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Discussion Starter · #1 ·
My 62 galaxie xl390 which was completly rebuilt in 07 has recently started backfiring thru the carb when i go from park to drive then it stalls.Ive got a pertronix ignrebuilt holley 1850 600 cfm carb and i only use 93 octane fuel.I set the timing to 12 btdc and it will idle all day in pasrk ,but put it in gear and it bfs and stalls.Any ideas???Thanks
 

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X2. also try disconnecting the vacuum from the distributor cannister.
 

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Discussion Starter · #4 ·
there is not supposed to be vacuum at the dist vac advance at idle on a holly thats portyed vacuum
 

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Discussion Starter · #6 ·
didnt regster on my vacuum gauge.I wonder if i blew a power valve this holly 1850 is an older one maybe it doesnt have the power valve protection they talk about.What is it anyway?
 

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Discussion Starter · #9 ·
car idles great in park.Steady 20"hg on vacuum gauge.at thistime i checked timing w/timing lite.it was at the 9oclock positionand pointer is at 11 oclock on the timing chain cover. the vac advance is pointing frontward toward the radiator as soon as i put it in drive it stallsand i see fuel not much but some spurting out the airhorn!im wondering if i blew the power valve from all the backfiring.i havent been able to get this on the road due to the stalling in drive.i will spray gumout all around looking for vac leaks.before this started happening i took it on the road it was fine for the first 3or 4 miles than cruising at 45 mph she died i pulled over and i couldnt restart it.i would crank but not fire.i towed it home next day she idled in park fine but put it in drive it would bf and stall .im confused about the fuel spurting out the airhorn when it backfires! maybe time for an edelbrock 1406 after i figure out whats causing the backfiring.Thanks for the help guys.it has pertronix ignition btw
 

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there is not supposed to be vacuum at the dist vac advance at idle on a holly thats portyed vacuum
Let me ask this...

If no vacuum @ idle, why is it you have to remove the vacuum signal from the vacuum advance when setting basic timing?

When you put it into range, the manifold vacuum changes (and in return changes ported vacuum signal). If the dist does not see this change (signal) the engine goes lean.

Do you have a dash-pot?
 

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Discussion Starter · #12 ·
thanks fe and all the other guys.I was taught to adjust timing in drive at 500-600 rpm with vac advance disconnected.im gonna get the edelbrock and get back on this when the weather warms up above 9* degrees.I work outside my gals in the driveway.
 

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Sounds more like jumped time by 1 tooth to me... Starting with no being timed correctly to begin with. M2C.....




MRO.....
 

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Of ALL of the "timing jumped" scenarios that have come under my scrutiny over the last 12 years only ONE had actually jumped time, and that was an FE with all the nylon teeth long busted off, it never jumped until one morning when the guy started it.
Well I havent ever had one do that in the manner he spoke of, but..... Not to muddy the waters but just an interjection of a thought was all. Easy enough to check for also. Just M2C was all...
I think a verification of the base(static) timing would be a good place to start, as the symptoms really sounds like a timing issue to me, BUT i HAVE been WRONG too. :) ;)
 

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Originally Posted by FEandGoingBroke

Of ALL of the "timing jumped" scenarios that have come under my scrutiny over the last 12 years only ONE had actually jumped time, and that was an FE with all the nylon teeth long busted off, it never jumped until one morning when the guy started it.


But it DID jump?



Well I havent ever had one do that in the manner he spoke of, but..... Not to muddy the waters but just an interjection of a thought was all.

Easy enough to check for also. Just M2C was all...

I think a verification of the base(static) timing would be a good place to start, as the symptoms really sounds like a timing issue to me, BUT i HAVE been WRONG too. :) ;)
Every problem should start by verifying basic timing. A stretched chain will give similar problems.
 

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Vac line good to the tranny if automatic? I think timing as some have mentioned and a vac leak somewhere. Which now probably blown PV also, i despise holley. They make great bookends though.
 

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FEandGoingBroke Said In POST #5 said:
There is NOT supposed to be, but you MIGHT have some... Check closely.
FEandGoingBroke Now Says said:
You should not be experiencing vacuum to your dist at idle. The reason you remove vacuum is in case someone has the carburetor maladjusted. Because NONE of my vehicles sit at idle with vacuum effecting the timing.....


I'm sure there are some distributor systems designed to be ran at idle with vacuum but his should not be one.

After reading his post #9 I to think he's got a blown PV, that would explain why he couldn't get it re-started.

But he's got further problems with fuel spurting out the air horn.

Dropping the holley which is hard for a beginner to tune and going with an edelbrock is a safe route and I like the edelbrock over the holley any day.
F,

There is a ported vacuum signal @ idle. You remove the vacuum signal when verifying basic timing along with establishing proper curb idle to make sure the vacuum/centrifugal advance is not coming in.

The above scenario covers a mis-adjusted carb.

There is nothing wrong with a HOLLEY. One of the most basic designs and easy to tune for any particular application.

If there was a blown PV, it would be loading up @ idle.

When you drop an AT application into range, the torque converter drag slows the engine and basic manifold vacuum drops making an immediate lean condition. The ported vacuum should raise the RPM @ this point to overcome the immediate lean condition.

Throwing another carb ($$$) at it will most likely not solve the problem. The lean backfire is most likely causing fuel to be ejected from the vent.
 

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I wonder if i blew a power valve this holly 1850 is an older one maybe it doesnt have the power valve protection they talk about.What is it anyway?
In 1992, Holley figured out how to fix an age-old power valve design flaw. Since the beginning of the 2300, 4150, 4160, 4165, and 4175 model production, there had been a common problem of blowing the power valves. If your engine backfired through the carburetor, the powerful surge of air through the passages would typically break the power valve diaphragm.

In 1992 Holley figured out a way to keep this from happening by adding a spring-loaded check ball in the power valve passage. All power valve-equipped Holleys produced since 1992 come factory-equipped with this power valve protection.

They also sell retrofit kits (PN:125-500) for about $20 to modify pre-’92 Holley carbs.
Historic Holley Carburetor Milestones | RodAuthority
 

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Vac line good to the tranny if automatic? I think timing as some have mentioned and a vac leak somewhere.
He posted a steady 20in HG @idle.
 
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