Guest Posted December 17, 2000 Share Posted December 17, 2000 I've got a 75' 455 that is going over a complete rebuild, heads, crank and all. Most likely going with the Hemi Killer Cam and JE racing pistons, headers, 2.5" exhaust. I've got a few questions. I want this setup to run about 450-500 hp and still burn pump gas, I figure 10.2-10.5 compression or so? The rear is getting a 3.55 posi and the tranny is a stock TH400. First question - what stall speed converter? This will be a mostly street car but I'd like to be able to throw on slicks and run her about 12.5 or so (in a 67 Skylark) Anyone happen to know the curb weight of this car offhand? Second question - What cfm carb? I'm thinking a Holley Double Pump between 750 - 850 cfm. What are the performance advantages of going to an 850 with the afformentioned setup, is it necessary? Thank you. <P>------------------<BR>67 Skylark 455 Link to comment Share on other sites More sharing options...
Guest Posted December 17, 2000 Share Posted December 17, 2000 The Holley is gonna kill you with gas milage (talking less than 7 mpg). My 750 vaccum secondary Holly was about 5.5 MPG, UHHHHHGGG!!!! I'm presently running a B4B with a '73 worked Rochester (approx. 840 cfm)over the top of a Hemi Killer w/110* Lobe Centers and seeing about 10 to 11 mpg. <P>I use the GSCA converter. 2800 stall, flashes to 3200. Probably should be a little higher, but it's fine for me. <P>------------------<BR>George C. Thomas<BR>70 GS 455 12.teens<BR>86 GN Low 13's/ high 12's Link to comment Share on other sites More sharing options...
Ted "Wildcat65" Nagel Posted December 17, 2000 Share Posted December 17, 2000 The double pumper is great for drag racing, but it is not great for street duty. THe Q-jet will be easier on your pocketbook buying it and paying for gas, and driveability will be great. You can get T/A to build you one, specificly for your engine combo. But! Do what you want! Its all good stuff if you can tune it and make it work together! I love to drive my cars on the street, so I'm extremely biased toward the driveability side.<P>------------------<BR>Ted Nagel<BR>65 WildcatConvSuperWcat<BR>65 WildcatAutoSuperWcat<BR>65 Wildcat4spdSuperWcat<BR>65 Riviera Wildcat 445<BR>65 Special Wagon 455<BR>70 GS Stage1 4speed<BR>66 Fleetwood Brougham? Link to comment Share on other sites More sharing options...
Guest Posted December 17, 2000 Share Posted December 17, 2000 The stock carb on your motor was rated at 800 cfm. I had a similar combo. i had a 3500 conv it worked well. I had a Q-jet by a reputable source . I got 13 mpg and went 12.30s. Drivabilty was fantastic. Later I switched to Holley 850 , lost mpg to around 5 and driveability stunk. I picked up no ET.Good luck .....Pat Link to comment Share on other sites More sharing options...
Guest Posted December 18, 2000 Share Posted December 18, 2000 Thanks for the good advice. I also noticed a big change when i switched from a rebuilt Q-Jet on the stock setup to a 650 Holley. She seemed to have much more pick up but my fuel econonmy dropped from like 14 to 10 mpg, and that was a stock motor with low compression. The problem with my old Q-Jet was that it really seemed to bog down on me off the line, perhaps with the better inner engine goodies I wouldn't have that problem. Is there any technical difference between the two carbs besides the name - ie if the cfm's are the same why is there such a MPG difference? I know that my old Q-Jet was a major pain in the ass to tune so that's why I changed to Holley, having the side bowls made it really accessable, especially when still on the car. <P>------------------<BR>67 Skylark 455 Link to comment Share on other sites More sharing options...
Guest Posted December 18, 2000 Share Posted December 18, 2000 I have learned the 850 or 1000 CFM Compitition Thermoquad is the hot setup for these motors. I sold a 1000 CFM on the GS Club OF America site a while a go and there was much interest in it. <A HREF="http://buickgsca.com/cgi-bin/ubb/Ultimate.cgi?action=intro" TARGET=_blank>http://buickgsca.com/cgi-bin/ubb/Ultimate.cgi?action=intro</A> <BR><P>------------------<BR>buickfam@aol.com<BR>Life long Buick Fan.<BR>1965 Skylark H/T<BR>1965 Gran Sport Convertible<BR>1948 Chevy Pickup with 401 Buick.<BR>"Fan of anything that moves human beings" Link to comment Share on other sites More sharing options...
Guest Posted December 20, 2000 Share Posted December 20, 2000 The Q jet has small primaries, helping your around town milage, just don't dump it too often. If yours was bogging off the line, it sounds like a bad accelerator pump. Easily repaired.<BR>I suggest that you get a copy of Doug Roe's book on Rochester carbs. <P>------------------<BR>George C. Thomas<BR>70 GS 455 12.teens<BR>86 GN Low 13's/ high 12's<p>[This message has been edited by Thundrr (edited 12-20-2000).] Link to comment Share on other sites More sharing options...
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