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How big is too big?
https://www.slantsix.org/forum/viewtopic.php?t=14347		 Page 1 of 2
Author:  CStryker [ Sun Sep 11, 2005 2:08 pm ]
Post subject:  How big is too big?
Ok, I just got a really good deal on a like new 600 CFM holley 4 barrel with vacuum secondaries (model 1850S, to be exact). I bought it with the intention of turning around and reselling it, but I started wondering. Is there any way that this wouldn't be too much carb for my six? I forsee a cam and some head work in my future, but I'm not sure if I'm gonna take the plunge to oversize valves or not.
Author:  SlantSixDan [ Sun Sep 11, 2005 3:14 pm ]
Post subject:  Re: How big is too big?
Quote:
Ok, I just got a really good deal on a like new 600 CFM holley 4 barrel with vacuum secondaries (model 1850S, to be exact). I bought it with the intention of turning around and reselling it, but I started wondering. Is there any way that this wouldn't be too much carb for my six? I forsee a cam and some head work in my future, but I'm not sure if I'm gonna take the plunge to oversize valves or not.
That is a really, really, really, really big carburetor.

MAYBE if you were building a full-race motor it'd be appropriate. I sure wouldn't want to tune or feed it on the street.
Author:  Dart270 [ Sun Sep 11, 2005 3:21 pm ]
Post subject: 
You can run it, but your time/$$ would be better spent on a smaller carb, espcially for a mild/medium motor. You would be MUCH happier with a 390 4bbl or Edel 500 4bbl or hly 500 2bbl, or...

Lou
Author:  DusterIdiot [ Sun Sep 11, 2005 7:36 pm ]
Post subject:  What build/cam?
That would be kinda ok, if you ran more cam than stock and had your car setup for higher performance. The Hpak Duster is currently running either a 1850 or an 80457 with stock valves, compcam 252, hpak intake...you have to use the black spring for the vacc.secondaries and jet down the primary side a little...all in all the car gets 2-3 mpg more with the 8007 Holley 390 though....


-D.Idiot
Author:  Russell Cable [ Mon Sep 12, 2005 3:21 pm ]
Post subject: 
I am running A 650 CFM. holly
on the street/strip. The gas
mileage is not good, but the power
is! :wink:
Author:  slantzilla [ Mon Sep 12, 2005 8:01 pm ]
Post subject: 
I use a 390 Holley on mine. I am trying a 600 DP shortly, but my car is slightly modified. :shock:
Author:  Doctor Dodge [ Tue Sep 13, 2005 5:31 am ]
Post subject: 
The 600 is too much for a stock SL6 but I have used the Holley 1850 (600 cfm) vacuum secondary carb on a "built-up" Slant with good success.
DD
Author:  argentina-slantsixer [ Tue Sep 13, 2005 10:35 am ]
Post subject: 
Hey DOc, must have been a really build up engine....

I remember reading a guy who used a 750 or 800 cfm on his rustang and got crappy driveability at low RPM, ugly torque and HP readings from the dyno, then and old mechanic told him to trash that big piece of junk (literally) and he installed a 500 cfm 2 barrel. His dyno readings went really up, especially in torque, and the low end was much more strong than before...

I think that most pepped up slants can hardly get any benefit when you pas over 500 cfm. Mine is @ 350 cfm and according to my calculations is already on the big side.
Author:  Russell Cable [ Tue Sep 13, 2005 3:03 pm ]
Post subject: 
Quote:
Hey DOc, must have been a really build up engine....

I remember reading a guy who used a 750 or 800 cfm on his rustang and got crappy driveability at low RPM, ugly torque and HP readings from the dyno, then and old mechanic told him to trash that big piece of junk (literally) and he installed a 500 cfm 2 barrel. His dyno readings went really up, especially in torque, and the low end was much more strong than before...

I think that most pepped up slants can hardly get any benefit when you pas over 500 cfm. Mine is @ 350 cfm and according to my calculations is already on the big side.
argentina-slantsixer I can't get any benefit under 600 CFM's
I got the 650 CFM on the car now and the car runs 14.2 in
the 1/4 , very good street driveable, and on the dyon I got
200 hP with 230 torq so I would say bigger is always better.
Author:  emsvitil [ Tue Sep 13, 2005 3:42 pm ]
Post subject:  Spreadbore???????
Anybody ever try a spreadbore????????

I'd think with the small primaries, the low end & light throttle should still be good, then you have those huge secondaries when you open it up..... :lol:
Author:  6PIN [ Wed Sep 14, 2005 4:59 am ]
Post subject:  Spreadbore carb
I think Frank Raso has been using a Quadrajet. That has very small primaries, translating to good velocity and driveability. The secondaries are huge, and are usually rated at 850cfm :shock:
The Pontiac OHC 6 from '66-'67 had a hipo version that used a Q-jet.
Author:  argentina-slantsixer [ Wed Sep 14, 2005 5:52 am ]
Post subject: 
I don't know.... I feel approaching to bigger performance thru bigger carburetion would be as dumb as getting a bigger gas pedal :lol:

Of course, if everything's accordingly set up, you can go all the CFM you want.

When I say that 600 CFM is overkill for a slant I mean a stocker or mildly pepped mill.

I suppose that rear axle ratio has to do with this since the taller the ratio is, the sooner it revs up, demanding more CFM's... is something like radical advance curves....
Author:  Dennis Weaver [ Wed Sep 14, 2005 7:36 am ]
Post subject: 
Quote:
I don't know.... I feel approaching to bigger performance thru bigger carburetion would be as dumb as getting a bigger gas pedal :lol:
Right as rain. :)

D/W
Author:  slantzilla [ Wed Sep 14, 2005 8:47 pm ]
Post subject: 
If his car actually runs low 14's a 600 probably isn't hurting anything. I tried a 600 on mine when it was running 14:20's. It was not quite as fast as with a 390, but it was tons more consistent. :shock:
Author:  Dennis Weaver [ Wed Sep 14, 2005 10:13 pm ]
Post subject: 
...you'd probably all have run better if you had tossed that holley trash and run an AFB! :roll: :twisted: :lol:

D/W
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