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235 Chevy carburetor upgrade...

Discussion in 'The Hokey Ass Message Board' started by Fat Hack, Apr 12, 2009.

  1. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    A while ago, I posted wondering if anyone knew whether or not a carburetor from a newer Chevy 194, 230 or 250 six cylinder engine would work on an older Shitbolt six, and never got a clear answer, so I figured I'd just try it and see!

    The 235 came with a Rochester one barrel that, like all Rochester carbs, ran like shit, leaked like a sieve and delivered horrible gas mileage. Add in the fact that the previous owner is one of those folks who suffer from an acute case of filterphobia, and you know it won't be long till a new carb is in order!

    Having had plenty of experience in the past with late 70s vintage Chevy 250 engines in a plethora of Novas and Camaros, I already knew that the best carb for THOSE engines is the semi-ellusive (these days) Holley Economaster replacement 1v carburetors. These fit in place of the awful Rochester carbs and boost fuel mileage and performance CONSIDERABLY on a 250 Chevy six, so I reasoned that it might be a good upgrade for a Shitbolt six as well! The only questions remaining now were could I find one of those carburetors and would it work on this car (55 Chevy)?!

    Lucky for me, Mayfair Speed & Machine Shop just happened to have a selection of NOS Holley Economaster carbs on hand that Dan dug outta the back room, and in the pile was one brand new-in-the-box Economaster 1v designed as a direct repplacement for 1977-78 Chevy 250 six cylinder engines...just what the doctor ordered! I was able to buy it stupid cheap, so the next quandry to address was making it work where the original Rochester failed so miserably!

    The first step, of course, was to rip that leaky old stock carb off and throw it as far from the vehicle as possible! Then, I was able to cut the steel fuel feed line and install a Wix 5/16" universal fuel filter, as the previous owner should have done!
     

    Attached Files:

    Mister E. likes this.
  2. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    The short answer is yes, the carburetor bolt pattern is the same on a late 70s 250 six cylinder 1v and a mid 50s 235 1v, so the Holley does physically bolt onto the 235 intake manifold. But, the throttle linkage is not compatible, obviously, which means some engineering is required to make it work.

    Whenever possible, I like to come up with a way to NOT modify the existing linkage, and also to NOT alter the carburetor itself...if I can! That way, a stock carb could always be put back onto this engine (why is beyond me, but it could)...and that obscure Holley carburetor could still be used on a much better 70s era 250 six if it ever had to be! Fortunately, after setting the new carb on the intake and staring at the linkage rod for a few minutes, I got an idea and set out to make up a linkage adapter that would bolt to the Holley using two existing holes on the carb linkage and also mate up to the stock 55 Chevy throttle rod.

    I found a piece of scrap metal (an old radio bracket of some kind actually) and cut, bent, filed, shaped and drilled it till it fit the need...then attached it to the carb using a coule screws, nuts, washers and lock washers. Naturally, I built a little bit of adjustability into the bracket in the form of slightly oversized holes so I could fine-tune the fit if neccessary...I mean, the car was in the driveway, and I was making the bracket in the garage at the workbench, so a little bit of my trademark "eyeball engineering" was employed, but the bracket turned out great and, as a bonus, it even fit and worked as I'd hoped!

    (the silver piece on the goldish colored bracket is the new piece I made, just to show you what you'll need to whip up to do a similar swap on your 235).
     

    Attached Files:

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  3. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    After an initial trial fit, I had to remove and trim my bracket a little bit to allow the stock retaining clip for the throttle rod to work, but after that quick operation, the carb bolted up fine, the linkage fell into place just like it did on the stock carb, and it moved freely with no hanging up or binding. Nothing modified on the linkage, and no permanent mods to the carb...perfect!
     

    Attached Files:

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  4. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    With the fuel line hooked up and the vacuum line to the distributor hooked up (via a small insert of rubber vacuum line to connect to the original steel line), and the throttle linkage in order, it was time to test-fire the engine and see if this carburetor, which had lived in a storeroom for a couple decades, would work or not!

    The engine fired up once fuel got to the carb, and it ran smoother than it ever did with the stock carb! I still have to wire up the electric choke and adjust the idle speed and fine tune the choke setting, but all indications at this point are that the swap will be a success! Hopefully, I'll button up the job in the next week or so with an air cleaner installation, oil change, new spark plugs and a little road testing!

