Carb Problems?

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Can't seem to get it to idle consistently. 850 Holley DP, 396, runs great off idle to full open, but can't get it to idle consistently. No vacuum leaks,
fresh carb rebuild. Was a marine carb. Rejetted and replaced pump cams with more friendly ones. Timing 8BTDC. Mixture screws out about 2.5 turns. Any ideas? Will idle sometimes, sometimes high and/or not at all.
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with the car running turn in the mixture screws until you hear it run worse then back each one out a quarter turn.
you'll have to play with both of them a couple times to get it right.
have you added a larger cam to the engine?
-- http://crazyedmonton.no-ip.com
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I am the darkest creation of god



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Were the power valves blocked?
If so get back to me and I'll tell you how to cure the problem of the erratic idle.
If the power valves were in fact blocked off and the car idles at all, without the fix for it, it;s a damn miracle!
Refinish King

worse
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Changing the settings on the screws makes no difference in idle. From all the way in to 3 turns out, no change. I was thinking wrong gaskets pluggin the ports, but dunno, just installed the same that were in there. It's got the 4 corner idle and yeah, all day, still no go. Took off carb, adjusted secondaries to spec and all. The engine ran before with a tunnel-ram & dual 550's, but I changed it to an air-gap and single 850. Same cam as before.

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A marine carburetor is a bit different than a OEM automotive carburetor, so some "tinkering" of the settings is going to be needed.
Assuming this is a GM application, a Quadrajet will out perform, out idle, pass the gas pump more, and overall make the vehicle run better than any aftermarket Holley unit you stick on there.
Keep your GM car all original--there's a reason why Rochester sold 5 million Q-jets a year in the heyday of carburetion :). Joe--ASE Certified Parts Specialist & 10th Ann.Club Tech Director '80 Carousel Red Turbo T/A, 26k orig. '79 "Y89" 400/4 speed 10th Ann. T/A, 57k orig '84 Olds 88 Royale Bgm 2 dr, 307 "Rocket" (lol), 141k and still going.... '80 T/A project car...
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so
pass
aftermarket
Yeah I know, on my others there is a q-jet, but this one had the square flange on the intake and i got a good deal on it. It's on my 69 Camaro with a 396. Had the tunnelram and 2 550's but wanted to fit it under a cowl hood. It's my toy and I'm not really too concerned about gas mileage, just performance for now. Thanks for the thought tho. Maybe I'll pull the intake off my 454 and install it on the 396 someday. Also just took off carb and checked power valves. They are ok and the anti blowout check balls are there. I took them out to see if it would make a difference, no go, still the same. Friggin doesn't want to idle. Seems like it's starving. Fuel pressure is 7psi. Was gonna just buy an Edelbrock/Carter to throw on there just to see if it'll run, but I'd rather get this one working if possible. All the settings seem to be on spec. What good is my ASE Master Auto Tech Cert if I can't get this thing going? lol

million
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Carburetion is a dinosaur in ASE's eyes!
LOFL
Refinish King

idle,
Had
like
Master
going....
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LOL Sad but true! Altho I've been in the automotive field 20+ years, just did the ASE tests a few years ago.
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There's an article in this month's Underhood Magazine (Babcox puts this out) about shops specializing in old iron and muscle cars.
They did a nice write-up about it. They jab about, "And you get to use all that obsolete equipment you have that was good for these old things---if you haven't traded it or sold it yet". LOL.
The article ends with, "Nothing like hearing a piece of American iron roar to life".
How true it is.... :)
Joe--ASE Certified Parts Specialist & 10th Ann.Club Tech Director '80 Carousel Red Turbo T/A, 26k orig. '79 "Y89" 400/4 speed 10th Ann. T/A, 57k orig '84 Olds 88 Royale Bgm 2 dr, 307 "Rocket" (lol), 141k and still going.... '80 T/A project car...
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Thanks for that Joe!
I just moved this message to my folder for important things, I'm going to subscribe and try to get a reprint!
My obsolete equipment is right where it belongs, with a guy who does work and restorations on old AMERICAN iron. Whether it roars or not, I love to be an American and work on what was a part of my heritage!
Now, to stop Hollywood from wrecking our heritage, and boycott Farmer's Insurance for what they did to that 68 Camaro Ragtop!
Refinish King

