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Chuff! Fluffing on takeoff.

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DaemonForce View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2017 at 9:13am
It's always a good idea to check your jet size, alignment and run of metering before during and after an overhaul. The issue with these carbureters as core rebuilds is their specific assignment to an engine that may not be an exact fit in another. My grandfather was all about the Motorcraft 2100 and I prefer the Holley Demon and Rochester Quadrajet series as they offer easier tuning despite more complicated building and more things to check. When you have choices on a rebuild, it makes sense to compare venturi sizes and jetting. When the jetting is too big, the engine is in a forced state of rich burn, prone to flooding and hesitation among other oddities. The chuff you had before with the bigger jets was most likely a liquid fuel dump combined with low air volume. Did you have low vacuum before the changeout? Do you still have low vacuum?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 990V8 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2017 at 9:44am
The carb I bought was supposed to have been rebuilt for this engine. I sent him the spec from the TSM. Guess he thought it would be near enough. So either I go through it and then buy any parts that are wrong, or just go on with it as is. Perhaps a session on a rolling road so the mixture can be checked - there is one 20 miles away where they claim to have Holley expertise.

The only time I looked at vacuum was when I was fixing the wiper motor and vacuum pump. Idle vacuum iirc was around 16in Hg measured on the manifold, at the vac pump takeoff.

Ivor
63 Canadian Ambo 990 V8 327
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2017 at 10:45am
Setting idle mixture with a vacuum gauge is good.
Setting timing by ear or with a vacuum gauge is begging for disastrous detonation.
Gremlin Dreams
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 990V8 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/06/2020 at 12:07pm
Revisiting this thread after a while, I just rebuilt the supposedly rebuilt carb.
 
Not only did it have an old and leaking fuel needle and seat, and toasted gaskets, but the wrong power valve. Should have an 8.5", it had a 6.5".
 
Rebuilt? Don't think so.
 
And it still had the wrong accelerator jet. That was my fault; I put a 21 in there, but rereading the tsm, I see I confused it with the 10 series, it should have a 28 so that's what I put in now.
 
I torqued all the hold-down nuts with a slim extension and a crow's foot.
 
Idle vac now is 18in, which I see is better than I had three years ago.
 
Haven't taken the car out on the road yet, it's raining. Perhaps next week.
 
Ivor
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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/09/2020 at 5:59am
Well, it should certainly run much better now, and probably not use as much petrol (as you say over there...)!!!
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 990V8 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/27/2020 at 11:40am
Did 300 miles over the holiday.
No fluffing at all. It just takes off without hesitation. Very pleased.
 
And still doing around 19mpg imperial.
 
Now, on to the next job.
 
Ivor
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rockAMX Quote  Post ReplyReply Direct Link To This Post Posted: Dec/29/2020 at 4:29pm
Was it rebuilt by a guy in a shed? Now you know how to rebuild your carb, forget the guy in the shed.
DWR
1968 AMX

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