    This swap is easy enough that even I could do it, so it rates as an excellent way to significantly upgrade any 235 Shitbolt Six in my book! With any luck, it'll allow this motor to live long enough to see it's replacement coming together on the engine stand!

    I'll post further updates to button this carb swap up in the next few days, so tune back in to see how to put an aftermarket air cleaner on it and all the little final details!

    :):cool:
     

    Attached Files:


  5. thewishartkid
    Joined: Jun 23, 2006
    Posts: 884

    thewishartkid
    Member

  6. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,292

    6inarow
    Member

    Shitbolt Six??? Thems fightin' words dude.

    It looks like you are half done. When you gonna put the second carb on?
     
  7. panic
    Joined: Jan 3, 2004
    Posts: 1,450

    panic

    Excellent, thanks for the R&D.
     
  8. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    Ha Ha!! I've long hated these engines, so that's been my term for them for years! :D

    Second carb? This IS the second carb...the first one was junk! ;):D
     
  9. I think you could use a hand pump weed sprayer over the open hole in the intake manifold and it would work better than the Rochester.
     
    Haden59 and volvobrynk like this.
  10. Wow, great info!!!!! I'll start searchin, as my carbs do happen to suck also....
     
  11. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,292

    6inarow
    Member


    Sign a couple checks and let me have at that 235 for a couple weeks. You will see a difference
     
  12. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    ...or you could sign a check and I'd let you have my 235...for good! :D

    (I'm just trying to make the thing as reliable as possible so I can drive the car some before ditching that motor in favor of a V8).
     
  13. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    No doubt in my mind about that!!! :cool:
     
  14. Danimal
    Joined: Apr 23, 2006
    Posts: 4,125

    Danimal
    Member

    How many more of them carbs does he have in the back room? I need 3 at least!

    And yell when you want to throw that I6. I'll come fetch it off of you and put it in my truck!
     
  15. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    He didn't have any more of those carbs for the Chevy 250 engines, but he had a few for Mopar sixes and V8s, and several of the staged two barrel Holleys commonly found on Pinto and Vega four cylinders.
     
  16. Danimal
    Joined: Apr 23, 2006
    Posts: 4,125

    Danimal
    Member

    At least I know what to watch for. Lots of old Chevy trucks around here running those 250s.
     
  17. hotrod-Linkin
    Joined: Feb 7, 2007
    Posts: 3,382

    hotrod-Linkin
    Member

    holley-weber from langdons stovebolt would have been easier and cheaper.
     
  18. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    I kinda doubt it. I got the brand new Holley Economaster 1v carb for $75, and it bolts onto the stock manifold. The linkage adapter cost nothing (made from a scrap bracket in the garage) and the rest of the installation items were included with the carb. I only had to buy a fuel filter, which I would've needed anyway. Got about $80 into the job thus far.

    Also, I've attempted to deal with Langdon's before and found him impossible. He doesn't answer his phone or return his calls. If you drive out there, you can talk to his wife, who is nice enough, but that still won't get you anything. Better off to make what you need yourself than to waste time trying to deal with him, at least in my experience, anyway!
     
  19. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    Hey! The rain finally stopped today, so I could button up the carb swap on this car! All that was really left at this point was to hook up a keyed 12v power wire to the electric choke on the new carburetor, and then put an air cleaner of some sort on it!

    The wiring was a simple task, so lets take a look at the air cleaner installation:

    Luckily, Holley is gracious enough to provide you with a nifty thick white plastic air cleaner spacer/adapter, which slips over the carb opening and accepts a GM two barrel air cleaner opening. I placed a common Mr Gasket 2v to 4v air cleaner adapter on top of the Holley 1v spacer thingy and that paves the way for you to run any common aftermarket 4v air cleaner you wish!

    Here we see the pieces laid out for your inspection, followed by a photo of them set in place with a typical "low profile" 14" aftermarket performance air cleaner base.
     

    Attached Files:

  20. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    I had an old Mr Gasket "Rodware" 14" blue annodized air cleaner lid on hand (one of several parts designed for Mr Gasket by the late John Buttera back in the 80s), so I picked up a new 14" air filter element from work today and made a receiver for the "smooth top" air cleaner lid by using a short stud and a 1/4"-20 treaded 'barrel nut' with a jam nut to keep things tight. The filter top spins into place and snugs down to seal the air cleaner assembly without a wingnut sticking through the top.
     

