Carburetor Issues NEED HELP!!!!

General engine tech -- Drag Racing to Circle Track

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lekid
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Sat May 05, 2018 4:24 pm

jmarkaudio wrote:
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.
Thanks Mark! Will do!!

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Re: Carburetor Issues NEED HELP!!!!

Post by MadBill » Sun May 06, 2018 2:27 pm

lekid wrote:
Thu May 03, 2018 1:55 pm
Forgot to say: no power valve in the carb, jets are 93fr/94rr, it has annular boosters.
Not related to your issue, but there's rarely a good case to be made for not running at least a primary PV. At the very least the engine will load up less on the return road or during any other part throttle operation. Just saying...
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Re: Carburetor Issues NEED HELP!!!!

Post by jmarkaudio » Sun May 06, 2018 8:41 pm

Depends on the RPM and how it's used, a lot of times it's on transition metering. Get that right and no plug loading issue.
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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Tue May 08, 2018 1:36 pm

Got the carb all back together and re-installes it and it does the exact same thing. Can't get it to idle any less than 1300rpm with mixture screws out 2-1/2 turns and does seem rich and when put in gear, stalls if I font keep playing with the throttle. I cannot even get on the brake (stumbles at 1400-1450rpm and wont be over 3200rpm).

Got upset and installed my buddies generic Holley 1000cfm car and it runs perfect!!! Idles at 1050rpm amd goes down to 950-1000cfm in gear! Gets on the brake clean!!

Issue is obviously in the carburetor. Feels like there is a vacuum leak somewhere. Where can it be? Baseplate issue maybe? Not sure where else it can have a vacuum leak from.

Any ideas??? I am at a lost!!!

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Re: Carburetor Issues NEED HELP!!!!

Post by FC-Pilot » Tue May 08, 2018 3:22 pm

This may sound stupid but I will share it anyway. A friend had an old 850 on an engine we dyno'ed for him. Like you it did not idle well and we ended up almost plugging the IAB to get it to idle. After hurting the motor he brought it back to be dyno'ed again. Well it was not till after he changed carbs that I found what was happening. The 50cc accelerator pump was hitting part of the carb flange on the intake and with his throttle linkage ( that bolted between the carb and intake) I was not able to notice it, but it was just enough to be a little bit of a leak.

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Re: Carburetor Issues NEED HELP!!!!

Post by ozyfordman » Tue May 08, 2018 11:11 pm

Wrong gasket between carb body and base plate will do that. You have to be careful when using a generic overhaul gasket kit. Do you still have the old gasket? Might be worth checking the new one against the old one. This happened to me a few few months back with a 3310.I was using up old left over gaskets from broken up kits. Took me a while to find it and I felt like a proper dill when I found the problem. Hope this helps.
Evan

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Re: Carburetor Issues NEED HELP!!!!

Post by steve cowan » Wed May 09, 2018 2:37 am

ozyfordman wrote:
Tue May 08, 2018 11:11 pm
Wrong gasket between carb body and base plate will do that. You have to be careful when using a generic overhaul gasket kit. Do you still have the old gasket? Might be worth checking the new one against the old one. This happened to me a few few months back with a 3310.I was using up old left over gaskets from broken up kits. Took me a while to find it and I felt like a proper dill when I found the problem. Hope this helps.
Evan
evan,
tuner mentioned the same thing early in the tread,
not having a pop at you mate just friendly reminder :D
steve c

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Re: Carburetor Issues NEED HELP!!!!

Post by ozyfordman » Wed May 09, 2018 4:31 am

Steve,
No offence taken. I lost count of the number of times that carb was on and off the engine looking for the fault. If the OP has checked this out already. I am at a loss. When I put mine together I just picked a base gasket that fit the throttle bores. It looked ok but I didn't,t ensure all the passages lined up. Rooky mistake but easily done. I'll watch this thread for the fix.
Evan

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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Wed May 09, 2018 5:58 am

I did not switch the main body gasket and I did confirm the gasket is proper.

Anything in the main body itself can cause this?

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Re: Carburetor Issues NEED HELP!!!!

Post by cjperformance » Wed May 09, 2018 6:16 am

Are your idle mix screws responsive? In your 1st post you say 2 1/2 turns out, , if you turn them out more can you get it over rich?
Are you still at minimum T slot exposure?
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Re: Carburetor Issues NEED HELP!!!!

