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Help choosing a carb

Help choosing a carb

Old 05-17-2020, 04:48 PM
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Default Help choosing a carb

I am having what I assume are carb issues. I donít know a lot about carb tuning, so when I had my motor rebuilt, I had a marina rebuild and install my carb. I am pretty sure itís not running like it should. First I think I am getting leakdown. If it sits for a little while, say a week, it is a bear to start. No matter the amount of pump and crank I do I end up having to pour fuel down the carb to start it. Then it runs pretty good. I can cruise all day. After it has ran for awhile though I start having issues idling. Usually while trying to load it on the trailer it will stall and die. Then it acts flooded. I am thinking fo just replacing the qudrajet with maybe an Edelbrock or Holley. Here is a list of what was done to my 454 alpha. What would you guys suggest?
  • block bore .070
  • valve job (ex valves, valve seats, HP valve springs)
  • cam bearings
  • VAT block
  • HP rod bearings
  • HP main bearings
  • marine head set
  • check align bore (ok)
  • replace brass freeze plugs
  • pressure check ex manifolds
  • marine conversion set gen IV
  • comp cam xe268-1 224/230 @ .050/.515/.520 "nitrided"
  • replace the crank, grind crank rods .010
  • balance assembly
  • hyd lifters
  • true roller chain set w/ thrust
  • .070 SRP flat top pistons
  • molly rings
  • HV oil pump
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Old 05-17-2020, 05:17 PM
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Before you start changing parts, check your fuel pressure and float level on carb.
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Old 05-17-2020, 05:39 PM
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I'm assuming you have a Holley carb. What CFM? There is a guy here PH1972 that is selling a QuickFuel 800 for a screaming deal. I just changed from Holley 800 to QuickFuel 850. No more bad starting or idle problems. The Holley was a constant hassle. The QuickFuel no hassle at all, 3/4 pump 2 clicks and spark it up EVERY TIME.
6-7 psi fuel pressure FYI, mechanical Holley pump.
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Old 05-17-2020, 05:50 PM
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Ayuh,..... I suggest ya have yer Quadra-jet rebuilt again, or bolt on an Edlebrock 1410,.....

That way, you can use Merc fuel lines, linkages, 'n brackets,......

Merc didn't use holleys, but did use the Quadra-jets, 'n then the Merc/ Weber AFB carbs, which are an exact carbon copy of the Edlebrock 1410s,......
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Old 05-17-2020, 05:57 PM
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You have classic symtoms of carb emptying from Your Ďwelch plugsí inside the carb very slowly leaking fuel. A quadrajet rebuild not epoxying these is not a thorough rebuild. Some say the ones in secondaries never leak, however Iíve done two that did.

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Bondo (05-17-2020)
Old 05-17-2020, 05:59 PM
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Originally Posted by Bondo View Post
Ayuh,..... I suggest ya have yer Quadra-jet rebuilt again, or bolt on an Edlebrock 1410,.....

That way, you can use Merc fuel lines, linkages, 'n brackets,......

Merc didn't use holleys, but did use the Quadra-jets, 'n then the Merc/ Weber AFB carbs, which are an exact carbon copy of the Edlebrock 1410s,......
I'm sorry, Merc DID use Holley, check out the 9022 Buldog 500, HP 500, etc. I believe. Merc used several carb combinations on several engine configurations..
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Old 05-17-2020, 06:31 PM
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Originally Posted by GLENAMY 242SS View Post
I'm sorry, Merc DID use Holley, check out the 9022 Buldog 500, HP 500, etc. I believe. Merc used several carb combinations on several engine configurations..
Ayuh,...... I guess I shoulda clarified, "on standard production motors",.....

Sorry,.....
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Old 05-17-2020, 07:16 PM
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Sorry, should have been more clear. My motor came with the Rodchester Quadrajet. I’m not sure if the Welch plugs were done but I assume he just put a basic kit in it. I know those kits don’t address the plugs.
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Old 05-17-2020, 07:20 PM
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Originally Posted by underpsi68 View Post
Before you start changing parts, check your fuel pressure and float level on carb.
Is there an easy way I could do this on my own?
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Old 05-18-2020, 07:00 AM
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I am assuming your float level is too high or your needle valve is hanging up allowing the carb to flood while ideling. Especially if it runs ok off idle. I just rebuilt 2 of these carbs and had the same issue on the port motor. I took it apart 4 times, on the 3rd time I reinstalled the original needle and seat, idled perfect. 4th time , I installed a new needle and seat that the carb kit guy sent me. Upon closer inspection, I found the first new needle and seat kit, the hanger spring was bent, probably in shipping and did not allow the needle to go up and down correctly in the seat. Thus making it leak and stall motor after several mins if ideling. Does your choke work correctly ? Most Quadrajets made after 91-92 have the newer tapered bottom plugs. Also, if you are running alcohol laden fuels, you should run a brass float. Look at Mikes Carburetors web site, there is a lot of information there on carburetor repairs.
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