out)
that
haven't
to
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all
roar
going....
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That's the article I believe... Joe--ASE Certified Parts Specialist & 10th Ann.Club Tech Director '80 Carousel Red Turbo T/A, 26k orig. '79 "Y89" 400/4 speed 10th Ann. T/A, 57k orig '84 Olds 88 Royale Bgm 2 dr, 307 "Rocket" (lol), 141k and still going.... '80 T/A project car...
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Agreed and 100% unarguable!
but in the mean time to get the Holley to idle!
Refinish King

so
pass
aftermarket
million
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Ditto!
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Firstly and most importantly:
Being that you have a primary metering block in both the primary and secondary positions, it will be a bit difficult. Because it is in fact a marine application carb.
First, remove the primary metering block, all the jetting to auto specs will not work, marine carbs are metered internally to make the motor run fatter.
Directly on the left and right sides of the nut of the power valve, you will see a V shaped indent with two orofices, the inners are the mid range and the outters are the idle circuit metering circuits. Get two pieces of .015 wire, about 5/8" long, and stick them into the mid range ports in the v grooved indent, then bend then. Reapply the gasket and reinstall the metering block.
Repeat for the back and use .020 or .025 wire, and you will see a difference. If the power valves are rubber valves, there is a possibility that one or both are fissured or dry rotted, allowing gasoline to go through. Look carefully to see if the side with the nut is wet, if it is, start with replacing the power valves.
Start with a low number, like 65.
I hope this helps somewhat?
Carburetors take a lifetime of experimentation to learn to tune, especially when you start playing with metering block passages.
Good luck,
Refinish King

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will
fatter.
will
especially
Thanks very much. Will try the aforementioned in the morn. I noticed the power valves had a 2 on them. I've read that that is the vac when they open. Seems quite low to me. Altho they hold vacuum, I'll get a couple of 65s to make sure. Thanks again and will let ya know the results. Ron
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My pleasure!
Refinish King

and
.015
possibility
is,
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Update and Success! Did the items you mentioned, still didn't want to idle, but by closing the choke down a tad it works for now. It's spring loaded so when I step on it, it opens up. Seems to work for now. Thanks very much for the help and insight into the wonderful world of holley carburation lol. Ron
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What I gave you was to lean out:
The midrange rich condition caused by blocking off the power valves. Now we're moving in the right direction.
I can help you a bit better from here, first get rid of the wire, LOL!
Now, look down the air horn for the primary barrels, there should be three little holes, from outside to center of carburetor in this order: Idle/low speed, Midrange, High Speed air bleeds. Check to see if any are restricted?
If not, that is a good thing, because air going past them goes into the venturi and pulls fuel for richening of that particular range, to let you jet the carb a bit leaner and avoid stumble on acceleration.
If it did idle with the choke blade closed somewhat, you richened the idle circuits, have you noticed if the carb has inverted idle mixture screws, where screwing them out actually is leaning them? Holley went to this in the mid to late 70's. That's when they improved the metering blocks so people could make their own secret sized metering block passages.
Try turning the screws all the way in, and also, look at the back throttle blade, it should be open about 1/30 of an inch at idle also. If not, the idle circuit will not pull enough vacum through the baseplate. there is a stop screw in the base plate to adjust that, and I am not exactly if 1/32" is the exact spec. I think this carb needs a good rebuild after soaking in a carb tank and it will work like new.
I hope this helps?
Refinish King

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LOL ok

restricted?
Will do, but i think they are all ok.

the
It doesn't really change from all the way in to 3 full turns out, but I'll retry.

a
Yes, opened the secondaries to uncover the idle slot about .020. I tried adjusting it with it closed and opened more, but finally just got it to idle somewhat about 1200rpm with the choke somewhat closed. Will fiddle with it some more as time permits, but was happy to get it to keep from stallin. I know it's not adjusted right, but at least it idles to make other adjustments. The carb is quite clean and was rebuilt just to make sure of all the innerds. I think i rejetted it to smaller ones since they were to largefor the 396 and I adjusted the pump cams to come on off idle. It sat for a couple of months afterwards while the engine was gone thru and installed. Will let ya know how it turns out and can go from there. Thanks again! Ron
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