Carburetor Issues NEED HELP!!!!

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lekid
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Carburetor Issues NEED HELP!!!!

Post by lekid » Thu May 03, 2018 1:53 pm

I have a 4150 1050cfm carb on my 409sbc engine. It ran fine last year (did drop a lot from Park to gear, but worked), but had a small hesitation when getting on the brake.

We freshen the motor this winter and now the carb seems all screwed up!!!

I would have to have the mixture screwed 2-1/2 turns out to get the thing to idle in park and as soon as I put in drive, would stall!!

I took the carb off and all apart, blew all the passages (paying even more attention on the idle circuit), setup the blades around 0.030" for transfdfr slots. Change the carb gaskets and even take the 1/2 spacer we run off just to be sure it is bot the issues. Start the car and this time it is way worse!! Cant make it to idle in Park! I take the 70fr/73rr idle air bleeds and put some roughly 65 (blanks that w3 had drilled with 1/16 for another carb) and I can finally get it to idle in park but again, with 2-1/2 turns out. Put in gear and it drops to 750-800 and hesitation at 1500 still there.

What I am doing wrong? I am completely lost!!!

I will try and borrow a buddies 1000cfm carb just to be sure the problem is in the carb.

lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Thu May 03, 2018 1:55 pm

Forgot to say: no power valve in the carb, jets are 93fr/94rr, it has annular boosters.

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Re: Carburetor Issues NEED HELP!!!!

Post by mag2555 » Thu May 03, 2018 2:09 pm

Blowing out passages that have had pump fuel sitting in them over the winter may not be enough to blow out sticky crud!
I would get a can of Carb cleaner like Berkable 2 +2 and blast that thru the metering block.

Headguy
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Re: Carburetor Issues NEED HELP!!!!

Post by Headguy » Thu May 03, 2018 2:14 pm

Did you check the obvious? Vacuum leaks or initial timing, park vs in gear.

lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Thu May 03, 2018 2:38 pm

Headguy wrote:
Thu May 03, 2018 2:14 pm
Did you check the obvious? Vacuum leaks or initial timing, park vs in gear.
Timing has been verified and locked at 34degree.

I cannot see where there could be a vacuum leak. Changed carb gaskets and removed spacers. No signs of leak at the intake gaskets.

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Re: Carburetor Issues NEED HELP!!!!

Post by Headguy » Thu May 03, 2018 2:48 pm

Did you notice any ET change towards the end of the year before you freshened it? A bad torque converter can make you think its a carb problem.

lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Thu May 03, 2018 3:04 pm

Headguy wrote:
Thu May 03, 2018 2:48 pm
Did you notice any ET change towards the end of the year before you freshened it? A bad torque converter can make you think its a carb problem.
Nope. Car always worked the same for 60ft and slip at the 1/8.

Been very hard to get it to idle properly in Park, and I would think that the convertor would not affect that until it goes in gear, or am I wrong?

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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Thu May 03, 2018 5:31 pm

** UPDATE **

I took everything off and installed the 650cfm crappy carb I have on my 63 Nova Wagon cruiser and it did the exact same thing, then I realized that I forgot to cap the rear vacuum port on it. Then it idled properly at 1350rpm and dropped to 800-850rpm and stayed there and ran good. (that is roughly where I was last year with our tight nitrous converter).

I put my race carb, nitrous plate, spacer back on and still issues, but now I was pretty sure it was vacuum leak so I looked further and used a lot of brake clean, lol, and found a vacuum leak between the spacer and intake manifold: rpms went up 500-600rpm when sprayed with brake clean (the problem was still there when I took the spacer out earlier cause the solenoid braket was hitting something and not sitting 100% on the intake).

I will go pick up a new (non-wood) spacer and a few new carb gaskets and try again tomorrow. Hopefully it was as easy as that!!!

I will report back!

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Re: Carburetor Issues NEED HELP!!!!

Post by Tuner » Thu May 03, 2018 7:21 pm

Sounds like the wrong gasket between the base and body. The curb idle passages are in a slightly different locations on the 1-11/16" and 1-3/4" throttle bore carbs and mismatch either way blocks the idle passage from the body to the base.

lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Thu May 03, 2018 8:03 pm

Tuner wrote:
Thu May 03, 2018 7:21 pm
Sounds like the wrong gasket between the base and body. The curb idle passages are in a slightly different locations on the 1-11/16" and 1-3/4" throttle bore carbs and mismatch either way blocks the idle passage from the body to the base.
Why would the carb run good one year and bad the next? The gasket was obviouly good last year.

Anyways, the problem is still there with the Race carb. I will take it apart ... again!! Not sure what else to do!!!

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Re: Carburetor Issues NEED HELP!!!!

Post by Tuner » Fri May 04, 2018 1:51 am

lekid wrote:
Thu May 03, 2018 1:53 pm
Change the carb gaskets and this time it is way worse!! Cant make it to idle in Park!
lekid wrote:
Thu May 03, 2018 8:03 pm
Tuner wrote:
Thu May 03, 2018 7:21 pm
Sounds like the wrong gasket between the base and body. The curb idle passages are in a slightly different locations on the 1-11/16" and 1-3/4" throttle bore carbs and mismatch either way blocks the idle passage from the body to the base.
Why would the carb run good one year and bad the next? The gasket was obviouly good last year.

Anyways, the problem is still there with the Race carb. I will take it apart ... again!! Not sure what else to do!!!

lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Fri May 04, 2018 7:50 am

I took the carb all apart again and this time I also took the idle jets out of thr metering blocks to clean everything better and I found that it appears like something is in one of the idle passages. Picture below. Anybody have a clue what that would or where it is from?

Does anybody know how to easily remove the plug on top of the metering block so I can have better access to that passage?
Capture+_2018-05-04-06-48-12.png
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Re: Carburetor Issues NEED HELP!!!!

Post by pamotorman » Fri May 04, 2018 8:03 am

i just drilled a hole and screwed in a sheet metal screw. grabbed the screw head in the bench vise and tapped on the metering block to pull out the plug.

lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Fri May 04, 2018 10:20 am

Got the plug out of there (thanks for thr advise). I cleaned that passage.

While doing that, I realized that the power valve plug was only finger tight (always forget the basics!!). This made me remember that when I cleaned the carb out the first time, there was fuel residue in the power valve well on the main body (should not be aby fuel going there with the plug tight).

Can fuel leaking from that block off plug be causing all my issues?

Waiting to get new metering block passage plugs before I can put the carb back together (seems like nobody has some in stock)

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Re: Carburetor Issues NEED HELP!!!!

Post by jmarkaudio » Sat May 05, 2018 9:24 am

Put some vasoline or similar grease on the new PV gasket, it will allow you to snug them up tighter and slow shrinkage that will have them loosen up later. BLP has the plugs, 1/4" cup plugs.
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