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weak throttle response - will a carb spacer help?
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af2
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Sat May 23, 2015 1:50 am    Post subject: Reply with quote

You need more primary jet. a 6.5 PV is not going to fix the problem....only confuse you more.. The secondary jetting needs to be addressed also.
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af2
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1933 Willys Coupe

PostPosted: Sat May 23, 2015 1:53 am    Post subject: Reply with quote

I have always been the one to jet it till it stutters then back off. It takes time but works every time.
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clay
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1972 Chevrolet Nova

PostPosted: Sat May 23, 2015 10:47 pm    Post subject: Reply with quote

I agree with af2. Power valve opening should be instantaneous when you go w.o.t. and I would try going up on jet size and see what happens. If it gets worse go down in jet but if you're at stock sizes now I wouldn't think you would have to do that. It's just a matter of finding out what your engine wants / needs. Clay
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Sun May 24, 2015 12:04 am    Post subject: Reply with quote

youre at the point i was when i gave up and went to a double pumper. however, these guys here know how to make one of these things work. there was no SMOKEmUP 25 years ago Wink
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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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aharris05
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1968 Chevrolet Camaro

PostPosted: Wed May 27, 2015 10:53 am    Post subject: Reply with quote

on Clay's advice, I decided to try increasing the primary jets. When I got the bowl off, I discovered that one jet had come out of the metering plate, the other was unscrewed halfway! So I changed them up anyway (68's were in it , sort-of, haha, and i had a pair of 77's, so I installed them). And I made sure they were TIGHT this time. Took a quick blast down the street, and WOW - HUGE improvement!!!

it pulls right through to 5k, breaks the tires loose from 1st to 2nd. Being wary of the deer around here at night, I decided that was enough, I will hit it again when there's daylight.

there's a little stumble when I stab it, so next I can work on the squirt nozzles and pump cam.
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aharris05
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1968 Chevrolet Camaro

PostPosted: Wed May 27, 2015 12:37 pm    Post subject: Reply with quote

af2 wrote:
I have always been the one to jet it till it stutters then back off. It takes time but works every time.


The first carb I tried on this motor was a 600 holley, and I had the stutter symptom with it. When I started to build RPMs, it would start to stutter real bad. I had "rebuilt" it before I tested it, but when that happened, I suspected I had goofed something up, so it went on the shelf for awhile. So, maybe I should try smaller primary jets in that one, that may be all that was wrong with it.
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af2
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1933 Willys Coupe

PostPosted: Thu May 28, 2015 1:18 am    Post subject: Reply with quote

aharris05 wrote:
af2 wrote:
I have always been the one to jet it till it stutters then back off. It takes time but works every time.


The first carb I tried on this motor was a 600 holley, and I had the stutter symptom with it. When I started to build RPMs, it would start to stutter real bad. I had "rebuilt" it before I tested it, but when that happened, I suspected I had goofed something up, so it went on the shelf for awhile. So, maybe I should try smaller primary jets in that one, that may be all that was wrong with it.


I would not even consider the 600 any day... You have a better one now just make it work!!!
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aharris05
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1968 Chevrolet Camaro

PostPosted: Sun May 31, 2015 9:10 pm    Post subject: Reply with quote

I have a 283 and a 327 that I may use the 600 carb on, so maybe what you are teaching me here will help me figure that one out in the future.
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aharris05
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1968 Chevrolet Camaro

PostPosted: Sat Jun 06, 2015 8:00 pm    Post subject: Reply with quote

I got out to T&T last night, and ran consistent 12.7 @ 107 mph. We pulled a plug, and it looked a bit lean. Since the secondary side isn't adjustable on this carb, how can I richen it up? Will bigger primary jets help at all?
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clay
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1972 Chevrolet Nova

PostPosted: Sat Jun 06, 2015 9:30 pm    Post subject: Reply with quote

On a 4160 there are a few methods you can choose. This is the route I took - http://m.ebay.com/itm/231202271663?nav=SEARCH. Downside is depending on how your fuel supply is setup you might also have to buy another fuel line since the carburetor is longer by the thickness of the metering block. Now everything is the same as a 4150 (double pumper). There is another method that is a metering plate that accepts Holley jets instead of a drilled orfice. You could simply drill your metering plate holes larger but downside is of course you can't back up. You should also be able to plug the bottom holes on your existing metering plate then drill and tap the face of it for Holley main jets (1/4 - 32). I wouldn't keep going up on the primaries alone. I try to maintain the original factory jet stagger if possible. I definately agree with looking at plugs but I'm betting like me you aren't a guru at it. If you're at the track jet it and set timing by mph and you won't go wrong. You made some excellent progress so far though! Clay
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Big Dave
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PostPosted: Thu Jun 11, 2015 8:57 am    Post subject: Reply with quote

If you are running lean then larger primaries will richen the mix at WOT. Going to a larger jet has two down sides which is you will go slower as you make the most power at 15.0:1, but you are also risking detonation. The second problem is it affects the carb's performance at partial throttle unless this car is a trailer queen.

In my opinion Holley carbs for sale used are too cheap to put money into converting a 4160 into a 4150 series. I would buy a second slightly larger carb (going from a 650cfm to a 750cfm) and tune that carb for race only; then swap the carb between the race track and the drive home if it is a street driven car. I usually drag home a Holley or two that I pick up for $25 for a 600 or 650 cfm 4160 to $100 for an 850 cfm 4150 DP at every major meet that has a car corral selling parts (it pays to buy a sellers permit, or help a friend selling a used car so you can cruise the tables before the doors open to the general public).

Big Dave
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af2
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1933 Willys Coupe

PostPosted: Mon Jun 15, 2015 7:07 pm    Post subject: Reply with quote

Hmmm Trailer Queen?

Dave, I hate to say BUT 15:1 is not making power. AROUND 12:1 will.
The guy is on the right track and 3310 will work. I have had my hands on a few. Like anything he needs to learn them, there are many books and people like me that read and made them work.

Heck I have made the few QuadraJets work with low pressure and high flow pumps to make up the small bowl.
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altered
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PostPosted: Wed Aug 05, 2015 9:11 am    Post subject: Reply with quote

definitely fatten it up we never run our gas motors leaner than 12:1 they make big power and keep the egt down.
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