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'59-'61 in line dual quad peeps-
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chefothefuture
Posted 2019-05-12 12:26 AM (#582045)
Subject: '59-'61 in line dual quad peeps-


Member

Posts: 31
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Hi all-
Running dual quads (2652 and 2653) on my '61 361 (over bored to 383) and am wondering what vacuum should it be pulling.
Currently at idle (@650RPM warm) it's at 16"hg. The engine hesitates at breakaway and speeds up to 15mph. I took my readings from the
accessory port on the back of the intake with no accessories connected(don't have power brakes so it's only the heater switch which is faulty).

Given the horrid "rebuild" that was inflicted on this engine before I got the car, I shudder to think if something is awry in the bottom end.
Found this out when having the heads redone...

Cheers :-)
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58coupe
Posted 2019-05-12 11:14 AM (#582058 - in reply to #582045)
Subject: Re: '59-'61 in line dual quad peeps-



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Location: Alaska
Vacuum at idle is very dependent on what cam is in the engine. First of all, I am amazed your engine was bored from 361 to 383. That is a full 1/8" over making the block very thin. What manifold are you running? A stock engine in good condition with no vacuum leaks should be about 16" to 20". My 383 with a long ram would read as much as 24" at idle. As you can see, there are many variables.
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1958300
Posted 2019-05-12 2:24 PM (#582063 - in reply to #582045)
Subject: RE: '59-'61 in line dual quad peeps-



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Location: Chattanooga
Just out of curiosity, what car is the engine powering?
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chefothefuture
Posted 2019-05-12 3:33 PM (#582070 - in reply to #582058)
Subject: Re: '59-'61 in line dual quad peeps-


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Posts: 31
25
58coupe - 2019-05-12 11:14 AM

Vacuum at idle is very dependent on what cam is in the engine. First of all, I am amazed your engine was bored from 361 to 383. That is a full 1/8" over making the block very thin. What manifold are you running? A stock engine in good condition with no vacuum leaks should be about 16" to 20". My 383 with a long ram would read as much as 24" at idle. As you can see, there are many variables.


This poor engine went through what I must say was a pretty hackneyed "re-build" before I got it. So the variables are sky high here. Cylinder decks that looked like they were done with a concrete saw, distributor gear off by several teeth, BBD carb missing internal parts, etc... I might pull the timing cover as I wonder about the gears being off... The intake I'm running is an early dual quad (I don't recall the casting #) for B blocks. I'm not sure of the cam, but I assume it is fairly flat given that the intake was 2 barrel.
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chefothefuture
Posted 2019-05-12 3:34 PM (#582071 - in reply to #582063)
Subject: RE: '59-'61 in line dual quad peeps-


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Posts: 31
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1958300 - 2019-05-12 2:24 PM

Just out of curiosity, what car is the engine powering?


1961 Newport convertible.
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Viper Guy
Posted 2019-05-12 8:55 PM (#582080 - in reply to #582045)
Subject: Re: '59-'61 in line dual quad peeps-



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Location: Branson, MO
If you have a stock 2 bbl cam in the car, that can explain much of your "bog" at low rpm from stand still. Air/fuel ratio is probably too rich (too much carb and not enough cam). You will undoubtedly have to change your cam sooner or later or go back to the 2 bbl.
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57chizler
Posted 2019-05-13 12:40 PM (#582108 - in reply to #582080)
Subject: Re: '59-'61 in line dual quad peeps-



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Location: NorCal
I've always attributed off-idle hesitation to too much air, not too much fuel i.e. dual quads or larger 4-barrels on small engines.
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chefothefuture
Posted 2019-05-14 11:07 PM (#582158 - in reply to #582045)
Subject: Re: '59-'61 in line dual quad peeps-


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Posts: 31
25
Thanks all for your suggestions. So far, before going deep, I pulled the primary (rear) carb and took it fully apart and something silly but overlooked is certainly going to make trouble: A broken idle mixture screw. Plus the Venturi feed and breather tubes were
pretty plugged. This carb was problematic but I was fussing more with the inlets and floats. The rest looked like it had been well cleaned and rebuilt but apparently not. Been too busy to put it back together and see how it performs with new "guts". But I do feel fairly silly to have neglected to really give the thing a good going over.
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