Thanks again to those of you who have already given me your 2 cents about this. I'm just throwing this out one last time to make sure I do the right thing. I recently picked up a '66 spreadbore intake for my '65 401. And it has been recommended that I use an 800 or 850 cfm Q-jet. If I understand correctly, by going with a bigger carb (I currently have an edelbrock 600 square bore) I will gain more high end power or at least it will rev faster. I currently top out at about 5k. I'm sure this will be great, but my main goal is to gain as much low end (off the line torque) as possible. And I don't want to run the risk of losing any of that low end. It's my understanding that smaller carbs actually have better low end... I've been considering the Edelbrock 850 which ostensibly has part throttle adjustability in addition to idle mixture, and primary and secondary rods, jets and hangers. It seems like I should be able to tune it to my motor - eventually. It just seems like a whole lot of carb for little old 401. I'm also concerned about that carb clearing the intake. Seems like a read somewhere that later intakes are narrower where the carb sits - and newer carbs have clearance issues on older intakes. But without headers, how much difference will I actually see? So far I've only found shorty headers for '65 Rivieras from T/A, but it seems that shorty headers lack the low end of (non shorty) headers. Anyone know of (non shorty) headers for my car? Thanks, Zach
I still like the q-jet. The primary bores are smaller which gives good low end response and economy. secondaries are huge and make a great sound when they open up-not to mention the air/fuel flow. The Eldobrock 850 is not a spread bore and you will need some kind of spacer for it to work right. That may cause hood clearance problems, check it out. I tried a 750 Edelbrock on my nailhead squarebore intake. Off the line the car never felt better! Then when the secondaries opened, there was all kinds of problems, bad miss, loss of power. The carb fit and looked perfect, but the bore of the intake was slightly smaller, causing turbulent flow and reversion, which is fuel dropping out of the air/fuel mix. Caused a lean condition and power loss. I think the bores could be opened up to work with the Edelbrock. Greg Gessler could do this, or Carmen, or Jim Burek. Good luck,
I thought he meant the Edelbrock 850 cfm QJet spreadbore, not to be confused with the Edelbrock 800 cfm AFB squarebore. All of the QJets, both GM OEM and Edelbrock, will let you change the rods and jets on the primary side to set up your part throttle. The QJets have small primaries, so you're not giving anything up over the AFB on the part throttle torque. I bought a 66 Qjet intake and a 74 800 cfm Qjet for my 64 Rivi. The secondary lockout mechanism doesn't clear on the passenger side of the mounting area, near where the exhaust crossover "smiley face" is. Have to take a grinder to it a little bit. Didn't matter for me, I block off crossovers and don't drive it in the winter to need to worry about chokes and the secondary lockout. All that stuff is gone, disabled, etc.
