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GMC V6 and V12 Engines Engine repair and rebuilding

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  #11  
Old July 22nd, 2021, 02:45 AM
bostru bostru is offline
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Default Re: 305A carburetor

To be a little more specific the leaky float bowls have always been problematic . This particular carb had a bent or misaligned power valve "stem" Swapped in another metering body with good stem from another carb off of six cylinder Ford The throttle body bore from that carb has a 2 5/8 "bolt spacing and a 1 9/16" bore (seems this is the most common 1904 ).The 305 GMC is measures 2 15/16" bolt spacing and 1 3/4" bore . With the metering body from the 'smaller carb' truck idles fine but surges at low speed and does not have top end power as before .I tried this with a couple other metering bodies with pretty much same results . Asked Mike's if they knew anything about swapping these bodies but he had never done that.I have a line on another carb with the 'larger throttle body' so I will try that metering body and see. As I said before I have had many of these carbs before used and pro rebuilt and eventually the bowls seem to leak . I have checked flatness on the bowl and cover and corrected as per Mike's . I'll keep ya posted when I swap the other metering body. Yes I would still be open to another bolt on carb but seems no one here knows of one. Thanks
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  #12  
Old July 22nd, 2021, 03:31 AM
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AZKen AZKen is offline
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Default Re: 305A carburetor

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Originally Posted by AZKen View Post
You just need a little newer 305 intake manifold, easy to find and install. Buy a WW, easy to find and install. Not much work.
What is wrong with this idea? Gets you a 2BBL. Era correct GMC.
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  #13  
Old July 22nd, 2021, 03:42 AM
bostru bostru is offline
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Default Re: 305A carburetor

Nothing wrong with that idea but not what I'm looking for . My truck is a pro restored body off ,nut and bolt restoration of a rust free Texas truck. Hiding a different direct fit carb under my oil bath air cleaner is as far as I will stray from original. Any input as far as metering bodies on the 1904 ?
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  #14  
Old July 22nd, 2021, 04:23 AM
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Default Re: 305A carburetor

I don't understand why you are messing around with meter bodies? Are you trying to save this carb because it is somehow numbers correct for 1960? What section of the carb is this number? You have not been able to find a 1960 1904? You are obsessed with metering bodies. How do you know that the lack of performance is the meter body. The word "pro" you are using means nothing. Many here are unsung pros also. This is where 6066 GMC pros live.
There is no one on earth that will care if you use a different 305 V6 GMC manifold with a WW carb. The manifolds look basically the same under the air cleaner. The truck won't be worth one penny more or less. No judge or buyer will ever have that knowledge that 1960 305A had 1904 1BBL but a 1960 305C had a WW. You are too tight on this. Maybe you are an expert on 1904, that's great. I'm not. I don't think you need to be this rigid. If you want me to find a specific carb out here in my area, give me the numbers and I will try to find one. It seems like the answer is obvious. They only metering body that will work for you is one from a carb like the one you were using when the truck ran good.
You are stuck on a carb that you say is crappy, they all leak, problematic, warp, no fix, can't find metering body.

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The Holley 1904 was prone to warpage of the main casting and the bowl, similar to the Rochester B. Since the bowl mounts vertically on to the main body on the 1904, warpage causes a fuel leak at the bottom of the bowl.

The earliest 1904's had the problem, but it took longer as the bowl was glass, which didn't warp. When the glass bowls were replaced with die-cast bowls approximately 1959 or so, the problem got worse, as the die-cast bowls also warped.

The Holley 1904 is available in two different flange sizes (like the Rochester B) and several different internal venturi sizes for use on engines from 144 to 305 CID; and used ones (except the ones for the 144) are much more common than even the Rochester B. The warpage is much easier to straighten than the Rochester, as there are no projections on the surface to straighten.

The flange is SAE No. 3, 2-15/16, I believe there are Carters and Rochester's that fit. When buying a replacement donor carb, the rule of thumb is get it from a motor within plus or minus 3 per cent Cu In of the receiving motor.

Last edited by AZKen; July 22nd, 2021 at 05:31 AM.
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  #15  
Old July 22nd, 2021, 04:51 AM
bostru bostru is offline
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Default Re: 305A carburetor

I was hoping to find someone with a working knowledge of the 1904 .I am not obsessed with the metering bodies of these carburetors other than the fact that this is the part that by process of elimination is where my problem lies. No point in debating how to build ones truck but you do yours and I will do mine . If you can help with the 1904 thank you otherwise let someone else will chime in.
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  #16  
Old July 23rd, 2021, 02:03 AM
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Default Re: 305A carburetor

Problem solved .Obtained another carb with the larger throttle body and swapped the metering body and truck performs as it should .Makes sense that the carbs that had the smaller throttle body were for smaller displacement engines and their metering bodies are calibrated accordingly. Also machined some material off the back side of the four bolt 'bosses' on the float bowl cover to give the gasket little more crush ,no more leak ! Thanks for all the input on this
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