborn setup for the 394 from what I could find seems to use 2 1/16" diameter butterflies. (Which I'd have to mic the throttle bodies) but I could possibly try to punch them out to use that size, but holy cow that's a lot of material to remove! Haha

    I do firmly believe that anything is possible and anything can be made to work. However that doesn't always mean that is the best route. And not gonna lie i would definitely prefer to actually have the proper unit, but these hilborn aren't exactly a dime a dozen ya know?
     
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  18. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 3,127

    ROADSTER1927
    Member

    This is a 324 intake gasket. Gary thumbnail (42).jpg
     
  19. Pete1
    Joined: Aug 23, 2004
    Posts: 2,253

    Pete1
    Member
    from Wa.

    To make venturi ports work, you need more port length. If you are not going to venturi ports find the right injector for the engine. Much cheaper.
     
  20. ManualOldsOnly
    Joined: Feb 15, 2021
    Posts: 50

    ManualOldsOnly

    Aha ok that's why you're saying to use 3in to basically make a spacer for the venturi to be more effective. I understand
     
  21. Harv
    Joined: Jan 16, 2008
    Posts: 974

    Harv
    Member
    from Sydney

    Up to a few years back, Hilborn had paper records for damn-near every injector they built. They were fantastic to deal with, even from as far away as Down Under - send them an email with the casting number, and they would send you the original build sheet. Now that Hilborn has been sold to Holley, do they still offer that service somehow? Suspect the answer is no, which would be a real shame... so few companies held that much history.

    Cheers,
    Harv
     
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  22. speedbump
    Joined: Mar 3, 2008
    Posts: 116

    speedbump
    Member

    too make life a bit easier just use the earlier heads. don't use the #23 394 later heads. you will need to do less port matching. plus you can use that manifold with alittle work. early 372 heads or 331 heads work need to use the head gasket for the head your going to use.. it will be hard to find the correct manifold that will work on the later 394 #23 heads. there are a few out there. I found one but wind up selling my complete olds stuff. good luck. hogging out your manifold will just turn into book ends.
     
  23. You said that you got a sweet deal on the Hilborn injector. It could have been a sweet deal if you had an early Pontiac. Now, that the sweetness has worn off, give someone else a sweet deal, and step up and buy the correct unit that you need. It will cost less money and aggravation, and you will have the correct unit.
     

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