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  #1  
Old 05-31-2007, 06:43 AM
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Scatman 340 Scatman 340 is offline
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Default Undercarbureted 360

Ultimately, I`m going to top off the 360 with a 750 Eddy. Currently, I`m running a wimpish 600 and it is running quite well. Can I expect any improvement with the 750? Mind that I really haven`t had it in the upper RPM range, but I`m really surprised at how well and responsive it is with this small carb in the range that I have been driving it (around town and brief highway). Am I missing something? You probably know the details of my build, but here is a refresher.

360 +.030

KB 107 flat tops (actually they are .018 in the hole using my trusty depth mic.)

Mopar 484/484-284/284 cam

Hughes 3000-3500 converter

Eddy Heads (no port work)

Hooker Super Comps

Eddy dual plane Performer (7176)

No fancy ignition

Thanks,
Rock
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  #2  
Old 05-31-2007, 09:46 AM
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dwc43 dwc43 is offline
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Biggrin

Youre way undercarbed for sure. Once you swap you will notice it quite a bit. Diff between night and day.
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  #3  
Old 05-31-2007, 12:18 PM
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Jim13 Jim13 is offline
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You have really good timing. I have ran a 750 Eddie, a Holly 600 Dp and a reman Thermoquad on the same build over the last 3 Wednesday nights in a quest to pick the best carb for my build.

75 Dart Swinger. 3480Lbs with me in it.

360 .030 over
Weiand x-cellerator intake
cam is sum 20-232-4 .480/.480 lift 280/280
9 1/2" X 26" MT's
Mp performance convertor 2400-2600 stall
8 1/4 suregrip with 4.10's
cheetah manual valve body
904 tranny
ss springs
3 way adjustable shocks
MP distributor with msd2 coil
Iron "J" heads with stock valves and mild port
Dynomax headers with X pipe, 2 1/2" exhaust
Magnaflow "wideopen" mufflers

And the best times are:

Last night I ran the Thermoquad.
60' 1.86
1/4 13.36 @101.69

Last Wednesday, the 600 Holly DP
60' 1.83
1/4 12.95@103.69

The Wed before, the 750 Eddelbrock
60' 1.84
1/4 12.98@103.54


The TQ pulled hard to 6,300 and I shifted. It likes the top end.
The Holly was better on bottem but stopped pulling about 5,800.
The Eddie was in better on bottem than the TQ but not as good as the Holly, It would also only pull to about 5,800.

The Eddie idles better and starts better than the other two so I am picking that one to use permanently on this car. To me the drivability is worth 3 hundreths and 0.15 MPH.



Keep in mind if I sent any of these carbs "off" to be tweaked (ie Demonsizzler etc) they would do even better. I have jetted the holly, I did not touch the Eddie, and I adjusted the air door on the TQ. They were initially ran with the same timing but I did play with it to get the best possible run with that particular carb.

Hope this helps.
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  #4  
Old 05-31-2007, 12:26 PM
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dust dust is offline
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Great info Jim13, thanks for posting.
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  #5  
Old 05-31-2007, 12:38 PM
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Scatman 340 Scatman 340 is offline
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Biggrin

Quote:
Originally Posted by dust View Post
Great info Jim13, thanks for posting.
Ditto! Thanks Jim
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  #6  
Old 05-31-2007, 04:49 PM
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Jim13 Jim13 is offline
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Your welcome.

You hear so many opinions about this sort of thing and it is hard to sort out what the best solution is, then you have to figure out the best solution on YOUR car. It might not be the same.

To bypass all of this I decided to just do my own test. I could probably spend some money on one of them and get them to work better than the others. But if I spend the same money on the others it would probably even out again.

So its the 750 for the 75 Dart
The holly 600 can sit on the shelf till I get My 71 (340) ready to race.
The TQ will go to Demonsizzler to get "Fixed" for daily driving/track duty for the Duster.
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  #7  
Old 06-01-2007, 09:51 AM
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rumblefish360 rumblefish360 is offline
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You'll see a diff. in the top end with the 750. The midrange should be better, but the actualll feel might not be noticed. It could be a compromise on the absoulte bottom.

