Does anybody out there have personal experience with a Holley model 4175 (p/n 80555C) "Q-jet Replacement" spreadbore carb? I'm considering replacing the custom late-model (i.e., '78 and later) Q-jet on my Buick 350 with the Holley for ease of maintenance, familiarity of local mechanics/tuners, etc. Now I understand that the Holley is only rated at 650 cfm (as opposed to a Q-jet 750). I'm quite sure that I'm not using the full capacity of the Q-jet, anyway, since I have ported cast-iron manifolds instead of headers. That is, I suspect that the exhaust manifolds will be the restriction, not the carb. This particular Holley carb uses the Q-jet bolt pattern, ahd has larger secondaries than primaries, so it is a real "spreadbore" carb. Anyway, has anyone had experience with that particular Holley carb? Hearing about your experiences will be greatly appreciated. Thanks in advance, Dan Gerber Anaheim, CA
Dan, I used that carb from new back in the late eighties on a 455. In theory a large enough carb for the 455; in practice it would go lean at high rpm as the fuel couldn't keep pace with the very rapid air flow. At all other engine speeds I found it to be a great choice. I think it would be a fine choice for a 350.
"Q-jet" Replacement car question hey Guys I'm restoring my skylark and the carb is broken. I need to get a new one my engine compartment has a lot of chrome So I was thinking about the q-series. I have a 72 convertanle 350 engine 2bb. Does anyone know the correct model
Dan, I did the same thing on a 1970 455 stage 1 and it worked very well, but I could tell that the engine could use more carb.... Holley did make a 800 cfm version of the spread bore.... I find the holley to be very tunable, reliable, and easy to work with.... the factory stock qjet is rated at 750 to 800 cfm.... if you reduce the cfm s by that much you will be able to tell a difference in the performance... quite a bit of difference... Buick engines like big carbs any way and reducing the size is not the way if you like performance.... Like Brad says , all carbs will lean out at high rpms... so the combination of smaller fuel/air flow and carb lean out at high rpms will really affect the performance.... but the gas milage is probably good... I picked up 3 mpg.... went from 10 mpg to 13...:laugh: :laugh: if you put the bigger version on that engine, you probably will be happier...