    Attached Files:

  21. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    After starting the engine and adjusting the idle speed, I drove the car around town for a couple of hours and although it's still a Stovebolt (single-digit horsepower with 0-60 times measured in minutes and delivery-truck gearing!), it didn't spew gasoline, didn't flood out and stall, and probably got better fuel mileage than it's ever gotten in it's life! The Economaster is a big improvement over the stock Rochester carb, for sure...and (if you can find one!), it makes for a simple and affordable upgrade!

    Maybe this'll tide the car over till a new motor takes the place of the old six banger?!

    ;):D:cool:
     
  22. poboyross
    Joined: Apr 29, 2009
    Posts: 2,142

    poboyross
    Member
    from West TN

    Admittedly, I'm both a n00b and a restoration virgin....but do you know if what you did would work on a 216 ci Stovebolt? The 51 Chevy I just picked up has the 216 engine, 1bbl Rochchester, and manual choke. It has been converted to 12v, btw. If you think it would work, how does the electric choke factor in to changes I'd have to make to my current manual choke? Again, I'm new to this....so please excuse any "ignernce" :)
     
  23. I'm definitely enjoying this tech info. I wonder if this could possibly work on my '54's 235 six. I have had nothing but trouble trying to keep that motor running since I got the car. I've always thought it was the carb. which I took out and rebuilt with a kit..In turn it worked for about a week and went back to it same old crazy ways. Do you think this swap could work for a '54 bel air as well? Thanks again, awesome thread!~Mojo
     
  24. GuyW
    Joined: Feb 23, 2007
    Posts: 555

    GuyW
    Member

    Hmm - I've never had such problems. Really.

    Glad you have a fix that satifies you, tho.
    .
     
    smoked1 likes this.
  25. claymore
    Joined: Feb 21, 2009
    Posts: 896

    claymore
    BANNED

    Gee what the heck is the grenade attached to the manifold for

    [​IMG]


    ..... just in case the mods don't work and you want to make the stovebolt into a steaming pile of twisted metal or what? :p

    Or maybe in case of zombies attack :eek:
     
  26. Cosmo49
    Joined: Jan 15, 2007
    Posts: 1,231

    Cosmo49
    Member

    I think it's funny that you're bad mouthing (justly so) the Rottenchester like it's 'NEW AND IMPROVED INFORMATION', dude that's Chevy entry level basic. If you really have the patience go over to inliners.org and click on the tech tips, they've figured out how to get them to stop leaking. I've had Langdon's Holley Webber on my '56 235 Fenton Header-equipped for eight years on a daily driver year round only vehicle. Several 2k trips with averages @ 21 mpg highway.

    http://i104.photobucket.com/albums/m177/49Cosmo/Horn-side56235.jpg

    You ain't going anywhere without overdrive or a higher rear end, quit scaring these kids. I have a '57 3.90 pumpkin in my '49 rear truck housing and a '62 3sp+od. Here's the math for ya .70 Overdrive X 3.90 rear = 2.73 3rd overdrive, I live in the left lane. If you're just staying in the county just drive it the way it is.
     
  27. leaded
    Joined: Nov 17, 2005
    Posts: 326

    leaded
    Member
    from Norway

    Get a adapter, put on a GM 305cid V8 2 bbl carb, without any changes (without minor adjustments) and you got better milage (at same gaspedal use ) and POWER beyond the 1bbl.
    Weber ( as Langdons 32/36 ) stumbles hard at mid acceleration, because carbs too small for this engine, and egine dont get enough before second port opens.
    Done it at 250cid & 235cid with great luck!
     
  28. MercMan1951
    Joined: Feb 24, 2003
    Posts: 2,654

    MercMan1951
    Member

    Guys, he's big block bound in his mind... so...I think he just wanted a quick and cheap fix to keep it running so he can save up for something else...eventually...
     
    shad88 likes this.
  29. yeah fat hack wants to be james taylor!:D but good info anyway..
     
  30. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,709

    Fat Hack
    Member
    from Detroit

    Okay...YES, this carb swap should work on any inline Chevy six with a 1v manifold and 12 volt wiring (for the choke). The choke DOES come off quickly, which is fine by me because it means better mileage, but it makes the engine just a little bit cranky until it's fully warmed up...which truthfully, doesn't take too long at all!

    I've been driving this car every day for the past couple of weeks and it's been great! MUCH more reliable than the total shit late-model beater it replaced, and decent gas mileage to boot! Overall, I'd recommend this carb swap to anyone with a Stovebolt six...it's SUCH a big improvement over the stock carb that you'll wish you'd done it soomer!
     

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