Post by barnym17 » Wed May 09, 2018 6:24 am

I had an issue with a generic gasket the hole for the idle feed on the block was slightly to large or off just a little.Fuel from the idle feed went directly into the ported vacuum cavity of the metering block, down into the intake and was rich as crap. It behaved with the symptoms you are describing and was a bear to find.

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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Wed May 09, 2018 6:50 am

cjperformance wrote:
Wed May 09, 2018 6:16 am
Are your idle mix screws responsive? In your 1st post you say 2 1/2 turns out, , if you turn them out more can you get it over rich?
Are you still at minimum T slot exposure?
T-slot exposure seems appropriate. If I bring the mixture screws in at all, the engine wont even idle in Park. It appears that I cannot turn the screws out enough to get it rich enough or over rich. Even going 10 size smaller on IAB seems to not have done anything to make the idle richer. That is why I believe (and might be wrong), that there must be a vacuum leak in the carb somewhere. When I bolt my buddy Holley 1000cfm out-of-the-box carb, the car runs flawlesly.

I am thinking of putting my metering blocks on my buddy main body to see id the problem is still there (to try and isolate the problem either in the blocks or the main body). Does that make sense?

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Re: Carburetor Issues NEED HELP!!!!

Post by cjperformance » Wed May 09, 2018 6:58 am

lekid wrote:
Wed May 09, 2018 6:50 am
cjperformance wrote:
Wed May 09, 2018 6:16 am
Are your idle mix screws responsive? In your 1st post you say 2 1/2 turns out, , if you turn them out more can you get it over rich?
Are you still at minimum T slot exposure?
T-slot exposure seems appropriate. If I bring the mixture screws in at all, the engine wont even idle in Park. It appears that I cannot turn the screws out enough to get it rich enough or over rich. Even going 10 size smaller on IAB seems to not have done anything to make the idle richer. That is why I believe (and might be wrong), that there must be a vacuum leak in the carb somewhere. When I bolt my buddy Holley 1000cfm out-of-the-box carb, the car runs flawlesly.

I am thinking of putting my metering blocks on my buddy main body to see id the problem is still there (to try and isolate the problem either in the blocks or the main body). Does that make sense?
Yes if you have compatable metering blocks that will help rule things out. Is your buddies carb the same as yours? Can you compare IAB and IFR sizes?
All else being correct , having the mixture screws out 2.5 turns and being too lean to idle in gear tells me you need larger IFR's.
Craig.

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Re: Carburetor Issues NEED HELP!!!!

Post by lekid » Wed May 09, 2018 7:06 am

cjperformance wrote:
Wed May 09, 2018 6:58 am
lekid wrote:
Wed May 09, 2018 6:50 am
cjperformance wrote:
Wed May 09, 2018 6:16 am
Are your idle mix screws responsive? In your 1st post you say 2 1/2 turns out, , if you turn them out more can you get it over rich?
Are you still at minimum T slot exposure?
T-slot exposure seems appropriate. If I bring the mixture screws in at all, the engine wont even idle in Park. It appears that I cannot turn the screws out enough to get it rich enough or over rich. Even going 10 size smaller on IAB seems to not have done anything to make the idle richer. That is why I believe (and might be wrong), that there must be a vacuum leak in the carb somewhere. When I bolt my buddy Holley 1000cfm out-of-the-box carb, the car runs flawlesly.

I am thinking of putting my metering blocks on my buddy main body to see id the problem is still there (to try and isolate the problem either in the blocks or the main body). Does that make sense?
Yes if you have compatable metering blocks that will help rule things out. Is your buddies carb the same as yours? Can you compare IAB and IFR sizes?
All else being correct , having the mixture screws out 2.5 turns and being too lean to idle in gear tells me you need larger IFR's.
Our carbs are not identical but I think they are close enough to switch stuff around and see if it idles better and not die when going in gear. He has a Holley 1000cfm with downleg boosters, mine is a Proform 1050 Main body with Annular boosters and Proform metering blocks. IAB and IFR are a little differently but I am guessing the Annular boosters would have to do with that. Mine is 70/73 IAB and his is 75 and IFR is stock on his (not sure what that is), mine is 0.035".

What I don't get, is beside a small stumble around 1400-1500 when getting on the brake, the carb ran great last year (no stumble with my buddy carb either).

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Re: Carburetor Issues NEED HELP!!!!

Post by barnym17 » Wed May 09, 2018 7:43 am

Is the carb to metering block face flat? maybe block warped?

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