Quote:
Am I missing something?
The reason, is the smaller carb is keeping the velocity up high through the smaller diameter bbl.s. This high velocity keeps fuel moving fast in a more misty for rather than larger droplets. The quick moving fuel speeds it way into the cylinder and remains misty longer and forms very little or few droplets that do not burn as well in the chamber.

That intake is the RPM right? Not the regular Performer.
Try a K&N extreme air filter set up.
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  #8  
Old 06-01-2007, 10:54 AM
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pcrmike pcrmike is offline
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All of you are echoing my thoughts on that. I am running 10:1, and only a .440 lift / 260* cam, with ported 915's, a performer intake, matched to the ports, and a 600 eddy. The mild (in a one ton truck, 4800 lb empty) combo likes a 600 better than the 750 for low end and economy. I don't rev past about 5500, and could do more on the 600 with a bigger intake, but I lose about 3 MPG on my combo when I do. I think your opinion on that is spot on with the eddy heads. They are a bit bigger ported (okay, a LOT) :-) PCRMike
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  #9  
Old 06-01-2007, 11:19 AM
JLM440 JLM440 is offline
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Jim13: looks like you ran the best ET & MPH with the 600, i'll assume all these carbs were factory with no mods, in a nutshell, the 600 holleys the winner IMO
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  #10  
Old 06-01-2007, 11:55 AM
dgc333 dgc333 is offline
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I have 360 with zero deck KB107 pistons for 10.6:1 compression using 64cc magnum heads. The cam is a Comp XE268H and I have a Crosswind dual plane and headers.

I have a holley 4160 600cfm vacuum secondary carb, a Road Demon 725 vacuum secondary and a Holley 4160 750cfm vacuum secondary carb. All three of these carbs have been on the car for extended intervals but the only one I have 1/4 mile times on is the 600.

The 600 has given me a best of 13.7@102 with a 60' of 2.2 seconds. My experience with the other two carbs is strickly an assessment by the butt dyno.

The 600 has superb throttle response right off idle and it pulls cleanly all the way up to 6500 rpm.

The 725 Road Demon has more get up and go from 5500 to 6500 but does not feel any stronger below that and the throttle response is no where near as crisp as the 600. I spent several months trying to get the transition from the idle to main circuit to work cleanly but could never get the car to run well below 2000 rpm.

The 750 Holley feels the same as the Road Demon on top but it has an initial bog off idle that I was unable to tune out but it's quite happy running below 2000 rpm and once past the initial bog the throttle response is close to the 600.

The other notable difference is I can get over 15 mpg with the 600 where as the other two carbs return about 14 mpg. Overall the car is much more enjoyable to drive with the 600.

IMHO, if your car is primarily a street car go with the smaller carb. For me anyway with three carbs of the same basic layout it takes about two minutes to swap them over so keep the bigger carb for the times you go to the track.
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  #11  
Old 06-01-2007, 03:47 PM
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LA360Dart LA360Dart is offline
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Default Vacuum gauge will tell all

Hi All;

Place a vacuum gauge manifold side under carb, when at full throttle
if vacumm shown is less than 1" leave it alone might go a little quicker
but driveability would suffer. My 365 runs high 12's low13's at 3645lbs with 650 speed demon double pumper close to your combo magnum heads

Denny
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  #12  
Old 06-01-2007, 04:28 PM
cudabob496 cudabob496 is offline
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I had a 750 eddy on my 440 cuda, with a similar setup as you, and when I put a 750 Holly dual feed double pumper with mechanical secondaries, I feel like I gained 25 hp on the top end, and a lot more responsive midrange. It really livened things up. You may also benefit/like a single plain manifold, unless you are more of a daily driver.
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  #13  
Old 06-03-2007, 02:03 PM
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Scatman 340 Scatman 340 is offline
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Biggrin

Thanks For the inputs. Good to know that others experience the same phenomena. I may stick with the 600 for a while. The car really drives well and has a nasty lumpy idle that gets attention. This is a driver and I don`t plan on hitting the high RPMs` that often. This car is a blast to drive as it is now. The build turned out to be exactly what I was after. However I think the noise police will get me soon as I`m running the exhaust with an H-Pipe and tiny little cherry bomb mufflers. The presentation when I`m cruisin` is almost indescribalble. I could go on but I better go take a cold shower.

Rock`
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