I would rather ask here among Ford guys than go to a Chevy forum and take the abuse......Got a 350 Chevy in a class C motor home, equipped with the obligatory quadrajet 4bbl........All the Chevy owners I know call them "quadrajunk", like to replace with a Holley or Edlebrock, what would be the correct cfm to look for in a stock 350?....Would not mind a little more power, this thing is a major DOG going over any kind of hills even with the nice 3" exhuast system........Everytime I drive this thing, I appreciate my F-250 that much more!

 

Any idea what kind of RPMs you're running? I have a table that gives you recommended minimum CFM versus displacement and RPMs.

Maybe I'm wrong here - but it seems like you need an adapter plate to mount a square-bore carburetor to a QJ manifold. It's worth checking.

 

RPMs are 3,000 at 55mph!.........To high to even force a downshift with the gas pedal with the TH/400!(4:10 rear axle).........Understand Holley makes a direct replacement spread bore carb to get rid of the quadrajunk.......Prob. to pricey, I was looking for a used carb.

 

RPMs are 3,000 at 55mph!.........To high to even force a downshift with the gas pedal with the TH/400!(4:10 rear axle).........Understand Holley makes a direct replacement spread bore carb to get rid of the quadrajunk.......Prob. to pricey, I was looking for a used carb.

 

Holley makes a 4175 that is a direct replacement for the spreadbore. But IMHO the Quadrajet is a better carb. The 4175 is around $350. I have owned one that I had on a Dodge 360 & I had nothing but trouble with it plus a loss of about 3 miles per gal. You can get replacement Q-Jets from Jegs.com

 

The Q-jet works reasonably well, but I understand Holleys much better. I have never had trouble with them in Fords, but like you said, none are perfect.......What cfm did the 360 dodge need?

 

The 4175 Holley is a 650 CFM. I never had trouble with a Holley until I bought (NEW) a 4175. I wished I would of bought a reman Q-Jet from Jegs when it was all done. I run a 4160 on my 86 F250 4x4 460 with NO TROUBLE in 6 years. My Dodge went from 14 MPG with a Q-jet & stock cat with single exhaust to 9 MPG with the Holley 4175 with NO cat & dual exhausts. This was a 88 D250 with a Utility bed 2wd 4 sp with Dana 60 3:54 gears. It had a little more power but at a GREAT COST. I had to lower floats to keep from flooding. Just a lot of fooling around that I should not of had to do. Also on the Dodge I had to add a spacer to let the primary throttle plates clear. I'm a Holley guy personally but with spread bores I believe the Q-Jet is a better overall carb. I went to school on the Q-Jet when I worked for a GM dealership in the 70s. I have owned several because I'm kind of a GM guy also. I have an 86 F250 4x4 460 that I bought back in the 90s because I wanted a BIG BLOCK in a 4x4 for towing. Once the 86 is gone (which never be) that will most likely be my last Ford. I prefer GM or Dodge. But I buy USED also. Ford has nothing that impresses me today. I thought I would buy a Crown Vic around a 2000 or newer for the wife to drive & after my friend bought one with 130,000 miles & right out of the gate blew a Spark Plug right out of the head that ended that thought.

 

Hey, Kermmy!...........I am with you, I am not impressed with anything new made by ANY of the manufacturers! I guess thats why the newest rig I own is a 97!.....650cfm sounds about right for a 350, think I will search for a std. squarebore Holley 650 and use the adapter plate....Performance is a relative term in a 11,250lbs vehicle with a 165 hp 350!, I would like to be able to do more than 38mph up a 6% grade. I would have liked to trade it in on a Ford chassis with a 460, but since I got this motor home for FREE and everything works well on it, I will just keep trying to cheaply gain a little more power out of it. MPG.....I did not know a 350 chev was capable of getting 9mpg!, and this motor is in good shape with 70,000 miles and recently tuned.

 

If you want better performance I would look at a 383 Stroker motor. I see them advertised for $1600-$1800 on the west coast complete remans.
A Chevy 350 just doesn't get it when you hook any weight to it. I'd say 38 MPH up a 6% grade is pretty good for that kind of weight. What gears are in your motorhome?
But if your like me you will just drive it as is until a good reason comes which may never come to do something else.
Craig

 

Its got 4:10 gears, which is why it turns 3,000rpms at 55 mph........Not gonna spend big money on this thing.....................Think I will find a way AROUND the Cascades, rather than over, with this thing!